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Return to Lowell Annual Summaries

2025

1. Lee, L., Trilling, D., Thomas, C., et al., (including Kareta, T., van Belle, G.), 2025, AGUFM, 2025, P21G-2682, Taxonomic Characterizations and Interpretations of Targets in the Emirates Mission to the Asteroid Belt
   Abstract

   The upcoming United Arab Emirates Mission to the Asteroid Belt (EMA) will conduct flybys of six asteroids and conclude with an extended rendezvous with a seventh target, Justitia. Of the seven targets, five have previously been assigned taxonomic classifications based on the slope and absorption features observed in their reflectance spectra, though past surveys have reported conflicting results for some. Asteroid taxonomic classification provides insight into the surface composition and potential origin of these bodies. We collected 0.45-0.95 m spectra of the EMA targets with the 4.3-meter Lowell Discovery Telescope (LDT) and spectrophotometry for a subset of the targets using the LDT and the 0.5-meter TiMo (Titan Monitor) telescope at Lowell Observatory. We have observed five of the seven targets and plan to observe the final two in the coming months. In this study, we present new ground-based spectral observations of the EMA targets, including updated interpretations for both previously unclassified and classified objects using Bus-Binzel (2002) taxonomy. These results refine our understanding of the compositional diversity of these targets and help inform expectations for the mission's upcoming in situ investigations.

2. Gimar, C., Raut, U., Teolis, B., et al., (including Grundy, W.), 2025, AGUFM, 2025, P23F-2728, Thermal and Radiolytic Reddening of Solid Ethane with Relevance to Charon's Mordor Macula
   Abstract

   Charon's unique red-hued northern polar region, Mordor Macula, may result from photolysis of cold-trapped methane by interplanetary medium Lyman- (IPM Ly-) photons, making tholin-like refractories which could impart the reddish color (Grundy et al., 2016). Follow-on investigations (Teolis et al., 2022 and Raut et al., 2022) constrained IPM Ly- induced photochemistry to mostly generate ethane on Charon's polar zones. These studies also posited that solar wind radiolysis of the photo-generated ethane retained on Charon's sunlit surface could lead to formation of reddish hydrocarbons. Here we present serendipitous results that highlight ethane nanoclusters as a "potential contributor" to Charon's red tone. We find the UV-Vis-NIR reflectance spectra of a thin C₂H₆ layer on top of compact water ice increasingly reddens with time when held at temperatures between 57 K and 60 K. We attribute this reddening to scattering by nanoclusters of hydrophobic ethane. The reddening rate as a function of temperature exhibits an Arrhenius behavior, allowing extrapolation of the reddening timescale for lower temperatures. In addition to the thermal reddening, we will present preliminary results on the chemical and color evolution of solid ethane irradiated with keV protons and electrons, replicating the solar wind radiolysis of ethane at Charon, which may contribute to the origin of the red polar zone.

   Grundy W. M. et al. (2016) Nature, 539, 65-68. Teolis B. D. et al. (2022) GRL, 49, e2021GL097580. Raut U. et al. (2022) Sci. Adv., 8, eabq5701.

3. Protopapa, S., Simon, A., Kaplan, H., et al., (including Grundy, W.), 2025, AGUFM, 2025, P32B-04, First Compositional Results from Lucy's Flyby of the C-Type Asteroid (52246) Donaldjohanson
   Abstract

   On April 20, 2025, NASA's Lucy spacecraft (Levison et al. 2021, PSJ 2, 171) performed a close flyby of the C-type asteroid (52246) Donaldjohanson (DJ), a member of the primitive Erigone collisional family in the inner main belt (Marchi et al. 2025, PSJ 6, 59). The encounter, designed as an in-flight test of Lucy's instruments ahead of its primary mission to Jupiter's Trojan asteroids, returned the first spatially resolved observations of DJ. The L'Ralph instrument (Reuter et al. 2023, SSRv 219, 69), which consists of the Multispectral Visible Imaging Camera (MVIC, covering the wavelength range 350-950 nm with a panchromatic channel and five color filters, including one sensitive to phyllosilicate absorption) and the Linear Etalon Imaging Spectral Array (LEISA; 0.95-3.95 m), provided complementary visible and near-infrared imaging spectroscopy of the elongated, bi-lobed body. The wavelength coverage of MVIC and LEISA enables the search for absorption features diagnostic of hydrated silicates, organics, and other primitive materials previously identified in Erigone family spectra, carbonaceous meteorites, and on Bennu and Ryugu. The Erigone family lies near the source regions of the New Polana and Eulalia families, thought to have produced Bennu and Ryugu, raising the question of whether DJ shares compositional traits with these asteroids or exhibits distinct characteristics possibly linked to its collisional history. Here we present initial results from the Lucy observations, focusing on DJ's average spectral properties, potential surface heterogeneity, and its relationships to other primitive inner-belt families. These findings place DJ in context with Bennu and Ryugu and provide new insights into the diversity and evolution of C-type asteroids.

4. Hanley, J., Thieberger, C., Corlies, P., et al., (including Llama, J.), 2025, AGUFM, 2025, P33D-2672, The Variability of Clouds on Titan: Observations and the Upcoming Saturnian Equinox
   Abstract

   Titan hosts a thick atmosphere with complex organic chemistry. We will present observations from Lowell's Discovery Telescope (LDT) centered across various longitudes in order to get an integrated global picture of the vertical distribution of methane and to look for global scale and temporal differences in these distributions.

   Previous observations of Titan from Cassini demonstrate the presence of clouds and surface darkening from potential rainfall. During Southern Summer (prior to 2010) clouds and darkening over the South Polar lakes were observed. During the equinox transition in 2010, clouds and darkening were seen in equatorial regions. Titan is going through equinox again in 2025, making this an excellent time to restart active cloud monitoring.

   We use LDT to study the spectral features of Titan visible spectrum from 0.4 - 0.75 m at a high resolution. The slope is set by absorption of light by aerosols, and will lead to constraints on the composition and vertical abundance of hazes in Titan's atmosphere. In addition, measuring the shape and strength of the methane absorption feature at 0.62 m at high resolution will allow for sensitive constraints on the vertical distribution of methane in Titan's atmosphere, similar to studies conducted with Keck. To complement the visible wavelengths, we also observe with a low-resolution (R ~ 200) NIR spectrograph, covering 0.86 - 2.4 m. This provides access to five methane windows that can see down to Titan's surface, permitting us to complete the vertical abundance retrievals through Titan's entire atmosphere. We also are using the newly operational Titan Monitoring Telescope (TiMo) at Lowell. The telescope is robotic and able to observe every night that Titan is visible. Filters of 10 nm width are centered at 880, 890, 910, and 940 nm to use methane windows to monitor clouds.

   Our ongoing observations with both LDT and TiMo provide complementary data, from high-spectral resolution visible wavelengths, lower-resolution NIR, and overlapping photometry to take advantage of the methane windows. We are able to discern longitudinal differences as expected, as well as detect transient features such as clouds. These high-cadence observations will allow for follow-up high spatial resolution imaging from other facilities.

5. Schulze, B., Doner, A., Horanyi, M., et al., (including Grundy, W.), 2025, AGUFM, 2025, P34B-07, New Horizons' Student Dust Counter: Measurements Beyond 61 AU Heliocentric Distance
   Abstract

   The New Horizons' Venetia Burney Student Dust Counter (SDC) continues to provide dust size and density distribution data as it travels farther into the outer solar system. These observations are essential for expanding our understanding of dust production and loss processes in this region. Contrary to our expectations, SDC has yet to observe a significant decline in dust flux measurements as New Horizons' heliocentric distance increases past the expected peak flux around 50 AU, highlighting the need for further research to identify the reason for the discrepancy between dust dynamics modeling and spacecraft data in the outer solar system.

   We present the most recent SDC data collected at a heliocentric distance of just beyond 61 AU, with updated modeling efforts that consider the effects of silicate versus volatile dust composition and the orbital perturbations acting on small dust particles due to the interstellar neutral (ISN) drag, in addition to radiation pressure and gravity. The orbital evolution of dust grains originating from the Kuiper Belt is evaluated using both analytical approximations and large-scale numerical models.

   As New Horizons is expected to operate until at least 2050, SDC measurements could detect the transition from inside our heliosphere to interstellar space. This is a unique opportunity to learn about our galactic environment and compare it to the astrospheres around other stars.

   Fig. 1: Column density of volatile dust in ecliptic plane of ECLIPJ2000 coordinates considering effects of ISN drag, SDC trajectory shown in black.

6. Saunders, W., Sayanagi, K., Anderson, C., et al., (including Breeland-Newcomb, K., Levine, S.), 2025, AGUFM, 2025, P41G-2686, Preliminary Uranus Atmospheric Results from the 2025 Stellar Occultation Campaign
   Abstract

   Background: UV occultations measured by Voyager 2 (V2) during its flyby of Uranus in 1986 detected a warm stratosphere and extremely hot thermosphere [1, 2], far in excess of solar irradiance [3, 4] or internal heating [5]. These V2 data disagree with Earth-based stellar occultations observed 1977-1996; reprocessing of the latter partially resolved the disagreement [6, 7]. Separately, H₃⁺ observations indicate the thermosphere of Uranus has cooled significantly since 1992 [8], but a dearth of stellar occultations prevents comparing these to stratospheric temperatures since 1996.

   2025 Campaign: On 2025 April 08 UT, we observed Uranus occult a bright star (BD+18 489; R mag 9.7; K mag 7.1) using 17 professional telescopes (35+ astronomers) in the USA and Mexico. See science.larc.nasa.gov/URANUS2025 for more details. To our knowledge, this was the largest Uranus stellar occultation campaign ever organized, and the highest S/N event in at least 30 years, or over a third of a Uranian year. We will present on the planning and organization of the campaign, the 14 successful observations, and preliminary results.

   Preliminary Results: We will present preliminary results on (1) atmospheric temperature structure, (2) long-term stratospheric variations, (3) ring occultations, and (4) implications for aerocapture. We will report the thermal structure of Uranus' stratosphere and lower thermosphere from inverting the observed light curves and compare them to past occultations from 1977-1996 as well as H₃⁺ thermospheric temperatures. We will report on the many detected ring occultations and how they have been used to precisely determine the event geometry and significantly improve Uranus' ephemeris. Last, we will discuss how our findings impact the potential use of aerocapture for a mission to Uranus. Aerocapture is a maneuver in which a spacecraft passes through a planet's stratosphere to decelerate, which may enable a shorter cruise and larger science payload [9, 10]. Our findings reduce uncertainties in Uranus' stratospheric densities, which improves aerocapture feasibility.

   [1] Herbert et al. (1987). [2] Stevens et al. (1993). [3] Marley & McKay (1999). [4] Li et al. (2018). [5] Pearl et al. (1990). [6] Saunders et al. (2023). [7] Saunders et al. (2024). [8] Melin (2020). [9] Soumyo et al. (2021). [10] ADRAT Final Report (2023).

7. Margara, B., Johnson, J., Hayes, A., et al., (including Grundy, W.), 2025, AGUFM, 2025, P51C-1225, Photometric Modeling of Mastcam-Z Observations at Van Zyl Overlook, Jezero Crater
   Abstract

   Between Sols 63-65 (Apr. 24-26, 2021), Mastcam-Z acquired visible/near-infrared multispectral images at Van Zyl Overlook (VZO), east of the Perseverance landing site [1]. Mosaics were collected at 7 local times per sol, spanning phase angles from ~0-150 [1]. Images were calibrated with onboard targets [2] and corrected following [3]. We modeled atmospherically corrected images to estimate photometric parameters, including single scattering albedo (w), phase functions, and surface roughness. Disparity maps from 800 nm stereo pairs enabled 3D surface mapping. ROIs were selected for seven units: gray soil, red soil, regolith, "blue" rocks, "red" rocks, intermediate rocks, and rover tracks. Hapke models were fit at each wavelength to extract w, macroscopic roughness (), the 1-term HG asymmetry parameter (), the 2-term HG parameters b and c, and where possible, opposition parameters B and h [3]. High bidirectional reflectance distribution function (BRDF) values at low phase angles indicate backscattering surfaces. Soil and tracks showed decreasing w with wavelength; red soil and regolith had flatter spectra >800 nm. Blue rocks had the lowest, flattest w spectra. values were slightly negative to near zero, with blue rocks showing strongest backscatteringsimilar to early MSL results [6]. Tracks had low and moderate backscattering, differing from typical forward-scattering behavior [3,6]. Intermediate rocks were more forward-scattering across wavelengths. These results align with those for similar rock/soil types modeled from prior missions except for tracks, which show backscattering phase behavior, possibly due to roughened texture from Perseverance wheels and/or limited phase angle coverage. [6,7].

   [1]Johnson et al., LPSC #1253, 2022;Hayes et al., SSRv, 217, 2020; [2]Bell et al., SSRv, 217, 2020;[3]Johnson et al., JGR/Icarus, 2006;[4]McGuire & Hapke, Icarus, 1995;[5]Johnson et al., LPSC/AGU, 2023;[6]Johnson et al., PSS, 2022;[7]Johnson et al., LPSC 2025.

8. Brandt, P., Hill, M., Elliott, H., et al., (including Grundy, W.), 2025, AGUFM, 2025, SH21D-2525, New Horizons' Encounter with the Heliospheric Boundary
   Abstract

   New Horizons is currently 62 au from the Sun moving outward at 2.88 au/yr along almost the same heliospheric longitude as Voyager 2, but near the ecliptic. Using LECP measurements from Voyager 1 and 2 it is predicted that New Horizons could cross the termination shock (TS) between 68 and 83 au from the Sun (2027 to 2034). As Voyager 2 crossed the TS, it unexpectedly observed the solar wind remaining supersonic, with only a factor of ten increase in temperature, leaving a conundrum that could not be solved with Voyager instrumentation. Although never directly measured by Voyager, these observations implied a critical role of interstellar Pick-Up Ions (PUIs) in the force balance of the global heliosphere. New Horizons is capable of obtaining continuous H⁺ PUI parameters at 29-min resolution, down to 64 s solar wind plasma moments, He⁺ PUI, and energetic particle spectra down to 3 s resolution enabling detection of flow anisotropies. New Horizons' TS crossing is expected to last several days with multiple crossings, each lasting 10-60 min depending on the relative speed of the TS. While the 29-min proton PUI measurements are statistics limited, it is of vital importance to achieve a resolution close to one minute of plasma moments to resolve the minute-scale shock structure expected to heat the PUIs. Given the challenges of forecasting the location of the TS and the massive amount of high-resolution data it demands, one must rely on daily DSN contacts and complementary weekly contacts with the Very Large Array or its next-generation network are desired to achieve a plasma resolution less than ten minutes. Projected to operate until 2050, New Horizons will continue to investigate plasma, PUIs, energetic particles, and galactic cosmic rays as it traverses the heliosheath towards the heliopause to help understand this important boundary region and provide also the only in-situ context for IMAP ENA observations. Additionally, both Lyman-/ intensities and the intriguingly elevated dust flux levels will continue to be tracked as New Horizons is expected to become the second mission to cross the heliopause in the 2040's. This presentation gives an overview of the New Horizons future science operations plan, the expected science return, challenges and the impact on our understanding of the heliosphere and its stellar neighborhood.

9. Wong, I., Grundy, W., Emery, J., et al., 2025, PSJ, 6, 295, Evidence of Possible Spectral Variability in the PatroclusMenoetius Binary System
   Abstract

   We present new visible-wavelength spectroscopic observations of the PatroclusMenoetius binary system in the Jupiter Trojan population. Motivated by previously published spectra from different instruments that showed evidence of significant longitudinal variability, we obtained two spectra spanning 440680 nm at near-opposite rotational phases with the Gemini Multi-Object Spectrograph on the Gemini South telescope during the late 2024 apparition. The same solar analog was used for both observations to remove one source of inconsistency. We measured spectral slopes of 2.51% 0.05%/100 nm and 8.13% 0.05%/100 nm at the two different rotational phases. The first of these measurements was serendipitously obtained during an occultation of Menoetius by Patroclus. Although the statistical significance of the spectral slope discrepancy persists even after considering possible systematic errors stemming from differences in slit position angles and air masses between the asteroid and solar analog exposures, we consider this report of variability to be tentative. We briefly explore several scenarios that could explain the measured spectral slope variability. Additional follow-up observations are necessary to definitively confirm and characterize any inhomogeneities across the surface, which will have major implications for the 2033 flyby of PatroclusMenoetius by the Lucy spacecraft.

10. Bellotti, S., Cristofari, P., Callingham, J., et al., (including LLama, J.), 2025, A&A, 704, A298, A magnetic field study of two fast-rotating, radio-bright M dwarfs: StKM 1-1262 and V374 Peg
    Abstract

    Context. Radio observations at low frequencies are sensitive to the magnetic activity of stars and the plasma environment surrounding them, so one can scrutinize the conditions under which stellar space weather develops and impacts exoplanets. The accurate interpretation of the processes underlying the radio signatures requires a detailed characterisation of stellar magnetism. Aims. We study two M dwarfs, namely StKM 1-1262 (M0 type, P_rot = 1.24 d) and V374 Peg (M4 type, P_rot = 0.4455 d), which were detected recently with the LOw Frequency ARray (LOFAR). StKM 1-1262 exhibited the typical signature of a type-II radio burst, potentially resulting from a coronal mass ejection event. V374 Peg manifested low-frequency radio emission with high brightness temperature and low degree of polarisation, suggesting an electron-cyclotron maser instability emission mechanism. In this work, we provide recent observational constraints on the magnetic field of both stars. Methods. We analysed spectropolarimetric observations of these M dwarfs, collected with the SpectroPolarimetre InfraRouge (SPIRou). Firstly, we refined the stellar parameters, such as effective temperature, surface gravity, and metallicity, and measured the average surface magnetic flux via modelling of Zeeman broadening in unpolarised spectra. We then applied Zeeman-Doppler imaging to least-squares deconvolution line profiles in circular polarisation to reconstruct their large-scale magnetic fields. We also reconstructed a brightness map for the two stars using Doppler imaging. Results. StKM 1-1262 has a total, unsigned magnetic field of 3.53 0.06 kG on average, and the large-scale magnetic field topology is predominantly poloidal, dipolar and moderately axisymmetric, with an average strength of 300 G. V374 Peg has an unsigned magnetic field of 5.46 0.09 kG, and the large-scale field is poloidal, dipolar and axisymmetric, with an average strength of 800 G. For StKM 1-1262, we found a strong (Pearson = 0.96) anti-correlation between the total magnetic field and the effective temperature, which is reminiscent of the tight link between small-scale magnetic fields and surface inhomogeneities. For V374 Peg, we found a moderate ( = 0.43) anti-correlation, possibly due to a more even distribution of surface features. Conclusions. The large-scale magnetic field topology of StKM 1-1262 is similar to other stars with similar fundamental parameters like mass and rotation period, and the brightness map features one dark spot, which is responsible for the rotational modulation of the total magnetic field and the retrieved effective temperature. For V374 Peg, the magnetic topology and the brightness map are similar to previous reconstructions, indicating a temporal stability of approximately 14-yr.

11. Einasto, M., Tenjes, P., Kipper, R., et al., (including West, M.), 2025, A&A, 704, A151, The richest clusters in the Coma and Leo superclusters: Properties and evolution
    Abstract

    Context. Superclusters of galaxies represent dynamically active environments in which galaxies and their systems form and evolve. Aims. We study the substructure, connectivity, and galaxy content of galaxy clusters A1656 and A1367 in the Coma supercluster and of A1185 in the Leo supercluster with the aim of understanding the evolution of clusters from turnaround to virialisation, and the evolution of whole superclusters. Methods. We used data from the Sloan Digital Sky Survey DR10 MAIN galaxy sample and from DESI cluster catalogues. The projected phase space diagram and the distribution of mass were used to identify regions of various infall stages (early and late infall, and regions of ongoing infall, i.e. regions of influence), their characteristic radii, embedded mass, and density contrasts in order to study the evolution of clusters with the spherical collapse model. We determined the substructure of clusters using normal mixture modelling and their connectivity by counting filaments in the cluster's regions of influence. We analysed galaxy content in clusters and in their environment and derived scaling relations between cluster masses. Results. All three clusters have a substructure with two to five components and up to six filaments connected to them. The radii of regions of influence are R_inf 4 h¹ Mpc, and the density contrast at their borders is _inf 50 60. The scaling relations between the masses of clusters have a very small scatter. The galaxy content of the clusters and of their regions of influence vary from cluster to cluster. In high-density regions (superclusters), the percentage of quiescent galaxies is higher than in low-density regions between superclusters, where approximately one-fourth of the galaxies are still quiescent. Conclusions. The collapse of the regions of influence of clusters started at redshifts z 0.4 0.5. Clusters will be virialised approximately in 3.3 Gyrs. Clusters in superclusters will not merge, and their present-day turnaround regions will be virialised in 10 Gyrs. The large variety of properties of clusters suggests that they have followed different paths during evolution.

12. Proudfoot, B., Grundy, W., Ragozzine, D., et al., 2025, PSJ, 6, 285, Beyond Point Masses. V. Weywot's Non-Keplerian Orbit
    Abstract

    We present a detailed dynamical analysis of the QuaoarWeywot system based on nearly 20 yr of high-precision astrometric data, including new Hubble Space Telescope observations and stellar occultations. Our study reveals that Weywot's orbit deviates significantly from a purely Keplerian model, requiring the inclusion of Quaoar's nonspherical gravitational field and center-of-bodycenter-of-light (COB-COL) offsets in our orbit models. We place a robust upper limit on Weywot's orbital eccentricity (e < 0.02), substantially lower than previous estimates, which has important implications for the strength of mean-motion resonances acting on Quaoar's ring system. Under the assumption that Quaoar's rings lie in its equatorial plane, we detect Quaoar's dynamical oblateness, J₂, at 2 confidence. The low J₂ value found under that assumption implies that Quaoar is differentiated, with a total bulk density of 1751 13 (stat.) kg m³. Additionally, we detect significant COB-COL offsets likely arising from latitudinal albedo variations across Quaoar's surface. These offsets are necessary to achieve a statistically robust orbit fit and highlight the importance of accounting for surface heterogeneity when modeling the orbits of dwarf planet moons. These findings improve our understanding of Quaoar's interior and surface while providing key insights into the stability and confinement mechanisms of its rings.

13. Wong, I., Holler, B., Protopapa, S., et al., (including Grundy, W.), 2025, PSJ, 6, 281, JWST/NIRSpec Observations of Salacia-Actaea and Mani: Exploring Population-level Trends among Water-ice-rich Kuiper Belt Objects
    Abstract

    We present observations of the midsized Kuiper Belt objects (KBOs) SalaciaActaea and Mani, obtained with the Near-Infrared Spectrograph on JWST. The satellite Actaea was fully blended with Salacia at the spatial resolution of the integral field unit, and we extracted the combined spectrum. The 0.75.1 m reflectance spectra of SalaciaActaea and Mani display prominent water-ice absorption bands at 1.5, 2, 3, and 45 m. The ₃ fundamental vibrational band of carbon dioxide ice at 4.25 m is present in both spectra. From a quantitative band-depth analysis of the entire current JWST spectroscopic sample of water-ice-rich KBOs, we find strong evidence for a positive covariance between relative water-ice abundance and size, which may indicate the emergent impacts of internal differentiation and cryovolcanic production of surface water ice on midsized KBOs. A detailed look at the distribution of 2 and 3 m band depths suggests additional sources of variability, such as different water-ice grain sizes. In addition, we report an apparent transition in the carbon dioxide band depth at object diameters of roughly 300500 km, with larger objects showing systematically weaker absorptions, although selection effects within the sample do not allow us to confidently distinguish between a size-dependent phenomenon and a correlation with dynamical class.

14. Massey, P., Morrell, N., Neugent, K., et al., (including Herzog, M., O'Brien, C.), 2025, ApJ, 994, 176, The Stellar Content of NGC 3603 Revisited: Is the IMF Top Heavy?
    Abstract

    Studies of the resolved stellar populations of young massive clusters have shown that the slope of the initial mass function (IMF) appears to be the same everywhere, with no dependence on stellar density or metallicity. At the same time, studies of integrated properties of galaxies usually conclude that the IMF does vary and must be top-heavy in starburst regions. In order to investigate this, we have carried out a long-term project to characterize the massive-star content of NGC 3603, the nearest giant H II region, known to have a rich population of massive stars. We used both ground-based and Hubble Space Telescope (HST) imaging to obtain photometry, and we employed Gaia to establish membership. We obtained spectra of 128 stars using the Magellan 6.5 m telescope and HST, and we combine these data to produce a reddening map. After analyzing the data in the same way as we have for 25 other star-forming regions in the Milky Way and the Magellanic Clouds, we find that the IMF slope of NGC 3603 is quite normal compared to other clusters, with = 0.9 0.1. If anything, there are fewer very high mass (>65M) stars than one would expect by extrapolation from lower masses. This slope is also indistinguishable from what several studies have shown for R136 in the LMC, an even richer region. We speculate that the depreciation of the highest-mass bins in NGC 3603, but not in R136, may indicate that it is harder to form extremely massive stars at the higher metallicity of the Milky Way compared to that of the LMC. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. It also uses observations made with the NASA/ESA Hubble Space Telescope (HST), obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations were made under proposals GO-10602 (PI: Maiz Apellaniz) and GO-11626 (PI: Massey).

15. Dattilo, A., Vanderburg, A., Barber, M., et al., (including Polanski, A.), 2025, AJ, 170, 318, THYME. XIII. Two Young Neptunes Orbiting a 75 Myr Star in the Alpha Persei Cluster
    Abstract

    Young planets with mass measurements are particularly valuable in studying atmospheric mass-loss processes, but these planets are rare and their masses difficult to measure due to stellar activity. We report the discovery of a planetary system around TOI-6109, a young, 75 Myr-old Sun-like star in the Alpha Persei cluster. It hosts at least two transiting Neptune-like planets within 10 day orbital periods. Using three TESS sectors, 30 CHEOPS orbits, and photometric follow-up observations from the ground, we confirm the signals of the two planets. TOI-6109 b has an orbital period of P = 5.69040.0004+0.0004 days and a radius of R = 4.870.12+0.16 R. The outer planet, TOI-6109 c has an orbital period of P = 8.53880.0005+0.0006 days and a radius of R = 4.830.06+0.07 R. These planets orbit just outside a 3:2 mean motion resonance. The near-resonant configuration presents the opportunity to measure the planet's mass via TTV measurements and to bypass difficult RV measurements. Measuring the masses of the planets in this system will allow us to test theoretical models of atmospheric mass loss.

16. Egal, A., Vida, D., Colas, F., et al., (including Moskovitz, N., Kareta, T.), 2025, NatAs, 9, 1624, Catastrophic disruption of asteroid 2023 CX1 and implications for planetary defence
    Abstract

    Mitigation of the threat from airbursting asteroids requires an understanding of the potential risk they pose for the ground. How asteroids release their kinetic energy in the atmosphere is not well understood due to the rarity of large impacts. Here we present a comprehensive, space-to-laboratory characterization of an impact of an L chondrite, which represents a common type of Earth-impacting asteroid. Small asteroid 2023 CX1 was detected in space and predicted to impact over Normandy, France, on 13 February 2023. Observations from several independent sensors and reduction techniques revealed an unusual but potentially high-risk fragmentation behaviour. The nearly spherical 650 160 kg (72 6 cm diameter) asteroid catastrophically fragmented at a dynamic pressure of 4 MPa around 28 km altitude, releasing 98% of its total energy in a concentrated region of the atmosphere. The resulting shock wave was spherical, not cylindrical, and released more energy closer to the ground. This type of fragmentation increases the risk of substantial damage at ground level. These results warrant consideration for a planetary defence strategy for cases where a >34 MPa dynamic pressure is expected, including planning for evacuation of areas beneath anticipated disruption locations.

17. Collyer, C., Fernandez-Valenzuela, E., Ortiz, J., et al., (including Grundy, W.), 2025, PSJ, 6, 270, Synchronous Rotation in the (120347) SalaciaActaea System
    Abstract

    We report on roughly 16 yr of photometric monitoring of the trans-Neptunian binary system (120347) SalaciaActaea, which provides significant evidence that Salacia and Actaea are tidally locked to the mutual orbital period in a fully synchronous configuration. The orbit of Actaea is updated, followed by a LombScargle periodogram analysis of the ground-based photometry, which reveals a synodic period similar to the orbital period and a peak-to-peak lightcurve amplitude of m = 0.0900 0.0036 mag (1 uncertainty). Incorporating archival Hubble Space Telescope photometry that resolves each component, we argue that the periodicity in the unresolved data is driven by a longitudinally varying surface morphology on Salacia, and we derive a sidereal rotation period that is within 1 of the mutual orbital period. A rudimentary tidal evolution model is invoked that suggests synchronization occurred within 1.1 Gyr after Actaea was captured/formed.

18. Ellwarth, M., Llama, J., Zhao, L., et al., (including Sikora, J., Polanski, A.), 2025, ApJ, 994, 104, The He I D3 Line as a Proxy for Magnetic Activity Using EXPRES Solar Observations
    Abstract

    Stellar activity remains one of the primary challenges in the detection and characterization of low-mass exoplanets, as it can induce radial velocity (RV) variations that mask or mimic planetary signals. Identifying reliable activity proxies is essential in order to distinguish stellar variability from genuine planetary signatures. In this study, we examine the variability of the chromospheric He I D3 line in high-resolution solar spectra and assess its potential as an activity indicator. We find a strong correlation between the He I D3 line intensity variation and the Sun's unsigned magnetic flux derived from Solar Dynamics Observatory/Helioseismic and Magnetic Imager data as well as with the solar RVs. Our results suggest that the He I D3 line offers a promising and straightforward proxy for magnetic activity, which may complement existing stellar activity indicators. Its inclusion could help disentangle stellar signals in RV measurements and ultimately improve the detection of Earth-like exoplanets.

19. Proudfoot, B., Nolthenius, R., Holler, B., et al., (including Grundy, W.), 2025, ApJL, 993, L38, Orbital Characterization of a Newly Discovered Small Satellite around Quaoar
    Abstract

    Recent observations of a stellar occultation have revealed the presence of a previously undiscovered small satellite around Quaoar. Orbiting near Quaoar's unusual ring system, this new satellite has the potential to provide significant insights into the formation and evolution of Quaoar and its ring system. In this Letter, we characterize the orbit of this newly discovered satellite, finding that it is likely on a 3.60.3+0.5 day orbit, plausibly placing it near a 5:3 mean motion resonance with Quaoar's outermost known ring. Examining the possibility of observing the newly discovered satellite with further stellar occultations, we estimate that hundreds of observing stations are required for recovery, since phase information about its orbit was rapidly lost after the lone detection. We also attempted to recover the satellite in JWST NIRCam imaging of Quaoar, but find no convincing detection. This nondetection is limited by the accuracy of the available NIRCam point-spread function models, as well as the satellite's extreme faintness and close-in orbital separation. Therefore, current-generation telescopes will likely struggle to directly image this new satellite, but near-future 30 m class telescopes should prove capable of detecting it. Discovery of such a satellite provides evidence that the rings around Quaoar may have been part of an initially broad collisional disk that has evolved considerably since its formation. To further explore this hypothesis, we encourage follow-up observations of the rings and satellites with stellar occultations and direct imaging, as well as updated hydrodynamical, collisional, and tidal modeling of the system.

20. Park, N., Shkolnik, E., Llama, J., 2025, ApJ, 994, 26, Constraining the Mass Loss and the Kinetic Energy of Stellar Coronal Mass Ejections with Solar Far-ultraviolet Flares
    Abstract

    Stellar eruptive events, such as flares and coronal mass ejections (CMEs), can affect planetary habitability by disturbing the stability of their atmospheres. For instance, strong stellar flares and CMEs can trigger atmospheric escape and, in extreme cases, may strip away the atmosphere completely. While stellar flares have been observed and explored at a wide range of wavelengths, the physical properties of stellar CMEs remain unconstrained due to the difficulty in observing them. In this context, the Sun provides our only window on the potential characteristics of CMEs on Sun-like stars. A correlation between solar X-ray flare peak flux and the mass of flare-associated solar CMEs has been reported using solar data collected during Solar Cycle 23. Here, we build upon that work. We extend the correlation into the far-UV (FUV), where stellar flares are, and will continue to be, routinely detected with existing and future FUV observatories by incorporating data spanning two entire Solar Cycles (23 and 24; 19962019). Using three different space missions (CMEs from Large Angle Spectrometric Coronagraph/Solar and Heliospheric Observatory, X-ray flare events from X-ray Spectrometer/GOES, and FUV flares from Atmospheric Imaging Assembly/Solar Dynamics Observatory), we report a correlation between FUV flare peak flux and energy centered at 1600 A and mass, kinetic energy, and linear speed of flare-associated CMEs. These empirical relations enable estimates of CME masses and kinetic energies from FUV flares on Sun-like stars. While direct stellar CME detections remain elusive, the correlations derived here are likely applicable to Sun-like stars and provide a working framework for evaluating exoplanet atmospheric erosion.

21. Peacock, S., Wilson, D., Richey-Yowell, T., et al., 2025, AJ, 170, 293, HWO Target Stars and Systems: A Survey of Archival UV and X-Ray Data
    Abstract

    We assess archival high-energy data for key stars on the Habitable Worlds Observatory (HWO) Target Stars and Systems 2025 list, as stellar radiation is critical to shaping and interpreting planetary atmospheres. Using a sample of 98 nearby stars (HWO Tier 1 targets), we compile and evaluate X-ray and ultraviolet (UV) data from archival eROSITA, Chandra, XMM-Newton, ROentgen SATellite, Extreme-Ultraviolet Explorer, Swift, Far Ultraviolet Spectroscopic Explorer, International Ultraviolet Explorer (IUE), Galaxy Evolution Explorer, and Hubble Space Telescope (HST). We examine spectral and temporal coverage, assess data quality, and identify major gaps. UV data are moderately available, with most coverage coming from near-UV spectra from IUE. Far fewer stars have far-UV spectra, especially from HST. In the X-ray regime, some stars have high-quality spectra, while others are limited to shallow detections or broadband photometry. A small fraction of the sample has both X-ray and UV spectra of sufficient quality to support full spectral energy distribution modeling. Truly comprehensive coverage across X-ray, extreme-UV, and both UV bands remains extremely rare. Most data sets are single-epoch, limiting assessments of variability and flareskey factors in atmospheric photochemistry and escape. Moreover, the lack of simultaneous or contemporaneous observations across bands adds further uncertainty. Our findings underscore the need for new space-based missions and coordinated multiwavelength campaigns, ideally with overlapping coverage, to improve stellar characterization for HWO. As several key observatories age and face potential decommissioning, there is a narrow window of opportunity to secure these critical data. Investing in this effort now will directly support the science goals of HWO and enhance future studies of planetary habitability.

22. Yamamoto, M., Becker, M., Sheldon, E., et al., (including Kuehn, K.), 2025, MNRAS, 543, 4156, Dark Energy Survey Year 6 results: cell-based coadds and METADETECTION weak lensing shape catalogue
    Abstract

    We present the METADETECTION weak lensing galaxy shape catalogue from the 6-yr Dark Energy Survey (DES Y6) imaging data. This data set is the final release from DES, spanning 4422 deg$^2$ of the southern sky. We describe how the catalogue was constructed, including the two new major processing steps, cell-based image coaddition, and shear measurements with METADETECTION. The DES Y6 M ETADETECTION weak lensing shape catalogue consists of 151 922 791 galaxies detected over $riz$ bands, with an effective number density of $n_{\rm eff}$ = 8.22 galaxies per arcmin$^2$ and shape noise of $\sigma _{\rm e} = 0.29$. We carry out a suite of validation tests on the catalogue, including testing for point spread function (PSF) leakage, testing for the impact of PSF modelling errors, and testing the correlation of the shear measurements with galaxy, PSF, and survey properties. In addition to demonstrating that our catalogue is robust for weak lensing science, we use the DES Y6 image simulation suite to estimate the overall multiplicative shear bias of our shear measurement pipeline. We find no detectable multiplicative bias at the roughly half-per cent level, with $m = (3.4 \pm 6.1) \times 10^{-3}$, at $3\sigma$ uncertainty. This is the first time both cell-based coaddition and M ETADETECTION algorithms are applied to observational data, paving the way to the Stage-IV weak lensing surveys.

23. Anna John, A., Al Moulla, K., O'Sullivan, N., et al., (including Llama, J.), 2025, MNRAS, 543, 1974, Granulation on a quiet K dwarf: HD 166620 I. Spectral signatures as a function of line-formation temperature
    Abstract

    As radial velocity (RV) spectrographs reach unprecedented precision and stability below 1 m s$^{-1}$, the challenge of granulation in the context of exoplanet detection has intensified. Despite promising advancements in post-processing tools, granulation remains a significant concern for the EPRV (extremely precise radial velocity) community. We present a pilot study to detect and characterize granulation using the High-Accuracy Radial-velocity Planet Searcher for the Northern hemisphere (HARPS-N) spectrograph. We observed HD 166620, a K2 star in the Maunder Minimum phase, intensely for two successive nights, expecting granulation to be the dominant nightly noise source in the absence of strong magnetic activity. After correcting for a newly identified instrumental signature, originating from CCD illumination variations under optimal seeing conditions, we detected the granulation signal using structure-function (SF) analysis and a single-component Gaussian process (GP) model. The granulation signal has a characteristic time-scale of $43.65^{+16.9}_{-14.7}$ min, within 1$\sigma$, and a standard deviation of $22.9^{+0.83}_{-0.72}$ cm s$^{-1}$, within 3$\sigma$ of the predicted value. By examining spectra and RVs as a function of line formation temperature, we investigated the sensitivity of granulation-induced RV variations across different photospheric layers. We extracted RVs from various photospheric depths using both the line-by-line and cross-correlation function methods to mitigate any extraction method biases. Our findings indicate that granulation variability is detectable in both temperature bins, with the cooler bins, corresponding to the shallower layers of the photosphere, aligning more closely with predicted values.

24. Shkolnik, E., Ardila, D., Jensen, L., et al., (including Llama, J.), 2025, JATIS, 11, 042212, Building SPARCS, an ultraviolet science CubeSat for exoplanet habitability studies, technology advancements, and mission training
    Abstract

    The Star-Planet Activity Research CubeSat (SPARCS) is a NASA-funded 6U-CubeSat mission designed to monitor ultraviolet (UV) radiation from low-mass stars. These stars' relatively high-frequency and high-energy UV flares significantly affect the atmospheres of orbiting exoplanets, driving atmospheric loss and altering the conditions for habitability. SPARCS aims to capture time-resolved photometric data in the far-UV and near-UV simultaneously to better characterize the flares and detect the strongest and rarest among them. In addition, SPARCS is testing innovative technology, such as delta-doped detectors with near 100% internal quantum efficiency and detector-integrated metal-dielectric UV bandpass filters. This mission will increase the technology readiness level of these critical components, positioning them for inclusion in future flagship missions such as the Habitable Worlds Observatory. We outline SPARCS' mission goals and provide an update as the spacecraft is completed and awaits its planned late-2025 launch to a sun-synchronous low-Earth orbit. We also highlight the critical role of small missions in providing training and leadership development opportunities for students and researchers, advancing technology for larger observatories, and share lessons learned from collaborations among academic, government, and industry partners.

