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2024

1. Park, N., Shkolnik, E., Llama, J., 2024, AGUFM, 2024, P01-08, Connecting the Mass of Solar Coronal Mass Ejections (CMEs) with Far-Ultraviolet Flares for Use in other Solar-type Stars
   Abstract

   Stellar eruptive events, such as flares and coronal mass ejections (CMEs), can disrupt the stability of planetary atmospheres, affecting planetary habitability. For instance, strong stellar flares and CMEs can trigger atmospheric instability (e.g., atmospheric escape and photochemistry). While stellar flares have been observed and characterized at a wide range of wavelengths, the properties of stellar CMEs remain relatively unconstrained due to the difficulty of observing them. In this context, the Sun can provide information on the potential characteristics of CMEs on solar-type stars. Here, we present our work that builds upon results from Aarnio et al (2011,2012) who correlated solar solar X-ray flare peak flux with the mass of flare-associated solar CMEs using solar data collected during Solar Cycle 23 (1996-2006). We extend the wavelength- and temporal-coverage of these correlations by incorporating far-UV (FUV; 1600A) data throughout Solar Cycle 23 and 24 (1996-2019). Using three different space missions: CME rate and mass from LASCO/SOHO; X-ray flare information from XRS/GOES, and FUV flare peak flux from SDO/AIA1600. We report a correlation between FUV peak flux and the mass of solar X-ray flare-associated CMEs. Our correlations are applicable to other Sun-like stars and can aid in the characterization of stellar mass-loss rates, and when assessing the potential habitability of exoplanets orbiting sun-like stars.

2. Protopapa, S., Johnson, P., Wong, I., et al., (including Grundy, W.), 2024, AGUFM, 2024, P21E-3016, JWST Observations of Makemake and Varuna: Informing on Volatile Loss and Irradiation Effects in the Outer Solar System
   Abstract

   Volatile loss and retention models based on surface-bounded Jeans escape (Schaller and Brown, 2007) have so far provided a good first-order representation of the composition of Trans-Neptunian Objects (TNOs) in terms of the presence or apparent absence of volatile ices such as carbon monoxide (CO), nitrogen (N₂), and methane (CH₄). Now, the capabilities of the James Webb Space Telescope (JWST), with its extended near-infrared wavelength coverage beyond 2.5 microns, allow for the detection of longer wavelength, stronger absorption bands of these volatiles, as well as other molecules, including carbon dioxide (CO₂) and ethane (C₂H₆), potentially challenging existing predictions.

   Makemake and Varuna are two objects with very different sizes and temperatures, placing them in distinct domains with respect to volatile loss and retention. Specifically, Makemake is expected to retain all volatiles mentioned above over the age of the Solar System, while Varuna is likely to retain CO₂ and C₂H₆ but lose CH₄, N₂, and CO.

   Makemake and Varuna were observed using the integral field unit (IFU) on the Near-Infrared Spectrograph (NIRSpec) instrument as part of the Cycle 1 Solar System Guaranteed Time Observations (GTO) program 1254. For the Makemake observations, three disperser-filter combinations were employed providing continuous wavelength coverage from 0.97 to 5.1 microns, with a spectral resolving power of approximately 1000. The Varuna data were acquired with the PRISM/CLEAR disperser-filter combination, covering the wavelength range 0.60-5.30 microns with a resolving power of approximately 100. The resulting spectra differ strongly from the predictions, with Makemake being spectroscopically dominated by CH₄ and C₂H₆, and Varuna displaying clear evidence of CO₂ and CO in addition to water (H₂O) ice.

   We present these results and interpret them against the expectations set by surface-bounded Jeans escape, while acknowledging the limitations of this model and taking into account the irradiation mechanisms active on the surfaces of TNOs.

3. Verbiscer, A., Porter, S., Fraser, W., et al., (including Grundy, W.), 2024, AGUFM, 2024, P21E-3017, Photometric Properties of Kuiper Belt Objects Observed by New Horizons and HST
   Abstract

   NASA's New Horizons (NH) spacecraft continues to acquire high solar phase angle, unresolved observations of large planetesimals, i.e. Kuiper Belt Objects (KBOs), and dwarf planets using its LOng Range Reconnaissance Imager (LORRI). The NH team continues to conduct a ground-based search using Subaru Telescope's Hyper Suprime-Cam to discover additional targets for LORRI to observe, both via distant and a possibly close flyby (Fraser et al. 2024; Yoshida et al. 2024). From 2020-2022, the search (near RA/Dec 288, -21) found and reported to the Minor Planet Center over 240 new KBOs. Among these new KBOs, 7 were located close enough to the NH trajectory that they could be observed by LORRI (V<21); however, the imager's narrow (0.29 x 0.29) field of view required astrometric refinement from Hubble Space Telescope (HST) observations (Programs 16183 and 16924, S. Porter, PI) to ensure accurate LORRI pointing. In addition to their astrometric refinements, these HST images also provide photometric observations at small phase angles. Because accurate photometric modeling requires observations that span the widest range possible in phase angle, we combine these 'low-phase' HST observations with those at 'high-phase' from NH LORRI to construct disk-integrated phase curves that range in phase angle from <2 to as high as 92. Subaru-discovered KBOs already observed by NH sample all but the dynamically coldest populations. We compare their photometric properties, derived from fits to their phase curves, to those of other KBOs and dwarf planets observed by LORRI at high phase angles to reveal any correlations between surface textural and scattering properties of Resonant, Scattered Disk, and Classical KBOs. Preliminary results indicate that phase curves of Subaru-discovered KBOs have shallower slopes and therefore different shapes from those of Cold Classical KBOs. Although NH can no longer observe Classical KBOs from its heliocentric distance of 60 au in December 2024, future NH observations will continue to sample the other populations. Furthermore, the NH high-phase observations can sample objects whose apoapses lie beyond the termination shock and the heliopause, enabling new kinds of studies of space weathering processes via photometric modeling of surfaces in the outermost regions of the Solar System.

4. Porter, S., Singer, K., Schenk, P., et al., (including Grundy, W.), 2024, AGUFM, 2024, P24B-03, Shapes of Arrokoth and other Kuiper Belt Objects from New Horizons
   Abstract

   Here we present both an updated shape model of (486958) Arrokoth, the bilobate Kuiper Belt Object (KBO) which the NASA New Horizons spacecraft flew past in 2019, as well as estimates for the shapes of several other KBOs which New Horizons observed unresolved at high phase angles. The combination of the shape of Arrokoth and the unresolved KBOs provides the first general survey of the shapes of sub-1000 km KBOs. The updated Arrokoth shape model uses all of the resolved images of Arrokoth obtained by the New Horizons LOng Range Reconnaissance Imager (LORRI), while the unresolved KBO shapes use photometry also obtained by LORRI. We developed an updated shape modeling algorithm which allowed the shape and rotational pole of Arrokoth to be fit to much better quality with an efficient use of GPU-accelerated features. The resulting model of Arrokoth's contact binary shape is significantly thicker and of larger volume than the one previously published immediately after the flyby by Spencer et al (2020). We show that Arrokoth's smaller lobe, Weeyo, is roughly spherical in shape, while the larger lobe, Wenu, is more flattened, with the volume ratio between the lobes being roughly 2:1. We then applied this Arrokoth model to the unresolved KBOs, and were able to constrain rotational pole and approximate shape information for several unresolved KBOs using the variation in their rotational lighcurves at different phase angles. Owing to Wenu's oblate shape, Arrokoth's rotational lightcurve would have significantly lower mean reflectance when viewed from sub-observer latitudes than would have shown lightcurve variation, and several of the unresolved KBOs show a similar effect. We discuss the impact this may have on estimates of the frequency of contact binaries in the Kuiper Belt. We also discuss the implications of these shapes for the formation of classical KBOs, particularly in the context of the Streaming Instability.

