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Research involving Lowell Observatory staff 2025
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    2025

  1. 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
    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.
  2. 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
    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.
  3. 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'?
    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.
  4. 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
    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.
  5. 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)
    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.
  6. 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
    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.
  7. 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
    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 MJup at 1.3 separation.
  8. 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
    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.
  9. 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
    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.
  10. Vincenzi, M., Kessler, R., Shah, P., et al., (including Kuehn, K.), 2025, MNRAS, Comparing the DES-SN5YR and Pantheon+ SN cosmology analyses: Investigation based on 'Evolving Dark Energy or Supernovae systematics'?
    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 (2024) compared overlapping SN events between Pantheon+ and DES-SN5YR (20 % SNe are in common), and reported evidence for a ~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. Second, improvements in host mass estimates in DES-SN5YR also affected SN standardized magnitudes and their bias corrections. Third, 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 to 3.3, 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 %. In conclusion, we confirm the validity of the published DES-SN5YR results.
  11. 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
    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.
  12. 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
    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.
  13. Rector, T., Prato, L., Kerr, R., 2025, AAS, 246, 212.04, Exploring New Paradigms in Star Formation with Gaia Kinematics and Herbig-Haro Objects
    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.
  14. 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
    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.
  15. 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
    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.
  16. Ardila, D., Shkolnik, E., Basset, C., et al., (including Llama, J.), 2025, AAS, 246, 233.03, SPARCS and the SmallSat Revolution: A Case Study
    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.

  17. Prato, L., 2025, AAS, 246, 406.02, Mapping Inner Disk Structure in the Closest Young Binaries with He I 10830A Lines
    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.
  18. 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
    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.

  19. 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
    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.
  20. Minker, K., Carry, B., Vachier, F., et al., (including Grundy, W.), 2025, A&A, 698, A136, Orbits of very distant asteroid satellites
    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.
  21. 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
    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.
  22. 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
    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.
  23. 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
    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.
  24. 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
    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.
  25. 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
    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.
  26. 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
    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.
  27. 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
    For the 696 trans-Neptunian objects (TNOs) with absolute magnitudes 5.5 < Hr < 8.2 detected in the Dark Energy Survey, we characterize the relationships between their dynamical state and physical propertiesnamely Hr, 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 Hr and A distributions are independent of current dynamical states, supporting their assignment as birth populations. All objects are consistent with a common rolling p(Hr), 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 Hr range. These results will strongly constrain models of the outer solar system.
  28. Slyusarev, I., Shevchenko, V., Belskaya, I., et al., (including Skiff, B.), 2025, P&SS, 260, 106103, Opposition effect of M-type asteroids
    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.
  29. Kareta, T., Schambeau, C., Firgard, M., et al., 2025, PSJ, 6, 119, Activity-induced Near-infrared Spectral Variability at 29P/SchwassmannWachmann 1, 20172022
    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.
  30. Kerr, R., Farias, J., Prato, L., et al., 2025, ApJ, 985, 111, SPYGLASS. VI. Feedback-driven Star Formation in the Circinus Complex
    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.
  31. 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
    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.
  32. Kao, M., Pineda, J., 2025, MNRAS, 539, 2292, Binarity enhances the occurrence rate of radiation belt emissions in ultracool dwarfs
    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.
  33. 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
    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.
  34. 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
    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.
  35. 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
    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.
  36. 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
    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.
  37. 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
    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 $H_{0}$.
  38. 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
    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.
  39. Lilly, E., Schambeau, C., Thirouin, A., et al., 2025, RNAAS, 9, 67, Observations and Characterization of the New Active Centaur 2023 RS61
    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 rH = 13.5 au makes RS61 the second-most distant active Centaur after 95P/Chiron. We estimate a nucleus size between 4.7 km rn 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.
  40. 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
    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.
  41. 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
    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).
  42. 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
    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.
  43. 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
    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.

  44. 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
    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.
  45. 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
    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.
  46. 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
    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.
  47. 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
    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/R200c)/(critR200c) 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.
  48. 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
    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.
  49. 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
    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.
  50. 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
    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.
  51. Crossfield, I., Polanski, A., Robertson, P., et al., 2025, AJ, 169, 89, OrCAS: Origins, Compositions, and Atmospheres of Sub-Neptunes. I. Survey Definition
    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.
  52. 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
    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.
  53. 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
    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.
  54. 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
    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.
  55. 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
    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.
  56. 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
    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.
  57. 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
    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.
  58. 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
    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.
  59. 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
    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.
  60. 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
    Asteroid discoveries are essential for planetary-defence efforts aiming to prevent impacts with Earth1, including the more frequent2 megaton explosions from decametre impactors3, 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) population8,9. 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 models10, 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 techniques16, 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 meteorites13,14 'in situ'.
  61. 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
    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.
  62. 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
    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.
  63. Menk, A., Zhang, Q., 2025, AAS, 245, 103.04, Investigating the Great September Comet of 1882
    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.
  64. 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?
    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.
  65. 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
    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.

  66. 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
    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.
  67. 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
    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.
  68. 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
    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.
  69. 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
    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.

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

  71. van Belle, G., Creech-Eakman, M., Baylis-Aguirre, D., 2025, AAS, 245, 211.06, A "Wonderful" Reference Data Set for Mira Variables
    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.
  72. 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
    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.
  73. 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
    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).
  74. 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
    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.
  75. 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
    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.
  76. 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
    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.
  77. 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
    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.
  78. 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
    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.
  79. 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
    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.
  80. Fernandez, N., Richey-Yowell, T., 2025, AAS, 245, 418.04, Characterizing Ultraviolet Flaring Behavior in K-Type Stars
    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.
  81. 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
    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.
  82. Kareta, T., Fuentes-Munoz, O., Moskovitz, N., et al., 2025, ApJL, 979, L8, On the Lunar Origin of Near-Earth Asteroid 2024 PT5
    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.
  83. 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)
    No abstract found.
  84. 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
    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.
  85. 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
    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.
  86. 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)
    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.
  87. 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
    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.
  88. 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
    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.
  89. 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
    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.
  90. 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
    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.
  91. 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
    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.
  92. 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
    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 $\Delta \alpha \sim 0.04$.
  93. 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
    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.
  94. Ferris, W., Koehn, B., Chambers, K., et al., 2025, MPEC, 2025-M65, 2009 DB45
    No abstract found.
  95. Skiff, B., Grimstad, T., Factory, P., et al., 2025, MPEC, 2025-H87, Comet P/2009 KF37
    No abstract found.

    96. 95 publications and 218 citations in 2025.

95 publications and 218 citations total.

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