25. Bair, A., Schleicher, D., 2025, PSJ, 6, 248, Comprehensive Analyses of the Strongly Carbon-chain Depleted Comets in Lowell Observatory's Narrowband Photometry Database
    Abstract

    We present measurements, analyses, and results for the 17 strongly carbon-chain depleted comets in Lowell Observatory's narrowband photometry database. The majority of comets exhibit a very similar, i.e., typical, composition in optical wavelengths, though the existence of anomalous comets with lower abundances of carbon-chain molecules relative to CN has long been known. M. F. A'Hearn et al. identified an entire class of these carbon-chain depleted comets, and the most recent full analysis of our database reveals that there are varying degrees of carbon-chain depletion. Here we focus on the most depleted comets, the strongly carbon-chain depleted class, which is the largest nontypical compositional class to emerge from our taxonomic analyses. All comets in this class are strongly depleted in both C₂ and C₃ with respect to OH and CN, with depletions for these ratios being 327 below the mean abundance ratios for comets with typical composition. Several comets in this class additionally exhibit depletion in NH, with the largest depletions being 11 below mean typical values. A number of these comets exhibit asymmetry in production rates as a function of time and heliocentric distance, and one exhibits evidence of small secular changes. Almost all of the strongly depleted comets are Jupiter-family comets, indicating a Kuiper Belt origin for this compositional class. Multiple lines of evidence from our full database indicate that this composition is due to primordial conditions when and where these comets were formed and is not due to thermal heating after their arrival in the inner solar system.

26. Polanski, A., Clark, C., 2025, RNAAS, 9, 291, An Inventory of Resolved Stellar Companions in the Ariel Target List
    Abstract

    Stellar companions impact many facets of planet formation and mature planetary systems. In this note, we investigate planet-hosting stars that are currently potential targets for the upcoming Ariel mission, and present an inventory of their stellar companions. We examine several catalogs that used Gaia astrometry to identify companions with similar phase-space parameters, and that therefore have a high probability of being gravitationally bound. The agreement between catalogs is good; the false-negative rate is 16%. We also search for stellar companions beyond 1 kpc and present four new candidate companions. All Gaia-resolved companions referenced in this work have now been added to the ExoFOP archive to facilitate future planet confirmation efforts.

27. Yalcinkaya, S., Barkaoui, K., Basturk, O., et al., (including Polanski, A.), 2025, A&A, 702, A209, TOI-1743 b, TOI-5799 b, TOI-5799 c, and TOI-6223 b: TESS discovery and validation of four super-Earth to Neptune-sized planets around M dwarfs
    Abstract

    We present the discovery by the TESS mission of one transiting Neptune-sized planet, TOI-6223 b, and two transiting super-Earths, TOI-1743 b and TOI-5799 b. We validate these planets using a statistical validation method, multi-color light curves, and other ancillary observations. We combined TESS and ground-based photometric data to constrain the physical properties of the planets. TOI-6223 b is slightly larger than Neptune R_p = 5.12_0.25^+0.24 R) orbiting an early M dwarf in 3.86 days, and it has an equilibrium temperature of T_eq = 714 14 K. TOI-1743 b orbits its mid-dwarf star every 4.27 days. It has a radius of R_p = 1.83_0.10^+0.11 R and an equilibrium temperature of T_eq = 485₁₃⁺¹⁴. TOI-5799 b has a radius of R_p = 1.733_0.090^+0.096 R and an equilibrium temperature of T_eq = 505 16 K. It orbit around an M2 dwarf in 4.17 days. We also present the discovery of an additional transiting planet, TOI-5799 c, which we identified in the TESS data and validated using the SHERLOCK pipeline. TOI-5799 c is a super-Earth with a radius of R_p = 1.76_0.10^+0.11 R. Its orbital period and its equilibrium temperature are 14.01 days and T_eq = 337 11 K, respectively, which place it near the inner edge of the habitable zone of its star. We show that these planets are suitable for both radial velocity follow-up and atmospheric characterization. They orbit bright (<11 K_mag) early M dwarfs, making them accessible for precise mass measurements. The combination of the planet sizes and stellar brightness of their host stars also make them suitable targets for atmospheric exploration with the JWST. Such studies may provide insights into planet formation and evolution, as TOI-1743 b, TOI-5799 b, and TOI-5799 c lie within what is known as the radius valley, while TOI-6223 b is located on the Neptunian ridge in the period-radius plane.

28. Hanassi-Savari, F., Pietrow, A., Druett, M., et al., (including Ellwarth, M.), 2025, A&A, 702, A97, Solar flux atlases: The new HARPS-N quiet Sun benchmark and continuum normalisation of the Ca II H & K lines
    Abstract

    Context. Solar flux atlases observe the spatially integrated light from the Sun, treating it as a star. They are fundamental tools for gaining insight into the composition of the Sun and other stars. They are utilised as reference material for a wide range of solar applications such as stellar chemical abundances, atmospheric physics, stellar activity, and radial velocity signals. Aims. We provide a detailed comparison of solar activity reported in some of the well-known solar atlases against the new High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) Quiet Sun (QS) and Measured Activity (MA) atlases published, for the first time, in this work. Methods. Ten of the widely used individual spectral lines from each flux atlas were selected to compare solar activity based on three methods: (1) equivalent widths; (2) a novel activity measure introduced in this work and referred to as the activity number; and (3) bisectors and radial velocity. Results. The significantly smaller activity levels measured in the MA atlas, compared to the other atlases, relative to the QS atlas, underscores the dominance of instrumental effects over solar activity in their impact on spectral lines, which cannot be corrected through simple line convolution to match resolutions of other atlases. Additionally, our investigation unexpectedly revealed a substantial intensity shift in the Ca II H & K lines of other atlases compared to our HARPS-N atlases, likely resulting from the assumptions made when applying normalisation techniques for the early Kitt Peak atlases. Conclusions. With an average spot number of zero, our QS atlas is well suited to serve as an absolute benchmark atlas representative of solar minimum for the visible spectrum, which other atlases can be compared against. Our recommendations going forward include: (1) the publication of a detailed log along with the observations to include exact dates and indications of solar activity; and (2) given the dominance of instrumental effects over variations caused by activity, quiet Sun reference atlases must be constructed with the same instruments to ensure high precision.

29. Protopapa, S., Wong, I., Lellouch, E., et al., (including Grundy, W.), 2025, ApJL, 991, L34, JWST Detection of Hydrocarbon Ices and Methane Gas on Makemake
    Abstract

    JWST/NIRSpec observations of Makemake reveal a chemically complex surface and evidence of gaseous CH₄. Our spectral modeling indicates a surface composition consisting of CH₄, CH₃D, and possibly CH₃OH, combined with aggregates of C₂H₂ and C₂H₆. The presence of C₂H₄ is also considered given its expected photochemical origin. Both areal and layered configurations reproduce the observed spectrum, with the latter being preferred. This composition confirms earlier hydrocarbon detections and suggests that CH₄ photolysis is either ongoing or occurred recently. The detection of CH₃D yields a D/H ratio in CH₄ ice of (3.98 0.34) 10⁴, consistent within 2 with previous estimates. We report the first detection of CH₄ fluorescence from Makemake, establishing it as only the second trans-Neptunian objectafter Plutowith confirmed volatile release. We explore two scenarios consistent with the observed CH₄ emission, though neither fully reproduces the data: an expanding coma, yielding production rates of (0.21.6) 10²⁸ molecules s¹ and a rovibrational temperature of 35 K, possibly originating from a localized plume, and a gravitationally bound atmosphere, which, if adopted, implies gas kinetic temperatures near 40 K and surface pressures of 10 pbarvalues consistent with stellar occultation constraints and an atmosphere in equilibrium with surface CH₄ ice. Discriminating between these scenarios will require higher spectral resolution and improved signal-to-noise observations. Together, the gas-phase CH₄, intermediate D/H ratio between that in water and CH₄ in comets, and complex surface composition challenge the traditional view of Makemake as a quiescent, frozen body.

30. Crawford, C., Li, Y., Huber, D., et al., (including Polanski, A.), 2025, MNRAS, 542, 3289, The highest mass Kepler red giants II. Spectroscopic parameters, the amplitudeactivity relation, and unexpected halo orbits
    Abstract

    The high-mass (M$\,>\,$2 $\text{M}_{\odot }$) Kepler red giant stars are less well-studied than their lower mass counterparts. In the previous article, we presented a sample of 48 high-mass Kepler red giants and measured their asteroseismic parameters. This article presents spectroscopic measurements from the same sample, using high-resolution Keck/HIRES spectra to determine $T_\text{eff}$, [Fe/H], $\log g$, and $v \sin i$. We refined our previous estimates of the stellar masses and radii based on the new $T_\text{eff}$. We also examined spectral features that could indicate binary activity, such as the Li line and [C/N] ratios. We found no Li-rich stars or clear [C/N] anomalies, but we observed a correlation between [C/N] and [Fe/H]. We measured chromospheric activity using the S-index of the Ca II H & K lines and found no correlation with internal magnetic fields. However, we confirmed an anticorrelation between surface chromospheric activity and radial mode oscillation amplitudes, which indicates that strong surface magnetic fields weaken stellar oscillations. Finally, we used the Gaia DR3 astrometric data to show that our sample of stars have orbits consistent with all three Galactic kinematic regions. Although these stars are quite young, their orbits carry them into the thick disc and even the halo, raising questions about the accuracy and viability of kinematics in unravelling Galactic history. In future work, we plan to use the spectroscopic parameters measured here to provide better constraints for boutique frequency modelling, which will allow us to test the asteroseismic scaling relations at the high-mass regime.

31. Lilly, E., Schambeau, C., Volk, K., et al., (including Thirouin, A.), 2025, epsc, 2025, EPSC-DPS2025-38, First results from the RENOIR survey: A Possible Evidence of Surface Transformation of Centaurs
    Abstract

    Centaurs are small bodies residing on unstable orbits between Jupiter and Neptune. As objects recently scattered from their sources in the Kuiper belt and beyond, they carry the compositional information of their parent populations into the realm of the giant planets. Unlike the TNO populations, Centaurs are known for their unusual bimodal distribution of optical surface colors, splitting them into two distinct groups - red and grey (neutral). It has been long disputed whether this color distribution points to Centaurs being sourced from two distinct formation locations in the protoplanetary disk, or alternatively that the present surface color distribution represents an ongoing dynamical-evolutionary pathway experienced by Centaurs that produces the two groups.Here we present results from a broadband visible photometric investigation using the SDSS-like g', r' and i' filters of 33 Centaurs obtained with the Gemini Observatories and the Lowell Discovery Telescope. The data have been collected as a part of the RENOIR (Revealing cENtaur cOlor hIstoRy) survey in 2022-2025. The ultimate goal of this program is to collect surface colors of Centaurs covering a wide range of diameters and occupying the entire heliocentric distance span of the Centaur region. Our preliminary results suggest that the (g'-r') color distribution of our target Centaurs is different from that of TNOs measured by the Col-OSSOS program (Buchanan et al. 2022) with a 2-sigma confidence level, and while our targets' colors do display bimodality in (g'-r') - space, they are also significantly shifted towards the neutral part of the color-color plot. This shift potentially points out to a surface color transformation the pristine TNOs undergo during their dynamical evolution in the Centaur region. We have also coupled our observational results with the analysis of each Centaur's orbital history in order to explore possible correlations of orbital evolution with present-day observed surface colors.

32. Howett, C., Kaplan, H., Protopapa, S., et al., (including Grundy, W.), 2025, epsc, 2025, EPSC-DPS2025-164, Resolved Color of Main-Belt Asteroid (52246) Donaldjohanson as seen by NASA's Lucy Mission
    Abstract

    Introduction: On the 20th of April 2025, NASA's Lucy mission [1] flew by the C-type main-belt asteroid (52246) Donaldjohanson (hereafter DJ). The encounter's goal was to test the spacecraft and instruments during an observation sequence commensurate with those to be used on Lucy's main targets - Jupiter's Trojan asteroids. Data returned from the panchromatic Lucy LOng Range Reconnaissance Imager (L'LORRI, 450-850 nm, [2]) during this testing sequence reveal the asteroid to be bi-lobed and elongated shape (Fig. 1).DJ is a member of the Erigone collisional family, named after the parent body asteroid (163) Erigone (see references in [3]). Ground-based color observations (Fig. 2) show it to decrease in color towards shorter wavelengths, possibly due to the presence of hydrated materials [4].In this work, we present an analysis of color images taken by Lucy's Multispectral Visible Imaging Camera (MVIC). MVIC consists of six time delay integration (TDI) charge-coupled devices (CCDs). TDI works by synchronizing the transfer rate of the image between CCD rows and the relative motion of the instrument allowing a high signal to noise image to be built up even for fast scans. It covers wavelengths between 375 nm and 950 nm using five color filters and a panchromatic one (see Table 1).Color Analysis: We focus our analysis on images acquired with the four wide band filters: violet, green, orange and near-IR. Our results will provide resolved color variations and contextualise DJ's color with respect to ground-based observations of DJ, Erigone (Fig. 2), other members of the Erigone family, and the broader asteroid and small body populations.Filter Wavelength Violet 375-480 Green 480-520 Orange 520-625 Phyllosilicate 625-750 Near-IR 750-950 Panchromatic 350-950 Table 1 - MVIC filters [5]Figure 1 - (52246) Donaldjohanson as seen by the panchromatic Lucy L'LORRI instrument, taken on April 20, 2025 at 17:51 UTC. Figure 2 - Ground-based normalized (at 0.55 m) visible spectrum of DJ (blue) acquired with the Gran Telescopio Canarias compared to the Bus-DeMeo's Cg-type (black) and the mean spectrum of the C-type members within the Erigone family (grey). Taken from [6]. Acknowledgments: The Lucy mission is funded through the NASA Discovery program on contract No. NNM16AA08C.References: [1] Levison et al. (2021) PSJ 2, 171. [2] Weaver et al. (2023), SSR 219, 82. [3] Marchi et al., (2025) PSJ 6, 59. [4] Vilas (1995) Icarus 115, 217-218. [5] Reuter et al. (2023), SSR 219, 69. [6] Souza-Feliciano et al. (2020), Icarus 338, 113463.

33. Cartwright, R., Grundy, W., Holler, B., et al., 2025, epsc, 2025, EPSC-DPS2025-182, JWST Observes the CO2-rich Surfaces of Uranus' Large Moons
    Abstract

    Over the past 20+ years, ground-based observations have determined that the surfaces of the large Uranian moons Ariel, Umbriel, Titania, and Oberon are enriched in CO2 ice via the detection of a CO2 "triplet band" between 1.9 and 2.1 m [1,2]. The spectral properties of the detected CO2 is strikingly similar to crystalline CO2 ice measured in the laboratory. The origin of CO2 on these moons and across the Uranus system, however, remains uncertain. CO2 ice is unstable at the estimated peak surface temperatures of these moons (80-90 K), and it must be replenished [3]. It has been suggested that CO2 could be formed radiolytically via irradiation of H2O ice mixed with carbon-bearing compounds, possibly explaining the stronger CO2 features detected on the trailing hemispheres of these satellites [1,2]. Alternatively, the large moons of Uranus are candidate ocean worlds that may host subsurface saline oceans, possibly enriched in carbonate (CO32-) species and CO2. These carbon-bearing compounds could be outgassed or exposed through geologic processes [4]. Understanding the origin of CO2 and other carbon oxides in the Uranus system is one of the key science questions driving the rationale for future measurements made by a near-infrared (NIR) mapping spectrometer onboard a Uranus orbiter [5].More recent observations made with the NIRSpec spectrograph (G395M, 2.9 - 5.1 m, R ~ 1000) on the James Webb Space Telescope (program 1786, [4]) were able to identify the strong CO2 asymmetric stretch fundamental mode (3), roughly spanning 4.2 to 4.4 m, a wavelength range inaccessible from the ground due to telluric CO absorption. The CO2 3 mode is a factor of ~1000 stronger than the CO2 triplet band measured in prior ground-based observations, and therefore, we predicted that the Uranian moons would exhibit strong and possibly saturated CO2 ice absorption features across the 4.2 to 4.4 m wavelength range, similar to NIRSpec data of Neptune's moon Triton [6]. However, the 12CO2 ice bands detected by NIRSpec on the trailing hemispheres of these moons are surprisingly weak, and instead, are convolved with scattering peaks that obscure these absorption features (Figure 1). NIRSpec also revealed 12CO2 on the leading hemispheres of these moons and hyper-volatile CO ice on their trailing sides. Furthermore, 13CO2 is present, primarily on the inner moons Ariel and Umbriel, and CO3-bearing species, carbon chain oxides (CXO2), and CN-bearing organics (nitriles) may also be present on Ariel and Umbriel (Figure 1). Thus, the surfaces of the large Uranian moons are enriched in carbon oxides, especially Ariel [4].Figure 1: JWST/NIRSpec data (G395M) of the large Uranian moons, normalized to 1 at 4.14 m and offset vertically for clarity.At first glance, the detected species and their hemispherical distributions are broadly consistent with prior ground-based observations, supporting radiolytic production of CO2 and other carbon oxides via charged particles trapped in Uranus' magnetosphere. However, none of the data display notable hydrogen peroxide (H2O2) combination modes near 3.51 m, features that laboratory experiments have shown to emerge in irradiated H2O ice substrates (< 100 K), in particular when mixed with small amounts of CO2 [7], representing conditions relevant to the surfaces of Uranus' moons. Furthermore, icy satellites at Jupiter and Saturn tend to display darker and redder trailing hemispheres over UV/VIS wavelengths due to irradiation by corotating plasma, but observations made with Hubble's Space Telescope Imaging Spectrograph (~200 - 550 nm) indicate no such hemispherical asymmetry in albedo for the large moons of Uranus [8]. Because Uranus' magnetosphere is notably offset from the orbital plane of its satellites (~59) and seemingly devoid of heavy ions (i.e., Cn+, On+), it is possible that moon-magnetosphere interactions may be somewhat limited at Uranus. Instead, perhaps CO2 is primarily native to the large moons and exposed by geologic processes, such as cratering, tectonism, cryovolcanism, and outgassing.Other observations by JWST (program 4645) have revealed that CO2 is present across the Uranian system, including in its rings, ring moons, and irregular satellites [9,10]. The origin(s) of CO2 on these smaller bodies and rings is presumably varied, but almost certainly includes native sources of CO2, especially on the far-flung irregular satellites that orbit well beyond the influence of Uranus' magnetosphere and exhibit strong 4.27 m and 2.7 m features, consistent with native CO2. Similar to the large moons, CO2 ice is unstable on these small bodies and rings and must be replenished and trapped in more refractory compounds.To gain a more complete understanding of the origin and nature of these species will require a Uranus orbiter equipped with a NIR mapping spectrometer and a charged particle suite making measurements during close passes [11]. We will present NIRSpec results and analyses for carbon oxides on the large moons Ariel, Umbriel, Titania, and Oberon and provide an update on the developing picture of the origin of carbon oxides in the Uranus system in the JWST era.[1] Grundy, W. et al., 2006. Icarus 184.[2] Cartwright, R.J. et al., 2022. The Planetary Science Journal, 3, 8.[3] Sori, M.M. et al., 2017. Icarus, 290, pp.1-13.[4] Cartwright, R.J. et al., 2024. The Astrophysical Journal Letters, 970, L29.[5] National Academies of Sciences, Engineering, and Medicine 2023. Origins, Worlds, and Life:Planetary Science and Astrobiology in the Next Decade.[6] Wong, I. et al., 2023. AGU Fall Meeting Abstracts. P44B-08.[7] Mamo et al. PSJ, submitted.[8] Cartwright, R.J. et al., 2022. AAS/DPS Meeting 54, abstract 106.01.[9] Belyakov, M. et al., 2024. AAS/DPS Meeting 56, abstract 405.02.[10] Belyakov, M. et al., April 2025. Ice Giant Systems Seminar Series.[11] Cartwright, R.J. et al., 2021. The Planetary Science Journal, 2 (3), p.120.

34. Thirouin, A., Sheppard, S., Grundy, W., et al., 2025, epsc, 2025, EPSC-DPS2025-225, Moon(s) around Contact Binary Trans-Neptunian Objects.
    Abstract

    A close/contact binary can be a small body with a bi-lobed shape, two objects touching at one point, and two objects with a small separation of less than a few hundred kilometers. Contact binaries are common in our Solar System's small body populations, as they are found in the near-Earth object, comet, main belt asteroid, and trans-Neptunian object populations. Several models have been proposed to explain the formation of trans-Neptunian contact binaries, and we can cite for example: (1) a wide binary system can shrink its orbit and end up in a compact configuration due to dynamical effects, (2) binaries formed directly from gravitationally unstable clouds of much smaller particles through pebble accretion and if clumps are formed close enough they will end up as contact binaries, and (3) a physical collision between two objects can result in their accretion, within the sphere of influence of a third objectUnfortunately, none of these proposed models have been thoroughly tested with observations, as the contact binary trans-Neptunian population remained elusive until recently. Now that we have a sizeable sample of confirmed and likely contact binaries in the trans-Neptunian belt, we can test these models as they predict different outcomes regarding the presence of a widely separated moon orbiting the contact binary. If the first model based on dynamical effects is responsible for contact binary formation, no contact binary should have a moon if created from a two-body system. With three-body interactions, one has to expect many triple systems, whereas the gravitational collapse should give a mix of triple systems and contact binaries with no moon.Using archival and new Hubble Space Telescope observations, we will present some preliminary results regarding the fraction of contact binaries with/without a moon and their distribution in several trans-Neptunian sub-populations. This work is supported by HST-GO-17524 and the National Science Foundation grants #1734484 and #2109207.

35. Trujillo, C., Farrell, K., Chandler, C., et al., (including Despain, J.), 2025, epsc, 2025, EPSC-DPS2025-300, Archival Search for Active Asteroids in Subaru Hyper Suprime-Cam Public Data Release 3
    Abstract

    We are searching for new active asteroids using data from the Subaru Hyper Suprime-Cam (HSC) Public Data Release 3 (PDR3). The active asteroids are a poorly understood class of asteroids, which have orbits similar to other asteroids but exhibit tails or comae like comets. Of the over 1.4 million catalogued minor planets, most of which are main belt asteroids, fewer than 100 of the asteroids have exhibited activity, and roughly half of those are thought to be driven by water ice. The true fraction and solar system distribution of active asteroids is poorly known as most have been discovered serendipitously by a variety of methods. In this work, we search for activity among the known asteroids using one of the deepest wide-area public datasets available, the HSC PDR3. The goal of this work is to discover new active asteroid candidates and recurring activity in known active asteroids in archival data, collect contemporary images of those asteroids using ground based telescopes, and assess the true rate of active asteroid activity in a consistent manner using a large dataset. This will lead to insights into the present day distribution of water ice in our solar system.The HSC PDR3 has been collected using one of the largest ground-based optical telescopes, the 8.2 m Subaru telescope atop Maunakea in Hawaii which regularly achieves image quality better than 0.7 arcseconds yielding single-image depths of 25 to 25.5 magnitudes in the typical exposure times used for the PDR3. In addition, HSC itself has an extremely wide field of view, about 1.8 square degrees, for such a large telescope. Over 13,000 fields were imaged in good conditions with HSC as part of the PDR3, representing over 23,000 square degrees. The PDR3 dataset was collected for scientific purposes unrelated to the asteroids but many fields contain serendipitous images of asteroids. We have cross-correlated the PDR3 fields and the Minor Planet Database using the SkyBoT project and find that over 230,000 minor planets (over 15% of all minor planets and the vast majority asteroids) were serendipitously imaged in the dataset for a total of over 1.6 million minor planet images. We have begun the process of constructing thumbnail images of these minor planets from the full HSC PDR3 data release and expect to finish this year.Initially, we are examining images by eye ourselves to determine activity candidates. However, we will launch a Citizen Science campaign akin to activeasteroids.net, which has to date only used data from the DECam public archive. This will allow us to mobilize volunteers to examine more images than we can reliably categorize ourselves. We present first results from this work including an assessment of activity levels for thousands of asteroids most likely to exhibit activity including: previously known active asteroids, distant C-type main belt asteroids, and Centaurs on unstable orbits that could have recently moved inward from the trans-Neptunian region.Figure 1: One of 4 images from the HSC PDR3 archive of known active outer main belt asteroid 331P/Gibbs, exhibiting a faint linear tail.Figure 2: One of 17 images from the HSC PDR3 archive of known Jupiter family comet 242P/Spahr, exhibiting a tail. While not a primary target of this work, many comets are present in the HSC PDR3.

36. Emery, J., Simon, A., Kaplan, H., et al., (including Grundy, W.), 2025, epsc, 2025, EPSC-DPS2025-379, Compositional analysis of (52246) Donaldjohanson from the Lucy flyby
    Abstract

    The NASA Lucy mission was designed to provide the first reconnaissance of Jupiter Trojan asteroids. These primitive bodies hold important clues to the origin and evolution of the Solar System. The Lucy spacecraft is currently en route to its encounters with Trojan asteroids in the L4 swarm in 2027 and 2028, and the L5 swarm in 2033 [1]. On its way through the Main Belt, Lucy flew past the asteroid (52246) Donaldjohanson on April 20, 2025. The main purpose of the flyby was to support mission preparation for the primary science targets, the Trojan asteroids. The Linear Etalon Imaging Spectral Array (LEISA) mapping spectrometer [2,3], part of the L'Ralph instrument, collected multiple spectral datasets during the encounter with Donaldjohanson. LEISA covers the spectral range 0.97 - 3.95 m with a variable spectral resolving power ranging from ~50 to 160 (<10 nm).Several primitive asteroid families have been identified in the inner Main Belt. These families are of interest for their potential to deliver primitive material into near-Earth space, and potentially even sourcing the carbonaceous meteorites that fall to Earth. Donaldjohanson is a member of one of these families, the Erigone collisional family. The collisional disruption of the Erigone family occurred ~155 Myr ago [4]. Ground-based observations have revealed that the Erigone family consists of primitive C-complex asteroids, the majority of which show evidence for a 0.7-m absorption due to Fe-bearing phyllosilicates [5] and spectral slopes that are neutral to slightly red [6]. The only ground-based near-infrared data published of Donaldjohanson itself [7] are too noisy for a reliable interpretation. We will report on the Lucy near-infrared spectral observations of Donaldjohanson, with a focus on a search for absorption features due to materials seen in ground-based spectra of Erigone family members and found in analog carbonaceous meteorites, including hydrated silicates and organic molecules. The spatially resolved LEISA data also enable assessment of any potential spectral heterogeneity on Donaldjohanson. AcknowledgementsThe Lucy mission is funded through the NASA Discovery program on contract No. NNM16AA08C. References[1] Levison, H.F., et al. 2021. Lucy Mission to the Trojan Asteroids: Science Goals. Planet. Sci. J. 2:171 (13pp)[2] Reuter, D.C., et al. 2023. L'Ralph: A Visible/Infrared Spectral Imager for the Lucy Mission to the Trojans. Space Sci. Rev. 219:69.[3] Simon, A.A., et al. 2025. Lucy LRalph In-flight Calibration and Results at (152830) Dinkinesh. Planet. Sci. J. 6:7 (11pp).[4] Marchi, S., et al. 2025. A Pre-flyby View on the Origin of Asteroid Donaldjohanson, a Target of the NASA Lucy Mission. Planet. Sci. J. 6:59 (19pp).[5] Morate, D., et al. 2016. Compositional study of asteroids in the Erigone collisional family using visible spectroscopy at the 10.4m GTC. Astron. Astrophys. 585, A129.[6] Harvison, B., et al. 2024. PRIMASS near-infrared study of the Erigone collisional family. Icarus 412, 115973.[7] Sharkey, B.N.L., et al. 2019. Compositional Constraints for Lucy Mission Trojan Asteroids via Near-infrared Spectroscopy. Astron. J. 158:204 (13pp).

37. Brunetto, R., Pinilla-Alonso, N., Stansberry, J., et al., (including Grundy, W.), 2025, epsc, 2025, EPSC-DPS2025-383, The spectral diversity of outer icy bodies revealed by JWST and its link to early Solar System processes
    Abstract

    Introduction:Small bodies in the trans-Neptunian region are key to understanding Solar System formation and evolution. Trans-Neptunian objects (TNOs) are relics of planetary formation in the outer protoplanetary disk, but most of them were later affected by the giant planet instability and the dynamical evolution of the Solar System, with the remarkable exception of the so-called "Cold Classical" population.TNOs incorporated ices and other solids from the protosolar disk and thus provide precious information about early conditions in the disk. However, many TNOs also underwent evolutionary processes such as melting, differentiation, segregation, fragmentation, and irradiation that modified the original protoplanetary composition. In this work, we focus on mid-sized objects (diameter between about 50 and 1000 km), representing a generation of outer planetesimals that suffered limited differentiation and collisional evolution. Methods:We used the low spectral resolution PRISM grating on the Near-Infrared Spectrograph (NIRSpec, 0.7-5 m) of the James Webb Space Telescope (JWST) to observe 75 medium-sized TNOs observed in several programs: the year 1 Guaranteed Time Observations (GTO) Program "Kuiper Belt Science with JWST" (GTO-KBO, ID1191, ID1231, ID1272, and ID1273), the Cycle 1 Large Program ID2418 "Discovering the Surface Composition of trans-Neptunian objects" (DiSCo-TNOs), the Cycle 2 Program ID3991 "Small Cold Classical TNOs as Witnesses of Outer Nebular Chemistry", and the Cycle 3 Program ID4665 "Constraining the origin and dynamical evolution of extreme trans-Neptunian objects through NIR spectroscopy". The objects within the sample span the diversity of the TNO population (excluding the volatile-rich dwarf planets and the Haumea family) in terms of size, visible colors, geometric albedo, and dynamical properties.For a larger comparison, we also include 10 Centaurs observed in the DiSCo-TNOs and GTO Programs, and 8 Neptune Trojans observed within the Cycle 1 Program ID2550 "The First Near-IR Spectroscopic Survey of Neptune Trojans".Following a similar approach to the one that we successfully used to analyze the DiSCo-TNOs data [1,2], we analyzed the extended set of spectra with different clustering techniques (Principal Component Analysis, k-means, hierarchical clustering) to highlight the spectral diversity of the targets. We obtained information about the icy molecular composition by identifying several bands of interests and by calculating their band areas and positions. To date, this represents the largest near-IR spectral dataset of icy bodies, providing the most complete picture of the molecular composition of outer Solar System planetesimals. Results:While the new objects have very diverse sizes and orbital parameters, the vast majority of their spectra fall into the three main compositional categories identified by DiSCo: the so-called "Bowl" surfaces, which are dominated by water ice features and are also dust-rich and CH-poor; the "Cliff" and "Double-dip" surfaces, which are carbon-rich and water-poor, with Double-dip being particularly rich in CO2 and CO, and Cliff surfaces being rich in organics. We confirm the detection of several icy molecules, including H2O, CO2, 13CO2, CO, CH3OH, and complex molecules and refractory materials containing aliphatic C-H, CN, O-H, and N-H bonds. The band areas of the different molecules, sensitive to both abundance and path length in solid-state ices, vary significantly among different icy bodies and correlate with the identified spectral categories.In addition, thanks to the larger sample, at least three sub-categories of Bowl-TNOs and three sub-categories of Cliff-TNOs can be identified. The surfaces of the Cliff1 sub-group are ice-rich, with prominent CH3OH, H2O, and CO2 ice features that are much weaker in the ice-poor Cliff2 sub-group [3]. The Cliff1-CO2 sub-group includes transitional objects that resemble Cliff1 surfaces, but exhibit very strong CO2 features, similar to the CO2 spectral properties (position and area) of Double-Dip TNOs. Finally, two TNOs and two Neptune Trojans are unclassified, showing weak icy features that are close to those observed in "shallow"-type Centaurs [2], possibly due to previous episodes of ice sublimation. Except for the rare Cliff1-CO2 TNOs, very sharp transitions are observed between the different spectral groups.Cold Classical TNOs belong almost entirely to the Cliff2 sub-group, while the other dynamical classes of icy bodies (Scattering Disk Objects, Resonant Objects, Hot Classicals, Detached and Extreme Objects, Neptune Trojans, Centaurs) exhibit variable proportions of the different spectral categories, with no statistically significant association between dynamical classes and any specific spectral category. Discussion:Generally speaking, most TNO surfaces show significant deviations from the protoplanetary and cometary ice compositions, revealing that specific evolutionary processes shaped the molecular composition in the outer Solar System before or just after the planetesimals' formation. The fact that, except for the Cold Classicals, the different dynamical classes show variable amounts of the spectral categories suggests that late evolutionary processes, such as prolonged exposure to the space environment and irradiation, are not the main drivers in shaping the spectral groups. So far, the only clear irradiation trend observed is in non-Cold Classical Cliff1-TNOs, whose methanol bands decrease with increasing residence outside the heliosphere, where cosmic ion fluxes are higher. [3].An early sculpting is necessary to create the distinct separation of the spectral clusters. In particular, a sharp process, such as the one associated with ancient icelines, must be invoked to explain the significant variations observed in the surface molecular constituents. The currently favored scenarios include either the pre-accretional CO iceline on grains in the protoplanetary disk, and/or the post-accretional retention icelines of CO2 and CH3OH at the surface of planetesimals just before a major planetary migration. In both cases, planetesimals probably formed in this order of increasing distance from the Sun: Bowl<Double-Dip<Cliff1<Cliff2.Finally, we observe a significant and intriguing lack of CO2-rich objects for perihelion distances smaller than about 31 AU. We explore two different scenarios to explain this dichotomy, the first one due to physicochemical processes of CO2 loss, and the second one related to dynamical processes of preferential injection of Bowl-type TNOs from the inner Oort-Cloud to the Centaurs region. [1] Pinilla-Alonso N., et al., 2025, NatAs, 9, 230. doi:10.1038/s41550-024-02433-2[2] Licandro J., et al., 2025, NatAs, 9, 245. doi:10.1038/s41550-024-02417-2[3] Brunetto R., et al., 2025, ApJL, 982, L8. doi:10.3847/2041-8213/adb977

38. Hemmelgarn, S., Moskovitz, N., Vida, D., 2025, epsc, 2025, EPSC-DPS2025-442, A Machine Learning Application to Meteor Classification
    Abstract

    IntroductionClassifying meteoroids based on their physical properties is important for understanding their origins, how they evolve, and what parent bodies they may be linked to. Current classification methods typically rely on simplified physical models like single-body ablation theory or use only a small number of observable characteristics. A commonly used approach is the Kb parameter, which estimates a meteoroid's material strength based on how it penetrates the atmosphere. But using Kb requires several derived quantities and depends on assumptions about the meteoroid's structure and behavior. This limits how broadly and objectively the method can be applied, especially when dealing with the large datasets produced by modern automated meteor camera networks.More advanced fragmentation models can provide better insights, but they're computationally intensive and have only been applied to relatively small datasets, typically just a few dozen meteors at a time. As these networks continue to grow, we need more scalable and objective methods that rely only on what we can directly observe.Here, we're developing a machine learning approach to classify meteoroids based purely on observed characteristics. We use 13 features that can be consistently measured from low-light video cameras, such as energy received before ablation, atmospheric density, and trail length. These inputs are analyzed using dimensionality reduction and clustering to find natural groupings in the data. The goal is to create a reliable, scalable way to classify meteoroids that can keep up with the size and complexity of current and future meteor datasets.MethodsThis project uses data collected in 2023 from two low-light meteor camera networks: the Croatian Meteor Network (CMN) and the Lowell Observatory Cameras for All-sky Meteor Surveillance (LOCAMS). The CMN network features cameras with 16mm lenses, allowing for fainter meteor detections and better orbit fits. LOCAMS operates across the state of Arizona and records high-resolution trajectory data for hundreds of meteors per night. Both networks contribute their observations to the Global Meteor Network (GMN), which publishes publicly accessible datasets that include physically meaningful features.We focused on directly observable parameters to ensure that our analysis is interpretable, scalable, and transferable across datasets. These include trail length, energy received, deceleration, peak brightness height, atmospheric density at multiple trajectory points (beginning, peak, end), mass and velocity in logarithmic form.Before applying machine learning methods, the dataset was standardized using Python-based scikit-learn's StandardScaler to ensure equal weighting across all features. This step is necessary for algorithms that rely onTo reduce dimensionality and highlight key patterns in the data, we applied Principal Component Analysis (PCA) to the normalized feature set. PCA identifies the principal axes along which the data varies most and projects the dataset onto these axes. The first two principal components capture approximately 95% of the total variance.The PCA matrix indicates that the first principal component (PC-1) is driven primarily by energy received (0.773) and negatively by trail length (0.608), with smaller contributions from mass and atmospheric density. This axis appears to reflect a combination of total energy and material penetration behavior. The second principal component (PC-2) is shaped by atmospheric density at the beginning, peak, and end of the trajectory (all 0.446), along with trail length (0.350) and mass (0.249), suggesting a link to fragmentation behavior and how a meteoroid interacts with varying atmospheric conditions during entry.After dimensionality reduction, we applied a Median Absolute Deviation (MAD) filter to further identify and remove features that contribute minimal variability to the overall dataset. For each feature, MAD was calculated as the median of the absolute deviations from that feature's median value. Features with MAD values less than 50% of the median of all MAD values were excluded. This step refined the input to include only those features contributing the most physical diversity to the dataset, leaving eight features: energy received, deceleration, beginning, peak, and end atmospheric densities, trail length, peak magnitude, and mass in kg.To identify potential groupings within the meteor population, we applied the scikit-learn's K-Means clustering algorithm to the PCA-transformed dataset. The elbow method was used to determine the ideal number of clusters by plotting the within-cluster sum of squares against the number of clusters and identifying the point where additional clusters no longer significantly reduce variance. Based on this analysis, three clusters were identified.ResultsUnsupervised clustering applied to the PCA-transformed dataset revealed three groups of meteoroids, which we interpret as representing carbonaceous, asteroidal, and cometary materials. The first principal component is most strongly influenced by energy received and trail length, suggesting a relationship with material strength and penetration depth. The second component highlights variation in atmospheric density and mass, which likely reflects differences in deceleration and fragmentation behavior. These clusters appear well-separated in principal component space (Figure 1), indicating physically meaningful differences in meteoroid behavior.The carbonaceous-type cluster shows intermediate values across most features. The asteroidal cluster includes high-energy meteors with low deceleration and deep atmospheric penetration, traits consistent with dense, rocky material. A subset of events within this cluster may represent iron-rich meteoroids, given their unusually high energy and deep penetration. The cometary cluster contains low-mass meteors with high deceleration and higher entry altitudes, aligning with expectations for fragile, porous cometary sources. These interpretations are supported by differences in initial velocity and begin height (Figure 2), with cometary meteors tending to enter faster and at higher altitudes. Figure 3 separates the clusters into individual subplots, illustrating how the density distributions vary across each classification.Unlike traditional methods that rely on derived quantities and model assumptions, this classification is based entirely on directly observed features. Future work will focus on linking these clusters to known meteor showers to further compare to this model.Figure 1: PCA scores plotted as a scatter plot and color coded by physical interpretation on the left. The same scatter plot transformed into a contour plot using kernel density estimation (KDE) on the right.Figure 2: Initial velocity vs. beginning height color coded by their physical interpretation.Figure 3: Figure 2 transformed into individual contour plots using KDE and titled by physical interpretation.

39. Proudfoot, B., Grundy, W., Ragozzine, D., 2025, epsc, 2025, EPSC-DPS2025-728, Upcoming and ongoing mutual events of trans-Neptunian binaries
    Abstract

    The population of bodies beyond Neptunegenerally called trans-Neptunian Objects (TNOs)are critical to our understanding of the solar system. As leftover debris from planet formation, their orbital and physical characteristics inform our knowledge of the earliest moments of the solar system. Imprinted onto the orbital characteristics of the TNOs are signatures of planet migration and disturbances from stars in the Sun's birth cluster. Similarly, the physical characteristics of TNOs encode information about the composition of the protoplanetary disk, the conditions during planet formation, and the processes which enabled planetesimal formation. Unfortunately, physical characteristics of TNOs are difficult to probe given their extreme distances and small sizes. Thankfully, the abundant population of TNO binaries (TNBs) allow detailed physical characterization to be accomplished. One of the best times to characterize a TNB is during its mutual event season. Twice during each TNB's heliocentric orbit, its binary mutual orbit appears edge-on (as seen from Earth) allowing for a series of occultations/eclipses between the binary components. Observing these events allows for detailed characterization of each components' size, albedo, surface features, and even their surface thermal properties. Although this technique was used to great success for Pluto and Charon, limited success in observing and/or interpreting mutual events of TNBs has been had in the past two decades.In this presentation, we will describe our threefold approach to improving the prediction of TNB mutual events. First, using the Hubble Space Telescope, we have observed 4 TNBs with upcoming/ongoing mutual event seasons. Second, we use precise ephemerides from the "Beyond Point Masses" project, which includes non-Keplerian precession into TNB orbital models. Third, we aim to provide well-characterized event predictions in a Bayesian framework that accounts for all sources of uncertainty in event predictions. With this approach, we will present updated predictions for the ongoing/upcoming mutual events of several TNBs.