5. Mishra, I., Plattner, T., Banerjee, S., et al., (including Kareta, T.), 2024, AGUFM, 2024, P33A-2863, A Concept for a New Frontiers Class Ceres Lander
   Abstract

   Ceres, the largest object in the asteroid belt, presents a compelling target for exploration due to its status as a relict ocean world and its relative accessibility compared to the outer solar system's ocean worlds. The Dawn mission revealed intriguing features, such as water vapor around Ceres and bright evaporite deposits, suggesting recent geological activity. These deposits, sourced from Ceres' interior, are associated with simple organics, yet the connection between them remains unclear.

   Our lander mission concept aims to deepen our understanding of Ceres through four objectives:

   Exosphere: Determine the source of water vapor in Ceres' exospherewhether it results from global sublimation of shallow subsurface ice, local sublimation from ice exposed by impacts or landslides, or cryovolcanic activity.

   Subsurface: Investigate the role of hydrothermal processes within Ceres' interior and determine whether these processes have led to: (a) a convecting mudball ocean preserved by suspended silicates, (b) an extensive brine ocean that has since frozen into a relic brine layer, or (c) an undifferentiated interior without a deep ocean layer.

   Organics: Examine whether the complex organics found on Ceres are a result of exogenic infall of simple organics or endogenic aqueous geochemical processes.

   Astrobiology: Assess if the evaporite deposits on Ceres contain sulfur and phosphorus, essential building blocks for life, that precipitated from subsurface brines.

   To achieve these objectives, we propose a suite of instruments including a UV imaging spectrometer, a gas analyzer, a gas chromatography-mass spectrometry (GC-MS) instrument, a magnetotelluric sounder, an X-ray spectrometer, and cameras for in-situ science.

   Our concept would launch in the early 2030s, with a ~75-month cruise to Ceres. The mission would begin with an initial orbital phase (~11 months) to study the exosphere and perform reconnaissance for a landing site at Occator crater. A landed phase (~1 month) would follow for subsurface and in-situ science. This comprehensive exploration would provide unprecedented insights into Ceres' geological and astrobiological potential, enhancing our understanding of ocean worlds in the solar system. This concept was developed in the 2024 JPL Planetary Science Summer School.

6. Porter, S., Leiva, R., Benecchi, S., et al., (including Grundy, W.), 2024, AGUFM, 2024, P52A-03, Probing Solar System Formation with HWO by Observing Binary and Contact Binary TNOs
   Abstract

   Recent investigations by the Hubble Space Telescope (Porter et al 2024), New Horizons (Weaver et al 2021), and stellar occultations (Leiva et al 2021) have shown that very tight (<1000 km) binaries are common among the Trans-Neptunian Objects (TNOs). This is consistent with Solar System formation models that show that Streaming Instability can trigger the formation of planetesimals directly as binary, triple, and higher systems (Nesvorny et al 2021), as well as the idea that the the survival of wider binaries in the classical Kuiper Belt implies that nearly all of them were initially binary (Fraser et al 2017). Understanding the frequency, binary orbital distribution, and heliocentric orbit distribution of the small-body TNO binaries is critical for constraining planetesimal formation in the Solar System. However, neither Hubble nor the James Webb Space Telescope can resolve TNO binaries much closer than 1000 km. In addition, ground-based lightcurve studies have shown that a very large number of TNOs are likely to be contact binaries (e.g. Thirouin & Sheppard 2018), similar to the New Horizons target Arrokoth. These contact binaries are likely to be the result of the same formation process that produced the separated binaries. The Habitable Worlds Observatory will offer the revolutionary capability to resolve much closer TNO binaries than ever before, and even resolve the largest contact binaries. We will discuss how this capability can be used to measure the orbits of hundreds of binary TNOs, providing the large scale statistics needed to understand the planetesimal formation process. We will also discuss the features of the spacecraft that would maximize the science possible from observing binary TNOs, such as the ability to observe at opposition.

7. Cartwright, R., Holler, B., Grundy, W., et al., 2024, AGUFM, 2024, P52B-08, JWST Reveals the CO2-rich Surfaces of Uranus' Largest Moons with Unprecedented Sensitivity
   Abstract

   The surfaces of the large Uranian moons Ariel, Umbriel, Titania, and Oberon exhibit a variety of tectonic and possibly cryovolcanic features. Prior ground-based observations had indicated that the surface compositions of these moons include a large fraction of crystalline CO₂ ice, in particular Ariel, with hints of NH-bearing species and CO ice that have yet to be confirmed. The origins of these species are not well understood, but they are likely replenished by a variety of processes, including internally-derived sources, especially on Ariel. To investigate these volatiles and gain insight into their origins, we analyzed reflectance spectra collected by the NIRSpec spectrograph on the James Webb Space Telescope (G395M, 2.9 - 5.1 m).

   These data reveal the spectral properties of the Uranian moons in stunning detail, showing a scattering peak near 4.20 m, flanked by a 4.27 m absorption band, which are both associated with the ₃ stretching mode of ¹²CO₂ ice. Furthermore, Ariel exhibits an additional peak near 4.25 m that may represent the largest CO₂ ice Fresnel peak yet observed in the Solar System. Numerous other CO₂ ice features are present, including prominent 4.38 m ¹³CO₂ and 4.90 m ¹²CO₂ bands. The JWST spectra confirm the presence of ¹²CO ice via its 4.67 m ₃ mode (and possibly the 4.78 m ¹³CO ₃ mode on Ariel). They also reveal a broad 4 m band, potentially resulting from carbonate minerals, as well as other subtle features between 4.4 and 4.6 m that could result from carbon suboxide and nitriles. We see no reliable evidence for NH-bearing species or hydrocarbons on any of the moons. Comparison to radiative transfer models suggests that some CO₂ ice deposits on Ariel could be more than 10 mm thick and segregated from H₂O ice.