40. Lopez-Oquendo, A., Kaplan, H., Simon, A., et al., (including Grundy, W.), 2025, epsc, 2025, EPSC-DPS2025-744, Spectral Imaging Analysis of Asteroid (152830) Dinkinesh by the Lucy Mission
    Abstract

    On November 1, 2023, NASA's Lucy spacecraft successfully imaged the Main-Belt asteroid (152830) Dinkinesh and its moon, Selam. Dinkinesh is an S- or Sq-type asteroid with multiple geologic features (i.e., craters, central ridge, and trough) [1]. The Dinkinesh system is complex, with satellite that itself is a contact binary [1]. Broadband visible (0.35-0.95 m) and near-IR (0.97-3.95 m) hyperspectral images collected by the L'Ralph instrument showed absorption features near 1-, 2-, and 3-m [2, 3]. The vibrational absorption between 2.6 and 3.3 m in asteroid spectra has generally been interpreted as OH and H2O (i.e., hydration). This ~3.0 m band, has been a crucial tool of characterization to understand the degree of hydration on the surface of asteroids [4]. Detection of hydration or volatile-rich materials on S-type objects is surprising due to the expected high temperature at which these bodies formed in the main-belt and presence of anhydrous silicates. Ground-based facilities have provided crucial detections and insights about the 3.0 m band on S-type asteroids [5,6], yet much remains unknown about its origin. Dinkinesh's close approach by Lucy offers a fortuitous opportunity to better understand the hydration of these bodies and assess any spatial variation on the surface that might be related to geologic features. The Lucy L'Ralph Dinkinesh observations can help differentiate the source of hydration. For example, exogenous material (e.g., carbonaceous or cometary material) is expected to appear in discrete areas associated with specific surface features such as craters [7]. Alternatively, solar wind implantation on asteroids occurs when high H+ fluxes doses from the Sun interact with surface minerals, embedding hydrogen atoms and potentially leading to the formation of OH or H2O in the regolith [8]. We will report on the spectral analysis of Dinkinesh, with a focus on the shape model registration of hyperspectral images from the L'Ralph Multi-spectral Visible Imaging Camera (MVIC) and Linear Etalon Imaging Spectral Array (LEISA). We will present colors, spectral slopes, and band depth to look for possible spectral heterogeneities associated with geologic morphologies. Results: We registered the digital shape model of Dinkinesh to the L'Ralph instrument detectors. Figure 1 shows a preliminary example of the MVIC panchromatic filter frame during the close approach registered to the respective incidence angle backplane obtained using SpiceyPy [9]. Figure 2 shows an example of a LEISA-calibrated frame (e.g., I/F) registered to Dinkinesh's shape model. After registration, the 3 m absorption feature is analyzed for each facet by computing the absorption strength (e.g., band depth) and looking for correlations with surface morphologies provided by stereophotogrammetry of L'LORRI images. Similarly, we obtained MVIC color maps and overlayed them on the shape model. Our preliminary analysis suggests a 3 m detection across the entire imaged surface, showing variabilities in band depth. We will further explore such variability to find its possible relationship with surface morphologies, local color variations, and illumination geometry.Figure 1. MVIC panchromatic frame of Dinkinesh overlayed with the SpiceyPy incidence angle backplane.Figure 2. Left: Dinkinesh shape model with overlayed LEISA cross-track I/F frame 700 during close approach. [1] Levison, H.F. et al. 2024. A contact binary satellite of the asteroid (152830)Dinkinesh. Nature 629, 1015-1020.[2] Simon, A. et al. 2025. Lucy L'Ralph In-flight Calibration and Results at (152830) Dinkinesh. Planet. Sci. J. 6, 7.[3] Kaplan, H., et al. 2024. "Multi-spectral imaging observations of asteroid (152830) Dinkinesh by the Lucy Mission." Proceedings of the Lunar and Planetary Science Conference 2024,abstract #1474. Houston, TX: Lunar and Planetary Institute.[4] Rivkin, A. S. et al. 2018. Evidence for OH or H2O on thesurface of 433 Eros and 1036 Ganymed. Icarus 304, 74-82.[5] McGraw, L. E. et al. 2022. 3 m Spectroscopic Survey of Near-Earth Asteroids. Planet. Sci. J. 3, 243.[6] McAdam, M. et al. 2024. Detection of Hydration on Nominally Anhydrous S-complex Main Belt Asteroids. Planet. Sci. J. 5, 254.[7] De Sanctis, M. C. et al. 2015. Mineralogy of Marcia, the youngest large crater of Vesta: Character and distribution of pyroxenes and hydrated material. Icarus 248, 392-406.[8] Hibbits, C. A., et al., 2011. Thermal stability of water and hydroxyl on the surface of the Moon from temperature-programmed desorption measurements of lunar analog materials. Icarus, 213, 64-72.[9] Annex, A. M., et al., 2020. SpiceyPy: a Pythonic Wrapper for the SPICE Toolkit. Journal of Open Source Software, 46, 2050.

41. Porter, S., Singer, K., Verbiscer, A., et al., (including Grundy, W.), 2025, epsc, 2025, EPSC-DPS2025-791, Measuring the Shapes of Kuiper Belt Objects with New Horizons Photometry
    Abstract

    NASA's New Horizons spacecraft provided the first look at the full shape of a primordial Kuiper Belt Object (KBO) when it encountered the Cold Classical KBO (486958) Arrokoth on January 1, 2019. Arrokoth proved to be a contact binary, composed of two distinct lobes, with the larger lobe roughly twice the volume of the smaller. Examination of Arrokoth's surface showed no tectonic evidence that lobes came together violently, implying that the present shapes of the lobes may be representative of the shapes of KBOs that formed directly from the protoplanetary disk. In particular, the shapes of the lobes of Arrokoth appear to be consistent with rapid formation from the disk through gravitational collapse triggered by the Streaming Instability (SI). SI also reliably creates large numbers of separated binaries that could evolve into contact binaries. The shapes of KBOs are thus important constraints on not only their own history, but also on the planet formation process in the Solar System as a whole. Historically, the only practical way to estimate the shapes of small Solar System objects from Earth for objects beyond the reach of radar was through measuring photometry at various Sun-Target-Observer (STO) phase angles. However, this is difficult for KBOs, as their slow orbits (hundreds to thousands of years) and great distances (>35 AU) means that their apparent geometry as seen from Earth changes very slowly, even over many years of observation. Lightcurve studies of bright KBOs have been able to detect that some show evidence of being contact binaries. However, these studies are fundamentally limited by the bias of past surveys to detect KBOs with consistent brightness, which preferentially excludes KBOs that show high amplitude lightcurves. Since cold classical KBOs (like Arrokoth) are preferentially smaller and fainter than resonant KBOs, this bias is even stronger for Cold Classicals (CCs). A different method is thus required to properly understand how common or rare Arrokoth's shape is among KBOs with a similar history. Immediately after the Pluto flyby, New Horizons began observing distant KBOs with observations of (15810) Arawn at much higher STO angles than is possible from Earth. This was followed by high STO angle observations of >30 KBOs. Seven additional KBOs to the two identified separated binaries were observed by New Horizons at more than two STO angles, and with enough time coverage to determine their rotational periods. Here we use these unique observations in order to estimate the shapes of those KBOs, and therefore test how common Arrokoth-style contact binaries may be in the Kuiper Belt. Initial results indicate 4/7 (57%) KBOs are best fit with a contact binary shape, including 3/5 (60%) Cold Classicals. Including Arrokoth in these statistics brings the fraction to 5/8 (63%) overall and 4/6 (67%) of CC KBOs that appear to be contact binaries, when discounting the two tight separated binaries (2011 JX31 and 2014 OS393). Previous studies estimated that 10-25% of CC KBOs were contact binaries based on ground-based lightcurves (in comparison to ~40% for 3:2 KBOs), but those results may be influenced by the fact that CCKBOs are on average fainter than known 3:2 KBOs, leading to a detection bias for CCKBOs with flat lightcurves. While these are clearly small numbers to draw general conclusions from, it should also be clear that a very large fraction of CC KBOs are likely contact binaries. The upcoming Vera C. Rubin Observatory (Rubin) will be able to detect very large numbers of KBOs, and because of the nature of the survey, it will be substantially less biased towards KBOs with flat lightcurves, particularly after several years of observations. We thus predict that the long-term photometric statistics for CC KBOs from Rubin will be more similar to our results (~66% contact binaries) than past studies (~10-25% contact binaries). Rubin may therefore be able to both test SI as the formation method for the Kuiper Belt and place a constraint on the effectiveness of its creation of Arrokoth-like contact binaries.

42. Souza Feliciano, A., Holler, B., Grundy, W., et al., (including Emery, J.), 2025, epsc, 2025, EPSC-DPS2025-848, Constraining the surface composition of trans-Neptunian binaries with NIRCAM instrument
    Abstract

    Introduction. The trans-Neptunian objects (TNOs) are icy remnants of planetary formation that orbit the Sun beyond Neptune. The study of their physical and compositional properties can be used to constrain the evolutionary process that took place in the early stages of the solar system. In particular, the trans-Neptunian binaries (TNBs) are used in several dynamical studies to constrain these processes (e.g. Nesvorny et al., 2011). The characterization of the TNBs is therefore of particular interest in the field from both the dynamical and compositional perspectives. Before the James Webb Space Telescope (JWST) era, the knowledge of the compositions of small and medium-sized TNOs was incomplete. Now, we are aware of 4 main compositional groups in the trans-Neptunian region based on the spectral behavior of carbon dioxide, water ice, methanol ice, carbon monoxide, and tholins (e.g., de Pra et al., 2025; Pinilla-Alonso et al., 2025). Another finding from NIRSpec observations comes from the observation of Mors-Somnus, a TNB in the 3:2 mean motion resonance with Neptune (the plutino TNOs) with components of almost equal size (around 100 km) and a wide orbital separation, with a color similar to the cold classical TNOs (Shepard et al., 2012). The observations of Mors-Somnus from NIRSpec revealed not only the colors of Mors and Somnus are similar in the visible range, but the spectral features are similar in both up to 5 microns (Souza-Feliciano et al., 2024). This result strengthened the outcomes from dynamical simulations regarding the transportation mechanisms in the trans-Neptunian region (Hahn & Malhotra, 2005) and shed light on the origin of this pair and its connection with the cold classical and plutino TNOs (Nesvorny & Vokrouhlicky, 2019). Goals and sample selection. Aiming to constrain the surface composition of TNBs of similar and different sizes (tight, medium, and wide separation) and shed light on the formation mechanisms of TNBs, we selected a sample of 10 TNBs of cold, hot, resonant, detached, and scattered dynamical groups in the trans-Neptunian region. Due to the faintness and tight separation of some pairs, we chose to use three sets of NIRCam filters as part of program 6064 (PI: Souza-Feliciano). By resolving the components of each system in these multiple filters, we can study their surface compositions up to 4 microns and 1) determine the level of similarity between the components, 2) evaluate if they agree with the current formation scenarios proposed in the literature, and 3) identify which TNBs cannot be explained by current formation scenarios. Status and processing. Nine of the ten pairs in our sample have already been observed. Calibration was performed using the most up-to-date reference files provided by the Calibration References Data System (CRDS) and the latest version of the JWST calibration pipeline. This step is necessary to ensure the images are flat-fielded, bias-corrected, and flux-calibrated. After a background estimation, the flux of each source was extracted using a circular aperture and corrected by empirical encircled energy measured with data from the Cycle 1 Absolute Flux calibration program (Gordon et al., 2022). Preliminary results. Nine of the ten TNB systems in our sample were resolved by NIRCAM observations. The cold classical TNB pairs observed in our sample (2006 BR284 and Teharonhiawako) show hints of similar surface composition, and differences are noticed for some TNBs that belong to other dynamical groups. The implications of the compositional similarities and differences between TNB components in the context of formation mechanisms in the early outer solar system will be discussed. References De Pra, M.N., Henault, E., Pinilla-Alonso, N. et al. Widespread CO2 and CO ices in the trans Neptunian population revealed by JWST/DiSCo-TNOs. Nat Astron 9, 252-261 (2025). Gordon, K. D., Bohlin, R., Sloan, G. C. et al. The James Webb Space Telescope Absolute Flux Calibration. I. Program Design and Calibrator Stars. The Astronomical Journal, 163, 6 (2022). Hahn, J. M., & Malhotra, R. 2005, AJ, 130, 2392. Nesvorny, D., Vokrouhlicky, D., Bottke, W.F. et al. Observed Binary Fraction Sets Limits on the Extent of Collisional Grinding in the Kuiper Belt. The Astronomical Journal, Volume 141, 5 (2011). Nesvorny, D., & Vokrouhlicky, D. 2019, Icarus, 331, 49. Pinilla-Alonso, N., Brunetto, R., De Pra, M.N. et al. A JWST/DiSCo-TNOs portrait of the primordial Solar System through its trans-Neptunian objects. Nat Astron 9, 230-244 (2025). Sheppard, S. S., Ragozzine, D., & Trujillo, C. 2012, AJ, 143, 58. Souza-Feliciano , A. C., Holler, B. J., Pinilla-Alonso, N. et al. Spectroscopy of the binary TNO Mors-Somnus with the JWST and its relationship to the cold classical and plutino subpopulations observed in the DiSCo-TNO project. A&A 681 L17 (2024).

43. Grundy, W., Umurhan, O., Raposa, S., et al., (including Engle, A., Hanley, J.), 2025, epsc, 2025, EPSC-DPS2025-862, Role of Subsurface Volatiles in the Formation of Pluto's Pits
    Abstract

    We hypothesize that Pluto's volatiles (N2, CO, and CH4) could be involved in the formation of enigmatic pits seen in New Horizons images of eastern Tombaugh Regio. These pits exhibit a variety of morphologies, potentially pointing to more than one formation mechanism or to regional differences in subsurface composition or structure. Larger, well-separated pits reach up to ~15 km diameter. Smaller pits occur in chains and clusters. Interior profiles vary from conical to more rounded or flat-floored, and a few have raised rims. We will present several hypotheses for the formation of these features involving Pluto's volatiles. The first involves sublimation or melting loss of subsurface volatile ices, producing voids that lead to collapse and pit formation. The second involves heating of subsurface volatiles, leading to build up of pressure and eruptive excavation of material. The third also involves eruptions, but of volatiles expelled during cooling and freezing of a mixed volatile liquid. We will discuss the physics and thermodynamics of these scenarios and consider how they fit with morphological and compositional evidence from New Horizons data.Acknowledgment: This work was partly supported by NASA SSW grants 80NSSC19K0556 and 80NSSC25K7114.

44. Knight, M., Scheirich, P., Pravec, P., et al., (including Moskovitz, N.), 2025, epsc, 2025, EPSC-DPS2025-866, Ground-based observations of (65803) Didymos 2.5 years after the DART impact: searching for ongoing evolution
    Abstract

    On 2022 September 26, NASA's DART mission intentionally impacted Dimorphos, the moon of near-Earth asteroid (65803) Didymos, changing the binary system's orbital period. The system was studied intensively from the ground over the ensuing months until February 2023 when its brightness and low solar elongation precluded further observations. These observations revealed a clear period change of 33 minutes due to the DART impact (Thomas et al. 2023). However, there is uncertainty on whether there was a single impulsive change in the orbital period resulting in a constant post-impact value, or if there is (or was) an evolution in the period with time as the system settled into a new configuration. Careful analysis of the full post-DART lightcurve dataset (through February 2023) showed that there was insufficient data to distinguish between constant or changing post-impact orbital periods (Naidu et al. 2024, Scheirich et al. 2024). In order to understand the final outcome of the DART mission, it is therefore critical to monitor the evolution of the Didymos system prior to the European Space Agency's Hera mission arrival in late 2026. Observations from Hera will be too far removed from the time of impact to reveal whether or not the orbit period was changing over months as the asteroid system reached a new equilibrium. Our team obtained data during 2024 June to August on Magellan (6.5-m, PI: Thomas), SOAR (4.1-m, Program ID 2024A-120042), NTT (3.6-m, PI: Snodgrass), and Faulkes Telescope South (2-m, PI: Lister), but poor weather at all sites plus Didymos's positioning in front of the galactic plane throughout the visibility window prevented our analyses from attaining the needed sensitivity. The next visibility window occurred from late January through early March 2025, and our team was awarded time on Faulkes Telescope North (FTN, 2-m, PI: Lister), Lowell Discovery Telescope (LDT, 4.3-m, PI: Moskovitz), Palomar (5.1-m, PI: Chesley), Gemini-N (8.1-m, Program ID GN-2025A-Q-142), and Gran Telescopio Canarias (GTC, 10.4-m, PI: de Leon). Here we report on Gemini-N observations obtained on 2025 February 24, 26, and 28 when Didymos was at an apparent V magnitude about 20.3. The GTC observing run was weathered out. Observations acquired with FTN, LDT, and Palomar were successfully acquired, but are still being analyzed. Our Gemini observations were timed to optimize coverage of the Didymos binary orbit within the run and to provide complementary observations with neighboring runs scheduled on Palomar and GTC. We observed Didymos for 3.7 hr at the start of each night using the SDSS-i filter. We tracked at the sidereal rate and limited individual exposure times to 20 sec to keep the asteroid's trailing from significantly exceeding the stellar point spread function. Images were processed using the Gemini DRAGONS pipeline (Labrie et al. 2023) and photometry was measured using Photometry Pipeline (Mommert 2017). After manually removing frames that were contaminated by nearby stars or other image artifacts, lightcurve deconvolution was performed using the binary asteroid lightcurve decomposition method as earlier Didymos datasets (Pravec et al. 2022, 2024). Our preliminary analysis finds that mutual events occurred about 70 min earlier than the nominal prediction (see Figure 1), a difference of 1.6-sigma. This yields a binary orbital period of 11.3667 +/- 0.0002 hr (3-sigma), assuming that the period has been constant since 2022/2023. With the much longer time baseline, these observations reduce the uncertainty in the binary period by about a factor of 6 compared to the previously published 3-sigma measurement of 11.3675 +/- 0.0012 hr (Scheirich et al. 2024). As expected, the data quality was insufficient to constrain Dimorphos' rotation (which needed rms residuals of 0.004-0.007 mag, while residuals of 0.017 mag were obtained). Deep stacking of all images collected on a night did not reveal evidence of a tail or any remaining large fragments, though we have not yet quantified these non-detections. We will provide updated results on the full 2025 dataset. If ongoing analyses of the FTN, LDT, and/or Palomar datasets yield sufficiently small rms residuals, the lightcurve deconvolution will be re-run on the larger dataset, though the solution is not expected to change appreciably. The question of whether or not the orbital period has changed or if the apparently shorter period is just a statistical fluke is unlikely to be resolved from these data since they were all acquired relatively close to the Gemini observations. We plan to propose for similar observations during Didymos's next apparition in 2026 July to attempt to resolve this question.Acknowledgements: The work at Ondrejov has been supported by the "Praemium Academiae" award by the Academy of Sciences of the Czech Republic, grant AP2401.References Labrie et al., RNAAS 7, id.214 (2023) Mommert, M. Astronomy & Computing 18, 47 (2017) Naidu et al., PSJ 5, 74 (2024) Pravec et al., PSJ 3, 175 (2022) Pravec et al., Icarus 418, id.116138 (2024) Scheirich et al., PSJ 5, 17 (2024) Thomas et al., Nature 616, 448 (2023) Figure 1: Decomposition of Didymos system lightcurve from 2025 February 24-28 (a) into signals from mutual events (b), and primary rotation (c). The top panel (a) shows the combined lightcurve over 11.37 hr. The full lightcurve can be decomposed into a contribution from the 2.260-hr rotation of Didymos (bottom panel c) and a contribution due to mutual events. The mutual events are indicated by horizontal lines underneath the lightcurve in panel (b). The blue lines are the observed mutual events (PE = primary eclipse, PO = primary occultation, SE = secondary eclipse, SO = secondary occultation), while the red lines are the nominal predictions of these same events from Scheirich et al. (2024), which occurred ~70 minutes later than observed.

45. Protopapa, S., Wong, I., Johnson, P., et al., (including Grundy, W.), 2025, epsc, 2025, EPSC-DPS2025-968, JWST/NIRSpec Observations of Makemake: Hydrocarbon Chemistry and Surface Processes on a Methane-Rich Trans-Neptunian Object
    Abstract

    Makemake is one of the brightest and most methane-rich bodies in the trans-Neptunian region, with a spherical-equivalent diameter of ~1430km and a high geometric albedo of pV ~0.8 [1,2]. Its near-infrared spectrum is dominated by strong methane (CH) ice absorption bands that appear broad and saturatedmarkedly different from those observed on other volatile-rich trans-Neptunian objects (TNOs) [3, and references therein]. Stellar occultation measurements revealed the absence of a global Pluto-like atmosphere, with a 1 upper limit of 4-12 nanobar [1]. This result was interpreted as evidence for a strong depletion of nitrogen (N) ice, whose vapor pressure exceeds the microbar level even at Makemake's coldest surface temperatures. Makemake's volatile-rich surface and lack of a global atmosphere make it a compelling target for probing how surface volatilesand CH4 in particularevolve under irradiation and thermal cycling in the absence of atmospheric shielding.Observations obtained with the JWST Near-Infrared Spectrograph (NIRSpec) provide unprecedented spectral coverage of Makemake from 1.0 to 4.8m. A previous analysis of the NIRSpec spectrum in the 3.9-4.8m range confirmed the presence of solid CH4 and placed tight upper limits on molecular N2 and carbon monoxide (CO) [4]. The same dataset also enabled the first measurement of the deuterium-to-hydrogen (D/H) ratio in CH4 ice on a TNO. The origin of methane on Makemake remains debated, with proposed scenarios ranging from primordial incorporation in the protosolar nebula [5] to production by internal geochemical processes and transport to the surface via cryovolcanism or other endogenic processes [6].We present a comprehensive analysis of the full NIRSpec dataset, including the identification and modeling of CH4 absorption bands across the entire wavelength range, improved precision on the D/H ratio, and characterization of hydrocarbon irradiation products. In particular, we focus on tracing the chemical progression from CH4 to more complex hydrocarbons, such as ethane, ethylene, and acetylene, which are predicted by laboratory irradiation experiments and supported by previous near-infrared detections on Makemake [7,8].In addition to compositional studies, we place our results in the broader thermal context of Makemake's surface by referencing complementary JWST/MIRI measurements, which show a prominent mid-infrared excess in the 18-25m wavelength range, corresponding to brightness temperatures near 150K [9]. This temperature significantly exceeds those expected from solar insolation alone. Possible interpretations include the presence of a localized thermally active surface region or an undetected dust ring composed of fine carbonaceous particles [9]. While no direct evidence for active outgassing has been observed, such phenomena remain plausible and underscore the need for continued monitoring.The goal of this work is to better understand how volatile-rich TNOs evolve chemically and thermally under the combined effects of solar radiation, cosmic ray irradiation, and internal activity. By extending previous spectral coverage and conducting detailed modeling of hydrocarbon features, we provide new constraints on the irradiation chemistry, isotopic composition, and potential endogenic processes shaping Makemake's surface. Our results contribute to a growing understanding of the diversity of TNO surfaces and the role of internal and external drivers in sculpting their volatile inventories.[1] Ortiz, J. L., Sicardy, B., Braga-Ribas, F., et al. 2012, Nature, 491, 566[2] Brown, M. E. 2013, ApJL, 767, L7[3] Brown, M. E. 2012, Annual Review of Earth and Planetary Sciences, 40, 467-494[4] Grundy, W. M., Wong, I., Glein, C. R., et al. 2024, Icarus, 411, 115923[5] Mousis, O., Werlen, A., Benest Couzinou, T., & Schneeberger, A. 2025, ApJL, 983, L12[6] Glein, C. R., Grundy, W. M., Lunine, J. I., et al. 2024, Icarus, 412, 115999[7] Brown, M. E., Barkume, K. M., Blake, G. A., et al. 2007, AJ, 133, 284[8] Brown, M. E., Schaller, E. L., & Blake, G. A. 2015, AJ, 149, 105[9] Kiss, C., Muller, T. G., Farkas-Takacs, A., et al. 2024, ApJL, 976, L9

46. Cantelas, R., Trilling, D., Chatelain, J., et al., (including Moskovitz, N.), 2025, epsc, 2025, EPSC-DPS2025-997, A Pilot Rapid-Response Project to Characterize Small Near Earth Objectswith LCO's MuSCAT Instruments.
    Abstract

    1. SummaryClose to 80% of meteorites are ordinary chondrites, commonly associated with S-type asteroids [1]. However, among Near-Earth Objects (NEOs), silicate-rich S-types are no more abundant than abundant as primitive (C-, D-, and X-) types [2]. The most likely parent bodies for meteorites are small NEOs, the composition of which are not well understood. The taxonomic make-up of small NEOs is further complicated by recent meteorite recoveries corresponding to rare taxonomic types, such as the Almahata Sitta ureilite [3] and an aubrite meteorite that was formerly 2024 BX1 [4]. Here we present the results of a pilot-project in preperation for a longer program to determine the rough taxonomies of at least 1000 very small (absolute magnitude >25, or diameters <30 meters) NEOs over a three year period using the MuSCAT3/4 simultaneous four-channel imagers on the Las Cumbres Observatory (LCO) 2-meter telescopes. 2. Observations and Data ReductionThe smallest NEOs are best observed during their closest approach to Earth shortly after discovery and are typically only visible for a few weeks. MuSCAT3/4's ability to perform simultaneous g, r, i, and zs observations make it possible to observe our targets accurately and efficiently, and LCOs queue-scheduled robotic observing system means targets can be observed within minutes of their submission and well within their window of visibility. We observed 10 NEOs between Nov 9 2024 and Feb 22 2025 using MuSCAT3 installed on the 2-meter Faulkes North Telescope in Haleakala. Each target was observed for 7 minutes, with seven tracked 60-second exposures in each filter sandwiched between two 10-second exposures that were used for photometric calibration. Targets were selected from newly discovered asteroids, and chosen based on several constraints. The object must have been discovered in the 5-weeks prior to observation and have an official designation. This group was further filtered to objects with an apparent magnitude (V) < 21, the limiting magnitude required to achieve an SNR of 10 within a 7-minute exposure, and an absolute magnitude (H) > 25. The rate of the object was also taken into consideration and limited to 1000 "/hour to avoid trailing in calibration frames. These targets were then submitted to the LCO observing queue. Data from successful observations were reduced and calibrated using LCO's in-house BANZAI reduction software [5]. Photometry was carried out with a simple procedure that utilizes the Python Photutils package. As part of the goals for this pilot project, we developed a pipeline to automate observations and analysis. Each step from selecting targets from the Minor Planet Center database, submitting targets to the LCO queue, acquiring reduced, calibrated data and photometry was carried out using this pipeline. Future work will incorporate a machine learning-based tool to assign objects to a probabilistic taxonomic classification. 3. ResultsPreliminary results, shown in Figure 1, indicate that 6 out of the 10 sampled objects exhibit colors consistent with S- and C-type classifications, evenly divided between the two. Unexpectedly, 4 objects resembled taxonomic types that are not commonly found amongst NEOs; the most surprising of these were the colors of 2025 AF and 2024 VC. 2025 AF (H = 25.10, D 28 m) shows a best match to O-type asterods. O-types are exceptionally rare, with only seven confirmed to date [6] primarily among NEOs with the notable exceptions of main-belt asteroid 3628 Boznemcova and potentially 7472 Kumakiri [7]. 2024 VC (H = 27.41, D 9.8 m) on the other hand did not match exactly to any known taxonomies, but fit best to A or R type asteroids. Both A- and R- types are also notably rare with 17 known A-types (mostly Inner Main Belt asteroids and Mars-crossers) and 5 R-types (4 main-belt and 1 Amor NEO) [6]. Spectrophotometric measurements such as those presented here are far more efficient than spectroscopy, but have much lower fidelity. Therefore, these colors are suggestive, but not conclusive. The relatively high fraction of uncommon taxonomic classes observed in our target sample may suggest greater diversity within the small NEO population; however, additional observations are required to substantiate this. Generally, these findings demonstrate that the MuSCAT3 and 4 instruments, along with our analysis tools, are sufficient to derive coarse taxonomies for small NEOs. Our full survey will begin on May 1, 2025. We will observe 1000 NEOs with the MuSCAT cameras through the end of 2027B. We will measure the implied compositional distribution of verysmall NEOs. Figure 1: Color-color diagram showing the colors of 10 pilot project NEOs presented here, grouped bytaxonomic class. 4. AcknowledgmentsThis work makes use of observations from the Las Cumbres Observatory global telescope network. This paper is based on observations made with the MuSCAT3 instrument, developed by Astrobiology Center and under financial supports by JSPS KAKENHI (JP18H05439) and JST PRESTO (JPMJPR1775), at Faulkes Telescope North on Maui, HI, operated by the Las CumbresObservatory. This project is supported by the Arizona Board of Regents Technology and Research Initiative Fund and by NASA YORPD award 80NSSC25K7438. References[1] Nakamura, T., Noguchi, T., Tanaka, M., et al. 2011, Itokawa Dust Particles: A Direct Link Between S-Type Asteroids and Ordinary Chondrites, Science, 333, 1113[2] Mommert, M., Trilling, D. E., Borth, D., et al. 2016, First Results from the Rapid-response Spectrophotometric Characterization of Near-Earth Objects using UKIRT, AJ, 151, 98[3] Jenniskens, P., Shaddad, M. H., Numan, D., et al. 2009, The impact and recovery of asteroid 2008 TC3, Nature, 458, 485[4] Cantillo, D. C., Ridenhour, K. I., Battle, A., et al. 2024, Laboratory Spectral Characterization of Ribbeck Aubrite: Meteorite Sample of Earth-impacting Near-Earth Asteroid 2024 BX1, , 5, 138[5] McCully, C., Turner, M., Volgenau, N., et al. 2018, LCOGT/banzai: Initial Release, 0.9.4, Zenodo[6] Bus, S. J., Binzel, R. P., & . 2002, Phase II of the Small Main-Belt Asteroid Spectroscopic Survey. A Feature-Based Taxonomy, Icarus, 158, 146[7] Burbine, T. H., Duffard, R., Buchanan, P. C., Cloutis, E. A., & Binzel, R. P. 2011, in 42nd Annual Lunar and Planetary Science Conference, Lunar and Planetary Science Conference, 2483

47. Thomas, C., McGraw, L., DeMeo, F., et al., (including Burt, B.), 2025, epsc, 2025, EPSC-DPS2025-1016, The MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS): Current Status
    Abstract

    Near-Earth objects (NEOs) represent an ongoing flux of small bodies from elsewhere in the Solar System to near-Earth space. The study of these objects teaches us about the original environment of the Solar System during formation, and the conditions as physical and chemical changes occur throughout Solar System history. The MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS) began in 2004 and has obtained ~1,350 spectral observations of over 1,000 objects. The current phase of the project has three key goals: (1) to improve our understanding of the compositional distribution of NEO spectra with respect to asteroid size via additional IRTF SpeX prism spectra, (2) to examine the distribution of volatiles in the NEO population through an analysis of SpeX LXD 3-micron spectra, and (3) to transition the program from MIT and update our infrastructure. We continue a regular cadence of SpeX prism (0.7 - 2.5 microns) observations with a key goal of increasing the sample of small NEOs in our data set. We assign the highest priority to targets with estimated diameters less than 600 meters (H~18.8). Other observational priorities include new discoveries, Potentially Hazardous Asteroids (PHAs), Virtual Impactors (VIs), and low-V objects (< 7 km/s), and asteroids at their most favorable observing geometries. Our efforts to increase the population of small objects observed has been successful (see our progress in Figure 1 ). Recent research highlights include pre- and post-close approach observations of S-type 2024 MK (McGraw et al. 2024). These spectra showed no evidence of surface refresh at a close approach of 0.76 lunar distance. Ongoing work includes studies of the compositional distribution with respect to size in our sample and an investigation of C-type objects with low MOID (Minimum Orbit Intersection Distance) values as a followup to Binzel et al. (2010).Observations with SpeX LXD (1.7 - 4.2 microns) are limited to objects with V < 14.0 for our program. We define this limit based on signal-to-noise considerations. Our LXD program consists of two components: (1) a traditional observing program with known targets and (2) a target of opportunity program to observe newly discovered targets. We have successfully obtained LXD spectra of 15 unique targets since the start of this program element in the 2022B semester.Our presentation will discuss the current status of MITHNEOS including our progress in the new 3-micron effort and our ongoing prism studies.

48. Singer, K., Stern, A., Verbiscer, A., et al., (including Grundy, W.), 2025, epsc, 2025, EPSC-DPS2025-1053, Update on NASA's New Horizons Mission: Kuiper Belt Science Results and Future Plans
    Abstract

    NASA's New Horizons spacecraft continues to explore the Kuiper belt after its historic close flybys of the Pluto system in 2015 at ~33 astronomical units (AU) [1] and the cold classical Kuiper belt object (KBO) Arrokoth in 2019 at ~43 AU [2]. New Horizons is located at ~61.7 AU as of this writing in May 2025, and travels about 3 AU per year. New Horizons has sufficient power, propellant, and communications capability to continue operations until the mid-to-late 2040s and, thus, should be able to collect data out to distances of ~120 AU or greater. In its extended mission, New Horizons' main planetary science focus is studying Kuiper belt dwarf planets and small KBOs, and their environment. We will provide an overview of results for the dwarf planets and smaller KBOs observed by New Horizons from a distance ([3-6]; also see Porter et al., 2025 abstract at this conference). New Horizons can observe KBOs from much higher phase angles than possible from Earth, and some of the observed KBOs come as close as 0.1 AU to the spacecraft. This allows for the study of shapes, poles, surface properties, and searches for close satellites in some cases. New Horizons also made high-phase, color observations of the ice giants Uranus and Neptune [7] in coordination with the Hubble Space Telescope and as an exoplanet observation analogue. Further, the New Horizons Student Dust Counter continues to observe elevated dust fluxes at larger distances than expected, and the team is exploring possible explanations for why the dust flux has not yet started to decrease as predicted by previous models [8, 9]. We will also highlight some new products and findings related to Arrokoth, including a new shape model [10], images draped onto the shape model, and a study placing Arrokoth's crater size-frequency distribution into the context of those on other small bodies [11]. Looking towards the future of New Horizons: We will provide a status update on the ground-based, Subaru Telescope search [12-14] for a future close flyby target and other KBOs that New Horizons could observe as point sources. We will also discuss how future work would enhance the chances of finding a future flyby target for New Horizons, including the additional use of machine learning/artificial intelligence, supercomputing, and potential observations from the Vera Rubin Observatory (also see Kavelaars et al. 2025 abstract in this conference) or the Roman Space Telescope.References:[1] Stern S. A. et al., 2015, The Pluto system: Initial results from its exploration by New Horizons, Science 350, id.aad1815. doi:10.1126/science.aad1815[2] Stern S. A. et al., 2019, Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object, Science 364. doi:10.1126/science.aaw9771[3] Verbiscer A. J. et al., 2024, The New Horizons Photometric Phase Angle Survey of Deep Outer Solar System Objects: From the Kuiper Belt to the Scattered Disk, 55th Lunar and Planetary Science Conference. 3040, 2531.[4] Verbiscer A. J. et al., 2022, The Diverse Shapes of Dwarf Planet and Large KBO Phase Curves Observed from New Horizons, The Planetary Science Journal 3, 95. doi:10.3847/PSJ/ac63a6[5] Verbiscer A. J. et al., 2019, Phase Curves from the Kuiper Belt: Photometric Properties of Distant Kuiper Belt Objects Observed by New Horizons, Astron. J. 158. doi:10.3847/1538-3881/ab3211[6] Porter S. B. et al., 2016, The First High-phase Observations of a KBO: New Horizons Imaging of (15810) 1994 JR1 from the Kuiper Belt, ApJ Letters 828. doi:10.3847/2041-8205/828/2/L15[7] Hasler S. N. et al., 2024, Observations of Uranus at High Phase Angle as Seen by New Horizons, The Planetary Science Journal 5, 267. doi:10.3847/PSJ/ad8cdb[8] Corbett T. et al., 2025, Production, Transport, and Destruction of Dust in the Kuiper Belt: The Effects of Refractory and Volatile Grain Compositions, Astrophys J. 979, L50. doi:10.3847/2041-8213/adab75[9] Doner A. et al., 2024, New Horizons Venetia Burney Student Dust Counter Observes Higher than Expected Fluxes Approaching 60 AU, pp. arXiv:2401.01230.[10] Porter S. B. et al., 2024, The Shape and Formation of Arrokoth, 55th Lunar and Planetary Science Conference. 3040, 2332.[11] Knudsen I. E. et al., 2024, An Analysis of Impact Craters on Small Bodies Throughout the Solar System, The Trans-neptunian Solar System.[12] Yoshida F. et al., 2024, A deep analysis for New Horizons' KBO search images, Publications of the Astronomical Society of Japan 76, 720-732. doi:10.1093/pasj/psae043[13] Fraser W. C. et al., 2024, Candidate Distant Trans-Neptunian Objects Detected by the New Horizons Subaru TNO Survey, The Planetary Science Journal 5, 227. doi:10.3847/PSJ/ad6f9e[14] Buie M. W. et al., 2024, The New Horizons Extended Mission Target: Arrokoth Search and Discovery, The Planetary Science Journal 5, 196. doi:10.3847/PSJ/ad676d

49. Kareta, T., Noonan, J., 2025, epsc, 2025, EPSC-DPS2025-1059, The Orbit and Size of the Active Jupiter Co-Orbital P/2023 V6 (PANSTARRS)
    Abstract

    P/2023 V6 (PANSTARRS) is the second-known active Jupiter co-orbital comet after the well-studied P/2019 LD2 (ATLAS). These two objects, along with other populations like the Gateway Centaurs and those comets temporarily captured by Jupiter, are some of the best analogues for the objects which impact Jupiter and thus their physical properties are of interdisciplinary relevance. Starting in 2023, we began a campaign of telescopic characterization of V6 that culminated in observations with the Hubble Space Telescope in December 2024. While V6 was always dimmer than LD2, even at its slightly warmer perihelion, initial characterization efforts reported in Kareta et al. (2024) suggested that this was most likely due to V6 being physically larger but with a significantly lower active fraction - in essence, it was more 'evolved' than LD2. The comet appeared to be experiencing stable (e.g., not outburst driven) activity around peak brightness much like LD2 has been four years prior.In this talk, we will present our analyses of later ground-based and HST observations which show that the opposite might be true; V6 is very small and was just as active as LD2 was at a similar distance, if not moreso. The HST images are consistent with an object with a diameter of just about a few hundred meters assuming a typical cometary albedo and phase curve, almost certainly the smallest cometary nucleus detected at such a distance. A precipitous decline in brightness and mass loss rates in V6 just months after its perihelion passage, however, is quite unlike its more active cousin and cannot be explained by the object crossing any major ice lines or as an observational bias. We could not detect V6 with any confidence in two nights of ground-based imaging late in 2024 and early 2025, and the HST images don't appear to show any dust around the point-source-like object at all. This indicates that the objects do still have significant differences in the physical states of their nuclei and in the talk we will present several hypotheses that might be tested through studies of other near-Jupiter comets in the Rubin era. We will also comment on how advances in understanding the properties of these comets might help interpret the cratering record of the Galilean satellites and thus in assessing how often material from impactors gets through the ice to the oceans beneath.