   The possible presence of carbonates is particularly interesting as they often form in aqueous environments, supporting the presence of subsurface oceans within these moons, either now or in the past. The surface distribution of CO₂ is likely shaped by seasonal volatile migration and interactions with Uranus' magnetosphere. The non-detection of ammonia and hydrocarbons over G395M wavelengths indicates that these species are efficiently oxidized and/or removed once exposed, restricted in their spatial occurrence, or that their spectral signatures are obscured by strong H₂O ice absorption.

8. Brandt, P., Hill, M., Elliott, H., et al., (including Grundy, W.), 2024, AGUFM, 2024, SH34B-01, Preparing for the Termination Shock Encounter with New Horizons
   Abstract

   Across the Termination Shock (TS) the solar wind was expected to transition from supersonic to subsonic and heat by two orders of magnitude. Voyager 2 instead observed a shock transition, where the solar wind stayed supersonic with only a factor of ten increase in temperature, leaving a conundrum that could not be solved with Voyager instrumentation but pointed to the unique role of Pickup Ions (PUIs).

   New Horizons (NH) is currently 60 au from the Sun moving at 2.88 au/year (July 2024) on a trajectory along the same heliospheric longitude as Voyager 2, but near the ecliptic and towards the IBEX ribbon. Scaling the radial profiles of energetic particles measurements across the heliosphere obtained by LECP on Voyager 1 and 2 predicts that NH will cross the TS no earlier than mid-2027 at 68 au from the Sun, whereas Voyager 1 and 2 crossings took place at 94 and 84 au at their higher ecliptic latitudes, respectively.

   NH currently plans to obtain continuous solar wind plasma moments and H⁺ (and partly He⁺) PUI parameters at 29-min resolution with its SWAP instrument and intermittent 64-s resolution plasma moments during the TS crossing. NH PEPSSI plans to produce continuous and simultaneous low- and high-resolution data of He⁺ PUIs and energetic particle spectra down to 3-s resolution enabling detection of flow anisotropies. Leading up to the TS crossing, and after, during the traversal of the heliosheath, NH will continue to provide the only in-situ measurements of the heating of PUIs. These measurements are important for understanding the apparent excess of ENA (Energetic Neutral Atom) intensities originating from the outer heliosphere observed by IBEX, Cassini, and soon IMAP.

   Continuous in-situ dust measurements by the NH SDC instrument currently show elevated fluxes, hinting at a production of ice grains not detected before. The excess of Kuiper Belt Objects between 60 and 80 au recently discovered by the Subaru Telescope, may also contribute to the elevated dust fluxes. Furthermore, NH plans to acquire scans of Lyman-a intensities using its Alice UV spectrograph to monitor the column density of interstellar neutral hydrogen along a great circle perpendicular to the radial trajectory. This presentation gives an overview of the NH TS crossing plan, the expected science return and its impact on our understanding of the heliosphere.

9. Marcus, J., Amundson, L., Schindler, K., et al., (including Skiff, B.), 2024, JAHH, 27, 796, Vesto Slipher's observational discovery of the expansion of the Universe: the unpublished, paradigm-shattering manuscript read to the 1914 Evanston Meeting of the American Astronomical Society
   Abstract

   Lowell Observatory astronomer Vesto M. Slipher discovered the systematic redshifts of galaxies ('spiral nebulae' then) during the miracle years 19121914. After presenting his findings on 15 spirals at the Seventeenth Meeting of the American Astronomical Society in August 1914, in Evanston, Illinois, the audience, with young Edwin Hubble in it, erupted in an unprecedented standing ovation. He had discovered what soon would be recognized as the expansion of the Universe. Slipher was reading from an unpublished manuscript (MS) now residing in the Lowell Observatory Archives. Here we present it as a full facsimile of the historic original. It reveals that Slipher clearly recognized then the radical nature of his discovery. He described the spirals as "fleeing", "leaving," and "receding" from the Milky Way at unheard of velocities, and ventured that the data might support the controversial "island universe" hypothesis. In contrast, in his follow-on formal publications, he dropped those robust descriptors in favor of the tepid term "scattering", concerned by the anisotropic distribution of the spirals and our peculiar motion among them. Words aside, from the outset the data spoke for him. By the end of his radial velocity program in 1921, 36 of his 41 spirals were shown to be redshiftedclear observational evidence for expansion.

   In this paper, we review and analyze the Slipher MS in the historical context of the controversy over the nature of the spirals, Percival Lowell's charge to study them spectrographically, Slipher's pioneering methods, his revolutionary data, his evolving interpretations, and why his monumental achievement is underrecognized to this day. Now that this MS is placed in the public domain it further fortifies Slipher's uncommemorated priority for the observational discovery of the expansion of the Universe.

10. Schleicher, D., Birch, P., Farnham, T., et al., (including Bair, A.), 2024, PSJ, 5, 281, The Extreme Activity in Comet HaleBopp (C/1995 O1): Investigations of Extensive Narrowband Photoelectric Photometry
    Abstract

    Conventional narrowband photoelectric photometry of Comet HaleBopp (1995 O1) was obtained on 99 nights from mid-1995 to early-2000, yielding gas and dust production rates over an unprecedented range of time and distance. The appearance of HaleBopp (H-B) presented a prime opportunity for active comet studies, and its inherent brightness and orbital geometry allowed the characterization of its long-term activity. Throughout the apparition, H-B released, by far, more gas and dust than any other comet ever measured. As a very high dust-to-gas ratio object, dust production was successfully measured throughout the apparition, with the dust consistently slightly red in color. All five gas species including OH and NH were detected just inside of 5 au inbound, while C₂ and C₃ were detected to just past 5 au outbound, and CN was followed until nearly 7.7 au. Heliocentric distance dependencies ranged between 1.2 and 2.7 in loglog space, with the extremes magnified by the large extrapolations in Haser model parameters at large distances. H-B's enormous size and associated extremely high outgassing resulted in a much larger collisional zone, which in turn yielded outflow velocities more than 2 higher than ever previously measured at comparable distances. Even so, volatile composition remained within the "typical" classification, consistent with most Oort Cloud comets, and water production follows the expected curve based on a standard water vaporization model. However, seasonal effects provided evidence for inhomogeneities among the major source regions on the surface of the nucleus. Preliminary modeling of the nucleus and coma successfully matches this seasonal behavior.

11. Barat, S., Desert, J., Goyal, J., et al., (including Sikora, J.), 2024, A&A, 692, A198, First comparative exoplanetology within a transiting multi-planet system: Comparing the atmospheres of V1298 Tau b and c
    Abstract

    The V1298 Tau system is a multi-planet system that provides the opportunity to perform comparative exoplanetology between planets orbiting the same star. Because of its young age (2030 Myr), this system also provides the opportunity to compare the planet's early evolutionary properties, right after their formation. We present the first atmospheric comparison between two transiting exoplanets within the same multiple planet system: V1298 Tau b and V1298 Tau c. We observed one primary transit for each planet with the Hubble Space Telescope (HST), using Grism 141 (G141) of Wide Field Camera 3 (WFC3). We fit the spectroscopic light curves using state-of-the-art techniques to derive the transmission spectrum for planet c and adopted the transmission spectrum of planet b obtained with the same observing configuration and data analysis methods from previous studies. We measured the mass of planet b and c (8₂⁺⁴, 17₆⁺¹³ M ; respectively) from the transmission spectrum and found the two planets to have masses in the Neptune or sub-Neptune regime. Using atmospheric retrievals, we measured and compared the atmospheric metallicities of planet b and c (logZ/Z=2.04_0.59^0.69, logZ/Z = 0.16_0.94^1.15, respectively), and found them to be consistent with the solar or sub-solar, which is low (at least one order of magnitude) compared to known mature Neptune and sub-Neptune planets. This discrepancy could be explained by ongoing early evolutionary mechanisms, which are expected to enrich the atmospheres of such young planets as they mature. Alternatively, the observed spectrum of planet c can be explained by atmospheric hazes, which is in contrast to planet b, where efficient haze formation can be ruled out. Higher haze formation efficiency in planet c could be due to differences in atmospheric composition, temperature and/or higher UV flux compared to planet b. In addition, planet c is likely to experience a higher fraction of mass loss compared to planet b, given its proximity to the host star.

12. Pinilla-Alonso, N., Licandro, J., Brunetto, R., et al., (including Stansberry, J.), 2024, A&A, 692, L11, Unveiling the ice and gas nature of active centaur (2060) Chiron using the James Webb Space Telescope
    Abstract

    Context. (2060) Chiron is a large centaur that has been reported active on multiple occasions at relatively large heliocentric distances, including during aphelion passage. Studies of Chiron's coma during active periods have resulted in the detection of CN and CO outgassing. Additionally, Chiron is surrounded by a disk of debris that varies with time. Significant work remains to be undertaken to comprehend the activation mechanisms on Chiron and the parent molecules of the gas phases detected. Aims. This work reports the study of the ices on Chiron's surface and coma and seeks spectral indicators of volatiles associated with the activity. Additionally, we discuss how these detections could be related to the activation mechanism for Chiron and, potentially, other centaurs. Methods. In July 2023, the James Webb Space Telescope (JWST) observed Chiron when it was active near its aphelion. We present JWST/NIRSpec spectra from 0.97 to 5.27 m with a resolving power of 1000, and compare them with laboratory data for identification of the spectral bands. Results We report the first detections on Chiron of absorption bands of several volatile ices, including CO₂, CO, C₂H₆, C₃H₈, and C₂H₂. We also confirm the presence of water ice in its amorphous state. A key discovery arising from these data is the detection of fluorescence emissions of CH₄, revealing the presence of a gas coma rich in this hyper-volatile molecule, which we also identify to be in non-local thermal equilibrium (non-LTE). CO₂ gas emission is also detected in the fundamental stretching band at 4.27 m. We argue that the presence of CH₄ emission is the first proof of the desorption of CH₄ due to a density phase transition of amorphous water ice at low temperature in agreement with the estimated temperature of Chiron during the JWST observations (61 K). Detection of photolytic and proton irradiation products of CH₄ and CO₂ on the surface, in the coma ice grains, or in the ring material is also detected via a forest of absorption features from 3.5 to 5.3 m.

13. Raposa, S., Tan, S., Grundy, W., et al., (including Hanley, J., Engle, A., Thieberger, C.), 2024, PSJ, 5, 275, Deriving the N₂CO Binary Phase Diagram Using Experimental Techniques and Thermodynamics
    Abstract

    In the distant outer solar system, carbon monoxide (CO) and nitrogen (N₂) ices tend to be colocated in the same deposits due to their similar molecular weights and sublimation properties. For instance, these volatiles are abundant on the surfaces of Pluto and Triton, so knowledge of their phase behavior is necessary for understanding surface evolution and geology. However, it is presently unclear how mixing between CO and N₂ molecules affects the physical properties of such mixtures. Here, we measured the liquidus, solidus, and alphabeta phase transitions for the N₂ and CO binary system. We observed the liquidus by using visual inspection. The solidus and alphabeta transitions were measured by using Raman spectroscopy. The laboratory results were later compared to a thermodynamic model, CRYOCHEM 2.0. The liquidus and solidus were consistent with CRYOCHEM 2.0. However, the alphabeta coexistence region is shown to be narrower in the laboratory results than in the thermodynamic model. Finally, we present a method for deriving the compositions of a sample using Raman spectroscopy (Appendices A.1 and A.2).

14. Hasler, S., Mayorga, L., Grundy, W., et al., 2024, PSJ, 5, 267, Observations of Uranus at High Phase Angle as Seen by New Horizons
    Abstract

    We present flux measurements of Uranus observed at phase angles of 43.9, 44.0, and 52.4 by the Multispectral Visible Imaging Camera on the New Horizons spacecraft during 2023, 2010, and 2019, respectively. New Horizons imaged Uranus at a distance of about 2470 au (2023) in four color filters, with bandpasses of 400550 nm, 540700 nm, 780975 nm, and 860910 nm. High-phase-angle observations are of interest for studying the energy balance of Uranus, constraining the atmospheric scattering behavior, and understanding the planet as an analog for ice giant exoplanets. The new observations from New Horizons provide access to a wider wavelength range and different season compared with previous observations from the Voyager spacecraft. We performed aperture photometry on the New Horizons observations of Uranus to obtain its brightness in each photometric band. The photometry suggests that Uranus may be darker than predicted by a Lambertian phase curve in the blue and red filters. Comparison to simultaneous low-phase Hubble WFC3 and ground-based community-led observations indicates a lack of large-scale features at full phase that would introduce variation in the rotational light curve. The New Horizons reflectance in the blue (492 nm) and red (624 nm) filters does not exhibit statistically significant variation and is consistent with the expected error bars. These results place new constraints on the atmospheric model of Uranus and its reflectivity. The observations are analogous to those from future exoplanet direct-imaging missions, which will capture unresolved images of exoplanets at partial phases. These results will serve as a "ground truth" with which to interpret exo-ice-giant data.

15. Torres, G., Boden, A., Monnier, J., et al., (including van Belle, G.), 2024, ApJ, 977, 43, Absolute Dimensions of the Interferometric Binary HD 174881: A Test of Stellar Evolution Models for Evolved Stars
    Abstract

    We report high-resolution spectroscopic monitoring and long-baseline interferometric observations with the Palomar Testbed Interferometer (PTI) of the 215 day binary system HD 174881 (K1 II-III), composed of two giant stars. The system is spatially resolved with the PTI, as well as in archival measurements with the CHARA Array. Our analysis of these observations, along with an analysis of the spectral energy distribution, have allowed us to infer accurate values for the absolute masses ( and ), radii (34.0 1.3 and 22.7 1.8 R ), effective temperatures (4620 100 and 4880 150 K), and bolometric luminosities of both components, as well as other properties including the orbital parallax (distance). These provide valuable tests of stellar evolution models for evolved stars, which are still relatively uncommon compared to the situation for main-sequence stars. We find generally good agreement of all of these properties of HD 174881 with two sets of recent models (MIST and PARSEC) at compositions near solar, for ages of 255273 Myr. We also find evidence of an infrared excess, based largely on the flux measurements from IRAS at 60 and 100 m.