50. Lierle, P., Schmidt, C., Morgenthaler, J., et al., (including Zhang, Q.), 2025, epsc, 2025, EPSC-DPS2025-1065, Sodium in Cometary Comae at Various Distances from the Sun
    Abstract

    Comets are among the most primitive bodies in the Solar System, preserving primordial materials from the early formation of the Solar System. Among various species observed in cometary comae, sodium is relatively lesser understood due to the high environmental temperature required for its sublimation, which restricts the observable samples to near-Sun comets. Here we present an analysis of five comets using a combination of narrowband imaging and high-resolution spectroscopy. Coronagraph ImagingIn early July 2020, comet C/2020 F3 (NEOWISE) approached the Sun for the first time in nearly 4,500 years. Comet NEOWISE was observed by the Planetary Science Institute's Io Input/Output Facility (IoIO; Morgenthaler et al., 2019) 35-cm coronagraph from July 7-16. Narrowband filters were used to isolate the dust and sodium gas emissions in the comae, and this apparition at only 0.33 AU from the Sun allowed some of the best quality images of a cometary sodium tail taken to date, as seen in Figure 1. For inner solar system comets, sodium is often the brightest emission line available to ground-based telescopes thanks to its efficient resonant scattering of sunlight near the maximum of the solar irradiance spectrum. Strong radiation pressure from resonant scattering shapes sodium gas into a vast anti-sunward tail.Figure 1: Narrowband filtered images of continuum dust reflectance and sodium D line emission in C/2020 F3 (NEOWISE). At 86 phase angle, the sodium tail here appears nearly orthogonal to the line of sight.Structure in cometary sodium emissions is shaped by the collisional entrainment in the bulk outflow from the nucleus, additional dusty sources, the temperature of the atoms, absorption of intervening sunlight in the dense coma regions, and radiation pressure. At a certain radius from the nucleus, Na atoms collisionally decouple from the bulk outflow velocity with a thermal distribution. While it is challenging to uniquely parameterize the collisional radius, outflow velocity, and gas temperature, additional insight can be gained from emission line profiles at ample spectral resolutions of R >100,000 thanks to Doppler broadening. Resolved Linewidth MeasurementsDuring the IoIO imaging campaign, C/2020 F3 (NEOWISE) was also observed with the Lowell Discovery Telescope's Extreme Precision Spectrometer (EXPRES; Jurgenson et al., 2016), at a resolving power of R = 150,000. At a phase angle of 108 and heliocentric distance of 0.46 AU, forward modeling of the line profiles that accounts for hyperfine structure retrieves effective temperatures ranging 1750 to 1950 K. The RMS velocity of this Doppler broadening is equivalent to 1.13 to 1.19 km/s, which suggests that collisional coupling to the bulk water outflow velocity is the dominant component in the emission line shape.Figure 2: Outflow velocity at five comets with varying heliocentric distances as derived from resolved Na D emissions. Comets near 90 phase angle roughly follow the r-0.5 relationship outlined by Budzien et al. (1994). C/2023 A3 was measured at both ~0.4 and 0.85 AU and shows variation consistent with this trend. Comets with phase angle >20 from quadrature are shown as outlines.The water outflow velocity in comets is well known to vary with heliocentric distance. The often-cited relationship of vH2O = 0.85r-0.5 applied by Budzien et al. (1994) is a compromise between hydrodynamical models, which suggest 0.7r-0.5 (Gombosi et al., 1986), and radio observations of OH and HCN at 1P/Halley, which suggest 1.1r-0.5 (Combi, 1989). By comparing Na linewidths in a survey of comets at varying heliocentric distance, we find that the thermal velocity derived from Na linewidths produces a similar relationship. Figure 2 shows linewidth-derived outflow velocity for five comets at a range of heliocentric distances. All spectra were obtained with EXPRES, with the exception of the C/2023 A3 data point at 0.85 AU, which was obtained using the Large Binocular Telescope's Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI; Strassmeier et al., 2015). Na D2 speeds appear systematically higher, implying that the line core may exceed unity optical depth. Comets 96P, 2P, and C/2023 A3 were observed at phase angles >20 from quadrature, which caused distortion of the line shape due to projection effects along the tail, resulting in outflow speeds higher than the overall trend. Monte-Carlo ModelingFigure 3: Preliminary results of Monte-Carlo modeling sodium gas in the coma of C/2020 F3 (NEOWISE), assuming here a collisional radius of 10,000 km, bulk outflow speed of 1.5 km/s and gas temperature of 150 K.Phase angle distortion of the emission line profiles can be accounted for with Monte-Carlo modeling, and with nearly concurrent imaging and spectroscopy in the case of C/2020 F3 (NEOWISE), this approach has good potential to uniquely quantify the parameters that control sodium dynamics in its coma. We adapt the Monte-Carlo model of C/2012 S1 (ISON) by Schmidt et al. (2015), and this presentation will describe attempts to self-consistently simulate both spatial structure in the tail and Doppler broadening near the optocenter, using C/2020 F3 (NEOWISE) as a case study. A preliminary model run is shown in Figure 3, though it does not yet include emission from within the collisional radius and emission from dusty sources, which will broaden the tail. Work thus far suggests that spectrally resolved sodium emissions could offer a proxy for the water outflow velocity, enabling a new method at optical wavelengths.

51. Hsieh, H., Noonan, J., Kelley, M., et al., (including Thirouin, A., Kareta, T.), 2025, epsc, 2025, EPSC-DPS2025-1108, The Ensemble Volatile Compositional Properties of 133P/Elst-Pizarro and Other JWST-Observed Main-Belt Comets
    Abstract

    Main-belt comets (MBCs) are small solar system objects that display comet-like activity with characteristics indicative of the sublimation of volatile ices yet have dynamically stable orbits in the main asteroid belt. Until recently, sublimation has only been inferred as the primary activity driver for MBCs, largely based on observations of recurrent activity near perihelion and the inability of other activity drivers to plausibly account for such behavior over a wide range of objects. Starting in 2022, however, JWST observations of four active MBCs 238P/Read, 358P/PANSTARRS, 133P/Elst-Pizarro, and 457P/Lemmon-PANSTARRS have provided unambiguous spectroscopic evidence of the presence of water vapor sublimation in at least three of these objects: 238P (JWST GTO program 1252; Kelley et al., 2023, Nature, 619, 720), 358P (JWST GO program 4250; Hsieh et al., 2025, PSJ, 6, 3), and 133P (JWST GO programs 4250 and 5551; this work). These observations have also shown that these MBCs have a striking relative absence of CO2, which is commonly found in other comets with similar water production rates, pointing to MBCs comprising a distinct volatile inventory compared to other classical comets. The enhanced sensitivity of JWST's NIRSpec instrument has significantly advanced the study of main-belt comets, shifting the focus from the long-standing question of whether volatile sublimation could be directly detected to now characterizing its properties and examining how they vary across different objects and observing conditions.We will present and discuss JWST observations of 133P, the archetype of the MBC population, obtained at two positions in its orbit. These observations confirm that the activity is driven by water ice sublimation and continue to show the relative absence of more volatile species, extending the emerging pattern established by 238P and 358P. JWST NIRCam and NIRSpec observations of 133P were obtained on UT 2024 June 12 and UT 2024 October 14 and 28 when the object was at a true anomaly of 8 and a heliocentric distance of 2.67 au, and a true anomaly of ~40 and a heliocentric distance of ~2.75 au, respectively. Preliminary measurements show water sublimation rates of Q(H2O)~1025 molecules/s during both sets of observations, while only upper limits were obtained for CO, CO2, and CH3OH sublimation rates. We will also present results from optical imaging campaigns conducted for all four JWST-observed MBCs over the courses of their entire corresponding active apparitions from a range of ground-based facilities giving us information on the photometric and morphological evolution of each target over many months before and after their JWST observations. We will specifically describe efforts to correlate measured water sublimation rates with estimated dust production rates (as parameterized by the Af parameter) for comparison to other types of comets, ascertain the feasibility of estimating water sublimation rates for non-JWST-observed comets from Af measurements alone, and examine how Af/Q(H2O) varies for objects with different physical and orbital properties, and different observational circumstances when observed by JWST.

52. Eduardo, M., Morgan, A., Fraser, W., et al., (including Grundy, W.), 2025, epsc, 2025, EPSC-DPS2025-1132, The Luminosity Function Of Ultra-Faint Trans-Neptunian Objects Detected By James Webb Space Telescope
    Abstract

    Trans-Neptunian Objects (TNOs), which are the small bodies beyond the orbit of Neptune, are regarded to be the most primitive members of the Solar System, and as such, provides valuable insights into both history and the current state of the outer Solar System.Their size distribution (SD), which can be inferred from their observed magnitude distributions, has remained relatively unaltered since the formation of the Solar System. This physical property is crucial for testing theoretical models of planet formation because it reflects the outcomes of accretion, collisional processes, and dynamical evolution over the history of the Solar System [1]. Therefore, comparing the observed size distribution with those predicted by models helps to constrain the proposed physical processes and underlying initial conditions that shaped the current Solar System. However, the relative faintness and distance of TNOs limits ground-based searches to only about m(r)~27 magnitude [2], while the lack of observations on the SD of TNOs smaller than m(r)~28 (D~20km) leaves theoretical models poorly constrained [3,4].Using images obtained from our JWST Cycle 1 program #1568 we searched for ultra-faint TNOs to further constrain planet formation models. With this program's NIRCam images, and simultaneous HST imaging, we detect and characterize TNOs as faint as m(r)~29.8 mag and as small as ~7 km (assuming 15% albedo) in diameter to explore never-before probed regions of the TNO size distribution. This is by far the deepest Solar System survey to date, with at least a visible magnitude deeper than the landmark survey by Bernstein et al. (2004) that used the Hubble Space Telescope (HST). Program #1568 is a 3-epoch pencil beam sky survey conducted using NIRCam filters with effective wavelengths of ~1.5m (F150W2) and 3.2m (F322W2), centered on a region of the sky near 13h RA, -10 Dec. The observations are near the ecliptic plane, where the sky density of cold classical TNOs is maximal. The observations were taken from Jan 24 - Feb 4, 2023, at solar elongation of ~100 degrees, where the TNOs are near their turnaround points and are least likely to move off of the NIRCAM field of view. Figure 1 shows the observation layout of this program. A deep combined background image is subtracted from individual exposures, which are then digitally tracked and stacked at different rates of motion to search for TNOs.The probability with which a TNO will be detected as a good track during a single epoch, whether it falls on a detector during both dithers, is quantified using the implanted artificial moving objects. It is well fit by the functional form , with the bright-end efficiency p0=0.96, the magnitude of half that efficiency at m0=28.92 (F150W2), and transition width w = 0.61 mag (see Figure 2).We present our preliminary set of candidate sources detected with a total SNR of 15. By constraining their orbital parameters, we measure the faint end of the luminosity function for both the dynamically cold and hot components, and present their implications to the TNO SD down to diameters of 7 km. In future work, we will conduct a detailed analysis to determine which functional form of the size distribution best characterizes the observed population. This will offer deeper insights into the physical mechanisms governing the formation and evolution of the cold and hot populations, as well as the Kuiper Belt as a whole. Figures:Figure 1. Observation footprints of the survey, consisting of 102 mosaic tiles. Each tile was observed with eight short-wavelength detectors (small squares with a 6464 FOV) and two long-wavelength detectors, each equivalent in size to four short-wavelength detectors, covering 129 129. Two exposures were taken at each of the 20 mosaic tiles. Each of the two exposures consisted of three 215s integrations, and were acquired at dither positions <1" apart. The total exposure time per tile was thus 1290 sec. Figure 2. Recovery efficiency for implanted sources in the JWST survey as a function of r-band magnitude, assuming a nominal color r-F150W2=~ 1.2 mag. The dashed curve represents the efficiency from a single-epoch observation, while the solid black curve shows the cube of the upper completeness function, which is the expected probability of detection in all three epochs, and agrees with the implant results. The vertical lines represent the (range of) 50% completeness levels in several previous and upcoming TNO surveys: DES [6], OSSOS [7], LSST [8], DEEP [4] and [5]. This plot was inspired from Figure 10 of [4]. References: [1] Fraser, W. C., Brown, M. E., Morbidelli, A., Parker, A., & Batygin, K. 2014, Astrophys J, 782, 100 [2] Fraser, W. C., & Kavelaars, J. J. 2009, Astron J, 137, 72 [3] Kavelaars, J. J., Petit, J.-M., Gladman, B., et al. 2021, Astrophys J Lett, 920, L28[4] Napier, K. J., Lin, H. W., Gerdes, D. W., et al. 2024, Planet Sci J, 5 (IOP Publishing), 50[5] Bernstein, G. M., Trilling, D. E., Allen, R. L., Brown, M. E., & Holman, M. 2004, 128[6] Bernardinelli, P. H., Bernstein, G. M., Sako, M., Yanny, B., Aguena, M., et al. 2022, ApJS, 258, 41.[7] Bannister, M. T., Gladman, B. J., Kavelaars, J. J., et al. 2018, ApJS, 236, 18[8] Ivezic, Z., Kahn, S. M., Tyson, J. A., et al. 2019, ApJ, 873, 111

53. Lewis, M., Sickafoose, A., Kneiling, B., et al., (including Levine, S.), 2025, epsc, 2025, EPSC-DPS2025-1136, Simulating Quaoar's Ring with Confinement by Weywot
    Abstract

    The large Trans-Neptunian object (50000) Quaoar has one known moon, Weywot [1]. Based on stellar occultation data from 2018-2021, a ring named Q1R was reported around Quaoar at an orbital radius of 4148.47.4 km and with variable width and optical depth [2]. Occultation data from 2022 were analyzed to reveal two rings [3]. Deriving a similar pole orientation to [2], the dense part of Q1R was interpreted to be ring arcs located at a radius of 4057.25.8 km, having Lorentzian shape extending over 60 km and full-width-at-half-maximum of 5 km, with peak normal optical depth =0.4 and a minimum arc length of multiple hundreds of km [3]. The more tenuous, continuous portion of Q1R had a typical width of 80-100 km and normal optical depth of =0.003 [3]. Secondary events from one location were consistent with a second ring, Q2R, at a radius of 252020 km, typical width of 10 km, and a normal optical depth of =0.004 [3].The location of Q1R is well outside the Roche limit, implying that the material should coalesce over reasonable timescales. [2] and [3] pointed out that the ring is close to a 3:1 spin-orbit resonance with Quaoar as well as the inner 6:1 mean-motion resonance with Weywot, both of which could act to perturb and/or confine material. Following on numerical models showing that a single satellite can confine ring material outside the Roche limit at Chariklo [4], we present global collisional simulations of ring material near the 6:1 mean-motion resonance in a system with parameters that mirror those of the Quaoar/Weywot system. We begin with simulations of low optical depth material, =0.01, spread uniformly over a 200 km radial range on roughly circular orbits to explore where the resonant forcing would cause material to be confined into a narrow ring. We then simulate a higher optical depth distribution, =0.1, that covers only the range of radii that were confined in the initial simulation. To model the 6:1 resonance with an eccentric moon, the simulations are global and include collisions only, not self-gravity, with oversized particles 20 m in radius, and a velocity-dependent coefficient of restitution from [5]. Notably, these simulations do not yet explore the impact of being outside the classical Roche limit. We find that a narrow ring of material is confined near resonance after a few hundred orbits. The width of the material that is pulled into the ring scales with the orbital eccentricity and mass of the simulated Weywot.In addition, we present a handful of new stellar occultation datasets by Quaoar between 2019 and 2024, some light curves of which contain detections of Q1R. Synthetic occultations from the numerical simulations can be compared with the occultation data to better constrain the physical properties of ring material. This work is supported by NSF AST Award Number 2206306.[1] Brown, M. E. and T.-A. Suer (2007). Satellites of 2003 AZ_84, (50000), (55637), and (90482). International Astronomical Union Circular 8812. [2] Morgado, B. E., et al. (2023). A dense ring of the trans-Neptunian object Quaoar outside its Roche limit. Nature 614, 239.[3] Pereira, C. L., et al. (2023). The two rings of (50000) Quaoar. A&A 673, id.L4.[4] Sickafoose, A. A. and M. C. Lewis, Numerical Simulations of (10199) Chariklo's Rings with a Resonant Perturber, PSJ, 5(2), id. 32, 2024.[5] Bridges, F., Hatzes, A. & Lin, D. (1984). Structure, stability and evolution of Saturn's rings. Nature 309, 333-335.

54. Thieberger, C., Hanley, J., Engle, A., et al., (including Grundy, W.), 2025, epsc, 2025, EPSC-DPS2025-1178, Laboratory Experiments of Ethylene and Acetylene in Titan Lakes
    Abstract

    Titan is the only extraterrestrial environment known to support bodies of standing liquid on its surface. The Cassini mission provided important composition measurements of a few lakes and seas, which suggest they may contain anywhere from 5 - 80 % methane and 8 - 79 % ethane mixtures, in addition to dissolved nitrogen from the atmosphere. Cassini also measured trace amounts of higher-order hydrocarbons, such as propane, ethylene, and acetylene, in Titan's atmosphere. When these trace species rain down onto the surface and mix with the lakes and seas, they create unique chemical conditions and alter the phase behavior, solubility, and stability of Titan's surface liquids. In an effort to study these environments, we present our experimental work done in the Astrophysical Materials Lab at Northern Arizona University (NAU). We studied two different trace species, ethylene and acetylene, in methane-ethane mixtures under a nitrogen atmosphere of 1.5 bar to replicate Titan lakes. Specifically, we incorporated 1-10% additions of either ethylene or acetylene to the methane-ethane-nitrogen system and performed cooling and warming cycles of our sample between 70 - 100 K. Through a combination of visual inspection and Raman spectroscopy, we found that these mixtures undergo phase changes at different temperatures than their individual end members. The observed phase changes under these conditions have exciting implications for Titan's lakes and seas, including compositional stratification of surface liquids, bubbles, and ice formation. We also measured the solubilities of both ethylene and acetylene in pure methane and pure ethane at 95 K. We will present the results of these experiments, in addition to thermodynamic models and how they relate to Titan environments. This work was supported by NASA SSW grant 80NSSC21K0168, the John and Maureen Hendricks Foundation, and the Lowell Observatory Slipher Society.

55. Hanley, J., Thieberger, C., Grundy, W., 2025, epsc, 2025, EPSC-DPS2025-1246, Ground-based Observing of the Galilean Moons in the Vis-NIR: Long-Term Monitoring and Detection of Transient Features
    Abstract

    We have observed the Galilean moons to determine their surface composition, any differences with longitude, and whether there are any temporal changes. One of the primary components we are trying to understand is the presence of salts. Salts play an important role in habitability because they can affect the stability of liquid water. Chlorine salts lower the freezing point of water significantly, while sulfate salts create a milder environment. For Europa, most of the "non-icy" spectra from NIMS are very similar to each other and have been suggested to be composed of heavily hydrated sulfate salts (McCord et al, 1999). However, Ligier et al., 2016 and King et al., 2022 observed Europa with VLT/SINFONI and SPHERE, respectively, and utilized recent NIR laboratory spectra (Hanley et al., 2014) to model spectral features, finding that Mg-bearing chlorinated species provide better spectral fits than sulfates in some areas. Additionally, studies suggest that magnesium is originally brought to the surface as magnesium chloride (Brown and Hand, 2013), and NaCl has been detected on the surface (Trumbo et al., 2019). The correlation with lineae and darker units suggests an endogenic origin for these salts.Any detection of chlorine salts at the surface would further constrain theories that the dark surface material might in fact be emplaced by movement of the ice sheet and possible subsurface ocean interaction and/or cryovolcanism, rather than implantation from Io's torus, as could be the case for sulfates. This is especially strengthened by observations of plumes on Europa. Identifying the primary constituent of Europa's ocean salts would lead to greater understanding of the ocean temperature and the thickness of the ice shell. The composition of the ocean puts limits on the habitability of ocean worlds.We have observed Europa, Io, Ganymede, Callisto and Titan with Lowell's 4.3 m Discovery Telescope (LDT) with the NIHTS and EXPRES instruments. The Near-Infrared High-Throughput Spectrograph (NIHTS) is a low-resolution (R ~ 200) near-infrared (NIR) spectrograph, covering 0.86 - 2.4 m. The EXtreme PREcision Spectrometer (EXPRES) observations measure the visible spectrum from ~0.35 - 0.85 m at a resolution of R ~ 137,500. A unique setup of EXPRES is that it is simultaneously connected to a Solar telescope which observes the Sun daily. Thus we are able to correct for actual Solar features in our spectra. The observations are disk-averaged, and those of Europa and Titan are centered around six different longitude bins to enable us to look for longitudinal differences. We also have access to telescope time every semester, so we will be able to monitor for any temporal variations. The wavelength regions covered by our instruments cover the necessary wavelengths for previous chlorine salt identifications. This work allows for monitoring of any temporal changes in Europa's surface composition, especially if plumes are depositing new material.Initial analysis of the NIHTS data for Europa shows water ice/hydration features in the NIR at 1.25, 1.5, 1.65, 2.0 and 2.4 m. The 1.65 m water ice band can be used to determine the temperature of the ice, while the others can be compared to literature spectra to determine composition. Preliminary analysis of the EXPRES data centered around 310 longitude do not show salt color centers, as expected, but do show a red slope at lower wavelengths (0.4 - 0.55 m) followed by a slight blue slope from 0.55 - 0.8 m. We do see transient molecular oxygen features on Ganymede as well (Figure 1). We will present these observations, as well as those to be collected in June 2025, along with analysis at various longitudes for both NIHTS and EXPRES, for all the Galilean Moons. These ongoing observations will be useful to the upcoming JUICE and Clipper missions to monitor the surface compositions over time. Figure 1: Visible Spectra of Ganymede from EXPRES. All data are disk-averaged, centered on the labelled longitude. Spectra have been normalized and offset for clarity. Dashed line represents the 0.5773 m molecular oxygen feature.References: Brown, M. E., and K. P. Hand. The Astronomical Journal 145.4 (2013): 110. Hanley, J., et al. Journal of Geophysical Research: Planets 119.11 (2014): 2370-2377. Ligier, N., et al. The Astronomical Journal 151.6 (2016): 163. King, O, L. N. Fletcher, and N. Ligier. The Planetary Science Journal 3.3 (2022): 72. McCord, T. B., et al. Journal of Geophysical Research: Planets 104.E5 (1999): 11827-11851. Trumbo, S. K., M. E. Brown, K. P. Hand. Science advances 5.6 (2019): eaaw7123.

56. Devogele, M., Micheli, M., Hainaut, O., et al., (including Moskovitz, N.), 2025, epsc, 2025, EPSC-DPS2025-1302, Coordinated Planetary Defence in action: Colors and lightcurve of asteroid 2024 YR4
    Abstract

    The Near-Earth Object 2024 YR4 (hereafter YR4) was discovered by the ATLAS survey [1] on December 27 2024. With an H magnitude estimated around H = 24 [2], YR4 size is estimated to be between 40 to 90 meters [2]. At time of discovery its brightness was around 16.5 magnitude and moving across the sky at high speed. Shortly after discovery, YR4 was found to display a high probability of impacting the Earth in 2032 and was classified as a Torino scale 1 virtual impactor [3]. For a few hours to days, its visual magnitude was ideal for detailed physical characterization observations such as polarimetry or spectroscopy. However, due to the timing of its discovery during the end of the year holidays, very few observations were performed at that time. A few days later, YR4 was already a few magnitudes fainter, limiting the number of telescopes able to gather physical characterization observations. On January 7, we obtained color observations with the Lowell Discovery Telescope when YR4 was already much fainter at a V~20 magnitude. The observations showed that YR4 could potentially be an S-type or L, K-type. S-types tend to have larger albedo than L or K-type (however, very few albedo of L and K-types for NEOs have been determined). It is thus highly important to distinguish between these two taxonomic classifications. To gather more information on the composition of YR4, a Director Discretionary Proposal (DDT) was submitted to the ESO Very Large Telescope to obtain Near Infra-Red colors of YR4 using the HAWK-I instrument [4]. The proposal was submitted on Sunday January 19 at night, accepted during the day of January 20 and observed during the night of the January 20 to 21. Analysis of the NIR color dataset shows good agreement with the S or L, K-type composition, but is unfortunately not sufficient to be able to distinguish between the two. To be able to assess if YR4 is a S or L, K-type, spectroscopy in both the visible and near-infrared would be needed. Visible spectroscopy has been obtained for YR4, but no NIR spectroscopy is available. Simultaneously to the HAWK-I observations, we also obtained observations in the R band with the FORS2 instrument on the VLT. These observations were used to connect the visible colors/spectroscopy of YR4 with our new NIR colors observations. We also used these observations to obtain a high signal to noise ratio lightcurve. Our lightcurve shows a rotation period around P=19.5 minutes with an amplitude of 0.4 magnitude. [1] Tonry, J. L. et al. ATLAS: A High-cadence All-sky Survey System. PASP 130, 064505 (2018)[2] https://neo.ssa.esa.int/search-for-asteroids?sum=1&des=2024YR4[3] https://neo.ssa.esa.int/risk-list[4] Pirard, J.-F. et al. HAWK-I: A new wide-field 1- to 2.5-m imager for the VLT. in vol. 5492 1763-1772 (2004)

57. Moskovitz, N., Hemmelgarn, S., Zigo, H., et al., (including Thirouin, A.), 2025, epsc, 2025, EPSC-DPS2025-1338, NEO Colors from The Mission Accessible Near-Earth Object Survey (MANOS)
    Abstract

    The Mission Accessible Near-Earth Object Survey (MANOS) conducts characterization observations of objects on low delta-v orbits and in the sub-km size regime where knowledge of physical properties is sparse. Spectroscopic characterization of these objects serves to constrain the distribution of taxonomic and compositional types across the population of the most frequent Earth-impacting asteroids, including the direct precursors of meteorites. Such data can probe how spectral properties may be dependent on factors such as object size (Devogele et al. 2019), Earth encounter distance (Binzel et al. 2010), and/or perihelion distance as a proxy for peak surface temperature (Graves et al. 2019). Constraints on the ensemble spectral properties of potential Earth impactors, as well as improved understanding of how those properties evolve over time, has implications for assessing the planetary defense risk associated with the NEO population.We will present the results of MANOS spectrophotometric observations for a sample of 199 NEOs (Figures 1 and 2). Observations were performed between 2014 and 2025 from the 4.3-m Lowell Discovery Telescope (LDT), the 4.1-m Southern Astrophysical Research Telescope (SOAR), and the 4-m Mayall Telescope. At all facilities we collected images using the SDSS griz filter set with respective band centers at 0.48, 0.62, 0.76 and 0.91 microns. These multi-band data were used to derive colors and to assign a spectral taxonomic type to each object based on a down-sampling of taxonomic templates from the Bus-DeMeo system (DeMeo et al. 2009). Observing strategies were employed to constrain the lightcurves of targets, which proved necessary to properly account for rotational brightness variations during the collection of non-simultaneous images in each filter. For example, we either measured a full rotational lightcurve before collecting a color sequence, or we interleaved images in a single reference filter to track and correct for lightcurve variations (e.g. a filter sequence of seven exposures in order r-g-r-i-r-z-r). Our sample of colors accessed objects as faint as r~22, which is about 1-2 magnitudes fainter than is typically observable with spectroscopic techniques. However, the reduction of spectral information down to just four channels can limit the ability to achieve unique spectral taxonomic classifications and is not well suited to detailed compositional analysis.This work highlights several key findings. First, the distribution of taxonomic types from the color data is consistent with previously published MANOS spectroscopic results (Devogele et al. 2019). However, this distribution is distinct from analogous surveys that sample the larger end of the NEO size distribution (H<22). In particular we find a deficit of S-type asteroids and an overabundance of X-complex asteroids amongst sub-km NEOs. It remains unclear the extent to which this is a size-dependent compositional trend in the NEO population, a size-dependence on physical surface properties such as regolith grain size, and/or a consequence of various observational biases that can be more pronounced for small (H>20) objects.Our second major finding is related to the influence of lightcurve variations on derived colors. Our approach of non-simultaneous multi-filter imaging found that ~75% of the sample required treatment of lightcurve variability to derive reliable colors. Not accounting for this variability would produce significantly different results, where some objects would appear as part of an entirely different taxonomic complex. This would clearly have consequences for interpretation of individual objects, but also manifests as a systematic bias in the distribution of spectral types based on colors derived from non-lightcurve corrected data. Specifically, we see an over-abundance of C-complex spectral types when lightcurve variability is not treated: with lightcurve correction we find 105% (1-sigma) of the sample is classified as C-type, without lightcurve correction this fraction increases to 277%. Finding a reason for this over-abundance is an area of ongoing work. However, it is clear that lightcurve variability must be considered in any color survey that involves non-simultaneous observations across multiple filters. Of course this issue is eliminated for instruments that can obtain simultaneous multi-band images.Finally, we identified a number of unusual objects in our sample. This includes objects observed on multiple epochs that demonstrated significantly different colors across epochs. For example, the colors 2011 CG2 were best fit by a Cgh-type on one epoch and a Q-type on a second epoch. Such variability is highly unexpected and is not well understood. We also note the unusual colors of 2022 BX5, which appears as the isolated object in the upper right of Figure 2. These are the reddest colors measured for any NEO to date and are most consistent with D-type spectra that are more common in the outer Solar System.This work acknowledges funding support from NASA grants 80NSSC21K1328, NNX17AH06G, and NNX14AN82G.References:Binzel et al. (2010), Nature 463, 331.Binzel et al. (2019) Icarus 324, 41.Birlan et al. (2024) A&A 689, A334.DeMeo et al. (2009) Icarus 202, 160.Devogele et al. (2019), AJ 158:196.Graves et al. (2019), Icarus 322, 1.Ivezic et al. (2019) AJ 122, 2749.Navarro-Meza et al. (2024) AJ 167:163.Perna et al. (2018) Planetary and Space Science 157, 82.Sanchez et al. (2024) PSJ 5:131.Figure 1: Cumulative size frequency distributions of key NEO spectral surveys. The number of objects sampled by each survey are given in parentheses in the legend. MANOS generally focuses on sub-km objects (H>20). The sample for our spectrophotometric survey is shown as the bold red curve. References for each survey: MITHNEOS (Binzel et al. 2019), NEOROCKS (Birlan et al. 2024), NEOSHIELD2 (Perna et al. 2018), RATIR (Navarro-Meza et al. 2024), Sanchez et al. (2024), and MANOS spectra (Devogele et al. 2019).Figure 2: g-i versus i-z color-color plot for the 199 objects observed in the MANOS spectrophotometric survey. The taxonomic assignment for each object is indicated by the plotted letters. Data from LDT are in black, from SOAR in red, and from Mayall in yellow. The blue density contours in the background represent the colors of 223 NEOs from the Sloan Digital Sky Survey Moving Object Catalog (Ivezic et al. 2001).

58. Sickafoose, A., Person, M., Zulaaga, C., et al., (including Levine, S.), 2025, epsc, 2025, EPSC-DPS2025-1363, Pluto's Atmosphere in Decline
    Abstract

    Pluto is the only minor planet (excluding satellites) that is known to host a thin, global atmosphere. The atmosphere has microbar-level surface pressure, is composed primarily of nitrogen, and contains a layered haze made of organic materials (e.g. Gladstone et al., 2016, Science, 351, id. aad8866). Notably, Pluto's atmosphere is intricately linked to its surface ices through vapor-pressure equilibrium (e.g. Elliot et al., 1989, Icarus, 77, 148). Because of the strong tie between the atmosphere and ices, the surface pressure is highly dependent on ice temperature, which is a function of orbital and seasonal timescales. On Pluto, with an eccentric orbit (e = 0.25) and high obliquity (~123 deg.), these changes are pronounced and the atmospheric properties can vary significantly on timescales of only a few decades. Thermophysical, volatile-transport models have been developed to study Pluto's atmospheric evolution; predictions range from atmospheric contraction or collapse over the coming decades to an atmosphere that remains throughout Pluto's entire revolution around the Sun (e.g. Young, 2013, ApJ Lett., 766, L22; Hansen et al. 2015, Icarus, 246, 183; Bertrand et al. 2018, Icarus, 309, 277; Johnson et al. 2021, Icarus, 356, id.114070).Stellar occultation data are the most direct way to measure Pluto's atmosphere from the Earth. Results from previous occultations reported that Pluto's atmospheric pressure monotonically increased since its definitive discovery in 1988 through 2016 (Meza et al. 2019, A&A, 625, id.A136) and then that the atmosphere had possibly begun freezing out in 2018-2019 (Arimatsu et al. 2020, A&A 638, L5; Young et al. 2021, AAS DPS Meeting #53, id.307.06). Observations of an occultation in 2020 did not show a pressure drop and were interpreted to be either a continued pressure increase (Poro et al. 2021, A&A, 652, L7) or a plateau phase (Sicardy et al. 2021, ApJ Lett, 923, L31). Here, we report results from ten successfully-observed stellar occultations by Pluto between 2017 August and 2023 July that have not yet been published. The stellar magnitudes ranged from G=12.91 to 18.4 with geocentric relative velocities between 1.7 and 24.5 km/s. Four of these events had successful chords from multiple sites, while six events were from single sites. We carried out atmospheric fits assuming clear, isothermal atmospheres as well as atmospheres with a haze layer. Our results indicate that Pluto's atmospheric pressure has begun decreasing in recent years.This work is supported by NASA grant 80NSSC21K043.

59. MacLennan, E., Pravec, P., Devogele, M., et al., (including Moskovitz, N.), 2025, epsc, 2025, EPSC-DPS2025-1689, Shape and Spin Properties of 2024 YR4 from Multi-filter Lightcurve Observations
    Abstract

    The potentially hazardous asteroid 2024 YR4 (hereafter YR4) made a close approach to Earth in December 2024 through February 2025 coinciding with its discovery. During this time period, it was targeted by several ground-based telescopes and its impact probability increased above 3%, prompting action by the International Asteroid Warning Network (IAWN). As a result of this observational effort, we make use of several dense-in-time photometric lightcurves, as acquired by several ground-based observing facilities: ESO's Very Large Telescope, the Lowell Discovery Telescope, Steward Observatory, the Danish 1.54 meter telescope, and the Nordic Optical Telescope. Photometry was acquired from these facilities using distinct astronomical filters, motivating the calculation of color transformations to a common wavelength.In addition to ground-based efforts, YR4 was targeted on 08 March by the James Webb Space Telescope's Near Infrared Camera (JWST/NIRCam) for which photometry was acquired in the wide F150W2 and F322W2 filters [1]. Thermal emission overcomes reflected light at longer wavelengths in the F322W2 filter and introduces complications for lightcurve interpretation, thus we use the relative photometry measured in the F150W2 filter.The entire dataset constitutes high-quality measurements of YR4's brightness over a roughly 3-month period (Figure 1). Using these lightcurves, we confirm the rotation period to be 0.324390 0.000005 hours and search for plausible shape and spin state solutions. The initial efforts from a pole-scanning search using ellipsoids [2] reveals a few preferred and some unfavored regions. We use these regions in a convex shape inversion procedure to derive four candidate spin poles, with corresponding shapes, representing local best-fit solutions. We then use a MCMC routine [3] to generate a large set of viable shape and spin solutions that are consistent with our lightcurve dataset.Figure 1. Model fits to our suite of optical lightcurves from various observatories over different dates.Observations of YR4's thermal emission with JWST's Mid Infrared Imager (MIRI) taken on 26 March and 11 May will be used to discern between the potential shape and spin solutions. In turn, the shapes and spins will be used to constrain the size, albedo, and thermal properties of YR4. We will present the latest results at the conference, compare to other shape solutions [4], and discuss the broader implications on the origin of YR4 as well as for planetary defense strategies. Acknowledgements:The work at Ondrejov and the observations with the Danish 1.54-m telescope at La Silla were supported by "Praemium Academiae" award to P. Pravec by the Academy of Sciences of the Czech Republic, grant AP2401.References:[1] Rivkin et al. (2025) RNAAS 9, 70. [2] Muinonen et al. (2015) P&SS, 118, 227-241. [3] Muinonen et al. (2020) A&A 642, A138. [4] Bolin et al. (2025) ApJL 984 L25.

60. To, C., Krause, E., Chang, C., et al., (including Kuehn, K.), 2025, PhRvD, 112, 063537, Dark energy survey: Modeling strategy for multiprobe cluster cosmology and validation for the full six-year dataset
    Abstract

    We introduce an updated To&Krause2021 model for joint analyses of cluster abundances and large-scale two-point correlations of weak lensing and galaxy and cluster clustering (termed CL+32 pt analysis) and validate that this model meets the systematic accuracy requirements of analyses with the statistical precision of the final Dark Energy Survey (DES) Year 6 (Y6) dataset. The validation program consists of two distinct approaches, (i) identification of modeling and parametrization choices and impact studies using simulated analyses with each possible model misspecification and (ii) end-to-end validation using mock catalogs from customized Cardinal simulations that incorporate realistic galaxy populations and DES-Y6-specific galaxy and cluster selection and photometric redshift modeling, which are the key observational systematics. In combination, these validation tests indicate that the model presented here meets the accuracy requirements of DES-Y6 for CL+32 pt based on a large list of tests for known systematics. In addition, we also validate that the model is sufficient for several other data combinations: the CL+GC subset of this data vector (excluding galaxygalaxy lensing and cosmic shear two-point statistics) and the CL+32 pt+BAO+SN (combination of CL+32 pt with the previously published Y6 DES baryonic acoustic oscillation and Y5 supernovae data).

61. Grouffal, S., Santerne, A., Bourrier, V., et al., (including Llama, J.), 2025, A&A, 701, A173, The star HIP 41378 potentially misaligned with its cohort of long-period planets
    Abstract

    The obliquity between the stellar spin axis and the planetary orbit, detected via the Rossiter-McLaughlin (RM) effect, is a tracer of the formation history of planetary systems. While obliquity measurements have been extensively applied to hot Jupiters and short-period planets, they remain rare for cold and long-period planets due to observational challenges, particularly their long transit durations. We report the detection of the RM effect for the 19-hour transit of HIP 41378 f, a temperate giant planet on a 542-day orbit, observed through a worldwide spectroscopic campaign. We measured a slight projected obliquity of 21 8 and a significant 3D spin-orbit angle of 52 6, based on the measurement of the stellar rotation period. HIP 41378 f is part a transiting system of five planets with planets close to mean motion resonances. The observed misalignment likely reflects a primordial tilt of the stellar spin axis relative to the protoplanetary disk, rather than dynamical interactions. HIP 41378 f is the first non-eccentric long-period planet (P>100 days) observed with the RM effect, opening new constraints on planetary formation theories. This observation should motivate the exploration of planetary obliquities across a longer range of orbital distances through international collaboration.

62. Kareta, T., Champagne, C., McClure, L., et al., 2025, ApJL, 990, L65, Near-discovery Observations of Interstellar Comet 3I/ATLAS with the NASA Infrared Telescope Facility
    Abstract

    Interstellar objects are comets and asteroids that formed around other stars but were ejected before they could accrete into exoplanets. They therefore represent a rare opportunity to compare the the building blocks of planets in the solar system to those in other stellar systems. The third interstellar object, 3I/ATLAS, is the newest, brightest, potentially largest, and fastest member of this population. We report observations of 3I/ATLAS taken on 2025 July 3 and 4 with the NASA Infrared Telescope Facility just days after its discovery. In r' -band imaging with 'Opihi, we see no obvious lightcurve variability and derive a g'i' color of 0.98 0.03, which is consistent in spectral slope to other near-discovery observations. We obtained the first near-infrared (NIR) reflectance spectrum of 3I/ATLAS with SpeX. The visible color and NIR spectrum show a linear, red visible slope, a somewhat less red slope between 0.7 and 1.1 m, and a neutral or slightly blue slope at longer wavelengths. Challenges in modeling the reflectivity of 3I may indicate that this comet has a complex grain size distribution, grain compositions unlike solar system comets, or both. Like 2I/Borisov, there are no obvious signatures of water ice in the coma of 3I/ATLAS. Observations closer to perihelion will help elucidate whether 3I has less water than anticipated or whether the interstellar objects might retain and release their ices somewhat differently from solar system comets.