16. Massey, P., Neugent, K., Morrell, N., et al., 2024, ApJ, 977, 82, The Nature of a Recently Discovered WolfRayet Binary: Archetype of Stripping?
    Abstract

    LMCe055-1 was recently discovered in a survey for WolfRayets (WRs) in the Large Magellanic Cloud, and classified as a WN4/O4, a lower-excitation version of the WN3/O3 class discovered as part of the same survey. Its absolute magnitude precluded it from being a WN4+O4 binary. Optical Gravitational Lensing Experiment photometry shows shallow primary and secondary eclipses with a 2.2 days period. The spectral characteristics and short period pointed to a possible origin due to binary stripping. Such stripped WR binaries should be common but have proven elusive to identify conclusively. In order to establish its nature, we obtained Hubble Space Telescope ultraviolet and Magellan optical spectra, along with imaging. Our work shows that the WR emission and He II absorption arise in one star, and the He I absorption in another. The He I contributor is the primary of the 2.2 days system and exhibits 300 km s¹ radial velocity variations on that timescale. However, the WR star shows 3040 km s¹ radial velocity variations, with a likely 35 days period and a highly eccentric orbit. Possibly LMCe055-1 is a physical triple, but that would require the 2.2 days pair to have been captured by the WR star. A more likely explanation is that the WR star has an unseen companion in a 35 days orbit and that the 2.2 days pair is in a longer-period orbit about the two. Such examples of multiple systems are well known among massive stars, such as HD 5980. Regardless, we argue that it is highly unlikely that the WR component of the LMCe055-1 system resulted from stripping. ^* This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. It also uses observations made with the NASA/ESA Hubble Space Telescope (HST), obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations were associated with programs GO-16299 (PI: Massey) and GO-16093 (ULLYSES, PI: Roman-Duval).

17. Protopapa, S., Raut, U., Wong, I., et al., (including Stansberry, J., Grundy, W.), 2024, NatCo, 15, 8247, Detection of carbon dioxide and hydrogen peroxide on the stratified surface of Charon with JWST
    Abstract

    Charon, Pluto's largest moon, has been extensively studied, with research focusing on its primitive composition and changes due to radiation and photolysis. However, spectral data have so far been limited to wavelengths below 2.5 m, leaving key aspects unresolved. Here we present the detection of carbon dioxide (CO₂) and hydrogen peroxide (H₂O₂) on the surface of Charon's northern hemisphere, using JWST data. These detections add to the known chemical inventory that includes crystalline water ice, ammonia-bearing species, and tholin-like darkening constituents previously revealed by ground- and space-based observations. The H₂O₂ presence indicates active radiolytic/photolytic processing of the water ice-rich surface by solar ultraviolet and interplanetary medium Lyman- photons, solar wind, and galactic cosmic rays. Through spectral modeling of the surface, we show that the CO₂ is present in pure crystalline form and, possibly, in intimately mixed states on the surface. Endogenically sourced subsurface CO₂ exposed on the surface is likely the primary source of this component, with possible contributions from irradiation of hydrocarbons mixed with water ice, interfacial radiolysis between carbon deposits and water ice, and the implantation of energetic carbon ions from the solar wind and solar energetic particles.

18. Hsieh, H., Sheppard, S., Thirouin, A., 2024, RNAAS, 8, 283, Confirmation of Recurrent Activity of Main-Belt Comet 456P/PANSTARRS (P/2021 L4)
    Abstract

    We report observations from the Magellan Baade Telescope and Lowell Discovery Telescope on UT 2024 October 3 and 26, respectively, confirming for the first time that active asteroid 456P/PANSTARRS is recurrently active (exhibiting a short anti-solar tail on both dates, following previous observations of activity in 2021 when it was discovered), indicating that its activity is likely driven by the sublimation of volatile ice, leading us to consider it a main-belt comet (MBC). We also report observations from the Gemini South Observatory on UT 2023 June 15 in which the object appears inactive, where we measure an absolute magnitude of HV=(17.50.1) mag for the nucleus (assuming G_V = 0.15), corresponding to an effective nucleus radius of rn=(1.00.2) km (assuming an albedo of pV=0.05) . 456P is now the 14th MBC for which recurrent activity has been observationally confirmed.

19. Brooks, H., Caselden, D., Kirkpatrick, J., et al., (including Tang, S.), 2024, AJ, 168, 211, Discovery of 118 New Ultracool Dwarf Candidates Using Machine-learning Techniques
    Abstract

    We present the discovery of 118 new ultracool dwarf candidates, discovered using a new machine-learning tool, named SMDET, applied to time-series images from the Wide-field Infrared Survey Explorer. We gathered photometric and astrometric data to estimate each candidate's spectral type, distance, and tangential velocity. This sample has a photometrically estimated spectral class distribution of 28 M dwarfs, 64 L dwarfs, and 18 T dwarfs. We also identify a T-subdwarf candidate, two extreme T-subdwarf candidates, and two candidate young ultracool dwarfs. Five objects did not have enough photometric data for any estimations to be made. To validate our estimated spectral types, spectra were collected for two objects, yielding confirmed spectral types of T5 (estimated T5) and T3 (estimated T4). Demonstrating the effectiveness of machine-learning tools as a new large-scale discovery technique.

20. Sanchez, B., Brout, D., Vincenzi, M., et al., (including Kuehn, K.), 2024, ApJ, 975, 5, The Dark Energy Survey Supernova Program: Light Curves and 5 Yr Data Release
    Abstract

    We present griz photometric light curves for the full 5 yr of the Dark Energy Survey Supernova (DES-SN) program, obtained with both forced point-spread function photometry on difference images (DiffImg) performed during survey operations, and scene modelling photometry (SMP) on search images processed after the survey. This release contains 31,636 DiffImg and 19,706 high-quality SMP light curves, the latter of which contain 1635 photometrically classified SNe that pass cosmology quality cuts. This sample spans the largest redshift (z) range ever covered by a single SN survey (0.1 < z < 1.13) and is the largest single sample from a single instrument of SNe ever used for cosmological constraints. We describe in detail the improvements made to obtain the final DES-SN photometry and provide a comparison to what was used in the 3 yr DES-SN spectroscopically confirmed Type Ia SN sample. We also include a comparative analysis of the performance of the SMP photometry with respect to the real-time DiffImg forced photometry and find that SMP photometry is more precise, more accurate, and less sensitive to the host-galaxy surface brightness anomaly. The public release of the light curves and ancillary data can be found at github.com/des-science/DES-SN5YR and doi:10.5281/zenodo.12720777.

21. Vincenzi, M., Brout, D., Armstrong, P., et al., (including Kuehn, K.), 2024, ApJ, 975, 86, The Dark Energy Survey Supernova Program: Cosmological Analysis and Systematic Uncertainties
    Abstract

    We present the full Hubble diagram of photometrically classified Type Ia supernovae (SNe Ia) from the Dark Energy Survey supernova program (DES-SN). DES-SN discovered more than 20,000 SN candidates and obtained spectroscopic redshifts of 7000 host galaxies. Based on the light-curve quality, we select 1635 photometrically identified SNe Ia with spectroscopic redshift 0.10 < z < 1.13, which is the largest sample of supernovae from any single survey and increases the number of known z > 0.5 supernovae by a factor of 5. In a companion paper, we present cosmological results of the DES-SN sample combined with 194 spectroscopically classified SNe Ia at low redshift as an anchor for cosmological fits. Here we present extensive modeling of this combined sample and validate the entire analysis pipeline used to derive distances. We show that the statistical and systematic uncertainties on cosmological parameters are M,stat+sysCDM= 0.017 in a flat CDM model, and (M,w)stat+syswCDM = (0.082, 0.152) in a flat wCDM model. Combining the DES SN data with the highly complementary cosmic microwave background measurements by Planck Collaboration reduces by a factor of 4 uncertainties on cosmological parameters. In all cases, statistical uncertainties dominate over systematics. We show that uncertainties due to photometric classification make up less than 10% of the total systematic uncertainty budget. This result sets the stage for the next generation of SN cosmology surveys such as the Vera C. Rubin Observatory's Legacy Survey of Space and Time.

22. Bhattacharyya, J., Peter, A., Martini, P., et al., (including Kuehn, K.), 2024, ApJ, 975, 244, Environmental Quenching of Low-surface-brightness Galaxies Near Hosts from Large Magellanic Cloud to Milky Way Mass Scales
    Abstract

    Low-surface-brightness galaxies (LSBGs) are excellent probes of quenching and other environmental processes near massive galaxies. We study an extensive sample of LSBGs near massive hosts in the local universe that are distributed across a diverse range of environments. The LSBGs with surface-brightness eff,g>24.2magarcsec2 are drawn from the Dark Energy Survey Year 3 catalog while the hosts with masses 9.0<log(M/M)<11.0 comparable to the Milky Way and the Large Magellanic Cloud are selected from the z0MGS sample. We study the projected radial density profiles of LSBGs as a function of their color and surface brightness around hosts in both the rich FornaxEridanus cluster environment and the low-density field. We detect an overdensity with respect to the background density, out to 2.5 times the virial radius for both hosts in the cluster environment and the isolated field galaxies. When the LSBG sample is split by g i color or surface brightness _{eff, g} , we find the LSBGs closer to their hosts are significantly redder and brighter, like their high-surface-brightness counterparts. The LSBGs form a clear "red sequence" in both the cluster and isolated environments that is visible beyond the virial radius of the hosts. This suggests preprocessing of infalling LSBGs and a quenched backsplash population around both host samples. More so, the relative prominence of the "blue cloud" feature implies that preprocessing is ongoing near the isolated hosts compared to the cluster environment where the LSBGs are already well processed.

23. Masters, A., Szalay, J., Zomerdijk-Russell, S., et al., (including Kao, M.), 2024, GeoRL, 51, 2024GL111623, Solar Wind Power Likely Governs Uranus' Thermosphere Temperature
    Abstract

    Observations of Uranus in the near-infrared by ground-based telescopes from 1992 to 2018 have shown that the planet's upper atmosphere (thermosphere) steadily cooled from 700 to 450 K. We explain this cooling as due to the concurrent decline in the power of the solar wind incident on Uranus' magnetic field, which has dropped by 50% over the same period due to solar activity trends longer than the 11-year solar cycle. Uranus' thermosphere appears to be more strongly governed by the solar wind than any other planet where we have assessed this coupling so far. Uranus' total auroral power may also have declined, in contrast with the power of the radio aurora that we expect has been predominantly modulated by the solar cycle. In the absence of strong local driving, planets with sufficiently large magnetospheres may also have thermospheres predominantly governed by the stellar wind, rather than stellar radiation.

24. Kareta, T., Vida, D., Micheli, M., et al., (including Moskovitz, N., Shafransky, B.), 2024, PSJ, 5, 253, Telescope-to-Fireball Characterization of Earth Impactor 2022 WJ1
    Abstract

    Comparing how an asteroid appears in space to its ablation behavior during atmospheric passage and finally to the properties of associated meteorites represents the ultimate probe of small near-Earth objects. We present observations from the Lowell Discovery Telescope and multiple meteor camera networks of 2022 WJ1, an Earth impactor that was disrupted over the North American Great Lakes on 2022 November 19. As far as we are aware, this is only the second time an Earth impactor has been specifically observed in multiple passbands prior to impact to characterize its composition. The orbits derived from telescopic observations submitted to the Minor Planet Center and ground-based meteor cameras result in impact trajectories that agree to within 40 m, but no meteorites have been found as of yet. The telescopic observations suggest a silicate-rich surface and thus a moderate-to-high albedo, which results in an estimated size for the object of just D = 4060 cm. Modeling the fragmentation of 2022 WJ1 during its fireball phase also suggests an approximate 0.5 m original size for the object as well as an ordinary chondrite-like strength. These two lines of evidence both support that 2022 WJ1 was likely an S-type chondritic object and the smallest asteroid compositionally characterized in space. We discuss how best to combine telescopic and meteor camera data sets, how well these techniques agree, and what can be learned from studies of ultrasmall asteroids.

25. Callingham, J., Pope, B., Kavanagh, R., et al., (including Kao, M.), 2024, NatAs, 8, 1359, Radio signatures of star-planet interactions, exoplanets and space weather
    Abstract

    Radio detections of stellar systems provide a window onto stellar magnetic activity and the space weather conditions of extrasolar planets information that is difficult to obtain at other wavelengths. The maturation of low-frequency radio instruments and the plethora of wide-field radio surveys have driven recent advances in observing auroral emissions from radio-bright low-mass stars and exoplanets. To guide us in putting these recent results in context, we introduce the foremost local analogues for the field: solar bursts and the aurorae found on Jupiter. We detail how radio bursts associated with stellar flares are foundational to the study of stellar coronae, and time-resolved radio dynamic spectra offer one of the best prospects for detecting and characterizing coronal mass ejections from other stars. We highlight the possibility of directly detecting coherent radio emission from exoplanetary magnetospheres, as well as early tentative results. We bridge this discussion with the field of brown dwarf radio emission the larger and stronger magnetospheres of these stars are amenable to detailed study with current instruments. Bright, coherent radio emission is also predicted from magnetic interactions between stars and close-in planets. We discuss the underlying physics of these interactions and the implications of recent provisional detections for exoplanet characterization. We conclude with an overview of outstanding questions in the theory of stellar, star-planet interaction and exoplanet radio emission and the potential of future facilities to answer them.