63. Yee, S., Winn, J., Hartman, J., et al., (including Polanski, A.), 2025, ApJS, 280, 30, The TESS Grand Unified Hot Jupiter Survey. III. Thirty More Giant Planets
    Abstract

    We present the discovery of 30 transiting giant planets that were initially detected using data from NASA's Transiting Exoplanet Survey Satellite mission. These new planets orbit relatively bright (G 12.5) FGK host stars with orbital periods between 1.6 and 8.2 days, and have radii between 0.9 and 1.7 Jupiter radii. We performed follow-up ground-based photometry, high angular resolution imaging, high-resolution spectroscopy, and radial velocity monitoring for each of these objects to confirm that they are planets and determine their masses and other system parameters. The planets' masses span more than an order of magnitude (0.17 M_J < M_p < 3.3 M_J). For two planets, TOI-3593 b and TOI-4961 b, we measured significant nonzero eccentricities of 0.110.03+0.05 and 0.180.05+0.04 , respectively, while for the other planets, the data typically provide a 1 upper bound of 0.15 on the eccentricity. These discoveries represent a major step toward assembling a complete, magnitude-limited sample of transiting hot Jupiters around FGK stars. *This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

64. Minker, K., Carry, B., Vachier, F., et al., (including Grundy, W.), 2025, A&A, 701, A42, A dynamical dichotomy in large binary asteroids
    Abstract

    Context. No less than 15% of large asteroids (with diameters greater than 140 km) have satellites. The commonly accepted mechanism for their formation is post-impact reaccumulation. However, the detailed physical and dynamical properties of these systems are not well understood, and many of them have not been studied in detail. Aims. We studied the population of large binary asteroid systems, in part through the characterization of (283) Emma and (762) Pulcova. To do so, we compared the gravitational fields predicted from the shape of the primary body with the non-Keplerian gravitational components identified in orbital models of the satellites of each system. We contextualize these systems in the greater population of large binary systems, thus providing clues to asteroid satellite formation. Methods. We reduced all historical high angular resolution adaptive optics (AO) images from ground-based telescopes to conduct astrometric and photometric measurements of each system's components. We then determined orbital solutions for each system using the genoid algorithm. We modeled the shapes of the system primaries using light curve-inversion techniques scaled with stellar occultations and AO images, and we developed internal structure models using SHTOOLS. Finally, we compared the distribution of the physical and orbital properties of the known binary asteroid systems. Results. We find a very low residual orbital solution for Emma with a gravitational quadrupole J₂ value that is significantly lower than expected from the shape model, implying that Emma has a significantly nonhomogeneous internal structure, and an overall bulk density of 0.9 0.3 g cm-3³. The circular co-planar orbit of Pulcova's satellite leaves substantial ambiguity in the orbital solution. We also find that the differences between these systems reflect an overall dichotomy within the population of large binary systems, with a strong correlation between primary elongation and satellite eccentricity observed in one group. Conclusions. We determine that there may be two distinct formation pathways influencing the end-state dichotomy in these binary systems, and that (762) Pulcova and (283) Emma belong to the two separate groups.

65. Polanski, A., Crossfield, I., Seifahrt, A., et al., 2025, AJ, 170, 182, An Aligned Sub-Neptune Revealed with MAROON-X and a Tendency Toward Alignment for Small Planets
    Abstract

    We present the RossiterMcLaughlin measurement of the sub-Neptune TOI-1759A b with MAROON-X. A joint analysis with MuSCAT3 photometry and nine additional TESS transits produces a sky-projected obliquity of = 4 18. We also derive a true obliquity of = 24 12 making this planet consistent with full alignment albeit to <1. With a period of 18.85 days and an a/R_* of 40, TOI-1759A b is the longest period single sub-Neptune to have a measured obliquity. It joins a growing number of smaller planets which have had this measurement made and, along with K2-25 b, is the only single, aligned sub-Neptune known to date. We also provide an overview of the emerging distribution of obliquity measurements for planets with R < 8 R. We find that these types of planets tend toward alignment, especially the sub-Neptunes and super-Earths, implying a dynamically cool formation history. The majority of misaligned planets in this category have 4 < R 8 R and are more likely to be isolated than planets rather than in compact systems. We find this result to be significant at the 3 level, consistent with previous studies. In addition, we conduct injection and recovery testing on available archival radial velocity data to put limits on the presence of massive companions in these systems. Current archival data is insufficient for most systems to have detected a giant planet.

66. Massey, P., Bodansky, S., Penny, L., et al., (including Neugent, K.), 2025, ApJ, 990, 52, A New Determination of the Mass of NGC 3603-A1: The Most Massive Binary Known?
    Abstract

    The star NGC 3603-A1 has long been known to be a very massive binary, consisting of a pair of O2-3If*/WN5-6 stars which show WolfRayetlike emission due to their luminosities being near the Eddington limit. The system has been poorly characterized until now, due to the difficulties of obtaining reliable radial velocities from broad, blended emission lines and the extreme crowding in the cluster. However, previously unpublished archival Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) spectra revealed that some of the upper Balmer lines (seen in absorption) are well separated at favorable orbital phases, prompting us to obtain our own carefully timed new HST/STIS spectra, which we have analyzed along with the older data. Radial velocities measured from these spectra allow us to obtain an orbit for this 3.77298-day binary. We also used archival STIS imaging of the cluster to obtain a more accurate light curve for this eclipsing system, which we then modeled, yielding the orbital inclination and providing values for the stellar radii and temperatures. Together, these data show that the NGC 3603-A1 system consists of a 93.3 11.0M O3If*/WN6 primary with an effective temperature of 37,000 K, and a 70.4 9.3M O3If*/WN5 secondary that is slightly hotter, 42,000 K. Although a more massive binary is known in the LMC, NGC 3603-A1 is as massive as any binary known in our own Galaxy for which a direct measurement of its mass has been made by a fundamental method. The secondary has been spun up by mass accretion from the primary, and we discuss the evolutionary status of this intriguing system.

67. Kroft, M., Beatty, T., Crossfield, I., et al., (including Polanski, A.), 2025, AJ, 170, 150, A Pair of Dynamically Interacting Sub-Neptunes around TOI-6054
    Abstract

    We confirm the planetary nature of a pair of transiting sub-Neptune exoplanets orbiting the bright F-type subgiant star TOI-6054 (V = 8.02, K = 6.673) as a part of the OrCAS radial velocity survey using WIYN/NEID observations. We find that TOI-6054b and TOI-6054c have radii of 2.64 0.15R and 2.82 0.17R, respectively, and masses of 12.5 1.7M and 9.3 1.9M. The planets have zero-albedo equilibrium temperatures of 1360 32 K and 1143 28 K. The host star has expanded and will evolve off of the main sequence within the next 500 Myr, and the resulting increase in stellar luminosity has more than doubled the stellar flux the two planets receive compared to the start of the host star's main-sequence phase. Consequently, TOI-6054b may be losing some of its primordial hydrogen/helium atmosphereif it has one. Based on dynamical simulations performed using the orbital parameters of the two planets, TOI-6054b, and TOI-6054c are very likely in a 5:3 mean motion resonance. The TOI-6054 system thus has the potential to be an excellent candidate for future atmospheric follow-up observations, with two similarly sized sub-Neptunes around a bright star. We also estimate that if TOI-6054b is currently losing its H/He atmosphere, this should be observable from space and from the ground.

68. Barat, S., Desert, J., Mukherjee, S., et al., (including Sikora, J.), 2025, AJ, 170, 165, A Metal-poor Atmosphere with a Hot Interior for a Young Sub-Neptune Progenitor: JWST/NIRSpec Transmission Spectrum of V1298 Tau b
    Abstract

    We present the JWST/NIRSpec G395H transmission spectrum of the young (1030 Myr) transiting planet V1298 Tau b (9.85 0.35 R, T_eq = 670 K). Combined Hubble Space Telescope and JWST observations reveal a haze-free, H/He-dominated atmosphere with a large scale height (1500 km), allowing detection of CO₂ (35), H₂O (30), CO (10), CH₄ (6), SO₂ (4), and OCS (3.5). Our observations probe several scale heights (4.4 in the CO₂ 4.3 m band and 3 in the 2.7 m water band). The planet's mass, inferred from atmospheric scale height using free retrieval and grid modeling, is 12 1 M and 15 1.7 M, respectively, which is significantly lower than previous radial velocity estimates and confirms it as "gas-dwarf" sub-Neptune progenitor. We find an atmospheric metallicity (log Z = 0.6 0.6+0.4 solar) and subsolar C/O ratio (0.22 0.05+0.06 ). The atmospheric metallicity is low compared to mature sub-Neptunes by an order of magnitude. The CH₄ abundance ([CH₄] = 6.2 0.5+0.3 ]) is 7 lower than the equilibrium chemistry prediction. To adjust for the low methane abundance, the self-consistent grids favor a high internal temperature (500 K) and vertical mixing (K_zz 10⁷10⁸ cm² s¹). These internal temperatures are inconsistent with predictions from evolutionary models, which expect 100200 K at the current system age. We estimate a gas-to-core mass fraction between 0.1% and 8%, with a core mass of 1112 M, consistent with in-situ gas-dwarf formation. A deep atmospheric metallicity gradient may explain both the high internal temperature and low observable metallicity. Over time, mass loss from such an atmosphere could enhance its metallicity, potentially reconciling V1298 Tau b with mature sub-Neptunes.

69. Seligman, D., Micheli, M., Farnocchia, D., et al., (including Kareta, T., Zhang, Q.), 2025, ApJL, 989, L36, Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS
    Abstract

    We report initial observations aimed at the characterization of a third interstellar object. This object, 3I/ATLAS or C/2025 N1 (ATLAS), was discovered on 2025 July 1 UT and has an orbital eccentricity of e 6.1, perihelion of q 1.36 au, inclination of 175, and hyperbolic velocity of V 58 km s¹. We report deep stacked images obtained using the CanadaFranceHawaii Telescope and the Very Large Telescope that resolve a compact coma. Using images obtained from several smaller ground-based telescopes, we find minimal light-curve variation for the object over a 4 day time span. The visible/near-infrared spectral slope of the object is 17.1% 0.2%/100 nm, comparable to other interstellar objects and primitive solar system small bodies (comets and D-type asteroids). Moreover, 3I/ATLAS will be observable through early 2025 September, then unobservable by Earth-based observatories near perihelion due to low solar elongation. It will be observable again from the ground in late 2025 November. Although this limitation unfortunately prohibits detailed Earth-based observations at perihelion when the activity of 3I/ATLAS is likely to peak, spacecraft at Mars could be used to make valuable observations at this time.

70. Hofgartner, J., Buratti, B., Grundy, W., et al., 2025, PSJ, 6, 188, Contrast Reversal and Emergent Features on Pluto
    Abstract

    Features that change in appearance between different NASA New Horizons images of Pluto are analyzed. Contrast reversal features (CRs) appear to transition from darker to brighter than their surroundings, more likely due to changes of imaging geometry, specifically increasing solar phase angle, than temporal change. Contrast emergent features (CEs) are not apparent in low- and intermediate-solar-phase-angle images but brighter than their surroundings in high-solar-phase-angle image(s), also more likely due to the increase of solar phase angle than temporal change. Hypotheses for Pluto's CRs and CEs include plumes, clouds, wind streaks, snow, frost, precipitated haze, lags, pits, glints, slopes, and particle size, compaction, and geometric effects. The CRs and CEs could be on and/or above Pluto's surface and/or within its shallow subsurface. These hypotheses are investigated via mapping, color, morphology, photometry, and comparison with Triton's fans. Pluto's CRs and CEs are likely different manifestations of the same or similar phenomena. They are likely not diffuse deposits of Pluto's dark red equatorial material(s) on or above or within volatile-ice-rich regions, sunglints, or geometric effects from spatially resolved slopes. They are consistent with less backward-scattering and more forward-scattering surfaces and shallow subsurfaces than their surroundings, as well as optically thin, preferentially forward scattering between the surface and global haze, including atmospheric (e.g., cloud) and surface-coating (e.g., condensation deposit) features. Surface and/or shallow subsurface features, possibly atmospheric derived, are favored over atmospheric features.

71. Clayton, G., Yanchulova Merica-Jones, P., Gordon, K., et al., (including Massey, P.), 2025, ApJ, 989, 61, Nature or Nurture: LMC-like Dust in the Solar Metallicity Galaxy M31
    Abstract

    Using the Hubble Space Telescope/Space Telescope Imaging Spectrograph, ultraviolet (UV) extinction curves have been measured in M31 along 13 new sight lines, increasing the M31 sample to 17. This sample covers a wide area of M31, having galactocentric distances of 516 kpc, enabling the analysis of UV extinction curve variations over a large region of an external galaxy similar to the Milky Way with global galactic characteristics such as metallicity for the first time. No correlation is found between the extinction parameters and galactocentric distance, which might be expected if there is a radial metallicity gradient in M31. Most of the new UV extinction curves presented here are significantly different from the average extinction curves of the Milky Way, Large Magellanic Cloud (LMC), and Small Magellanic Cloud (SMC), but the average M31 extinction curve is similar to the average extinction curve in the 30 Dor region of the LMC. The wide range of extinction curves seen in each individual Local Group galaxy suggests that global galactic properties such as metallicity may be less important than the local environmental conditions, such as density, UV radiation field, and shocks along each sight line. The combined behavior of the Milky Way, LMC, SMC, and now M31 UV extinction curves supports the idea that there is a family of curves in the Local Group with overlapping dust grain properties between different galaxies.

72. Firgard, M., Kareta, T., 2025, PSJ, 6, 184, Modeling Ice and Dust in Comet C/2017 K2 (Pan-STARRS)'s Coma
    Abstract

    C/2017 K2 (Pan-STARRS) is a long-period comet that has been active since 24 au inbound and likely as far out as 35 au, far beyond where the sublimation of water ice can power cometary activity. Near-infrared spectroscopic observations were obtained with SpeX on the NASA Infrared Telescope Facility at a heliocentric distance of R_H = 6.50 au, which show clear signs of water ice in K2's coma. Subsequently, more near-infrared spectra of K2 were collected with the Near-Infrared High-Throughput Spectrograph instrument on the Lowell Discovery Telescope and FLAMINGOS-2 on the Gemini South Telescope in order to further characterize the initially detected water ice. The SpeX data show strong water ice absorption features with an overall red slope while the later observations show decreasing ice fractions. We ran several different spectral models utilizing a Markov chain Monte Carlo approach to characterize the dust and ice in the coma, resulting in a range of ice fractions from 5% to 12% in the SpeX data depending on the mixing method, ice crystallinity, and assumed scattering regime(s). Modeling the SpeX data showed two classes of solutions, one with redder dust and more ice and one with less red dust and less ice, with significant differences in the derived properties of interest like the typical size of the ice grains. We utilize the later dust-dominated observations to recontextualize our observations of K2's icier coma further out and to facilitate a discussion of how its coma evolved as a function of heliocentric distance. We also discuss best practices in modeling reflected light from cometary comae.

73. Lizotte, D., Rowe, J., Sikora, J., et al., 2025, AJ, 170, 128, Exoplanet Atmospheric Refraction Effects in the Kepler Sample
    Abstract

    We present an analysis on the detection viability of refraction effects in Kepler's exoplanet atmospheres using binning techniques for their light curves in order to compare against simulated refraction effects. We split the Kepler exoplanets into subpopulations according to orbital period and planetary radius, then search for out-of-transit changes in the relative flux associated with atmospheric refraction of starlight. The presence of refraction effectsor lack thereofmay be used to measure and set limits on the bulk properties of an atmosphere, including mean molecular weight or the presence of hazes. In this work, we use the presence of refraction effects to test whether exoplanets above the periodradius valley have H/He atmospheres, which high levels of stellar radiation could evaporate away, in turn leaving rocky cores below the valley. We find strong observational evidence of refraction effects for exoplanets above the periodradius valley based on Kepler photometry; however, those related to optically thin H/He atmospheres are not common in the observed planetary population. This result may be attributed to signal dampening caused by clouds and hazes, consistent with the optically thick and intrinsically hotter atmospheres of Kepler exoplanets caused by relatively close host star proximity.

74. Sikora, J., Rowe, J., Splinter, J., et al., (including Llama, J.), 2025, AJ, 170, 105, Seasonal Changes in the Atmosphere of HD 80606 b Observed with JWST's NIRSpec/G395H
    Abstract

    High-eccentricity gas giant planets serve as unique laboratories for studying the thermal and chemical properties of H/He-dominated atmospheres. One of the most extreme cases is HD 80606 ba hot Jupiter orbiting a Sun-like star with an eccentricity of 0.93which experiences an increase in incident flux of nearly 3 orders of magnitude as the starplanet separation decreases from 0.88 au at apoastron to 0.03 au at periastron. We observed the planet's periastron passage using JWST's NIRSpec/G395H instrument (2.85.2 m) during a 21 hr window centered on the eclipse. We find that, as the planet passes through periastron, its emission spectrum transitions from a featureless blackbody to one in which CO, CH₄, and H₂O absorption features are visible. We detect CH₄ during postperiapse phases at 4.110.7 depending on the phase and on whether a flux offset is included to account for NRS1 detector systematics. Following periapse, H₂O and CO are also detected at 4.25.5 and 3.74.4, respectively. Furthermore, we rule out the presence of a strong temperature inversion near the IR photosphere based on the lack of obvious emission features throughout the observing window. General circulation models had predicted an inversion during periapse passage. Our study demonstrates the feasibility of studying hot Jupiter atmospheres using partial phase curves obtained with NIRSpec/G395H.

75. Brinkman, C., Weiss, L., Huber, D., et al., (including Polanski, A.), 2025, AJ, 170, 109, The Compositions of Rocky Planets in Close-in Orbits Tend to Be Earth-like
    Abstract

    Hundreds of exoplanets between 1 and 1.8 times the size of Earth have been discovered on close-in orbits. However, these planets show such a diversity in densities that some appear to be made entirely of iron, while others appear to host gaseous envelopes. To test this diversity in composition, we update the masses of five rocky exoplanets (HD 93963 A b, Kepler-10 b, Kepler-100 b, Kepler-407 b, and TOI-1444 b) and present the confirmation of a new planet (TOI-1011) using 187 high-precision radial velocities from Gemini/MAROON-X and Keck/KPF. Our updated planet masses suggest compositions closer to that of Earth than previous literature values for all planets in our sample. In particular, we report that two previously identified "super-Mercuries" (Kepler-100 b and HD 93963 A b) have lower masses that suggest less iron-rich compositions. We then compare the ratio of iron to rock-building species with the abundance ratios of those elements in their host stars. These updated planet compositions do not suggest a steep relationship between planet and host star compositions, contradictory to previous results, and suggest that planets and host stars have similar abundance ratios.

76. Vincenzi, M., Kessler, R., Shah, P., et al., (including Kuehn, K.), 2025, MNRAS, 541, 2585, Comparing the DES-SN5YR and Pantheon+ SN cosmology analyses: investigation based on 'evolving dark energy or supernovae systematics'?
    Abstract

    Recent cosmological analyses measuring distances of type Ia supernovae (SNe Ia) and baryon acoustic oscillations (BAO) have all given similar hints at time-evolving dark energy. To examine whether underestimated SN Ia systematics might be driving these results, Efstathiou (2025) compared overlapping SN events between Pantheon+ and DES-SN5YR (20 per cent SNe are in common), and reported evidence for an $\sim$0.04 mag offset between the low- and high-redshift distance measurements of this subsample of events. If this offset is arbitrarily subtracted from the entire DES-SN5YR sample, the preference for evolving dark energy is reduced. In this paper, we show that this offset is mostly due to different corrections for Malmquist bias between the two samples; therefore, an object-to-object comparison can be misleading. Malmquist bias corrections differ between the two analyses for several reasons. First, DES-SN5YR used an improved model of SN Ia luminosity scatter compared to Pantheon+ but the associated scatter-model uncertainties are included in the error budget. Secondly, improvements in host mass estimates in DES-SN5YR also affected SN standardized magnitudes and their bias corrections. Thirdly, and most importantly, the selection functions of the two compilations are significantly different, hence the inferred Malmquist bias corrections. Even if the original scatter model and host properties from Pantheon+ are used instead, the evidence for evolving dark energy from CMB, DESI BAO Year 1 and DES-SN5YR is only reduced from 3.9$\sigma$ to 3.3$\sigma$, consistent with the error budget. Finally, in this investigation, we identify an underestimated systematic uncertainty related to host galaxy property uncertainties, which could increase the final DES-SN5YR error budget by 3 per cent. In conclusion, we confirm the validity of the published DES-SN5YR results.

77. Hartman, Z., van Belle, G., Lepine, S., et al., 2025, AJ, 170, 91, Resolving the Unresolved: Using NESSI to Search for Unresolved Companions in Low-mass Disk Wide Binaries
    Abstract

    Stellar systems consisting of three or more stars are not an uncommon occurrence in the Galaxy. Nearly 50% of solar-type wide binaries with separations >1000 au are actually higher-order multiples with one component being a close binary. Additionally, the higher-order multiplicity fraction appears to be correlated with the physical separation of the widest component. These facts have motivated some of our current theories behind how the widest stellar systems formed, which can have separations on the order of or larger than protostellar cores. However, it is unclear if the correlation between wide binary separation and higher-order multiplicity extends to low-mass binaries. We present initial results of an ongoing speckle imaging survey of nearby low-mass wide binaries. We find an overall higher-order multiplicity fraction for our sample of 42.0% 10.9%. If we include systems where Gaia indicates that a companion is likely present, this fraction increases to 62.0% 14.2%. This is consistent with previous results from both higher-mass stars and a previous result for low-mass wide binaries. However, we do not detect the expected increase in higher-order multiplicity fraction with separation, as was seen with previous studies. We briefly explore why higher-order multiplicity statistics could be different in low-mass stars, and what the significance might be for models of wide binary formation.

78. Koch, E., Leroy, A., Rosolowsky, E., et al., (including Archer, H., Hunter, D.), 2025, ApJS, 279, 35, The Karl G. Jansky Very Large Array Local Group L-Band Survey (LGLBS)
    Abstract

    We present the Local Group L-Band Survey, a Karl G. Jansky Very Large Array (VLA) survey producing the highest-quality 21 cm and 12 GHz radio continuum images to date, for the six VLA-accessible, star-forming, Local Group galaxies. Leveraging the VLA's spectral multiplexing power, we simultaneously survey the 21 cm line at high 0.4 km s¹ velocity resolution, the 12 GHz polarized continuum, and four OH lines. For the massive spiral M31, the dwarf spiral M33, and the dwarf irregular galaxies NGC 6822, IC 10, IC 1613, and the WolfLundmarkMelotte Galaxy, we use all four VLA configurations and the Green Bank Telescope to reach angular resolutions of <5 (1020 pc) for the 21 cm line with <10²⁰ cm² column density sensitivity, and even sharper views (<2; 510 pc) of the continuum. Targeting these nearby galaxies (D 1 Mpc) reveals a sharp, resolved view of the atomic gas, including 21 cm absorption, and continuum emission from supernova remnants and H II regions. These data sets can be used to test theories of the abundance and formation of cold clouds, the driving and dissipation of interstellar turbulence, and the impact of feedback from massive stars and supernovae. Here, we describe the survey design and execution, scientific motivation, data processing, and quality assurance. We provide a first look at and publicly release the wide-field 21 cm H I data products for M31, M33, and four dwarf irregular targets in the survey, which represent some of the highest-physical-resolution 21 cm observations of any external galaxies beyond the LMC and SMC.

79. Hunter, D., Zhang, H., Elmegreen, B., et al., (including Castelloe, E., Ledford, H., Nisley, I., Hatano, R.), 2025, AJ, 170, 76, Ultradeep Imaging of Nearby Dwarf Irregular Galaxies: Young Objects in the Far Outer Disk
    Abstract

    Ultradeep UBVI imaging of 10 nearby (7.8 Mpc) noninteracting dwarf irregular galaxies are used to examine their far outer stellar disks. The annulus between 26 mag arcsec² and 29 mag arcsec² in the V band is what we define as the far outer disk and is our focus here. Photometry of distinct objects in the far outer disks, including far-UV images, is used to determine ages of the objects in order to look for those that are young. In three of the galaxies we find objects with high-confidence ages 30 Myr. These objects are too young to have scattered into the far outer disk from the central regions. Therefore, they likely formed in situ. How star-forming gas clouds formed in the extreme environment of the outer stellar disks of dwarfs is a primary unanswered question.

80. Craig, M., Crawford, S., Seifert, M., et al., (including Ellsworth Bowers, T.), 2025, zndo, astropy/ccdproc: 2.5.1: The final 2.x release
    Abstract

    What's Changed Remove license for bitfield [ci skip] by @mwcraig in https://github.com/astropy/ccdproc/pull/899 Full Changelog: https://github.com/astropy/ccdproc/compare/2.5.0...2.5.1

81. Proudfoot, B., Fernandez-Valenzuela, E., Grundy, W., et al., 2025, hst, 18002, Probing the Interior of the Dwarf Planet Haumea
    Abstract

    In the region beyond Neptune, a diverse population of small, icy bodies exists. These transneptunian objects (TNOs) are some of the most enigmatic bodies in our solar system. The most mysterious of these bodies is Haumea, a large (~1500 km diameter), rapidly rotating body (3.9 hours) hosting two moons (Hi'iaka and Namaka). Haumea, like most of the other large TNOs, is thought to be differentiated, with a dense, rocky core surrounded by a water-ice mantle. Between these layers, a thin subsurface ocean may have once existed, with significant astrobiological potential. Although indirect evidence indicates Haumea may be differentiated, no direct probe of Haumea's interior has yet to be made. In this program, we use astrometric tracking of Haumea's moons to infer the interior structure of Haumea. We require 3, well-timed single-orbit visits using WFC3/UVIS, which will enable detection of Haumea's differentiated core at a significance of ~3 sigma. This low-risk, high-reward program will provide the first direct probe into the interior of a TNO, acting as a touchstone for understanding the interiors of the icy transneptunian population.

82. Proudfoot, B., Grundy, W., Thirouin, A., 2025, hst, 18005, 2014 WC510: A second trans-Neptunian triple?
    Abstract

    Small planetesimals in the trans-Neptunian region are thought to be formed as the result of gravitational collapse triggered by the streaming instability mechanism. Simulations of such gravitational collapses commonly produce hierarchical triple systems (and other higher multiples), suggesting that they may be common in the trans-Neptunian region. However, to date, only one hierarchical triple has been found, suggesting that either triples are rare or telescopes have not yet reached the necessary resolution to resolve them. Recent HST observations have revealed that 2014 WC510, previously seen to be a closely separated binary, could have a more distant third companion. Alternatively, the system may be a wide binary that happens to be in an edge-on orbit. To determine if WC510 is the Solar System's second confirmed hierarchical triple, we propose a simple 6 orbit program to recover the orbit of the newly discovered distant companion. This provides a sensitive test of the streaming instability formation of planetesimals. Even if not a triple system, our program will precisely measure WC510's mass, providing one of the most precisely known densities in its size range. There is also potential to predict mutual events, which can provide a powerful tool to study WC510 in exquisite detail.

83. Proudfoot, B., Grundy, W., Holler, B., et al., 2025, hst, 18006, Geophysical Characterization of the Distant Ocean World Makemake
    Abstract

    Recent JWST observations have revealed that the trans-Neptunian object (TNO) Makemake has a prominant IR excess indicating the existence of Enceladus-style hotspots on its surface. This makes Makemake possibly one of the Solar System's most distant ocean worlds. Unfortunately, little is known about many of the basic properties of Makemake, making high-fidelity geophysical investigations almost impossible. To solve this, we propose an investigation to measure the mass, density, and pole-axis orientation of Makemake via astrometric tracking of its small satellite, nicknamed MK2. Measuring mass and density will help to constrain the ongoing radiogenic heating of Makemake and provide firm footing for models of Makemake's interior structure. Determining Makemake's pole-axis orientation will provide critical context for interpreting the JWST thermal measurements and could help to constrain the geographical extent of any hotspots. Leveraging over a dozen orbits from past HST programs, we require just 4 well-timed HST orbits to complete our investigation, which will revolutionize our knowledge of Makemake and enable high-fidelity geophysical modeling of this distant ocean world.

84. Proudfoot, B., Fernandez-Valenzuela, E., Grundy, W., et al., 2025, hst, 18010, A Search For The Moons of Mid-Sized TNOs
    Abstract

    Mid-sized trans-Neptunian objects (TNOs) are the perfect probe for understanding the collisional process that creates terrestrial planets and giant planet cores. Interestingly, although the largest TNOs have a high binary fraction--likely due to collisions--mid-sized TNOs have few known collisional moons (binary fraction ~ 15%), even though they were likely subject to a similar collisional environment as the large TNOs. This may be due to observational bias, where the moons of mid-sized TNOs are too small to have been seen in large numbers in past surveys. To explore this dichotomy, we propose a 98 target SNAP survey of mid-sized TNOs with a goal of discovering moons around mid-sized TNOs and precisely measuring the binary fraction of this interesting population. Our program will push upper limits on moons to one mag fainter than past programs and will use detailed PSF analysis to recover (or place upper limits on) close-in moons. We expect to discover at least ~3-5 new companions, with potential to discover more than 20, if the mid-sized TNO binary fraction is large. Our target list is made up of all TNOs with H magnitude < 5.5 that have yet to be surveyed for moons in detail, and have sufficient ephemeris quality for observations with WFC3. Discovering moons around our targets hold great scientific value in determining the importance of collisions in the earliest moments of our solar system, with broad application to (exo)planet formation, protoplanetary disks, and debris disks. Our program enables a variety of interesting and high-impact investigations into the origins of mid-sized TNOs.

85. O'Toole, C., Fitzgerald, M., Gibbs, A., et al., (including Kao, M.), 2025, hst, 18113, UV Exo-Aurorae: Multi-Wavelength Observations of a Radio Emitting T-dwarf to confirm Auroral Activity in the Ultraviolet.
    Abstract

    We propose simultaneous UV and radio observations with HST/STIS and the VLA of 2M1047+21, a cool, radio-emitting brown dwarf, to measure the first UV auroral emission from an extrasolar world. Over the last two decades, brown dwarfs have been discovered to emit powerful radio signatures indicative of aurorae. However, a conclusive detection of auroral UV emission on a brown dwarf has remained elusive. This program will constrain electron precipitation energies, resolve the magnetosphere structure and verify if auroral processes in brown dwarfs follow similar scaling relations to planetary aurorae. Detecting auroral emission in the UV would bridge the gap between the stellar and planetary regimes and complete picture of extrasolar auroral emission.

86. Thirouin, A., Grundy, W., Noll, K., et al., 2025, hst, 18124, Logos-Zoe: a triple or quadruple trans-Neptunian system?
    Abstract

    (58534) 1997 CQ29 (a.k.a Logos-Zoe) is a dynamically Cold Classical system in the trans-Neptunian belt. The primary, Logos, and its satellite, Zoe, have similar brightness inferring a nearly equal-sized binary. Based on Hubble Space Telescope (HST) images obtained since 2001, it has been noticed that both system's components have large lightcurve variabilities on very different timescales. Logos' variability is over a short-time scale of hours whereas Zoe's variability seems to be on a long-time scale of days to months. New ground-based observations obtained over five years with 4 to 6-m class telescopes have proven that this system is more complicated than initially thought. Logos is a high mass ratio contact binary with a rotational period of about 17 hours. But, despite five years of unresolved ground-based observations, the rotational period of Zoe remains unknown. The brightness variation of Zoe is consistent with a highly elongated object or even a contact binary based on HST images. We request eight non-consecutive orbits to observe the Logos-Zoe system to 1) constrain the rotational lightcurve of Zoe inferring its rotational period and shape, 2) update the mutual orbit determination, 3) model and predict the upcoming mutual events season of this highly complex system, and 4) challenge the current formation models for binary/multiple systems. The Logos-Zoe mutual event season will start in 2026 and will end in 2029 with only up to two events per year, implying that we are running out of time to characterize this system. The next mutual event season will be in 151 years, therefore, this is the only chance in our lifetimes to understand this system.

87. Ragozzine, D., Grundy, W., Proudfoot, B., et al., 2025, hst, 18133, Probing the TNO Density Transition with Mid-Size 2013 FY27
    Abstract

    The density distribution of Trans-Neptunian Objects (TNOs) provides key insights into the composition and interiors of outer solar system bodies, with broad implications for planet formation and evolution. Only ~20 TNOs have measured densities which seem to fall into three categories: small TNOs have similar low densities and large TNOs have similar high densities. The "transition region" (diameters of 400-900 km) only has 5 known densities which show a surprisingly rapid transition between these two regimes. While the density-size relationship was thought to be linear, a recent measurement breaks this trend, suggesting the need to explore other interpretations.

    This proposal targets 2013 FY27, a rare TNO in the transition region with a known satellite and a diameter of ~760 km. Previous HST observations were insufficient to determine its orbit due to a small near edge-on orbit.

    We propose a focused 5-orbit program to obtain precise relative astrometry of FY27 and its satellite to measure the density of FY27 and to determine the possibility of information-rich mutual events. Previous observations are used to design an optimal observing program, including iterative updates to the observing schedule using state-of-the-art orbit fitting and prediction tools. Success in these goals is only plausible with HST.

    This program will add a valuable new data point to the poorly-understood density distribution of TNOs in the density transition, helping to resolve whether composition or porosity drives the transition. The resulting insights on composition and interiors have broad importance in astrometry through improved constraints on planet formation and evolution.

88. Ragozzine, D., Grundy, W., Proudfoot, B., et al., 2025, hst, 18141, Characterizing Planet Formation through a Outer Solar System Binary Survey Simulator
    Abstract

    Solar System Small Bodies provide direct insight into the formation and evolution of the solar system and to planet formation in general. Of particular value are Outer Solar System Binaries (OSSBs) since they encode information about a variety of planetesimal formation processes like the Streaming Instability, collisional evolution, and dynamical stirring. HST has invested a significant amount of solar system observations to discovering these binaries, but almost no effort has been devoted to measuring the observational biases to determine the true underlying frequency of OSSB binaries. Without information on the binary fraction as a function of size, dynamical class, and other properties, many important questions about planet formation are left unanswered. In this Archival proposal, we will characterize the Detection Probability of over 500 outer solar system small bodies observed with HST. Using the same pipeline on real and injected objects minimizes biases and allows a "Binary Survey Simulator" to leverage hundreds of non-detections to rigorously test binary population models. Bayesian parameter inference on binary population statistics (like frequency as a function of size, orbit and relative brightness) will finally provide OSSB population models. This enables a variety of investigations but we focus on three major questions related to differences between Trojans, Centaurs, Cold TNOs, and Hot TNOs that inform specific planet formation processes. This project maximally leverages HST's unique archival dataset to answer open questions in planet formation. Since it uses only HST archival data, it is ideally and uniquely suited for Archival Program support.

89. Garreau, G., Defrere, D., Ertel, S., et al., (including Maier, E.), 2025, A&A, 699, A107, The HOSTS survey: Suspected variable dust emission and constraints on companions around Boo
    Abstract

    Context. During the Hunt for Observable Signatures of Terrestrial Systems (HOSTS) survey by the Large Binocular Telescope Interferometer (LBTI), an excess emission from the main-sequence star, Boo (F7V spectral type, 14.5 pc distance) was observed. This excess indicates the presence of exozodiacal dust near the star's habitable zone (HZ). Previous observations with Spitzer and Herschel show no evidence of outer cold dust within their respective detection limits. Because exozodiacal dust is generally believed to originate from material located farther out in the system, its source around Boo remains unclear. Aims. We conducted additional nulling and high-contrast adaptive optics (AO) observations to spatially constrain the dust distribution, search for variability, and directly image potential companions in the system. This study presents the results of these observations and provides an interpretation of the inner system's architecture. Methods. We observed the star using the LBTI's N'-band nulling mode during three epochs in 2017, 2018, and 2023. For each epoch, we modeled and constrained the dust distribution using the standard LBTI nulling pipeline, assuming a vertically thin disk with a face-on inclination. We also performed high-contrast AO observations in the L'-band and H-band to constrain the presence of substellar companions around the star. Results. We find several solutions for the dust distribution for each epoch. However, the LBTI nulling observations are unable to discriminate between them. Using upper limits from previous observations, we constrain the representative size of the dust grains to approximately 3-5 m. We also measured a tentative increase in dust brightness at the Earth-equivalent insolation distance between 2017 and 2023. This increase corresponds to the injection of 4 10⁸4 10⁷ M of new material into the disk. We consider several options to explain the origin of the observed dust and its variability, but no clear sources are identified from the current observations, partly because our high-contrast AO observations could only constrain the presence of companions only down to 11 M_Jup at 1.3 separation.

90. West, M., De Propris, R., Einasto, M., et al., 2025, ApJL, 987, L24, Evolution of Cluster Alignments as Evidence of Large-scale Structure Formation in the Universe
    Abstract

    The Universe's large-scale structure forms a vast, interconnected network of filaments, sheets, and voids known as the cosmic web. For decades, astronomers have observed that the orientations of neighboring galaxy clusters within these elongated structures are often aligned over separations of tens of Mpc. Using the largest available catalog of galaxy clusters, we show for the first time that cluster orientations are correlated over even larger scalesup to 200300 comoving Mpcand such alignments are seen to redshifts of at least z 1. Comparison with numerical simulations suggests that coherent structures on similar scales may be expected in CDM models.

91. Farrell, K., Chandler, C., Trujillo, C., et al., 2025, ApJL, 987, L35, Recurrent Cometary Activity Discovered on Quasi-Hilda Jupiter Family Comet 362P/(457175) 2008 GO₉₈
    Abstract

    We report the discovery of recurrent activity on quasi-Hilda comet (QHC) 362P/(457175) 2008 GO₉₈. The first activity epoch was discovered during the perihelion passage of 362P in 2016, so we were motivated to observe it for recurrent cometary activity near its next perihelion passage (UT 2024 July 20). We obtained observations with the Lowell Discovery Telescope, the Astrophysical Research Consortium telescope, and the Vatican Advanced Technology Telescope and identified a second activity epoch when 362P had a true anomaly () as early as 318 . 1. We conducted archival searches of six repositories and identified images obtained with CanadaFranceHawaii Telescope MegaCam, Dark Energy Camera, Pan-STARRS 1, SkyMapper, Zwicky Transient Facility, and Las Cumbres Observatory Global Telescope network data. Using these data, we identified activity from a previously unreported time span, and we did not detect activity when 362P was away from perihelion, specifically 83 < < 318. Detection of activity near perihelion and absence of activity away from perihelion suggest thermally driven activity and volatile sublimation. Our dynamical simulations suggest 362P is a QHC, and it will remain in a combined Jupiter-family comet (JFC) and quasi-Hilda orbit over the next 1 kyr though it will become increasingly chaotic nearing the end of this timeframe. Our reverse simulations suggest 362P may have migrated from the orbit of a long-period comet (53%) or Centaur (32%); otherwise it remained a JFC (15%) over the previous 100 kyr. We recommend additional telescope observations from the community as 362P continues outbound from its perihelion on UT 2024 July 20, as well as continued observations for a third activity epoch.