26. Hemmelgarn, S., Moskovitz, N., Pilorz, S., et al., 2024, PSJ, 5, 242, How Meteor Showers Can Guide the Search for Long-period Comets
    Abstract

    With orbital periods longer than 200 yr, most long-period comets (LPCs) remain undiscovered until they are in-bound toward perihelion. The comets that pass close to Earth's orbit are potentially hazardous objects. Those with orbital periods up to 4000 yr tend to have passed close to Earth's orbit in a previous orbit and produced a meteoroid stream dense enough to be detected at Earth as a meteor shower. In anticipation of Rubin Observatory's Legacy Survey of Space and Time (LSST), we investigate how these meteor showers can guide dedicated searches for their parent comets. Assuming search parameters informed by LSST, we calculated where the 17 known parent bodies of LPC meteor showers would have been discovered based on a cloud of synthetic comets generated from the shower properties as measured at Earth. We find that the synthetic comets predict the on-sky location of the parent comets at the time of their discovery. The parent comet's location on average would have been 1.51 1.19 from a line fit through the synthetic comet cloud. The difference between the heliocentric distance of the parent and mean heliocentric distance of synthetic comets on the line was 2.09 1.89 au for comets with unknown absolute nuclear magnitudes and 0.96 0.80 au for comets with known absolute nuclear magnitudes. We applied this method to the -Hydrids, the proposed meteor shower of comet Nishimura, and found that it successfully matched the pre-covery location of this comet 8 months prior to Nishimura's discovery.

27. Jenniskens, P., Moskovitz, N., 2024, eMetN, 9, 397, 2024 outburst of September psi-Cassiopeiids
    Abstract

    A meteor outburst was detected by low-light level video camera networks in Arizona and California on September 4, 2024. The outburst was of short duration. Past data show a weak annual shower at these coordinates, which stands out from the nearby sporadic meteors by having a slightly lower entry speed. The shower was in outburst before in 2014.

28. Clark, C., van Belle, G., Horch, E., et al., (including von Braun, K., Llama, J.), 2024, AJ, 168, 229, Erratum: "The POKEMON Speckle Survey of Nearby M Dwarfs. II. Observations of 1125 Targets" (2024, AJ, 167, 56)
    Abstract

    No abstract found.

29. Clark, C., van Belle, G., Horch, E., et al., (including von Braun, K., Skiff, B., Llama, J.), 2024, AJ, 168, 228, Erratum: "The POKEMON Speckle Survey of Nearby M Dwarfs. III. The Stellar Multiplicity Rate of M Dwarfs within 15 pc" (2024, AJ, 167, 174)
    Abstract

    No abstract found.

30. Popovic, B., Wiseman, P., Sullivan, M., et al., (including Kuehn, K.), 2024, MNRAS, 534, 2263, Modelling the impact of host galaxy dust on type Ia supernova distance measurements
    Abstract

    Type Ia Supernovae (SNe Ia) are a critical tool in measuring the accelerating expansion of the universe. Recent efforts to improve these standard candles have focused on incorporating the effects of dust on distance measurements with SNe Ia. In this paper, we use the state-of-the-art Dark Energy Survey 5 year sample to evaluate two different families of dust models: empirical extinction models derived from SNe Ia data and physical attenuation models from the spectra of galaxies. In this work, we use realistic simulations of SNe Ia to forward-model different models of dust and compare summary statistics in order to test different assumptions and impacts on SNe Ia data. Among the SNe Ia-derived models, we find that a logistic function of the total-to-selective extinction $R_V$ best recreates the correlations between supernova distance measurements and host galaxy properties, though an additional 0.02 mag of grey scatter is needed to fully explain the scatter in SNIa brightness in all cases. These empirically derived extinction distributions are highly incompatible with the physical attenuation models from galactic spectral measurements. From these results, we conclude that SNe Ia must either preferentially select extreme ends of galactic dust distributions, or that the characterization of dust along the SNe Ia line-of-sight is incompatible with that of galactic dust distributions.

31. Demirbozan, U., Nadathur, S., Ferrero, I., et al., (including Kuehn, K.), 2024, MNRAS, 534, 2328, The gravitational lensing imprints of DES Y3 superstructures on the CMB: a matched filtering approach
    Abstract

    Low-density cosmic voids gravitationally lens the cosmic microwave background (CMB), leaving a negative imprint on the CMB convergence $\kappa$. This effect provides insight into the distribution of matter within voids, and can also be used to study the growth of structure. We measure this lensing imprint by cross-correlating the Planck CMB lensing convergence map with voids identified in the Dark Energy Survey Year 3 (DES Y3) data set, covering approximately 4200 deg$^2$ of the sky. We use two distinct void-finding algorithms: a 2D void-finder that operates on the projected galaxy density field in thin redshift shells, and a new code, Voxel, which operates on the full 3D map of galaxy positions. We employ an optimal matched filtering method for cross-correlation, using the Marenostrum Institut de Ciencies de l'Espai N-body simulation both to establish the template for the matched filter and to calibrate detection significances. Using the DES Y3 photometric luminous red galaxy sample, we measure $A_\kappa$, the amplitude of the observed lensing signal relative to the simulation template, obtaining $A_\kappa = 1.03 \pm 0.22$ ($4.6\sigma$ significance) for Voxel and $A_\kappa = 1.02 \pm 0.17$ ($5.9\sigma$ significance) for 2D voids, both consistent with Lambda cold dark matter expectations. We additionally invert the 2D void-finding process to identify superclusters in the projected density field, for which we measure $A_\kappa = 0.87 \pm 0.15$ ($5.9\sigma$ significance). The leading source of noise in our measurements is Planck noise, implying that data from the Atacama Cosmology Telescope, South Pole Telescope and CMB-S4 will increase sensitivity and allow for more precise measurements.

32. Jenniskens, P., Estrada, P., Pilorz, S., et al., (including Avner, D., Blomquist, S., Gialluca, M., Hemmelgarn, S., Moskovitz, N.), 2024, Icar, 423, 116229, Properties of outer solar system pebbles during planetesimal formation from meteor observations
    Abstract