92. Sheppard, S., Hsieh, H., Pokorny, P., et al., (including Thirouin, A.), 2025, ApJL, 987, L18, Colors and Dynamics of a Near-Sun Orbital Asteroid Family: 2021 PH27 and 2025 GN1
    Abstract

    We observed the dynamically similar near-Sun asteroids 2021 PH27 and 2025 GN1 for their optical colors. These objects have the lowest known semimajor axes of any asteroids. 2021 PH27 has the largest general relativistic effects of any known solar system object. The small semimajor axis and very close passage to the Sun suggest the extreme thermal and gravitational environment should highly modify these asteroids' surfaces. From g'-, r'-, i'-, and z'-band imaging, we find the colors of 2021 PH27 ( g'r'=0.580.02 , r'i'=0.120.02 , and i'z'=0.080.05 mag) to be between the two major asteroid types: the S and C classes. With a spectral slope of 6.8 0.03 percent per 100 nm, 2021 PH27 is an X-type asteroid and requires albedo or spectral features to further identify its composition. We find the dynamically similar 2025 GN1 also has very similar colors ( g'r'=0.550.06 and r'i'=0.140.04 ) as 2021 PH27, suggesting these objects are fragments from a once larger parent asteroid or 2021 PH27 is shedding material. The colors are not blue like some other near-Sun asteroids such as 3200 Phaethon that have been interpreted to be from the loss of reddening substances from the extreme temperatures. There is no evidence of activity or a large amplitude period for 2021 PH27, whereas 2025 GN1 might have a more significant rotational light curve. 2025 GN1 may have a very close encounter or hit Venus in about 2300 yr and likely separated from 2021 PH27 in the last 10 kyr.

93. Ferreira, F., Camargo, J., Boufleur, R., et al., (including Kuehn, K.), 2025, MNRAS, 540, 460, Year six photometric measurements of known Trans-Neptunian Objects and Centaurs by the Dark Energy Survey
    Abstract

    We identified known Trans-Neptunian Objects (TNOs) and Centaurs in the complete Dark Energy Survey (DES) year six catalogue (DES Y6) through the Sky Body Tracker (SkyBoT) tool. We classified our data set of 144 objects into a widely used 4-class taxonomic system of TNOs. No such previous classification was available in the literature for most of these objects. From absolute magnitudes and average albedos, an estimation of the diameters of all these objects is obtained. Correlations involving colours, orbital parameters, dynamical classes, and sizes are also discussed. In particular, our largest reddest object has a diameter of $390^{+68}_{-53}$ km and our largest cold classical, $255^{+19}_{-17}$ km. Also, a weak correlation between colour and inclination is found within the population of resonant TNOs in addition to weak correlations between colour and phase slope in different bands.

94. Choukroun, A., Marciniak, A., Durech, J., et al., (including Skiff, B.), 2025, A&A, 698, A298, Asteroid sizes determined with thermophysical model and stellar occultations
    Abstract

    Context. The sizes of many asteroids, especially slowly rotating, low-amplitude targets, remain poorly constrained due to selection effects. These biases limit the availability of high-quality data, leaving size estimates reliant on spherical shape assumptions. Such approximations introduce significant uncertainties propagating, for example, into density determinations or thermophysical and compositional studies, affecting our understanding of asteroid properties. Aims. This work targets poorly studied main-belt asteroids, for most of which no shape models were previously available. Using only high-quality, dense light curves, thermal infrared observations (systematically including WISE data), and stellar occultations, we aimed to produce reliable shape models and scale them using two independent techniques, allowing for size comparison at the end. We conducted two observing campaigns to achieve this: one to obtain dense photometric light curves and another to acquire multi-chord stellar occultations by these objects. Methods. Shape and spin models were reconstructed using light curve inversion techniques. Sizes were determined via two methods: (1) advanced thermophysical modelling using the convex inversion thermophysical model (CITPM), which optimises spin and shape models to light curve data in the visible range together with infrared data, and (2) scaling the shape models with stellar occultations. Results. We obtained precise sizes and shape models for 15 asteroids. CITPM and occultation-derived sizes agree within 5% for most cases, demonstrating the reliability of the modelling approach. Larger discrepancies are usually linked to incomplete occultation chord coverage. The study also provides insights into surface properties, including albedo, surface roughness and thermal inertia. Conclusions. The use of high-quality data, coupled with an advanced TPM that uses both thermal and visible data while allowing the shape model to be adjusted according to both types of data, enabled us to determine sizes with precision comparable to those derived from multichord stellar occultations. We resolved substantial inconsistencies in previous size determinations for target asteroids, providing good input for future studies on asteroid densities and surface properties.

95. Rector, T., Prato, L., Kerr, R., 2025, AAS, 246, 212.04, Exploring New Paradigms in Star Formation with Gaia Kinematics and Herbig-Haro Objects
    Abstract

    How does our Galaxy form stars? Some regions show rapid star formation that quickly builds star clusters, while others show much more gradual formation. What factors determine these different star formation rates? Gaia programs such as SPYGLASS have revealed an incredible diversity of young (< 50 Myr) stellar populations with a wide range of scales and star formation histories that show several compelling new patterns. In the Circinus Complex and several other populations, multi-generational star formation sequences have been discovered that can span tens of millions of years. Herbig-Haro (HH) objects embedded in the youngest components of these populations are a clear indicator of active star formation. Multi-band imaging surveys of HH objects thus provide a powerful means for determining the evolutionary state of the youngest areas within a complex star-forming region, and can therefore determine whether star formation within a multi-generational sequence is still underway and propagating into adjacent clouds. In our work to date we have identified over 180 new HH objects, revealing the youngest generation of star formation in the Aquila, Ophiuchus, and Circinus star-forming regions, among others. We present our latest results using Gaia and HH object surveys to characterize the star formation paradigms in the solar neighborhood.

96. Sciamma-O'Brien, E., Cook, J., Emran, A., et al., (including Grundy, W.), 2025, AAS, 246, 217.05, Integrated laboratory, modeling, and observational investigations of the origins of Pluto's surface dark materials
    Abstract

    Pluto's flyby by the New Horizons mission unveiled a world with surprisingly diverse surface compositions and colors and an extensive haze in its N₂-dominated atmosphere. The range of brown to yellow- and red-brown hues observed on Pluto's surface by the Ralph instrument indicate the presence of one or more colored components mixed in or superimposed on the ices. On Pluto, the volatile species in both solid and gaseous states are exposed to ultraviolet photons, galactic cosmic rays, and charged particles from the Sun, which can fragment and ionize them, resulting in chemical reactions. Haze particles resulting from the photolysis and radiolysis of gaseous N₂, CH₄, and CO in Pluto's atmosphere are expected to settle and accumulate onto the surface and could thus darken the surface and contaminate the ices. Here we present the results of an interdisciplinary research effort combining the expertise of experimentalists, modelers, and observers to assess the contribution of Pluto's atmospheric haze particles (in pure form, layers of different compositions, or as contaminants in N₂ and CH₄ ices) to the dark materials present on various regions across Pluto's surface, in order to reach a better understanding of the processes that result in the surprising diversity of colors and spectral features observed by New Horizons. We focused our study on three main regions that are covered with dark materials of very different colors and spectral features: Lowell Regio (yellow), Sputnik Planitia (pale orange), and Cthulhu (red). We first produced new laboratory Pluto aerosol analogs with the NASA Ames COsmic SImulation Chamber (COSmIC) from various gas mixtures representative of different seasons and epochs, in order to assess the climatic context and epochs of formation for the dark materials observed in each region. We then determined their complex refractive indices from reflectance and transmission measurements performed from 0.4 to 2.5 m with the NASA Ames Optical Constants Facility (OCF). In parallel we processed and conducted a statistical clustering of Pluto observations from the MVIC (Multispectral Visible Imaging Camera) and LEISA (Linear Etalon Imaging Spectral Array) instruments. Finally, we compared the resulting clustered spectra with synthetic spectra obtained with a Hapke spectral reflectance model using the complex indices of refraction of our Pluto tholins produced in COSmIC. We will discuss the results obtained from this investigation.

97. Breeland-Newcomb, K., Moskovitz, N., Levine, S., et al., (including Wasserman, L.), 2025, AAS, 246, 218.01, Quantifying Nightly Occultation Rates from a Single Telescope
    Abstract

    A stellar occultation occurs when an object in the solar system crosses an observer's line of sight to a star. The structure of the ingress or egress of an occultation can provide insight into the star's angular diameter and atmospheric structure, while an event's depth and duration can yield information about the occulting body's size and shape. This work aims to quantify the nightly frequency of these events from a single site, ultimately defining the parameters of a facility optimized for systematic observations of occultations. We start by cross-referencing the equatorial coordinates of stars in Gaia's DR3 catalogue with ephemerides of Main Belt asteroids in Lowell Observatory's astorb database. For simplicity, we run this analysis for a representative observer location at the geocenter. We calculate the number of events per night for a representative date in each season, finding 189 occultations/night in the spring, 244/night in the summer, 345/night in the fall, and 45/night in the winter. Extrapolation of these statistics suggests an upper limit of ~70,000 occultations observable from a single site annually. We evaluate the feasibility of observing each occultation based on the contrast in brightness between the object and the star, and by considering the signal-to-noise ratio achieved for a given event duration and stellar magnitude. For a 0.5-m telescope, we found roughly 9 events/night (~3,000 annually) with S/N values >2 (maximum of 150) and integration times ranging from 40 ms to 1.6 s. For a 1-m telescope, these scale to roughly 14 events/night (~5,000 annually) with S/N values >2 (maximum of 300) and integration times ranging from 20 ms to 1.6 s. This result shows that a single automated site could potentially observe as many Main Belt occultations per night as are now typically reported online. As LSST is expected to increase the number of known asteroids by a factor of 10, we anticipate these statistics to scale by a similar factor in the coming years.

98. Ardila, D., Shkolnik, E., Basset, C., et al., (including Llama, J.), 2025, AAS, 246, 233.03, SPARCS and the SmallSat Revolution: A Case Study
    Abstract

    The Star-Planet Activity Research CubeSat (SPARCS) is a NASA-funded 6U CubeSat mission designed to monitor ultraviolet (UV) radiation from low-mass stars. These stars' relatively high-frequency and high-energy UV flares significantly affect the atmospheres of orbiting exoplanets, driving atmospheric loss and altering the conditions for habitability. SPARCS aims to capture time-resolved photometric data in the far- and near-ultraviolet simultaneously, to better characterize the flares and detect the strongest and rarest among them. In addition, SPARCS is testing innovative technology, such as -doped UV detectors with near 100% internal quantum efficiency and detector-integrated metal dielectric UV bandpass filters. SPARCS has passed pre-shipment review, and it is scheduled for launch in the Fall of 2025.

    The landscape for exoplanets has changed significantly since SPARCS was first proposed, and the mission provides an interesting case study to illuminate these changes. We discuss here the role that SmallSats play in the NASA Astrophysics portfolio, and some of the lessons we have learned in the process of designing, fabricating, and testing SPARCS. These lessons include the importance of transparent communication, the difficulties in dealing with changing contractors, the challenges for NASA-funded, university-led missions, the importance of budget margins, and the crucil role that peer-learning with other small missions can have.

99. Prato, L., 2025, AAS, 246, 406.02, Mapping Inner Disk Structure in the Closest Young Binaries with He I 10830A Lines
    Abstract

    Most young stellar objects in nearby star forming regions reside in binary and multiple systems. Although circumstellar disks in these configurations are less massive and evolve more rapidly than their single star disk counterparts, many nevertheless persist for millions of years and have been shown to host young planets. Disks around the stars in the closest resolved young binaries, with separations of a few to tens of AU, are truncated at outer radii of ~1/3 the binary semi-major axis. Component-resolved, high-resolution spectra of the He I 10830A line show evidence for accretion plus winds from the stars and disks, launched over a range of radii and betraying the inner disk structure and activity. I will present results from recent He I 10830A observations, complemented with high-angular resolution data from ALMA and other facilities, for several binary systems in the Taurus region.

100. Tusay, N., Kesseli, A., Polanski, A., et al., 2025, AAS, 246, 413.02, Observations of the Ultra-Hot Jupiter WASP-82 using ESPRESSO and KPF
     Abstract

     The intense irradiation that Ultra-Hot Jupiters (UHJs) experience from their host star dissociates molecular species in the planet's atmosphere, creating gaseous neutral and ionized metals, such as Fe, Mg, Ni, etc. These planets are tidally locked due to their short orbital periods, causing a large day-to-night temperature contrast. This leads to non-uniform cloud formation, strong atmospheric winds that blow from the hot dayside to the cool nightside, and a super-rotational jet in the direction of tidally locked rotation. The relatively large signals from transmission spectra of the hot, extended atmospheres of UHJs offers the best opportunity to test atmospheric circulation and dynamics models from state-of-the-art global circulation models (GCMs). The fine radial velocity spacing offered by high resolution optical spectrographs are able to resolve ~km s^-1 winds in these exoplanetary atmospheres. Cross-correlation of atmospheric models can also measure relative abundances of metals, which primarily exhibit narrow absorption features in optical wavelengths.

     The preliminary results of our analysis of recent observations of WASP-82, using the ESPRESSO and KPF instruments, yield measurements of the spin-orbit angle (obliquity) of the UHJ around this F-type (6500 K) star using the Rossiter-McLaughlin technique. Retrieval frameworks of atmospheric models are being used to determine precise abundances of the dominant atomic and molecular species. Altogether, the results of this analysis will be compared against the similar WASP-76 to identify commonalities and differences in their heat circulation profiles.

101. Thakore, B., Negro, M., Regis, M., et al., (including Kuehn, K.), 2025, JCAP, 2025, 037, High-significance detection of correlation between the unresolved gamma-ray background and the large-scale cosmic structure
     Abstract

     Our understanding of the -ray sky has improved dramatically in the past decade, however, the unresolved -ray background (UGRB) still has a potential wealth of information about the faintest -ray sources pervading the Universe. Statistical cross-correlations with tracers of cosmic structure can indirectly identify the populations that most characterize the -ray background. In this study, we analyze the angular correlation between the -ray background and the matter distribution in the Universe as traced by gravitational lensing, leveraging more than a decade of observations from the Fermi-Large Area Telescope (LAT) and 3 years of data from the Dark Energy Survey (DES). We detect a correlation at signal-to-noise ratio of 8.9. Most of the statistical significance comes from large scales, demonstrating, for the first time, that a substantial portion of the UGRB aligns with the mass clustering of the Universe as traced by weak lensing. Blazars provide a plausible explanation for this signal, especially if those contributing to the correlation reside in halos of large mass ( 10¹⁴ M ) and account for approximately 3040% of the UGRB above 10 GeV. Additionally, we observe a preference for a curved -ray energy spectrum, with a log-parabolic shape being favored over a power-law. We also discuss the possibility of modifications to the blazar model and the inclusion of additional -ray sources, such as star-forming galaxies, misalinged active galactic nuclei, or particle dark matter.

102. Minker, K., Carry, B., Vachier, F., et al., (including Grundy, W.), 2025, A&A, 698, A136, Orbits of very distant asteroid satellites
     Abstract

     Context. The very wide binary asteroid (VWBA) population is a small subset of the population of known binary and multiple asteroids made of systems with very widely orbiting satellites and long orbital periods, on the order of tens to hundreds of days. The origin of these systems is debatable, and most members of this population are poorly characterized. Aims. We aim to develop orbital solutions for some members of the VWBA population, allowing us to constrain possible formation pathways for this unusual population. Methods. We compiled all available high-angular-resolution imaging archival data of VWBA systems from large ground- and space-based telescopes. We measured the astrometric positions of the satellite relative to the primary at each epoch and analyzed the dynamics of the satellites using the Genoid genetic algorithm. Additionally, we used a NEATM thermal model to estimate the diameters of two systems, and we modeled the orbit of Litva's inner satellite using photometric light curve observations. Results. We determine the effective diameters of binary systems (17246) Christophedumas and (22899) Alconrad to be 4.7 0.4 km and 5.2 0.3 km, respectively. We determine new orbital solutions for five systems, (379) Huenna, (2577) Litva, (3548) Eurybates, (4674) Pauling, and (22899) Alconrad. We find a significantly eccentric (e = 0.30) best-fit orbital solution for the outer satellite of (2577) Litva, moderately eccentric (e = 0.13) solutions for (22899) Alconrad, and a nearly circular solution for (4674) Pauling (e = 0.04). We also confirm previously reported orbital solutions for (379) Huenna and (3548) Eurybates. Conclusions. It is unlikely that BYORP expansion could be solely responsible for the formation of VWBAs, as only (4674) Pauling matches the necessary requirements for active BYORP expansion. It is possible that the satellites of these systems were formed through YORP spin-up and then later scattered onto very wide orbits. Additionally, we find that some members of the population are unlikely to have formed satellites through YORP spin-up, and a collisional formation history is favored. In particular, this applies to VWBAs within large dynamical families, such as (22899) Alconrad and (2577) Litva, or large VWBA systems such as (379) Huenna and NASA's Lucy mission target (3548) Eurybates.

103. Howard, A., Sinukoff, E., Blunt, S., et al., (including Polanski, A.), 2025, ApJS, 278, 52, Planet Masses, Radii, and Orbits from NASA's K2 Mission
     Abstract

     We report the masses, sizes, and orbital properties of 86 planets orbiting 55 stars observed by NASA's K2 Mission with follow-up Doppler measurements by the HIRES spectrometer at the W. M. Keck Observatory and the Automated Planet Finder at Lick Observatory. Eighty-one of the planets were discovered from their transits in the K2 photometry, while five were found based on subsequent Doppler measurements of transiting planet-host stars. The sizes of the transiting planets range from Earth-size to larger than Jupiter (13 R is typical), while the orbital periods range from less than a day to a few months. For 32 of the planets, the Doppler signal was detected with significance greater than 5 (51 were detected with >3 significance). An important characteristic of this catalog is the use of uniform analysis procedures to determine stellar and planetary properties. This includes the transit search and fitting procedures applied to the K2 photometry, the Doppler fitting techniques applied to the radial velocities (RVs), and the spectral modeling to determine bulk stellar parameters. Such a uniform treatment will make the catalog useful for statistical studies of the masses, densities, and system architectures of exoplanetary systems. This work also serves as a data release for all previously unpublished RVs and associated stellar activity indicators obtained by our team for these systems, along with derived stellar and planet parameters.

104. Thirouin, A., Noll, K., Grundy, W., et al., (including Escarzaga, F.), 2025, AJ, 169, 316, Logos-Zoe: A Contact Binary Triple System in the Trans-Neptunian Belt
     Abstract

     The trans-Neptunian object (58534) 1997 CQ₂₉ (a.k.a. Logos) is a resolved wide binary in the dynamically Cold Classical population. With Hubble Space Telescope resolved observations where the primary Logos is well separated from its secondary Zoe it can be established that Logos has a time-variable brightness. Logos' brightness varied by several tenths of a magnitude over a short timescale of hours while the brightness variability of Zoe was on a longer timescale. New unresolved ground-based observations obtained with the Lowell Discovery Telescope and the Magellan-Baade telescope confirm at least one highly variable component in this system. With our ground-based observations and photometric constraints from space-based observations, we suggest that the primary Logos is likely a close/contact binary whose rotational period is 17.43 0.06 hr for a lightcurve amplitude of 0.70 0.07 mag, while Zoe is potentially a (very) slow rotator with an unknown shape. Using the Candela software, we model the Logos-Zoe system and predict its upcoming mutual events season using rotational, physical, and mutual orbit parameters derived in this work or already published. Zoe's shape and rotational period are still uncertain, so we consider various options to better understand Zoe. The upcoming mutual event season for Logos-Zoe starts in 2026 and will last for four years with up to two events per year. Observations of these mutual events will allow us to significantly improve the physical and rotational properties of both Logos and Zoe.

105. Richey-Yowell, T., Shkolnik, E., Llama, J., et al., (including Sikora, J.), 2025, AJ, 169, 327, Stringent Limits on H 3+ Emission from the Hot Jupiters WASP-80b and WASP-69b
     Abstract

     Observations of auroras on exoplanets would provide numerous insights into planetstar systems, including potential detections of the planetary magnetic fields, constraints on host-star wind properties, and information on the thermal structures of planets. However, there have not yet been any discoveries of auroras on exoplanets. In this paper, we focus on the search for infrared auroral emission from the molecular ion H 3+ , which is common in the atmospheres of solar system planets Jupiter, Saturn, and Uranus. Using Keck/NIRSPEC high-resolution spectroscopy, we search for H 3+ emission from two hot Jupiters, WASP-80b and WASP-69b. We do not see any evidence of emission in the observed spectra when cross correlating with an H 3+ spectral model or when using an autocorrelation approach to search for any significant features. We therefore place upper limits on the total emission of 5.32 10¹⁸ W for WASP-80b and 1.64 10¹⁹ W for WASP-69b.These upper limits represent the most stringent limits to date and approach the regime of emission suspected from theoretical models.

106. Rector, T., Prato, L., Kerr, R., et al., 2025, AJ, 169, 313, The HerbigHaro Outflow Content and Star-forming Environment of Circinus West and East
     Abstract

     We report the results of a spatially compete, high-sensitivity survey for HerbigHaro (HH) outflows in the Western and Eastern Circinus molecular clouds. We have detected 28 new HH objects in Circinus West, doubling the number known in this dark nebula. We have also discovered nine outflows in Circinus East, the first to be identified here. Although both Circinus West and East appear to be located at 800 pc, their morphologies are distinct. Circinus West shows filamentary structure, while Circinus East is dominated by amorphous dark clouds. NorthEast of Circinus East, an extended distribution of young stars is centered on the 6 Myr old open cluster ASCC 79, which may have triggered the sequential formation of younger surrounding populations. New transverse velocities from Gaia show two dynamically distinct stellar populations in Circinus East; their velocity distribution is consistent with an active cloud-cloud collision between material ejected by the formation of O and B stars in ASCC 79, and a dynamically similar interloping cloud. Given the similar distances to Circinus West and East, and the presence in both of HH objectsa phenomenon associated with stellar ages of 1 Myrit is likely that these clouds are nominally related, but only Circinus East is subject to substantial feedback from the central cluster in the parent complex. This feedback appears to guide the morphology and evolution of Circinus East, resulting in a complex and possibly disruptive dynamical environment rich in star-formation potential that contrasts with the relatively quiescent environment in Circinus West.

107. Archer, H., Hunter, D., Elmegreen, B., et al., 2025, AJ, 169, 301, Stellar Populations and Molecular Gas Composition in the Low-metallicity Environment of WLM
     Abstract

     We investigate the stellar populations and molecular gas properties of a star-forming region within the dwarf irregular (dIrr) galaxy WolfLundmarkMellote (WLM). Low-metallicity dIrrs like WLM offer a valuable window into star formation in environments that are unlike those of larger, metal-rich galaxies such as the Milky Way. In these conditions, carbon monoxide (CO), typically used to trace molecular clouds, is more easily photodissociated by ultraviolet (UV) radiation, leading to a larger fraction of CO-dark molecular gas, where H₂ exists without detectable CO emission, or CO-dark gas in the form of cold H I. Understanding the molecular gas content and the stellar populations in these star-forming regions provides important information about the role of CO-bright and CO-dark gas in forming stars. Using Hubble Space Telescope imaging across five Wide Field Camera 3 UVIS bands and CO observations from the Atacama Large Millimeter Array, we examine stellar populations within and outside CO cores and the photodissociation region. Our findings indicate similar physical characteristics such as age and mass across the different environments. Assuming 2% of molecular gas is converted to stars, we estimate the molecular gas content and determine that CO-dark gas constitutes a large fraction of the molecular reservoir in WLM. These results are consistent with molecular gas estimates using a previous dust-derived CO-to-H₂ conversion factor (_CO) for WLM. These findings highlight the critical role of CO-dark gas in low-metallicity star formation.

108. Bernardinelli, P., Bernstein, G., Abbott, T., et al., (including Kuehn, K.), 2025, AJ, 169, 305, Photometry of Outer Solar System Objects from the Dark Energy Survey. II. A Joint Analysis of Trans-Neptunian Absolute Magnitudes, Colors, Light Curves and Dynamics
     Abstract

     For the 696 trans-Neptunian objects (TNOs) with absolute magnitudes 5.5 < H_r < 8.2 detected in the Dark Energy Survey, we characterize the relationships between their dynamical state and physical propertiesnamely H_r, indicating size; colors, indicating surface composition; and flux variation semiamplitude A, indicating asphericity and surface inhomogeneity. We seek "birth" physical distributions that can recreate these parameters in every dynamical class. We show that the observed colors of these TNOs are consistent with two Gaussian distributions in griz space, "near-infrared bright" (NIRB) and "near-infrared faint" (NIRF), presumably an inner and outer birth population, respectively. We find a model in which both the NIRB and NIRF H_r and A distributions are independent of current dynamical states, supporting their assignment as birth populations. All objects are consistent with a common rolling p(H_r), but NIRF objects are significantly more variable. Cold classicals (CCs) are purely NIRF, while hot classical (HC), scattered, and detached TNOs are consistent with 70% NIRB and the resonance NIRB fractions show significant variation. The NIRB components of the HCs and of some resonances have broader inclination distributions than the NIRFs, i.e. their current dynamics retains information about birth location. We find evidence for radial stratification within the birth NIRB population, in that HC NIRBs are on average redder than detached or scattered NIRBs; a similar effect distinguishes CCs from other NIRFs. We estimate total object counts and masses of each class within our H_r range. These results will strongly constrain models of the outer solar system.

109. Slyusarev, I., Shevchenko, V., Belskaya, I., et al., (including Skiff, B.), 2025, P&SS, 260, 106103, Opposition effect of M-type asteroids
     Abstract

     We present results of the observational program dedicated to search for possible diversity in opposition effect behavior of M-type asteroids. New photometric BVR observations were obtained for 10 asteroids, (325) Heidelberga, (382) Dodona, (558) Carmen, (639) Latona, (758) Mancunia, (789) Lena, (1046) Edwin, (1352) Wawel, (2582) Harimaya-Bashi, and (5615) Iskander. Five of these asteroids have diameters in the range from 5 to 40 km. For all of observed asteroids, we obtained lightcurves and magnitude-phase curves in a wide range of phase angles. We determined values of rotation periods and absolute magnitudes of these asteroids. With our new data, we doubled the number of M-type asteroids with measured opposition effect and for the first time observed opposition effect of M-type asteroids less than 40 km in diameter. We found that three asteroids, (558) Carmen, (789) Lena and (5615) Iskander, exhibit lower values of opposition effect compared to other measured M- and S-type asteroids but the slope of the linear part of the phase curve is typical for moderate-albedo surfaces. A possible explanation of their lower opposition effect is an assumption of a higher metal content on their surfaces as compared to other asteroids.

110. Kareta, T., Schambeau, C., Firgard, M., et al., 2025, PSJ, 6, 119, Activity-induced Near-infrared Spectral Variability at 29P/SchwassmannWachmann 1, 20172022
     Abstract

     29P/SchwassmannWachmann 1 (SW1) is both the first-discovered active Centaur and the most outburst-prone comet known. The nature of SW1's many outbursts, which regularly brighten the comet by 5 mag or more, and what processes power them has been of particular interest since SW1's discovery in the 1920s. In this paper, we present and model four epochs of low-resolution near-infrared spectroscopy of SW1 taken with the NASA Infrared Telescope Facility and Lowell Discovery Telescope between 2017 and 2022. This data set includes one large outburst, two periods of low activity ("quiescence" or "quiescent activity"), and one midsized outburst a few days after one of the quiescent observations. The two quiescent epochs appear similar in both spectral slope and modeled grain size distributions, but the two outbursts are significantly different. We propose that the two can be reconciled if smaller dust grains are accelerated more than larger ones, such that observations closer to the onset of an outburst are more sensitive to the finer-grained dust on the outside of the expanding cloud of material. These outbursts can thus appear very rapid, but there is still a period where the dust and gas are well coupled. We find no strong evidence of water-ice absorption features in any of our spectra, suggesting that the areal abundance of ice-dominated grains is less than 1%. We conclude with a discussion of future modeling and monitoring efforts that might be able to further advance our understanding of this object's complicated activity patterns.

111. Kerr, R., Farias, J., Prato, L., et al., 2025, ApJ, 985, 111, SPYGLASS. VI. Feedback-driven Star Formation in the Circinus Complex
     Abstract

     Young associations provide a record that traces the star formation process, and the youngest populations connect progenitor gas dynamics to the resulting stellar populations. We therefore conduct the first comprehensive overview of the Circinus Complex, an understudied and massive (1500 M) region consisting of approximately 3100 recently formed stars alongside the Circinus Molecular Cloud. We find a clear age pattern in the contiguous central region (CirCe), where younger stars are found farther from the massive central cluster, and where the velocities are consistent with uniform expansion. By comparing this structure to an analogous STARFORGE simulation, we find that the age structure and dynamics of the association are consistent with star formation in two stages: the global collapse of the parent cloud that builds the 500M central cluster ASCC 79, followed by triggered star formation in a shell swept up after the first massive stars form. We also find that filaments with a range of distances from the central cluster can naturally produce multigenerational age sequences due to differences in feedback strength and exposure. Outlying populations show velocities consistent with formation independent from the CirCe region, but with similar enough velocities that they may be difficult to distinguish from one another later in their expansion. We therefore provide a new alternative view of sequential star formation that relies on feedback from a single central cluster rather than the multiple sequential generations that are traditionally invoked, while also providing insight into the star formation history of older populations.

112. Yang, Y., Lewis, G., Erkal, D., et al., (including Kuehn, K.), 2025, ApJ, 984, 189, Flipping of the Tidal Tails of the Ophiuchus Stream due to the Decelerating Galactic Bar
     Abstract

     The Ophiuchus stellar stream presents a puzzle due to its complicated morphology, with a substructure perpendicular to the main track (spur), a broadened tail (fanning), and a shorter than expected angular extent given its old stellar population and short orbital period. The location of the stream approaches the Galactic center, implying a possible connection between its orbit and its unusual morphology. Here we demonstrate that the morphology of Ophiuchus can be attributed to its interaction with the decelerating Galactic bar, which leads to the flipping or transposition of its tidal tails. The short length of the stream is the result of stars stripped in the ancient past still remaining concentrated, and the spur, as well as the fanning, are composed of either leading or trailing tails built up of stars released at different time intervals. Our new spectroscopic data, obtained as part of the Southern Stellar Stream Spectroscopic Survey, and modeling of Ophiuchus indicate that, in the presence of the bar, an initial leading tail can be redistributed to the trailing side and vice versa, and the morphology of a stream can be reshaped. This result confirms that the Galactic bar plays a vital role in reconstructing the orbital behavior of streams passing close to the central region of the Milky Way.

113. Kao, M., Pineda, J., 2025, MNRAS, 539, 2292, Binarity enhances the occurrence rate of radiation belt emissions in ultracool dwarfs
     Abstract

     Despite a burgeoning set of ultracool dwarf (M7) radio detections, their radio emissions remain enigmatic. Open questions include the plasma source and acceleration mechanisms for the non-auroral 'quiescent' component of these objects' radio emissions, which can trace Jovian synchrotron radiation belt analogues. Ultracool dwarf binary systems can provide test beds for examining the underlying physics for these plasma processes. We extend a recently developed occurrence rate calculation framework to compare the quiescent radio occurrence rate of binary systems to single objects. This generalized and semi-analytical framework can be applied to any set of astrophysical objects conceptualized as unresolved binary systems with approximately steady-state emission or absorption. We combine data available in the literature to create samples of 179 single ultracool dwarfs (82 M dwarfs, 74 L dwarfs, and 23 T/Y dwarfs) and 25 binary ultracool dwarf systems. Using these samples, we show that quiescent radio emissions occur in $47^{+12}_{-12}$$60^{+12}_{-13}$ per cent of binaries where both components are ultracool dwarfs, depending on priors. We also show that binarity enhances the ultracool dwarf quiescent radio occurrence rate relative to their single counterparts. Finally, we discuss potential implications for the underlying drivers of ultracool dwarf quiescent radio emissions, including possible plasma sources.

114. Hon, M., Rappaport, S., Shporer, A., et al., (including Polanski, A.), 2025, ApJL, 984, L3, A Disintegrating Rocky Planet with Prominent Comet-like Tails around a Bright Star
     Abstract

     We report the discovery of BD+05 4868 Ab, a transiting exoplanet orbiting a bright (V = 10.16) K-dwarf (TIC 466376085) with a period of 1.27 days. Observations from NASA's Transiting Exoplanet Survey Satellite reveal variable transit depths and asymmetric transit profiles that are characteristic of comet-like tails formed by dusty effluents emanating from a disintegrating planet. Unique to BD+05 4868 Ab is the presence of prominent dust tails in both the trailing and leading directions that contribute to the extinction of starlight from the host star. By fitting the observed transit profile and analytically modeling the drift of dust grains within both dust tails, we infer large grain sizes (110 m) and a mass-loss rate of 10 M Gyr¹, suggestive of a lunar-mass object with a disintegration timescale of only several Myr. The host star is probably older than the Sun and is accompanied by an M-dwarf companion at a projected physical separation of 130 au. The brightness of the host star, combined with the planet's relatively deep transits (0.8%2.0%), presents BD+05 4868 Ab as a prime target for compositional studies of rocky exoplanets and investigations into the nature of catastrophically evaporating planets.

115. Mazoun, A., Bocquet, S., Mohr, J., et al., (including Kuehn, K.), 2025, PhRvD, 111, 083543, Interacting dark sector within ETHOS: Cosmological constraints from SPT cluster abundance with DES and HST weak lensing data
     Abstract

     We use galaxy cluster abundance measurements from the South Pole Telescope enhanced by multicomponent matched filter confirmation and complemented with mass information obtained using weak-lensing data from Dark Energy Survey Year 3 (DES Y3) and targeted Hubble Space Telescope observations for probing deviations from the cold dark matter paradigm. Concretely, we consider a class of dark sector models featuring interactions between dark matter (DM) and a dark radiation (DR) component within the framework of the effective theory of structure formation (ETHOS). We focus on scenarios that lead to power suppression over a wide range of scales, and thus can be tested with data sensitive to large scales, as realized, for example, for DMDR interactions following from an unbroken non-Abelian SU(N) gauge theory (interaction rate with power-law index n=0 within the ETHOS parametrization). Cluster abundance measurements are mostly sensitive to the amount of DR interacting with DM, parametrized by the ratio of DR temperature to the cosmic microwave background (CMB) temperature, DR=TDR/TCMB. We find an upper limit DR<17% at 95% credibility. When the cluster data are combined with Planck 2018 CMB data along with baryon acoustic oscillation (BAO) measurements we find DR<10%, corresponding to a limit on the abundance of interacting DR that is around 3 times tighter than that from CMB + BAO data alone. We also discuss the complementarity of weak lensing informed cluster abundance studies with probes sensitive to smaller scales, explore the impact on our analysis of massive neutrinos, and comment on a slight preference for the presence of a nonzero interacting DR abundance, which enables a physical solution to the S8 tension.

116. Lee, R., Dai, F., Howard, A., et al., (including Polanski, A.), 2025, ApJL, 983, L36, TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf
     Abstract

     We report the confirmation of TOI-6324 b, an Earth-sized (1.059 0.041 R) ultra-short-period (USP) planet orbiting a nearby (20 pc) M dwarf. Using the newly commissioned Keck Planet Finder spectrograph, we have measured the mass of TOI-6324 b 1.17 0.22 M. Because of its extremely short orbit of just 6.7 hr, TOI-6324 b is intensely irradiated by its M dwarf host and is expected to be stripped of any thick H/He envelope. We were able to constrain its interior composition and found an iron-core mass fraction (CMF = 27% 37%) consistent with that of Earth (33%) and other confirmed USPs. TOI-6324 b is the closest to an Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase-curve and secondary eclipse observations (emission spectroscopy metric = 25), which may reveal its surface mineralogy, daynight temperature contrast, and possible tidal deformation. From seven sectors of TESS data, we report a tentative detection of the optical phase-curve variation with an amplitude of 42 28 ppm.

117. Lokken, M., van Engelen, A., Aguena, M., et al., (including Kuehn, K.), 2025, ApJ, 982, 186, Superclustering with the Atacama Cosmology Telescope and Dark Energy Survey. II. Anisotropic Large-scale Coherence in Hot Gas, Galaxies, and Dark Matter
     Abstract

     Statistics that capture the directional dependence of the baryon distribution in the cosmic web enable unique tests of cosmology and astrophysical feedback. We use constrained oriented stacking of thermal SunyaevZel'dovich (tSZ) maps to measure the anisotropic distribution of hot gas 2.540 Mpc away from galaxy clusters embedded in massive filaments and superclusters. The cluster selection and orientation (at a scale of 15 Mpc) use Dark Energy Survey (DES) Year 3 data, while expanded tSZ maps from the Atacama Cosmology Telescope Data Release 6 enable a 3 more significant measurement of the extended gas compared to the technique's proof-of-concept. Decomposing stacks into cosine multipoles of order m, we detect a dipole (m = 1) and quadrupole (m = 2) at 810, as well as evidence for m = 4 signal at up to 6, indicating sensitivity to late-time non-Gaussianity. We compare to Cardinal simulations with spherical gas models pasted onto dark matter halos. The fiducial tSZ data can discriminate between two models that deplete pressure differently in low-mass halos (mimicking astrophysical feedback), preferring higher average pressure in extended structures. However, uncertainty in the amount of cosmic infrared background contamination reduces the constraining power. Additionally, we apply the technique to DES galaxy density and weak lensing to study for the first time their oriented relationships with tSZ. In the tSZ-to-lensing relation, averaged on 7.5 Mpc (transverse) scales, we observe dependence on redshift but not shape or radial distance. Thus, on large scales, the superclustering of gas pressure, galaxies, and total matter is coherent in shape and extent.

118. Dixon, M., Mould, J., Lidman, C., et al., (including Kuehn, K.), 2025, MNRAS, 538, 782, Calibrating the absolute magnitude of type Ia supernovae in nearby galaxies using [O II] and implications for H₀
     Abstract

     The present state of cosmology is facing a crisis where there is a fundamental disagreement in measurements of the Hubble constant ($H_{0}$), with significant tension between the early and late Universe methods. Type Ia supernovae (SNe Ia) are important to measuring $H_{0}$ through the astronomical distance ladder. However, there remains potential to better standardize SN Ia light curves by using known dependencies on host galaxy properties after the standard light curve width and colour corrections have been applied to the peak SN Ia luminosities. To explore this, we use the 5-yr photometrically identified SNe Ia sample obtained by the Dark Energy Survey, along with host galaxy spectra obtained by the Australian Dark Energy Survey. Using host galaxy spectroscopy, we find a significant trend with the equivalent width (EW) of the [O II] $\lambda \lambda$ 3727, 29 doublet, a proxy for specific star formation rate, and Hubble residuals. We find that the correlation with [O II] EW is a powerful alternative to the commonly used mass step after initial light-curve corrections. Applying this [O II] EW correction to 20 SNe Ia in calibrator galaxies observed with WiFeS, we examined the impact on SN Ia absolute magnitudes and $H_{0}$. Our [O II] EW corrections result in $H_{0}$ values ranging between 73.04 and 73.51 $\mathrm{km \, s^{-1} \, Mpc^{-1}}$, with a combined statistical and systematic uncertainty of $\sim 1.31 \, \mathrm{km \, s^{-1} \, Mpc^{-1}}$. However, even with this additional correction, the impact of host galaxy properties in standardizing SNe Ia appears limited in reducing the current tension ($\sim 5\sigma$) with the cosmic microwave background result for $H_{0}$.

119. Golden-Marx, J., Zhang, Y., Ogando, R., et al., (including Kuehn, K.), 2025, MNRAS, 538, 622, The hierarchical growth of bright central galaxies and intracluster light as traced by the magnitude gap
     Abstract

     Using a sample of 2800 galaxy clusters identified in the Dark Energy Survey across the redshift range $0.20 \lt z \lt 0.60$, we characterize the hierarchical assembly of bright central galaxies (BCGs) and the surrounding intracluster light (ICL). To quantify hierarchical formation we use the stellar mass-halo mass (SMHM) relation, comparing the halo mass, estimated via the mass-richness relation, to the stellar mass within the BCG + ICL system. Moreover, we incorporate the magnitude gap (M14), the difference in brightness between the BCG (measured within 30 kpc) and fourth brightest cluster member galaxy within 0.5 $R_{200,c}$, as a third parameter in this linear relation. The inclusion of M14, which traces BCG hierarchical growth, increases the slope and decreases the intrinsic scatter, highlighting that it is a latent variable within the BCG + ICL SMHM relation. Moreover, the correlation with M14 decreases at large radii. However, the stellar light within the BCG + ICL transition region (30 -80 kpc) most strongly correlates with halo mass and has a statistically significant correlation with M14. Since the transition region and M14 are independent measurements, the transition region may grow due to the BCG's hierarchical formation. Additionally, as M14 and ICL result from hierarchical growth, we use a stacked sample and find that clusters with large M14 values are characterized by larger ICL and BCG + ICL fractions, which illustrates that the merger processes that build the BCG stellar mass also grow the ICL. Furthermore, this may suggest that M14 combined with the ICL fraction can identify dynamically relaxed clusters.

120. Lilly, E., Schambeau, C., Thirouin, A., et al., 2025, RNAAS, 9, 67, Observations and Characterization of the New Active Centaur 2023 RS₆₁
     Abstract

     We report the cometary activity of the Centaur 2023 RS₆₁ (RS61) evident in our UT 2025 January 2 observations with the Lowell Discovery Telescope, showing a coma and a 5 9-long tail. The archival observations from the Pan-STARRS1 survey reveal two previously unnoticed activity episodes in 2017 and 2023, suggesting SR61 could be a rare outbursting Centaur similar to 174P/Echeclus. The outburst on UT 2017 October 10 at r_H = 13.5 au makes RS61 the second-most distant active Centaur after 95P/Chiron. We estimate a nucleus size between 4.7 km r_n 7.0 km, assuming typical Centaur geometric albedos, an upper-limit Af 245 cm and dust production rate kg s¹. As RS61 approaches the perihelion in 2028 its activity will likely increase, making this object an exciting observing target.

121. Faherty, J., Alejandro Merchan, S., Bardalez Gagliuffi, D., et al., (including Kao, M.), 2025, jwst, 7793, A Deep Dive Spectroscopic Study of an Auroral Emitting World
     Abstract

     In this JWST proposal, we will obtain NIRSpec and MRS spectra of the cold brown dwarf WISEP J193518.59-154620.3 in order to characterize a spectroscopic example of an auroral emitting extrasolar world. The methane emission seen in a Cycle 1 program on this source is also found in the G395H spectra of planetary objects (e.g. Jupiter, Uranus, Pluto) and expected in extrasolar planets therefore the detailed characterization we propose crosses substellar, exoplanet, and planetary sub-fields. At a Spitzer [3.6] band mag of ~18.1, W1935 is impossibly faint for ground based observatories therefore JWST is the only facility that can complete our science agenda. The power of this proposal will be in answering the following questions: (1) Is there a forest of CH4 and H3+ emission in W1935 like that seen in solar system objects (e.g. Jupiter, Uranus, Neptune) observed with the same NIRSpec G395H set-up? (2) Do the W1935 emission characteristics extend into the mid infrared where a retrieved model predicts we will see more emission from CH4 and NH3+? (3) Will modeling the spectrum of W1935 lead to conclusive evidence about whether the 300K temperature inversion in local thermodynamic equilibirum (LTE) is the correct interpretation of the cause of the emission or if a non-LTE (NLTE) process linked somehow to a magnetic interaction with the atmosphere might be at play? The NIRSpec and MRS spectra of W1935 would be the first ever spectroscopic study of an auroral emitting world beyond our own and would showcase the power of JWST at atmospheric characterization crossing from extrasolar worlds into the solar system.

122. Cartwright, R., Beddingfield, C., DeColibus, R., et al., (including Grundy, W.), 2025, jwst, 7813, The origin of CO2 in the Uranian system and possible geologic activity at Ariel
     Abstract

     Uranus' moons Ariel, Umbriel, Titania, and Oberon have surfaces rich in CO2 ice, and they could have subsurface saline oceans, especially Ariel. At the estimated peak surface temperatures of these moons (80-90 K), CO2 ice is volatile and should sublimate and migrate to their winter poles (20-30 K). Over time, CO2 is gradually lost due to Jeans escape and photolysis. The continued presence of CO2 indicates ongoing replenishment, either from endogenic outgassing or by radiolytic production via charged particle bombardment. Furthermore, volatile transport models suggest that the Uranian moons experience seasonal atmospheric density spikes near equinox as their cold and dark winter poles are exposed to sunlight, driving rapid sublimation of seasonal CO2 ice caps, temporarily ballooning their predicted, but yet-to-be-detected, exospheres. These seasonally-enhanced exospheres are likely very short lived, shrinking to low background levels in early spring. Ariel, however, has a young surface with large-scale fissures that might be conduits to its interior, and it exhibits some of the strongest CO2 (and CO) bands yet detected on an icy moon. Consequently, Ariel might have a sizable exosphere, sustained by venting of CO2 and CO from its interior. Cycle 4 coincides with late northern spring in the Uranus system (subsolar lat. >68N), long after a density spike from a devolatilized CO2 cap would have dissipated. The detection of a dense exosphere at Ariel would therefore support ongoing outgassing. We will observe these moons with NIRSpec IFU to investigate the origin of CO2 ice on all four moons (G235H) and determine whether Ariel has a geologically-sustained exosphere (G395H).

123. Pope, B., Blakely, D., Clark, C., et al., (including van Belle, G.), 2025, jwst, 8330, Calibration of the Brighter-Fatter Effect in AMI with a Reference Binary
     Abstract

     High resolution, high contrast imaging with JWST is severely limited by the 'brighter-fatter effect', or charge migration, whereby bright pixels nonlinearly bleed charge into their neighbours. If this problem can be resolved, the door is open to much more extensive use of JWST for high contrast imaging. We propose using the Aperture Masking Interferometer on NIRISS as an ideal calibration system, as the non-redundant mask makes phase retrieval a well-posed problem and the PSF can be accurately characterized, so that systematic effects from the detector can be separately determined. We propose training a differentiable optical model end-to-end with a neural network to represent this nonlinear detector, but existing data on point sources and flat fields do not contain enough PSF diversity to avoid over-fitting in training the neural network. We therefore request AMI and clear-pupil NIRISS observations of the nearby, well-characterized, moderately-bright M dwarf system EZ Aqr, as a 'ruler' on the sky whose precisely-known geometry will unambiguously constrain a detector model in conjunction with existing point source and flat field observations. With an accurate, data-driven model of the brighter-fatter effect in hand, it will be possible to recover strong science outcomes in exoplanet, disk, and AGN science from archival GO and GTO AMI data; plan future observations with this instrument; and pave the way for applications to enhancing coronagraphic NIRCam and Roman observations.

124. Cryan, S., Brunetto, R., Cartwright, R., et al., (including Grundy, W.), 2025, jwst, 8445, Complex Cyanides as Tracers for Unlocking the Chemical History of Trans-Neptunian Objects
     Abstract

     Cyanidescompounds that contain one or more CN functional groupshave a ubiquitous presence in astrophysical environments. The CN functional group can be incorporated into a diverse range of molecular structures, from simpler cyanides like HCN to larger, more complex polymeric structures. These compounds form and evolve through thermal, photochemical, and irradiation-driven chemical pathways. As such, cyanides are key tracers of nitrogen chemistry in a wide range of astrophysical environments.

     While C=N-bearing species have been detected in comets, the moons of giant planets, and in micrometeorites, their presence on trans-Neptunian objects (TNOs) is poorly understood. This proposal aims to firmly detect complex cyanides TNOs and investigate their origin and evolution to shed light on the molecular diversity of the primordial Solar System. By linking the molecular composition of TNOs to that of other icy bodies like comets and moons, and interstellar structures such as molecular clouds, our study will bridge crucial gaps in understanding nitrogen chemistry across different environments.

     We request observations of six medium-sized TNOs and one Centaur using the NIRSpec Fixed Slit (FS) mode to reach unprecedented high-SNR that only this observing mode of the JWST can reach. These observations will enable the robust detection of complex cyanides and associated molecules like N-H-bearing compounds and HCN, providing insights into the processes shaping N-bearing species in the Solar System. Ultimately, this work will enhance our understanding of the role of nitrogen in the emergence of biochemically relevant molecules, contributing to the broader field of astrobiology.

125. Sharkey, B., Bauer, J., Kareta, T., et al., 2025, jwst, 8663, Is the Moon an Active Source of Near-Earth Asteroids? Testing the Origins of Earth Quasi-Satellite Kamo`oalewa
     Abstract

     We propose NIRSpec IFU observations of (469219) Kamo'oalewa, a unique Earth quasi-satellite asteroid discovered in 2016. This is the first quasi-satellite to have its physical properties studied to assess its composition and origins. Analysis of previous observations with 8m-class ground observatories produced the hypothesis that it may represent the first known asteroid to have formed from lunar collisional ejecta. However, Kamo'oalewa's faintness limits any stricter tests of its material composition from ground-based observatories. Such tests require knowledge of its silicate mineralogy, the presence or absence of organic or hydrated material(s), and measurements of its size/albedo. By observing Kamo'oalewa with NIRSpec, we will comprehensively characterize the presence of these materials and provide the first measurements of its size and albedo. This program will enable strict tests of the possible lunar origin for this object, testing whether the moon acts as an entirely unpredicted source of near-Earth asteroids in conflict with fundamental population models.

126. Bocquet, S., Grandis, S., Krause, E., et al., (including Kuehn, K.), 2025, PhRvD, 111, 063533, Multiprobe cosmology from the abundance of SPT clusters and DES galaxy clustering and weak lensing
     Abstract

     Cosmic shear, galaxy clustering, and the abundance of massive halos each probe the large-scale structure of the Universe in complementary ways. We present cosmological constraints from the joint analysis of the three probes, building on the latest analyses of the lensing-informed abundance of clusters identified by the South Pole Telescope (SPT) and of the auto- and cross-correlation of galaxy position and weak lensing measurements (32pt) in the Dark Energy Survey (DES). We consider the cosmological correlation between the different tracers and we account for the systematic uncertainties that are shared between the large-scale lensing correlation functions and the small-scale lensing-based cluster mass calibration. Marginalized over the remaining cold dark matter (CDM) parameters (including the sum of neutrino masses) and 52 astrophysical modeling parameters, we measure m=0.3000.017 and 8=0.7970.026. Compared to constraints from Planck primary cosmic microwave background (CMB) anisotropies, our constraints are only 15% wider with a probability to exceed of 0.22 (1.2) for the two-parameter difference. We further obtain S88(m/0.3)0.5=0.7960.013 which is lower than the Planck measurement at the 1.6 level. The combined SPT cluster, DES 32pt, and Planck datasets mildly prefer a nonzero positive neutrino mass, with a 95% upper limit m<0.25 eV on the sum of neutrino masses. Assuming a wCDM model, we constrain the dark energy equation of state parameter w=-1.15-0.17+0.23 and when combining with Planck primary CMB anisotropies, we recover w=-1.20-0.09+0.15, a 1.7 difference with a cosmological constant. The precision of our results highlights the benefits of multiwavelength multiprobe cosmology and our analysis paves the way for upcoming joint analyses of next-generation datasets.

127. Brunetto, R., Henault, E., Cryan, S., et al., (including Grundy, W.), 2025, ApJL, 982, L8, Spectral Diversity of DiSCo's TNOs Revealed by JWST: Early Sculpting and Late Irradiation
     Abstract

     The spectral diversity of trans-Neptunian objects (TNOs) is crucial for understanding the processes that led to the formation and evolution of planetesimals in the outer solar system. Using near-IR (NIR) spectra obtained by the James Webb Space Telescope (JWST) as part of the DiSCo-TNOs large program, we report the detection of well-clustered subgroups of TNOs. A first subgroup has strong NIR features with contributions from H₂O, CO₂, CO, CH₃OH, and other organic molecules. The 2.27 m band area, commonly attributed to methanol, decreases with increasing eccentricity, which is compatible with a late destruction of CH₃OH by cosmic ion irradiation at the edge of the heliosphere. The absence of the strongest CH₃OH bands in the JWST spectra is compatible with an irradiation-induced surface stratification, with CH₃OH abundance increasing with increasing depth. A second subgroup has much weaker NIR bands, and these cannot be explained by a late irradiation scenario. This group is further divided into two subgroups (cold classical TNOs and objects with low perihelion) that are spectrally very similar except for their CO₂ band area. We propose two possible interpretations. In one scenario, the TNO subgroups sampled a similar molecular inventory in the protoplanetary disk, after which early surface processes, such as primordial sublimation or irradiation from the young Sun, sculpted the two groups before planetary migration occurred. In a second scenario, the subgroups formed in different locations of the disk where molecules were available in different abundances. A combination of both scenarios is also possible.

128. Singh, A., Mohr, J., Davies, C., et al., (including Kuehn, K.), 2025, A&A, 695, A49, Galaxy cluster matter profiles: I. Self-similarity, mass calibration, and observable-mass relation validation employing cluster mass posteriors
     Abstract

     We present a study of the weak lensing inferred matter profiles (R) of 698 South Pole Telescope (SPT) thermal Sunyaev-Zel'dovich effect (tSZE) selected and MCMF optically confirmed galaxy clusters in the redshift range 0.25 < z < 0.94 that have associated weak gravitational lensing shear profiles from the Dark Energy Survey (DES). Rescaling these profiles to account for the mass dependent size and the redshift dependent density produces average rescaled matter profiles (R/R_200c)/(_critR_200c) with a lower dispersion than the unscaled (R) versions, indicating a significant degree of self-similarity. Galaxy clusters from hydrodynamical simulations also exhibit matter profiles that suggest a high degree of self-similarity, with RMS variation among the average rescaled matter profiles with redshift and mass falling by a factor of approximately six and 23, respectively, compared to the unscaled average matter profiles. We employed this regularity in a new Bayesian method for weak lensing mass calibration that employs the so-called cluster mass posterior P(M₂₀₀|, , z), which describes the individual cluster masses given their tSZE () and optical (, z) observables. This method enables simultaneous constraints on richness -mass and tSZE detection significance -mass relations using average rescaled cluster matter profiles. We validated the method using realistic mock datasets and present observable-mass relation constraints for the SPTDES sample, where we constrained the amplitude, mass trend, redshift trend, and intrinsic scatter. Our observable-mass relation results are in agreement with the mass calibration derived from the recent cosmological analysis of the SPTDES data based on a cluster-by-cluster lensing calibration. Our new mass calibration technique offers a higher efficiency when compared to the single cluster calibration technique. We present new validation tests of the observable-mass relation that indicate the underlying power-law form and scatter are adequate to describe the real cluster sample but that also suggest a redshift variation in the intrinsic scatter of the -mass relation may offer a better description. In addition, the average rescaled matter profiles offer high signal-to-noise ratio (S/N) constraints on the shape of real cluster matter profiles, which are in good agreement with available hydrodynamical CDM simulations. This high S/N profile contains information about baryon feedback, the collisional nature of dark matter, and potential deviations from general relativity.

129. Toy, M., Wiseman, P., Sullivan, M., et al., (including Kuehn, K.), 2025, MNRAS, 538, 181, Reduction of the type Ia supernova host galaxy step in the outer regions of galaxies
     Abstract

     Using 1533 type Ia supernovae (SNe Ia) from the 5-yr sample of the Dark Energy Survey (DES), we investigate the relationship between the projected galactocentric separation of the SNe and their host galaxies and their light curves and standardization. We show, for the first time, that the difference in SN Ia post-standardization brightnesses between high- and low-mass hosts reduces from $0.078\pm 0.011$ mag in the full sample to $0.036 \pm 0.018$ mag for SNe Ia located in the outer regions of their host galaxies, while increasing to $0.100 \pm 0.014$ mag for SNe in the inner regions. The difference in the size of the mass step between inner and outer regions is $0.064\pm 0.023$ mag. In these inner regions, the step can be reduced (but not removed) using a model where the $R_V$ of dust along the line of sight to the SN changes as a function of galaxy properties. We investigate the remaining difference using the distributions of the SN Ia stretch parameter to test the inferred age of SN progenitors. Comparing red (older) environments only, outer regions have a higher proportion of high-stretch SNe and a more homogeneous stretch distribution. However, this effect cannot explain the reduction in significance of any Hubble residual step in outer regions. We conclude that the standardized distances of SNe Ia located in the outer regions of galaxies are less affected by their global host galaxy properties than those in the inner regions.

130. Nelsen, M., Ragozzine, D., Proudfoot, B., et al., (including Grundy, W.), 2025, PSJ, 6, 53, Beyond Point Masses. IV. Trans-Neptunian Object Altjira Is Likely a Hierarchical Triple Discovered through Non-Keplerian Motion
     Abstract

     Dynamically studying trans-Neptunian object (TNO) binaries allows us to measure masses and orbits. Most of the known objects appear to have only two components, except (47171) Lempo, which is the single known hierarchical triple system with three similar-mass components. Though hundreds of TNOs have been imaged with high-resolution telescopes, no other hierarchical triples (or trinaries) have been found among solar system small bodies, even though they are predicted in planetesimal formation models such as gravitational collapse after the streaming instability. By going beyond the point-mass assumption and modeling TNO orbits as non-Keplerian, we open a new window into the shapes and spins of the components, including the possible presence of unresolved "inner" binaries. Here we present evidence for a new hierarchical triple, (148780) Altjira (2001 UQ₁₈), based on non-Keplerian dynamical modeling of the two observed components. We incorporate two recent Hubble Space Telescope observations, leading to a 17 yr observational baseline. We present a new open-source Bayesian point-spread function fitting code called nPSF that provides precise relative astrometry and uncertainties for single images. Our non-Keplerian analysis measures a statistically significant (2.5) nonspherical shape for Altjira. The measured J ₂ is best explained as an unresolved inner binary, and an example hierarchical triple model gives the best fit to the observed astrometry. Using an updated non-Keplerian ephemeris (which is significantly different from the Keplerian predictions), we show that the predicted mutual event season for Altjira has already begun, with several excellent opportunities for observations through 2030.

131. Gatti, M., Campailla, G., Jeffrey, N., et al., (including Kuehn, K.), 2025, PhRvD, 111, 063504, Dark Energy Survey Year 3 results: Simulation-based cosmological inference with wavelet harmonics, scattering transforms, and moments of weak lensing mass maps. II. cosmological results
     Abstract

     We present a simulation-based cosmological analysis using a combination of Gaussian and non-Gaussian statistics of the weak lensing mass (convergence) maps from the first three years of the Dark Energy Survey. We implement the following: (1) second and third moments; (2) wavelet phase harmonics; (3) the scattering transform. Our analysis is fully based on simulations, spans a space of seven w Cold Dark Matter (wCDM) cosmological parameters, and forward models the most relevant sources of systematics inherent in the data: masks, noise variations, clustering of the sources, intrinsic alignments, and shear and redshift calibration. We implement a neural network compression of the summary statistics, and we estimate the parameter posteriors using a simulation-based inference approach. Including and combining different non-Gaussian statistics is a powerful tool that strongly improves constraints over Gaussian statistics (in our case, the second moments); in particular, the figure of merit (S8,m) is improved by 70% (CDM) and 90% (wCDM). When all the summary statistics are combined, we achieve a 2% constraint on the amplitude of fluctuations parameter S88(m/0.3)0.5, obtaining S8=0.7940.017 (CDM) and S8=0.8170.021 (wCDM), and a 10% constraint on m, obtaining m=0.2590.025 (CDM) and m=0.2730.029 (wCDM). In the context of the wCDM scenario, these statistics also strengthen the constraints on the parameter w, obtaining w<-0.72. The constraints from different statistics are shown to be internally consistent (with a p-value>0.1 for all combinations of statistics examined). We compare our results to other weak lensing results from the first three years of the Dark Energy Survey data, finding good consistency; we also compare with results from external datasets, such as Planck constraints from the cosmic microwave background, finding statistical agreement, with discrepancies no greater than <2.2.

132. Crossfield, I., Polanski, A., Robertson, P., et al., 2025, AJ, 169, 89, OrCAS: Origins, Compositions, and Atmospheres of Sub-Neptunes. I. Survey Definition
     Abstract

     Sub-Neptunesvolatile-rich exoplanets smaller than Neptuneare intrinsically the most common type of planet known. However, the formation and nature of these objects, as well as the distinctions between subclasses (if any), remain unclear. Two powerful tools to tease out the secrets of these worlds are measurements of (i) atmospheric composition and structure revealed by transit and/or eclipse spectroscopy, and (ii) mass, radius, and density revealed by transit photometry and Doppler spectroscopy. Here, we present OrCAS, a survey to better elucidate the origins, compositions, and atmospheres of sub-Neptunes. This radial velocity survey uses a repeatable, quantifiable metric to select targets suitable for subsequent transmission spectroscopy and address key science themes about the atmospheric and internal compositions and architectures of these systems. Our survey targets 26 systems with transiting sub-Neptune planet candidates, with the overarching goal of increasing the sample of such planets suitable for subsequent atmospheric characterization. This paper lays out our survey's science goals, defines our target prioritization metric, and performs light-curve fits and statistical validation using existing TESS photometry and ground-based follow-up observations. Our survey serves to continue expanding the sample of small exoplanets with well-measured properties orbiting nearby bright stars, ensuring fruitful studies of these systems for many years to come.

133. Corbett, T., Doner, A., Horanyi, M., et al., (including Grundy, W.), 2025, ApJL, 979, L50, Production, Transport, and Destruction of Dust in the Kuiper Belt: The Effects of Refractory and Volatile Grain Compositions
     Abstract

     The Venetia Burney Student Dust Counter (SDC) on board the New Horizons spacecraft measures the spatial and size distributions of dust along its trajectory. Models based on early SDC measurements predicted a peak dust number density at a heliocentric distance of 40 au, followed by a rapid decline. Instead, SDC observed dust fluxes 23 times higher than predicted between 40 and 60 au. One potential explanation for this discrepancy is that SDC may be encountering icy grains with different dynamical behavior than previously modeled silicate grains. Due to ultraviolet photosputtering, waterice grains rapidly erode and migrate outward, significantly contributing to the measured dust number densities only at distances 40 au. We present a model of silicate and ice grain dynamics in the outer solar system, considering gravitational and radiation forces and grain erosion. Using SDC data, we estimate that the mass production rate of ice grains between 0.1 and 10 m in the Kuiper Belt (KB) would need to be 2070 times higher than that of silicate grains. However, KB grains are expected to be refractory/volatile mixtures rather than pure silicate or ice. Thus, we briefly explore simple models of more realistic mixed-grain cases to further gauge the effects of grain composition on the equilibrium dust distribution. Future SDC measurements at greater distances will test the model predictions and further constrain silicate and ice grain production rates in the KB.

134. Battle, A., Reddy, V., Sanchez, J., et al., (including Kareta, T.), 2025, PSJ, 6, 31, Long-term Spectral Monitoring of Active Asteroid (6478) Gault: Implications for the H Chondrite Parent Body
     Abstract

     Active asteroid (6478) Gault underwent outbursts between late 2018 and early 2019 with tails morphologically similar to the ejecta from Dimorphous following the Double Asteroid Redirection Test impact. Multiple studies investigated the dust properties, confirmed that Gault is an S-type Phocaea-family asteroid, and obtained a 2.5 hr rotation period consistent with being near the critical rotation period for breakup. We present results from near-infrared spectral monitoring of Gault on one night during a period of activity and five nights across 3 yr after activity ceased in order to understand the evolution of surface mineralogy over time. Spectral band parameters show an average Band I center of 0.920 0.005 m, Band II center of 2.04 0.13 m, and band area ratio of 1.33 0.04. These values correspond to an olivinepyroxene ratio of 0.40, 18.7 mol% fayalite, and 17.2 mol% ferrosiliteall of which are consistent with an H chondrite that has low levels of thermal metamorphism. Three meteorite analogs were identified that are H chondrites with petrologic types between H3.4 and H4. The low-level thermal metamorphism interpretation of Gault's surface suggests that it formed from the outermost portion of the progenitor of the Phocaea family, assuming an "onion shell' structure, which was catastrophically disrupted 1.2 Gyr ago. We discuss implications of Gault's surface composition to better understand this H chondrite parent body, with the suggestion that more dynamical and spectral analyses be performed for members of the Phocaea family.

135. Pinilla-Alonso, N., Brunetto, R., De Pra, M., et al., (including Stansberry, J.), 2025, NatAs, 9, 230, A JWST/DiSCo-TNOs portrait of the primordial Solar System through its trans-Neptunian objects
     Abstract

     The detection of molecules on the coldest and outermost objects in our Solar System has long been limited by the terrestrial atmosphere and sensitivity of the available instrumentation. However, near-infrared observations by the James Webb Space Telescope have provided an unprecedented view of the molecular diversity on the surfaces of trans-Neptunian objects (TNOs). Using the low spectral resolution PRISM mode on the near-infrared spectrograph as part of the Cycle 1 large programme, `Discovering the Surface Composition of trans-Neptunian objects', we report the detection of several molecular ices throughout the TNO population, including H₂O, CO₂, ¹³CO₂, CO, CH₃OH and complex molecules and refractory materials containing aliphatic C-H, CN, O-H and N-H bonds. As a result of the imprint that these molecules leave on the spectra, three main compositional groups consistently emerge from multiple independent cluster analyses. Our results unlock the long-standing question of the interpretation of colour diversity, providing the much-needed compositional information. The marked separation of the three spectral clusters reveals sharp variations in the surface molecular constituents. The C/O and (CH + NH)/(C + O) ratios on the surface of TNOs are the primary indicators of the spectral differences among the three TNO compositional groups observed. We propose that these objects are fossil remnants of icy planetesimals, and that the three compositional groups provide a picture of the ice retention lines in the Solar System that likely occurred in the outer protoplanetary disk, possibly just before a major planetary migration.

136. Licandro, J., Pinilla-Alonso, N., Holler, B., et al., (including Stansberry, J.), 2025, NatAs, 9, 245, Thermal evolution of trans-Neptunian objects through observations of Centaurs with JWST
     Abstract

     Centaurs are small bodies orbiting between Jupiter and Neptune and behave as an intermediate population between trans-Neptunian-belt objects and Jupiter-family comets. As such, their surface composition and evolutionary processes are key to understanding the Solar System's history. However, the mechanisms driving their transformation and the impact of thermal processing on their surfaces remain open questions. Here we examined the surface properties of five Centaurs using the James Webb Space Telescope near-infrared spectrograph reflectance spectra (0.6-5.3 m). They exhibit considerable diversity in surface composition. Our analysis indicates that Centaurs can be split into two main categories, which is also observed for trans-Neptunian objects: one group has surfaces composed of refractory materials with some water ice, whereas the other is dominated by carbon-based materials. Additionally, two of the five objects have primarily refractory surfaces with minimal volatiles, suggesting a high concentration of primitive, comet-like dust. We suggest that the observed Centaur surfaces reflect their transitional states, as they are shifting from being ice-rich bodies to progressively becoming more dominated by non-volatile materials as they approach the Sun. Such thermal processing may have changed the surface properties of other similar Solar System bodies, like comets, Jupiter trojans and D-type asteroids.

137. Rommel, F., Fernandez-Valenzuela, E., Proudfoot, B., et al., (including Grundy, W.), 2025, PSJ, 6, 48, Stellar Occultation Observations of (38628) Huya and Its Satellite: A Detailed Look into the System
     Abstract

     The physical and orbital parameters of trans-Neptunian objects provide valuable information about the solar system's formation and evolution. In particular, the characterization of binaries provides insights into the formation mechanisms that may be playing a role at such large distances from the Sun. Studies show two distinct populations, and (38628) Huya occupies an intermediate position between the unequal-sized binaries and those with components of roughly equal sizes. In this work, we predicted and observed three stellar occultation events by Huya. Huya and its satellitewere detected during occultations in 2021 March and again in 2023 June. Additionally, an attempt to detect Huya in 2023 February resulted in an additional single-chord detection of the secondary. A spherical body with a minimum diameter of D = 165 km can explain the three single-chord observations and provide a lower limit for the satellite size. The astrometry of Huya's system, as derived from the occultations and supplemented by observations from the Hubble Space Telescope and Keck Observatory, provided constraints on the satellite orbit and the mass of the system. Therefore, assuming the secondary is in an equatorial orbit around the primary, the limb fitting was constrained by the satellite orbit position angle. The system density, calculated by summing the most precise measurement of Huya's volume to the spherical satellite average volume, is ₁ = 1073 66 kg m³. The density that the object would have assuming a Maclaurin equilibrium shape with a rotational period of 6.725 0.01 hr is ₂ = 768 42 kg m³. This difference rules out the Maclaurin equilibrium assumption for the main body shape.

138. Hirabayashi, M., Raducan, S., Sunshine, J., et al., (including Moskovitz, N.), 2025, NatCo, 16, 1602, Elliptical ejecta of asteroid Dimorphos is due to its surface curvature
     Abstract

     Kinetic deflection is a planetary defense technique delivering spacecraft momentum to a small body to deviate its course from Earth. The deflection efficiency depends on the impactor and target. Among them, the contribution of global curvature was poorly understood. The ejecta plume created by NASA's Double Asteroid Redirection Test impact on its target asteroid, Dimorphos, exhibited an elliptical shape almost aligned along its north-south direction. Here, we identify that this elliptical ejecta plume resulted from the target's curvature, reducing the momentum transfer to 44 10% along the orbit track compared to an equivalent impact on a flat target. We also find lower kinetic deflection of impacts on smaller near-Earth objects due to higher curvature. A solution to mitigate low deflection efficiency is to apply multiple low-energy impactors rather than a single high-energy impactor. Rapid reconnaissance to acquire a target's properties before deflection enables determining the proper locations and timing of impacts.

139. Henault, E., Brunetto, R., Pinilla-Alonso, N., et al., (including Stansberry, J.), 2025, A&A, 694, A126, Irradiation origin and stability of CO on trans-Neptunian objects: Laboratory constraints and observational evidence from JWST/DiSCo-TNOs
     Abstract

     Context. The James Webb Space Telescope large program DiSCo-TNOs has recently shown that CO₂ ice is ubiquitous on 54 mediumsize trans-Neptunian objects (TNOs). TNO surfaces are found to define three main spectral and thus compositional groups that are likely linked to their position before planetary migration. CO ice is observed on the spectral type that is richest in CO₂ and on the type that is richer in CH₃OH and organics. Considerations on the thermal evolution of TNOs predicted the depletion of hypervolatiles such as CO from their surface layers, however. Aims. We investigate a potential irradiation origin of CO as well as its stability by studying the distribution of CO in two TNO compositional types and compared it with irradiation experiments. Methods. We studied the 4.68 m band of CO and the 2.70 m band of CO₂ to probe the relation between the two molecules in 33 TNOs. We performed ion irradiation experiments on CO₂ and CH₃OH ices at 45 and 60 K with 30 keV H⁺ . We compared the laboratory spectra to TNO observations by focusing on the band areas and positions. Results. We find that the two types of surfaces in which CO is detected are very distinct in terms of their relative abundances and chemical environment. CO that is observed on surfaces that are rich in CO₂ are consistent with being produced by CO₂ irradiation, specifically, at 45 K. On objects that are rich in CH₃OH and complex organics, CO is more likely formed by irradiation of CH₃OH. As the CO band areas are only partly related with temperature, the chemical environment plays a major role in the CO retention. Conclusions. We find that the CO that is observed on TNO surfaces is compatible with being a secondary molecule that is entirely formed by late irradiation processes. Its abundance and stability is mostly controlled by the matrix from which it formed.

140. Thomas, L., Hebrard, G., Kellermann, H., et al., (including Polanski, A.), 2025, A&A, 694, A143, TOI-5108 b and TOI 5786 b: Two transiting sub-Saturns detected and characterized with TESS, MaHPS, and SOPHIE
     Abstract

     We report the discovery and characterization of two sub-Saturns from the Transiting Exoplanet Survey Satellite (TESS) using high- resolution spectroscopic observations from the MaHPS spectrograph at the Wendelstein Observatory and the SOPHIE spectrograph at the Haute-Provence Observatory. Combining photometry from TESS, KeplerCam, LCOGT, and MuSCAT2, along with the radial velocity measurements from MaHPS and SOPHIE, we measured precise radii and masses for both planets. TOI-5108 b is a sub-Saturn, with a radius of 6.6 0.1 R and a mass of 32 5 M. TOI-5786 b is similar to Saturn, with a radius of 8.54 0.13 R and a mass of 73 9 M. The host star for TOI-5108 b is a moderately bright (Vmag 9.75) G-type star. TOI-5786 is a slightly dimmer (Vmag 10.2) F-type star. Both planets are close to their host stars, with periods of 6.75 days and 12.78 days, respectively. This puts TOI-5108 b just within the bounds of the Neptune desert, while TOI-5786 b is right above the upper edge. We estimated hydrogen-helium (H/He) envelope mass fractions of 38% for TOI-5108 b and 74% for TOI-5786 b. However, when using a model for the interior structure that includes tidal effects, the envelope fraction of TOI-5108 b could be much lower (~20%), depending on the obliquity. We estimated mass-loss rates between 1.0 x 10⁹ g/s and 9.8 x 10⁹ g/s for TOI-5108 b and between 3.6 x 10⁸ g/s and 3.5 x 10⁹ g/s for TOI-5786 b. Given their masses, both planets could be stable against photoevaporation. Furthermore, at these mass-loss rates, there is likely no detectable signal in the metastable helium triplet with the James Webb Space Telescope (JWST). We also detected a transit signal for a second planet candidate in the TESS data of TOI-5786, with a period of 6.998 days and a radius of 3.83 0.16 R. Using our RV data and photodynamical modeling, we were able to provide a 3- upper limit of 26.5 M for the mass of the potential inner companion to TOI-5786 b.

141. Burdanov, A., de Wit, J., Broz, M., et al., (including Grundy, W., Kareta, T., Moskovitz, N., Thirouin, A.), 2025, Natur, 638, 74, JWST sighting of decametre main-belt asteroids and view on meteorite sources
     Abstract

     Asteroid discoveries are essential for planetary-defence efforts aiming to prevent impacts with Earth¹, including the more frequent² megaton explosions from decametre impactors^{3, 4, 56}. Although large asteroids (100 kilometres) have remained in the main belt since their formation⁷, small asteroids are commonly transported to the near-Earth object (NEO) population^8,9. However, owing to the lack of direct observational constraints, their sizefrequency distribution (SFD)which informs our understanding of the NEOs and the delivery of meteorite samples to Earthvaries substantially among models^{10, 11, 12, 1314}. Here we report 138 detections of some of the smallest asteroids (10 metres) ever observed in the main belt, which were enabled by JWST's infrared capabilities covering the emission peaks of the asteroids¹⁵ and synthetic tracking techniques^{16, 1718}. Despite small orbital arcs, we constrain the distances and phase angles of the objects using known asteroids as proxies, allowing us to derive sizes through radiometric techniques. Their SFD shows a break at about 100 metres (debiased cumulative slopes of q = 2.66 0.60 and 0.97 0.14 for diameters smaller and larger than roughly 100 metres, respectively), suggestive of a population driven by collisional cascade. These asteroids were sampled from several asteroid familiesmost probably Nysa, Polana and Massaliaaccording to the geometry of pointings considered here. Through further long-stare infrared observations, JWST is poised to serendipitously detect thousands of decametre-scale asteroids across the sky, examining individual asteroid families¹⁹ and the source regions of meteorites^13,14 'in situ'.

142. Camilleri, R., Davis, T., Hinton, S., et al., (including Kuehn, K.), 2025, MNRAS, 537, 1818, The Dark Energy Survey Supernova Program: an updated measurement of the Hubble constant using the inverse distance ladder
     Abstract

     We measure the current expansion rate of the Universe, Hubble's constant $H_0$, by calibrating the absolute magnitudes of supernovae to distances measured by baryon acoustic oscillations (BAO). This 'inverse distance ladder' technique provides an alternative to calibrating supernovae using nearby absolute distance measurements, replacing the calibration with a high-redshift anchor. We use the recent release of 1829 supernovae from the Dark Energy Survey spanning $0.01\lt z\lt 1.13$ anchored to the recent baryon acoustic oscillation measurements from Dark Energy Spectroscopic Instrument (DESI) spanning $0.30 \lt z_{\mathrm{eff}}\lt 2.33$. To trace cosmology to $z=0$, we use the third-, fourth-, and fifth-order cosmographic models, which, by design, are agnostic about the energy content and expansion history of the universe. With the inclusion of the higher redshift DESI-BAO data, the third-order model is a poor fit to both data sets, with the fourth-order model being preferred by the Akaike Information Criterion. Using the fourth-order cosmographic model, we find $H_0=67.19^{+0.66}_{-0.64}\mathrm{~km} \mathrm{~s}^{-1} \mathrm{~Mpc}^{-1}$, in agreement with the value found by Planck without the need to assume Flat-$\Lambda$CDM. However, the best-fitting expansion history differs from that of Planck, providing continued motivation to investigate these tensions.

143. Simon, A., Kaplan, H., Reuter, D., et al., (including Grundy, W.), 2025, PSJ, 6, 7, Lucy L'Ralph In-flight Calibration and Results at (152830) Dinkinesh
     Abstract

     The L'Ralph instrument is a key component of NASA's Lucy mission, intended to provide spectral image data of multiple Jupiter Trojans. The instrument operates from 0.35 to 4 m using two focal plane assemblies: a 350950 nm multispectral imager, Multi-spectral Visible Imaging Camera (MVIC), and a 0.974 m imaging spectrometer, Linear Etalon Imaging Spectral Array (LEISA). Instrument calibration was established through ground testing before launch and has been monitored during cruise utilizing internal calibration sources and stellar targets. In-flight data have shown that the instrument thermal performance is exceeding expectations, allowing for early updates to LEISA radiometric and pointing calibrations. MVIC radiometric performance remains stable more than 3 yr since launch. The serendipitous identification of a new flyby target, (152830) Dinkinesh, allowed testing of instrument performance and interleaved LEISA and MVIC acquisitions on an asteroid target. Both MVIC and LEISA obtained data of Dinkinesh and its moon, Selam, demonstrating that they show good spectral agreement with an S- or Sq-type asteroid, along with evidence of a 3 m absorption feature.

144. Menk, A., Zhang, Q., 2025, AAS, 245, 103.04, Investigating the Great September Comet of 1882
     Abstract

     The Great September Comet of 1882 was the brightest known member of the Kreutz family, the only known group of sungrazing comets. We modeled the coma dust surrounding the comet's nucleus to find its physical radius using past observations of the comet between the Earth and the Sun. Measuring the comet "before the disappearance [in front of the Sun] gave 4 arcseconds for the diameter[...]" (Elkin, 1882, p. 22), and another sighting "estimated [the comet] to be still some 5 arcseconds in diameter" (Finlay, 1882, p. 23). The model is based on reports of the comet's observed angular diameters and forward scattering appearance created when the incoming and diffracted sunlight are in the same direction. To account for the reported color of the comet, the average dust size produced needed to be no larger than 1 m in diameter. The calculated dust production rate of 3.8710⁷ 1.710⁷ kg/s and the derived estimate that 4.2[+1.1,-1.0]% of the sunlight reaching the comet was used to sublimate water yielded a comet size of 17.4[+7.3,-3.3] km in radius. Unlike daily visible Kreutz objects, the Great Comet likely resembled the original progenitor, containing a large fraction of the total mass of the family.

145. Joshi, L., Belkhodja, I., Naaman, L., et al., (including Burt, B.), 2025, AAS, 245, 103.12, Spectral Analysis of Mars Trojans: Is there a Martian Link?
     Abstract

     Understanding the compositions of Mars Trojans is crucial in determining their potential relationship to Mars or other parent bodies. This study employs the Pearson's chi-square () test to compare the visible and near-infrared (VNIR) reflectance spectra of seven asteroids against approximately 11,000 laboratory spectra from meteoritic, terrestrial, synthetic, Apollo, and Luna samples. First, we validate the technique using three well-studied asteroids - (4) Vesta, (6) Hebe, and (19) Fortuna - to confirm previously established spectral matches. To determine spectral analogs, we then apply the test to four Mars Trojans: (5261) Eureka, (101429) 1998 VF31, (311999) 2007 NS2, and (385250) 2001 DH47. For asteroids potentially affected by space weathering, reddening effects are removed. The top matches for the Mars Trojans show notable spectral similarities with Martian meteorites and minerals formed by igneous processes, suggesting a possible Martian origin for the Mars Trojans. However, the possibility that these bodies could be fragments of a disrupted differentiated parent body cannot be ruled out. This study highlights the value of the test as a preliminary tool for identifying spectral analogs and exploring possible surface compositions of asteroids.

146. Spiro, L., Knight, M., Schleicher, D., et al., (including Skiff, B.), 2025, AAS, 245, 103.21, Analyzing CN Coma Morphology to Investigate Correlations Between Cometary Age and Dynamical Classification
     Abstract

     Comets are considered the most primitive remnants of the solar system's formation. However, little work has been done to analyze comet morphology spanning a large comet imaging database. Almost all research regarding cometary coma morphology has been focused on individual comets. Little large-scale comparative analysis has been done to investigate correlations between coma morphological properties and the overall evolution of comets as they undergo repeated passes through the inner solar system. Our database is one of the largest available to study coma morphology.

     We have and are continuing to collect imaging data for roughly 80 comets with specialized CN gas narrowband imaging taken using the Lowell Discovery Telescope (4.3m), Lowell 42in Hall Telescope, the Lowell 31in telescope, and/or the Southern Astrophysical Research (SOAR) Telescope (4.1m). Our current work in adding two more CN imaging datasets, 12P/Pons-Brooks and 13P/Olbers, is of particular significance as it adds to only five datasets in our archive that fall within the infrequently studied Halley-type class of comets. Halley-type comets are in their simplest form Oort Cloud comets which have been perturbed into shorter "long-period" orbits. They are thought to be more evolved than other Oort Cloud comets, but less evolved than Jupiter family comets which originate in the Kuiper Belt region. Given the conventional wisdom that older surfaces have activity confined to smaller regions on the surface, there should be a direct correlation between the amount of distinct features observed in the coma of a comet such as jets and its dynamical age. We will analyze qualitative and quantitative morphological properties of our database which has been enhanced using standard image processing and enhancement techniques. Analyzing various visual properties (jet analysis, dust features, etc.) in conjunction with orbital properties (dynamical class, Tisserand parameter, etc.) and, when available, various other physical properties (rotation period, pole orientation, etc.), we will look for statistical correlations between cometary "age" and the aforementioned properties.

147. Smith, N., Beasor, E., Close, L., et al., (including Kueny, J.), 2025, AAS, 245, 163.13, MagAO-X images of the inner core of VY Canis Majoris: A disk and a companion
     Abstract

     We present optical images of VY Canis Majoris obtained with the extreme adaptive-optics system MagAO-X that resolve new detailed structure in the bright core of the nebula around this extreme red supergiant. There are two key results: (1) We detect a separate point source located about 0.12 arcsec away from the central RSG's position. This is plausibly a moderately massive main-sequence star that may be a companion in a binary system. Although the separation is quite wide, this companion may nevertheless cause strong interaction if it has an eccentric orbit, since the radius of the RSG is so large. (2) The central source is not a point source, but instead shows complex resolved asymmetric structure. In particular, the bright central source has a resolved size comparable to the radius where dust forms in the wind, and it appears to be bisected by a dark lane and has elongated structure that may be indicative of an extended circumstellar disk with a radius of 10 R. The orientation of this potential disk (elongated SE/NW) is aligned with larger structures in the nebula, and is perpendicular to a proposed bipolar outflow axis. These two features may be related if the candidate companion star has an eccentric orbit that sweeps through the inner wind/envelope of the RSG. Regardless of the physical origin, this dense asymmetric circumstellar material is emblematic of disks or shells inferred to exist around Type II and Type IIn supernova progenitors, and is vastly different from the winds of normal RSGs.

148. Park, N., Shkolnik, E., Llama, J., 2025, AAS, 245, 172.05, Correlating Solar Coronal Mass Ejections (CMEs) with Far-Ultraviolet (FUV) Flares to better understand the space weather of exoplanets around Sun-like Stars
     Abstract

     Stellar coronal mass ejections (CMEs) affect planetary habitability by disrupting the stability of planetary atmospheres. While stellar flares have been characterized at a wide range of wavelengths, the physical properties of stellar CMEs remain completely unconstrained due to the lack of conclusive stellar CME detections. In this context, our Sun is critical for CMEs from solar-type stars. Using three different space missions detecting CMEs, X-ray flares and far-ultraviolet (FUV), where the stellar flares are and will be routinely observed (CME rate and mass from LASCO/SOHO, X-ray flare information from XRS/GOES, and far-ultraviolet flare peak flux from AIA1600/SDO), we present a peak flare flux-CME mass correlation that builds upon results from Aarnio et al. (2011). The solar data used in this study covers two entire Solar Cycles (Cycle 23 and 24; 1996-2019). These correlations can predict the extent of CME mass release from associated flare observations for other Sun-like stars. Our result can aid in characterizing stellar mass-loss rates and in assessing the impact on exoplanet atmospheric evolution that affects the potential habitability of exoplanets.

149. Richey-Yowell, T., Shkolnik, E., Llama, J., et al., (including Sikora, J.), 2025, AAS, 245, 172.06, In Search of Exoplanet Infrared Aurorae: Constraints from Two Hot Jupiters
     Abstract

     Infrared (IR) H3+ aurorae are dynamic probes of star-planet interactions. Aurorae can provide detections of the planetary magnetic fields, constrain host-star wind properties, and deliver information on the thermal structures of planets. Decades of work towards understanding the IR aurorae of Jupiter, Saturn, and Uranus prepared us for applying similar methods to exoplanets. We will present the history of IR auroral searches on exoplanets and our team's own recent work with Keck NIRSPEC to search for molecular H3+ auroral signatures on the hot Jupiters WASP-69b and WASP-80b. While we do not detect H3+ from these planets, we place the most stringent upper limits on H3+ emission to date and approach the regime of emission suspected from theoretical models. Finally, we will discuss the future of H3+ searches and how next-generation observatories may open the path to potentially numerous detections of IR aurorae.

150. Spencer, L., Benson, C., Bonato, M., et al., (including van Belle, G.), 2025, AAS, 245, 209.22, Sub-arcsecond Far-infrared space-based double Fourier interferometer simulations and simulation tools
     Abstract

     Sub-arcsecond angular resolution hyperspectral observations are significant future milestones in the Far-Infrared (far-IR) region of the electromagnetic spectrum. Such observations require a space-based interferometer observatory with baselines of at least tens of meters in length. While end-to-end demonstration of such technology from a space-based platform has yet to be done, many of the instrument subsystems are already at a flight-ready TRL level. Furthermore, such mission concepts have been considered in design studies and related activities in the past. The Space Infrared Interferometric Telescope (SPIRIT) and the Far Infrared Interferometer (FIRI) are two such examples of two-element, structurally connected spatial-spectral far-IR space-based interferometers that have been previously considered by NASA and ESA as mission concepts. Building on this groundwork, the Far Infrared Space Interferometer Critical Assessment (FISICA) studied FIRI in detail, and to this end, developed both the Far-infrared Interferometer Instrument Simulator (FIInS), and an open-source Python based version (pyFIInS). This software functions as a simulation tool for modeling a FIRI-like interferometer and simulating the output hyperspectral datacubes of double-Fourier interferometer (DFI) astronomical observations.

     Here we present recent simulation results of model astronomical targets of interest for a far-IR DFI instrument suite for a sample of unique science cases. We also present ongoing expansion of pyFIInS code towards an end-to-end simulation software suite. This software suite, provided as an open-source community tool, includes default configurations for multiple interferometer point design concepts and observing modes, allowing users to explore the promise and potential of space-based far-IR DFI instrumentation. The software tools presented in this work enable detailed study of double Fourier interferometry in the far-IR and thus allow exploration of the unique capabilities of such instrumentation.

151. Marin, L., Massey, P., Skiff, B., et al., 2025, AAS, 245, 211.04, The Discovery of Three Galactic Wolf-Rayet Stars
     Abstract

     Wolf-Rayet stars (WRs) are evolved massive stars in the brief, evolved stage before they undergo core collapse. Not only are they rare, but they also can be particularly difficult to find in the Milky Way due to the high extinction in the Galactic plane. We found three new Galactic WRs that were previously classified as H emission stars. Thanks to Gaia spectra, we were able to identify the broad, strong emission lines that characterize WRs. Using the Lowell Discovery Telescope and the DeVeny spectrograph, we obtained spectra for each star. Two are WC9s, and the third is a WN6 + O6.5 V binary. The latter is a known eclipsing system with a 4.4 day period from ASAS-SN data. We found the absolute visual magnitudes for all three stars to be between -7 and -6, which is consistent with our expectations of these subtypes. These discoveries highlight the incompleteness of the WR census in our local volume of the Milky Way and suggest the potential for future Galactic WR discoveries from Gaia low-dispersion spectra. Furthermore, radial velocity studies of the newly found binary will provide direct mass estimates and orbital parameters, providing insight into the role that binarity plays in massive star evolution.

     This work was supported by the National Science Foundation through AST-2307594 to PM, and through the Research Experiences for Undergraduates program at Northern Arizona University (AST-2349774).

152. van Belle, G., Creech-Eakman, M., Baylis-Aguirre, D., 2025, AAS, 245, 211.06, A "Wonderful" Reference Data Set for Mira Variables
     Abstract

     Mira variable atmospheres are excellent laboratories to study stellar physics, included molecule and grain formation, dust production, stellar winds, mass-loss, opacity driven pulsation, and shocks. Using a decade of observations from the Palomar Testbed Interferometer (PTI), our team has been generating a Reference Data Set for 106 Mira variables, including M, S, and C-types, over a variety of pulsation periods. The measured K-band angular diameters allow us to establish effective temperatures, radial size. Supplemental observations include ongoing period-dependent bolometric flux measurements, as well as previous Spitzer IRS measurements. All the data produced for the Reference Data Set will be hosted on a public website for researchers to exploit this "wonderful" data set.

153. Beaumont, C., Massey, P., Hillier, D., et al., 2025, AAS, 245, 233.01, The Physical Parameters of a WN3 Wolf-Rayet Star in the LMC
     Abstract

     The goal of this project is to answer the longstanding question in massive star evolution of what effect binarity has on the formation of Wolf-Rayet stars. By understanding the processes involved in the formation of these massive stars, we can gain a greater understanding of the role they play in the evolution of galaxies and create tools that will allow us to better understand the spectra of distant galaxies. We have been using the radiative transfer program CMFGEN to determine the physical parameters of early-type WN stars in the LMC in order to compare their properties with those of single-star and binary-star evolutionary models. At this meeting, we will give the results for our first star, BAT99-15. The UV spectrum of BAT99-15 was measured using NASA's International Ultraviolet explorer, while the optical and NIR spectra were taken with MagE and FIRE on the Baade 6.5-meter telescope. At the culmination of this project, we will be able to report on fundamental properties of a large sample of WN stars, such as the luminosity, temperature, element abundances, etc. This work was supported by the National Science Foundation through grant AST 2307594.

154. Hunter, D., Zhang, H., Elmegreen, B., et al., (including Castelloe, E., Ledford, H., Nisley, I., Hatano, R.), 2025, AAS, 245, 251.05, Star Formation in the Extreme Far Outer Disk of a Dwarf Irregular Galaxy
     Abstract

     We have obtained ultra-deep UBVI imaging of nearby non-interacting dwarf irregular galaxies in order to examine their far outer stellar disks (out to 29 mag/arcsec²). Photometry of distinct objects in the far outer disks is used to determine ages of the objects in order to look for those that are young. We present the results for one galaxy - DDO 43. We find five objects with high-confidence ages 3-10 Myrs. These objects are too young to have scattered into the far outer disk from the central regions. Therefore, they likely formed in situ. This leaves us with the question of how star-forming gas clouds could form in the extreme environment of the far outer stellar disks of dwarfs. We are grateful to NSF for funding for the building of the camera on the Lowell Discovery Telescope that was used for these observations (NSF AST-1005313).

155. Kutra, T., Prato, L., Tofflemire, B., et al., (including Tang, S.), 2025, AAS, 245, 268.04, An ALMA Survey of Circumstellar Disks in Young Binaries
     Abstract

     Young binary systems offer a unique opportunity to study the fragility of circumstellar disks in dynamically tumultuous environments. In this talk, I will present preliminary ALMA continuum and 12CO emission for several systems, including the puzzling DF Tau. DF Tau is a close visual binary with a semi-major axis of only 14 AU; we find circumstellar disks around both the primary and secondary star. Other disk signatures, i.e. accretion measurements and H-band veiling, indicate only a disk around the primary star. Because the two stars likely formed together, with the same composition, in the same environment, and at the same time, we expect their disks to be co-eval. However the absence of an inner disk around the secondary suggests uneven dissipation. We resolve this contradiction by proposing that the inner disk of DF Tau B is, at minimum, beyond ~0.06 AU and consider several processes which have the potential to accelerate inner disk evolution.

156. Ayala, C., Escapa, I., Wade, E., et al., 2025, AAS, 245, 354.19, A Study of the Irregular Variable BH Lac via Observations from the Yerkes Astronomical Glass Plate Collection
     Abstract

     We present results from a study of the stellar variability of the Ross variable star BH Lac using photometric magnitude estimates obtained from the digitization of glass plates containing it. The Ross variable star catalog consists of 379 variable stars identified by Yerkes astronomer Frank Elmore Ross upon comparing glass plates he took between 1924 to 1930 with those taken by Yerkes astronomer E.E Barnard between 1904 to 1915. Today, the 180,000 glass plates of the Yerkes Glass Plate Collection represent the second largest glass plate collection in the world, and the largest collection which has not been fully digitized. The irregular variable BH Lac, identified as R 93 in the Ross variable star catalog, was found to contain a total of 39 glass plates dating between 1907-1929 by the Yerkes Astronomical Plate Search System (YAPSS). Upon performing plate solving methods and aperture photometry on these 39 plates, we were able to estimate the changes in the photometric magnitude of BH Lac from 1907 to 1929 and produce a light curve. We compare our results with light curves generated using the digitized Harvard College Observatory's Astronomical Photographic Glass Plate Collection, as well as with TESS light curves. Additional stellar measurements, acquired via crossmatching our observations with multiwavelength catalogs including Gaia, 2MASS, and WISE, further helped us deduce the potential nature of the star and the processes responsible for its irregular variability, suggesting that stellar youth could possibly be responsible for it. Even in the age of large ground-based optical telescopes, the application of modern tools and techniques towards the Yerkes Glass Plate Collection suggests that its century-long historical astronomical data retains a potential critical role in furthering studies such as identifying changes in stellar proper motion, estimating the periods of binary star systems, and characterizing the stellar variability of long period variables.

157. Speckert, M., Rector, T., Prato, L., 2025, AAS, 245, 357.05, High-Sensitivity Detections of New Herbig Haro Objects in the Ophiuchus Star Forming Region
     Abstract

     Herbig-Haro objects are tracers of early star formation. By studying them, we can get a better grasp of the presence of young stars with ages of ~1 Myr. Herbig-Haro objects form when jets of gas, ejected from these young protostars, interact with the surrounding medium and create observable shocks. We have imaged numerous star forming regions to facilitate comparisons of Herbig-Haro frequency and morphology across different environments, shedding light on the conditions influencing molecular cloud evolution. Our highly sensitive approach is to use multi-filter (g', i', and H) imaging from the Dark Energy Camera on the Blanco 4-meter telescope and to follow up with confirmation observations in the [SII] N673 filter. This process yields detections of some of the faintest Herbig-Haro objects ever identified. We have discovered ~50 new Herbig-Haro objects in the Ophiuchus region. Herbig-Haro objects are important because their presence indicates ongoing protostar formation within a young region, even when the protostars themselves are not directly visible because they are still embedded in the dark cloud cores. By studying these phenomena we can improve our understanding of the connections between molecular cloud environments of early star formation.

158. Knowlton, P., Hyden, J., Speckert, M., et al., (including Prato, L., Kutra, T.), 2025, AAS, 245, 357.11, Young Stellar Inclinations Derived from Photometric and Spectroscopic Data
     Abstract

     Understanding the inclinations of stellar spin axes is fundamental for studying planet formation and young binary star evolution. Obliquities between exoplanet orbits and their host stars can be traced to the misalignment of circumstellar disks and stellar rotation. In both single and binary systems, these misalignments can impact disk lifetimes and hinder the formation of planets altogether. Our goal is to derive the inclinations for single and binary systems in the Taurus star-forming region using a unique method that relies on estimates of stellar radii. We first identify rotation periods from TESS and K2 light curves for over a hundred sources. In order to test that these periods reflect the stellar rotation of CTTSs, we model the impact of accretion and other activity on our ability to extract the underlying sinusoidal signal we expect from rotation. We combine these data with projected stellar rotation velocities and effective temperatures derived by fitting a synthetic model grid to IGRINS spectra of our sources. Alongside all of these parameters, we use stellar ages and evolutionary track models from the literature to determine inclination. We present the details of this novel approach and the results from our derived distribution of stellar inclinations.

159. Tang, S., Johns-Krull, C., Prato, L., 2025, AAS, 245, 367.01D, Searching for the Youngest Hot Jupiters Around T Tauri Stars using Spectroscopic Data
     Abstract

     Characterizing the spot-induced variability of T Tauri Stars (TTSs) is essential for discovering planets orbiting them. Spot activity significantly affects radial velocity (RV) measurements, often overwhelming or mimicking planetary signalsespecially in young, active stars where stellar activity-induced RV variations can be several times larger than those induced by planets. Large cool spots covering up to 80% of the stellar disk complicate the detection and can even mask signals from hot Jupiters (HJs), planets with large sizes but short orbital periods. Over the past two decades, our team has collected hundreds of high-resolution optical and near-infrared spectra in our Young Exoplanet Spectroscopic Survey. Analyzing temperature-sensitive spectral lines, I developed an empirical equivalent width ratio (EWR)-effective temperature (Teff) relationship for late K and M-dwarfs with interferometrically determined Teff, spanning 3400 to 5000 K. This relationship allows me to study the short-term average surface Teff variations of TTSs, serving as a new stellar activity index. My findings reveal temperature variations exceeding 150 K in individual TTSs, confirming substantial stellar activity beyond measurement scatter. Our team observed a correlation between average surface magnetic field strengths and Teff variations, consistent with the interplay between magnetic fields and stellar surface features. Notably, a quarter-phase delay between EWR and RV phase curves points to spot-driven RV modulation. In contrast, CI Tau's zero phase delay suggests more complex dynamics, possibly of planetary origin, and V830 Tau's three-quarter-phase delay hints at a hot spot's involvement. I will also present simulation results, including fits to our observations, and explore how spot sizes and spot-to-photosphere temperature contrast affect the RV and EWR signal strength as functions of wavelength.

160. Moreland, J., Clark, C., van Belle, G., et al., (including von Braun, K.), 2025, AAS, 245, 403.02, The POKEMON Speckle Survey of Nearby M-Dwarfs. An Analysis of Stellar Multiplicity, Orbital Period, and Mass Ratio Distributions Based on Fitted Spectral Data
     Abstract

     M dwarfs are strong candidate planet hosts due to their abundance, longevity, small sizes, and low luminosities. Yet stellar multiples can induce false positives and overall complicate the process of exoplanet detection and characterization. We have therefore carried out the Pervasive Overview of Kompanions of Every M dwarfs in Our Neighborhood (POKEMON) survey. Using high-angular-resolution speckle imaging, we have characterized the stellar multiplicity of 455 M dwarfs within 15 pc. In this continuation of the study, we are using sedFit to compare photometry from Gaia, 2MASS, and the Titan Monitor facility at Lowell Observatory with the PHOENIX spectral library, allowing us to infer stellar attributes such as effective temperature, luminosity class, and spectral type for each M dwarf primary and secondary in the sample. In addition to a stellar multiplicity rate as a function of spectral subtype, this analysis will allow us to establish updated mass ratio and orbital period distributions down to the bottom of the Main Sequence, revealing the nature of our low-mass neighbors.

161. Fernandez, N., Richey-Yowell, T., 2025, AAS, 245, 418.04, Characterizing Ultraviolet Flaring Behavior in K-Type Stars
     Abstract

     To better understand the environment of exoplanets, it is essential to first characterize the behavior of their host stars. The flare activity of these stars, particularly in ultraviolet (UV) light, is a critical factor in assessing the potential for exoplanets to develop and sustain life. UV flares can significantly alter the photochemistry of exoplanetary atmospheres, and over time, may even lead to atmospheric loss, rendering exoplanets uninhabitable. While the UV flare behavior of M-type stars has been extensively studied, K-type stars remain less understood. Using Hubble Space Telescope observations of more than a dozen K-type stars across various age groups, we aim to analyze their UV flare activity and compare the results to those of M-type stars. This comparison will help determine whether K-type stars warrant increased attention in the search for potentially habitable exoplanetary systems.

162. Burgasser, A., Gerasimov, R., Alvarado, E., et al., (including Brooks, H.), 2025, AAS, 245, 464.06, Arcana of the Ancients: First Results from a JWST Spectral Survey of Metal-poor Ultracool Dwarfs
     Abstract

     Elemental composition guides the formation, evolution, and atmosphere processes of the lowest-mass stars and brown dwarfs, or ultracool dwarfs (UCDs). While the vast majority of known UCDs are solar-metallicity objects in the Milky Way's thin disk, a rare subsample of metal-poor stellar and substellar subdwarfs are known in the Solar Neighborhood. We report the first results from our 0.6-14 m spectroscopic survey of 32 L and T dwarfs and subdwarfs, including 11 wide companions to FGK stars, aimed at investigating the influence of metallicity on chemistry, condensation, and disequilibrium mixing in the coolest atmospheres. We show the first temperature and metallicity spectral grid for ultracool dwarfs spanning 0.6-14 m, and identify key metallicity-sensitive features in this regime including evidence of PH3 absorption in the moderate-resolution spectrum of the metal-poor companion T dwarf Wolf 1130C. We demonstrate robust fits to these data to select model grids, including the first self-consistent fits to the extreme T subdwarfs J1810-1010 and J0414-5854 with the SAND model grid, and report preliminary atmosphere parameters from NIRSpec+MIRI low-resolution spectra and radial velocities from moderate-resolution NIRSpec spectra. This program is supported by NASA through program JWST-GO-04688.

163. Kareta, T., Fuentes-Munoz, O., Moskovitz, N., et al., 2025, ApJL, 979, L8, On the Lunar Origin of Near-Earth Asteroid 2024 PT5
     Abstract

     The near-Earth asteroid (NEA) 2024 PT5 is on an Earth-like orbit that remained in Earth's immediate vicinity for several months at the end of 2024. PT5's orbit is challenging to populate with asteroids originating from the main belt and is more commonly associated with rocket bodies mistakenly identified as natural objects or with debris ejected from impacts on the Moon. We obtained visible and near-infrared reflectance spectra of PT5 with the Lowell Discovery Telescope and NASA Infrared Telescope Facility on 2024 August 16. The combined reflectance spectrum matches lunar samples but does not match any known asteroid typesit is pyroxene-rich, while asteroids of comparable spectral redness are olivine-rich. Moreover, the amount of solar radiation pressure observed on the PT5 trajectory is orders of magnitude lower than what would be expected for an artificial object. We therefore conclude that 2024 PT5 is ejecta from an impact on the Moon, thus making PT5 the second NEA suggested to be sourced from the surface of the Moon. While one object might be an outlier, two suggest that there is an underlying population to be characterized. Long-term predictions of the position of 2024 PT5 are challenging due to the slow Earth encounters characteristic of objects in these orbits. A population of near-Earth objects that are sourced by the Moon would be important to characterize for understanding how impacts work on our nearest neighbor and for identifying the source regions of asteroids and meteorites from this understudied population of objects on very Earth-like orbits.

164. Tang, S., Johns-Krull, C., Prato, L., et al., 2025, ApJ, 978, 119, Erratum: "Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines" (2024, ApJ, 973, 124)
     Abstract

     No abstract found.

165. Esteves, J., Pereira, M., Soares-Santos, M., et al., (including Kuehn, K.), 2025, MNRAS, 536, 931, Copacabana: a probabilistic membership assignment method for galaxy clusters
     Abstract

     Cosmological analyses using galaxy clusters in optical/near-infrared photometric surveys require robust characterization of their galaxy content. Precisely determining which galaxies belong to a cluster is crucial. In this paper, we present the COlor Probabilistic Assignment of Clusters And BAyesiaN Analysis (Copacabana) algorithm. Copacabana computes membership probabilities for all galaxies within an aperture centred on the cluster using photometric redshifts, colours, and projected radial probability density functions. We use simulations to validate Copacabana and we show that it achieves up to 89 per cent membership accuracy with a mild dependence on photometric redshift uncertainties and choice of aperture size. We find that the precision of the photometric redshifts has the largest impact on the determination of the membership probabilities followed by the choice of the cluster aperture size. We also quantify how much these uncertainties in the membership probabilities affect the stellar mass-cluster mass scaling relation, a relation that directly impacts cosmology. Using the sum of the stellar masses weighted by membership probabilities ($\rm \mu _{\star }$) as the observable, we find that Copacabana can reach an accuracy of 0.06 dex in the measurement of the scaling relation at low redshift for a Legacy Survey of Space and Time type survey. These results indicate the potential of Copacabana and $\rm \mu _{\star }$ to be used in cosmological analyses of optically selected clusters in the future.

166. Chandler, C., Sedaghat, N., Oldroyd, W., et al., (including Farrell, K.), 2025, RNAAS, 9, 3, AI-enhanced Citizen Science Discovers Cometary Activity on Near-Earth Object (523822) 2012 DG61
     Abstract

     We report the discovery of cometary activity in the form of a pronounced tail emanating from Near-Earth Object (523822) 2012 DG₆₁, identified in UT 2024 April 18 Dark Energy Camera images by our AI assistant TailNet. TailNet is an AI designed to filter out images unlikely to show activity for volunteers of our NASA Partner "Active Asteroids" Citizen Science campaign, from which our AI is trained. Subsequently, our archival investigation revealed 2012 DG61 is recurrently active after we found it displaying a pronounced tail in a UT 2018 April 16 Steward Observatory Bart Bok 2.3 m telescope image and UT 2018 May 14 observations by G. Borisov with the 0.3 m telescope at MARGO Observatory. Our dynamical integrations reveal that 2012 DG61, an Apollo dynamical class member, is likely in 2:1 mean-motion resonance with Jupiter. We encourage additional observations to help characterize the activity morphology of this near-Earth comet.

167. Jenniskens, P., Johannink, C., Moskovitz, N., et al., 2025, eMetN, 10, 20, Short note on what appears to have been a 2024 outburst of epsilon-Ursae-Minorids (IAU#1044)
     Abstract

     A meteor outburst with a radiant in Ursa Minor was detected by low-light level video cameras of the Global Meteor Network and by Belarusian and Ukranian meteor camera networks on September 2325, 2024. Here, we report on the results from the CAMS network and discuss the possible association with the epsilon-Ursae-Minorids outburst observed in 2019. If this is the same stream, a return of the shower is expected in 2025, and again in 2030/2031.

168. Awad, P., Li, T., Erkal, D., et al., (including Kuehn, K.), 2025, A&A, 693, A69, S⁵: New insights from deep spectroscopic observations of the tidal tails of the globular clusters NGC 1261 and NGC 1904
     Abstract

     As globular clusters (GCs) orbit the Milky Way, their stars are tidally stripped and form tidal tails that follow the orbit of the cluster around the Galaxy. The morphology of these tails is complex and shows correlations with the phase of orbit and the orbital angular velocity, especially for GCs on eccentric orbits. Here we focus on two GCs, NGC 1261 and NGC 1904, that were potentially accreted alongside Gaia-Enceladus and that have shown signatures of having, in addition to tidal tails, structures formed by distributions of extra-tidal stars that are misaligned with the general direction of the clusters' respective orbits. To provide an explanation for the formation of these structures, we made use of spectroscopic measurements from the Southern Stellar Stream Spectroscopic Survey (S⁵) as well as proper motion measurements from Gaia's third data release (DR3), and applied a Bayesian mixture modelling approach to isolate high-probability member stars. We recovered extra-tidal features surrounding each cluster matching findings from previous work. We then conducted N-body simulations and compared the expected spatial distribution and variation in the dynamical parameters along the orbit with those of our potential member sample. Furthermore, we used Dark Energy Camera (DECam) photometry to inspect the distribution of the member stars in the colour-magnitude diagram (CMD). We find that potential members agree reasonably with the N-body simulations, and that the majority follow a simple stellar population distribution in the CMD, which is characteristic of GCs. We link the extra-tidal features with their orbital properties and find that the presence of the tails agrees well with the theory of stellar stream formation through tidal disruption. In the case of NGC 1904, we clearly detect the tidal debris escaping the inner and outer Lagrange points, which are expected to be prominent when at or close to the apocentre of its orbit. Our analysis allows for further exploration of other GCs in the Milky Way that exhibit similar extra-tidal features.

169. Hsieh, H., Noonan, J., Kelley, M., et al., (including Thirouin, A., Moskovitz, N.), 2025, PSJ, 6, 3, The Volatile Composition and Activity Evolution of Main-belt Comet 358P/PANSTARRS
     Abstract

     We report the detection of water vapor associated with main-belt comet 358P/PANSTARRS on UT 2024 January 89 using the NIRSPEC instrument on board JWST. We derive a water production rate of molecules s¹, marking only the second direct detection of sublimation products of any kind from a main-belt comet, after 238P/Read. Similar to 238P, we find a remarkable absence of hypervolatile species, finding molecules s¹, corresponding to %. Upper limits on CH₃OH and CO emission are also estimated. Photometry from ground-based observations shows that the dust coma brightened and faded slowly over 250 days in 20232024, consistent with photometric behavior observed in 20122013, but also indicates a 2.5 decline in the dust production rate between these two periods. Dynamical dust modeling shows that the coma's morphology as imaged by JWST's NIRCam instrument on 2023 November 22 can be reproduced by asymmetric dust emission from a nucleus with a midrange obliquity ( 80) with a steady-state mass-loss rate of 0.8 kg s¹. Finally, we find similar Af -to-gas ratios of for 358P and for 238P, suggesting that Af could serve as an effective proxy for estimating water production rates in other active main-belt comets. The confirmation of water vapor outgassing in both main-belt comets observed by JWST to date reinforces the use of recurrent activity near perihelion as an indicator of sublimation-driven activity in active asteroids.

170. Faga, L., Andrade-Oliveira, F., Camacho, H., et al., (including Kuehn, K.), 2025, MNRAS, 536, 1586, Dark energy survey year 3 results: cosmology from galaxy clustering and galaxy-galaxy lensing in harmonic space
     Abstract

     We present the joint tomographic analysis of galaxy-galaxy lensing and galaxy clustering in harmonic space (HS), using galaxy catalogues from the first three years of observations by the Dark Energy Survey (DES Y3). We utilize the REDMAGIC and MAGLIM catalogues as lens galaxies and the METACALIBRATION catalogue as source galaxies. The measurements of angular power spectra are performed using the pseudo-$C_\ell$ method, and our theoretical modelling follows the fiducial analyses performed by DES Y3 in configuration space, accounting for galaxy bias, intrinsic alignments, magnification bias, shear magnification bias and photometric redshift uncertainties. We explore different approaches for scale cuts based on non-linear galaxy bias and baryonic effects contamination. Our fiducial covariance matrix is computed analytically, accounting for mask geometry in the Gaussian term, and including non-Gaussian contributions and super-sample covariance terms. To validate our HS pipelines and covariance matrix, we used a suite of 1800 log-normal simulations. We also perform a series of stress tests to gauge the robustness of our HS analysis. In the $\Lambda$CDM model, the clustering amplitude $S_8 =\sigma _8(\Omega _m/0.3)^{0.5}$ is constrained to $S_8 = 0.704\pm 0.029$ and $S_8 = 0.753\pm 0.024$ (68 per cent C.L.) for the REDMAGIC and MAGLIM catalogues, respectively. For the wCDM, the dark energy equation of state is constrained to $w = -1.28 \pm 0.29$ and $w = -1.26^{+0.34}_{-0.27}$, for REDMAGIC and MAGLIM catalogues, respectively. These results are compatible with the corresponding DES Y3 results in configuration space and pave the way for HS analyses using the DES Y6 data.

171. Chen, R., Scolnic, D., Vincenzi, M., et al., (including Kuehn, K.), 2025, MNRAS, 536, 1948, Evaluating cosmological biases using photometric redshifts for Type Ia Supernova cosmology with the Dark Energy Survey Supernova Program
     Abstract

     Cosmological analyses with Type Ia Supernovae (SNe Ia) have traditionally been reliant on spectroscopy for both classifying the type of supernova and obtaining reliable redshifts to measure the distance-redshift relation. While obtaining a host-galaxy spectroscopic redshift for most SNe is feasible for small-area transient surveys, it will be too resource intensive for upcoming large-area surveys such as the Vera Rubin Observatory Legacy Survey of Space and Time, which will observe on the order of millions of SNe. Here, we use data from the Dark Energy Survey (DES) to address this problem with photometric redshifts (photo-z) inferred directly from the SN light curve in combination with Gaussian and full $p(z)$ priors from host-galaxy photo-z estimates. Using the DES 5-yr photometrically classified SN sample, we consider several photo-z algorithms as host-galaxy photo-z priors, including the Self-Organizing Map redshifts (SOMPZ), Bayesian Photometric Redshifts (BPZ), and Directional-Neighbourhood Fitting (DNF) redshift estimates employed in the DES 3 2 point analyses. With detailed catalogue-level simulations of the DES 5-yr sample, we find that the simulated w can be recovered within $\pm 0.02$ when using SN+SOMPZ or DNF prior photo-z, smaller than the average statistical uncertainty for these samples of 0.03. With data, we obtain biases in w consistent with simulations within ${\sim} 1\sigma$ for three of the five photo-z variants. We further evaluate how photo-z systematics interplay with photometric classification and find classification introduces a subdominant systematic component. This work lays the foundation for next-generation fully photometric SNe Ia cosmological analyses.

172. Kutra, T., Prato, L., Tofflemire, B., et al., (including Tang, S.), 2025, AJ, 169, 20, Sites of Planet Formation in Binary Systems. II. Double the Disks in DF Tau
     Abstract

     This article presents the latest results of our Atacama Large Millimeter/submillimeter Array (ALMA) program to study circumstellar disk characteristics as a function of orbital and stellar properties in a sample of young binary star systems known to host at least one disk. Optical and infrared observations of the eccentric, 48 yr period binary DF Tau indicated the presence of only one disk around the brighter component. However, our 1.3 mm ALMA thermal continuum maps show two nearly equal-brightness components in this system. We present these observations within the context of updated stellar and orbital properties, which indicate that the inner disk of the secondary is absent. Because the two stars likely formed together, with the same composition, in the same environment, and at the same time, we expect their disks to be co-eval. However the absence of an inner disk around the secondary suggests uneven dissipation. We consider several processes that have the potential to accelerate inner disk evolution. Rapid inner disk dissipation has important implications for planet formation, particularly in the terrestrial-planet-forming region.

173. Shah, P., Davis, T., Vincenzi, M., et al., (including Kuehn, K.), 2025, MNRAS, 536, 946, Constraints on compact objects from the Dark Energy Survey 5-yr supernova sample
     Abstract

     Gravitational lensing magnification of Type Ia supernovae (SNe Ia) allows information to be obtained about the distribution of matter on small scales. In this paper, we derive limits on the fraction $\alpha$ of the total matter density in compact objects (which comprise stars, stellar remnants, small stellar groupings, and primordial black holes) of mass M > 0.03 ${\rm M}_{\odot }$ over cosmological distances. Using 1532 SNe Ia from the Dark Energy Survey Year 5 sample (DES-SN5YR) combined with a Bayesian prior for the absolute magnitude M, we obtain < 0.12 at the 95 per cent confidence level after marginalization over cosmological parameters, lensing due to large-scale structure, and intrinsic non-Gaussianity. Similar results are obtained using priors from the cosmic microwave background, baryon acoustic oscillations, and galaxy weak lensing, indicating our results do not depend on the background cosmology. We argue our constraints are likely to be conservative (in the sense of the values we quote being higher than the truth), but discuss scenarios in which they could be weakened by systematics of the order of $\Delta \alpha \sim 0.04$.

174. Reuter, D., Simon, A., Lunsford, A., et al., (including Grundy, W.), 2025, pds, 256, Lucy Ralph Multispectral Visible Imaging Camera (L'Ralph MVIC) Donaldjohanson Calibrated Data
     Abstract

     This collection contains calibrated data products produced by Lucy's L'Ralph MVIC instrument during the Donaldjohanson mission phase.

175. Reuter, D., Simon, A., Lunsford, A., et al., (including Grundy, W.), 2025, pds, 261, Lucy Ralph Linear Etalon Imaging Spectral Array (L'Ralph LEISA) Donaldjohanson Calibrated Data
     Abstract

     This collection contains calibrated data products produced by Lucy's L'Ralph LEISA instrument during the Donaldjohanson mission phase.

176. Reuter, D., Simon, A., Lunsford, A., et al., (including Grundy, W.), 2025, pds, 262, Lucy Ralph Linear Etalon Imaging Spectral Array (L'Ralph LEISA) Calibration Files, Version 2.0
     Abstract

     This collection contains products used in the calibration of data from Lucy's L'Ralph LEISA instrument. This version adds Fringe Flat and Space Stare FITS images related to the Donaldjohanson flyby.

177. Reuter, D., Simon, A., Lunsford, A., et al., (including Grundy, W.), 2025, pds, 263, Lucy Ralph Multispectral Visible Imaging Camera (L'Ralph MVIC) Donaldjohanson Raw Data
     Abstract

     This collection contains raw data products produced by Lucy's L'Ralph MVIC instrument during the Donaldjohanson mission phase.

178. Reuter, D., Simon, A., Lunsford, A., et al., (including Grundy, W.), 2025, pds, 265, Lucy Ralph Linear Etalon Imaging Spectral Array (L'Ralph LEISA) Donaldjohanson Raw Data
     Abstract

     This collection contains raw data products produced by Lucy's L'Ralph LEISA instrument during the Donaldjohanson mission phase.

179. Reuter, D., Simon, A., Lunsford, A., et al., (including Grundy, W.), 2025, pds, 284, Lucy Ralph Multispectral Visible Imaging Camera (L'Ralph MVIC) Calibration Files, Version 2.0
     Abstract

     This collection contains products used in the calibration of data from Lucy's L'Ralph MVIC instrument. This version adds five Space Stare FITS images related to the Donaldjohanson mission phase.

180. Skiff, B., Yeung, W., Hill, R., et al., 2025, MPEC, 2025-O159, Observations and Orbits of Comets and a/ Objects
     Abstract

     No abstract found.

181. Jorgensen, A., Mozurkewich, D., Schmitt, H., et al., (including van Belle, G.), 2025, JAI, 14, 2550002, Bootstrapping a Five-Telescope Linear Array with the New Classic Beam Combiner at the Navy Precision Optical Interferometer
     Abstract

     The optical interferometer array configuration that attains highest angular resolution for a given number of array elements is a linear array with equal spacing between array elements, in which the array is phased by tracking fringes on the neighbor-to-neighbor baselines. We demonstrate this technique with observations taken with a nearly-linear configuration of the Navy Precision Optical Interferometer (NPOI). This chain bootstrapping technique required an upgrade to the NPOI beam combiner, which we dub New Classic. We describe the control scheme for New Classic for phasing the array and present observations of two stars to demonstrate the technique. To analyze the data, we use the post-processing technique of coherent averaging, in which the fringe phases on the neighbor-to-neighbor baselines are used to correct the phases on the longer baselines before averaging the complex visibilities.

182. Ferris, W., Koehn, B., Chambers, K., et al., 2025, MPEC, 2025-M65, 2009 DB45
     Abstract

     No abstract found.

183. Skiff, B., Grimstad, T., Factory, P., et al., 2025, MPEC, 2025-H87, Comet P/2009 KF37
     Abstract

     No abstract found.

183 publications and 861 citations in 2025.

183 publications and 861 citations total.