    Observations of proto-planetary disks, as well as theoretical modeling, suggest that in the late stages of accretion leading up to the formation of planetesimals, particles grew to pebbles the size of 1-mm to tens of cm, depending on the location and ambient conditions in the disk. That is the same size range that dominates the present-day comet and primitive asteroid mass loss. Meteoroids that size cause visible meteors on Earth. Here, we hypothesize that the size distribution and the physical and chemical properties of young meteoroid streams still contain information about the conditions in the solar nebula during these late stages of accretion towards planetesimal formation. If so, they constrain where long-period (Oort Cloud) comets, Jupiter-family (Scattered Disk Kuiper Belt) comets, and primitive asteroids (Asteroid Belt) formed. From video and visual observations of 47 young meteor showers, we find that freshly ejected meteoroids from long-period comets tend to have low bulk density and are distributed with equal surface area per log-mass interval (magnitude distribution index 1.85), suggesting gentle accretion conditions. Jupiter-family comets, on the other hand, mostly produce meteoroids twice as dense and distributed with a steeper 2.15 or even 2.5, which implies that those pebbles grew from particles fragmenting in a collisional cascade or by catastrophic collisions, respectively. Some primitive asteroids show > 2.5, with most mass in small particles, indicating an even more aggressive fragmentation by processes other than mutual collisions. Both comet populations contain an admixture of compact materials that are sometimes sodium-poor, but Jupiter-family comets show a higher percentage (8% on average) than long-period comet showers (4%) and a wider range of percentages among comets. While there are exceptions in both groups, the implication is that most long-period comets formed under gentle particle growth conditions, possibly near the 30 AU edge of the Trans Neptunian Disk, while most Jupiter family comets formed closer to the Sun where pebbles reached or passed the fragmentation barrier, and primitive asteroids formed in the region where the cores of the giant planets formed. This is possible if the Scattered Disk represents all objects scattered by Neptune during its migration, while the present-day outer Oort cloud formed only during and after the time of the planet instability, well after the Sun had moved away from sibling stars.

33. Tang, S., Johns-Krull, C., Prato, L., et al., 2024, ApJ, 973, 124, Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines
    Abstract

    As part of the Young Exoplanets Spectroscopic Survey, this study explores the spot variability of 13 T Tauri Stars (TTSs) in the near-infrared H band, using spectra from the Immersion GRating INfrared Spectrometer. By analyzing effective temperature (T _eff) sensitive lines of atomic Fe I at 1.56259 m and 1.56362 m, and molecular OH at 1.56310 and 1.56317 m, we develop an empirical equivalent width ratio (EWR) relationship for T _eff in the range of 34005000 K. This relationship allows for precise relative T _eff estimates to within tens of Kelvin and demonstrates compatibility with solar metallicity target models. However, discrepancies between observational data and model predictions limit the extension of the T _effEWR relationship to a broader parameter space. Our study reveals that both classical and weak-line TTSs can exhibit T _eff variations exceeding 150 K over a span of 2 yr. The detection of a quarter-phase delay between the EWR and radial velocity phase curves in TTSs indicates spot-driven signals. A phase delay of 0.06 0.13 for CI Tau, however, suggests additional dynamics, potentially caused by planetary interaction, inferred from a posited 1:1 commensurability between the rotation period and orbital period. Moreover, a positive correlation between T _eff variation amplitude and stellar inclination angle supports the existence of high-latitude spots on TTSs, further enriching our understanding of stellar surface activity in young stars.

34. Baylis-Aguirre, D., Creech-Eakman, M., van Belle, G., 2024, Galax, 12, 72, A "Wonderful" Reference Dataset of Mira Variables
    Abstract

    The conditions in Mira variable atmospheres make them wonderful laboratories to study a variety of stellar physics such as moleculegrain formation, dust production, shock chemistry, stellar winds, mass loss, opacity-driven pulsation, and shocks. We were awarded an NSF grant to analyze over a decade of synoptic observations from the Palomar Testbed Interferometer (PTI) of 106 Miras to curate a Mira Reference Dataset. The Miras included in this dataset include M-types, S-types, and C-types, and span a wide range of pulsation periods. PTI measured K-band angular sizes that when combined with a distance allow us to directly determine fundamental stellar parameters such as effective temperature, radial size, and bolometric flux. Supplementing observations with interferometric measurements of the stars opens the Mira laboratory to a wealth of different experiments. We provide two case studies to serve as examples of the power of the Mira Reference Dataset. The first case study describes combining PTI measurements with Spitzer IRS spectra of M-type Miras, which allowed us to fully characterize CO2 gas in their atmospheres. The second case study examines how PTI narrow-band data can be used to study phase-dependent pulsation effects on the stellar atmosphere. We provide a list of all the Miras (with coordinates) included in the set for anyone who would like to add them to their observing programs. All the data we produce and collate for this Mira Reference Dataset will be hosted and curated on a website open to the public so that other researchers and citizen scientists can participate in expanding the utility and body of knowledge on this set of "wonderful" stars.

35. Reipurth, B., Briceno, C., Geballe, T., et al., (including Skiff, B.), 2024, AJ, 168, 143, Haro 5-2: A New Pre-main-sequence Quadruple Stellar System
    Abstract

    We have discovered that the H emission-line star Haro 5-2, located in the 36 Myr old Ori OB1b association, is a young quadruple system. The system has a 2+2 configuration, with an outer separation of 2.6 and with resolved subarcsecond inner binary components. The brightest component, Aa, dominates the A-binary; it is a weak-line T Tauri star with spectral type M2.51. The two stars of the B component are equally bright at J, but the Bb star is much redder. Optical spectroscopy of the combined B pair indicates a rich emission-line spectrum with a M31 spectral type. The spectrum is highly variable and switches back and forth between a classical and a weak-line T Tauri star. In the near-IR, the spectrum shows Paschen and Brackett in emission, indicative of active accretion. A significant mid-IR excess reveals the presence of circumstellar or circumbinary material in the system. Most multiple systems are likely formed during the protostellar phase, involving flybys of neighboring stars followed by an inspiraling phase driven by accretion from circumbinary material and leading to compact subsystems. However, Haro 5-2 stands out among young 2+2 quadruples, as the two inner binaries are unusually wide relative to the separation of the A and B pair, allowing future studies of the individual components. Assuming the components are coeval, the system could potentially allow stringent tests of pre-main-sequence evolutionary models.

36. Marin, L., Massey, P., Skiff, B., et al., (including Farrell, K.), 2024, AJ, 168, 167, The Discovery of Three Galactic WolfRayet Stars
    Abstract

    WolfRayet stars (WRs) are evolved massive stars in the brief stage before they undergo core collapse. Not only are they rare, but they also can be particularly difficult to find due to the high extinction in the Galactic plane. This paper discusses the discovery of three new Galactic WRs previously classified as H emission stars, but 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 calculate 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, adding to our knowledge of the role that binarity plays in massive star evolution.

37. Pingel, N., Chen, H., Stanimirovic, S., et al., (including Hunter, D.), 2024, ApJ, 974, 93, The Local Group L-band Survey: The First Measurements of Localized Cold Neutral Medium Properties in the Low-metallicity Dwarf Galaxy NGC 6822
    Abstract

    Measuring the properties of the cold neutral medium (CNM) in low-metallicity galaxies provides insights into heating and cooling mechanisms in early Universe-like environments. We report detections of two localized atomic neutral hydrogen (H I) absorption features in NGC 6822, a low-metallicity (0.2 Z ) dwarf galaxy in the Local Group. These are the first unambiguous CNM detections in a low-metallicity dwarf galaxy outside the Magellanic Clouds. The Local Group L-band Survey (LGLBS) enabled these detections, due to its high spatial (15 pc for H I emission) and spectral (0.4 km s¹) resolution. We introduce LGLBS and describe a custom pipeline for searching for H I absorption at high angular resolution and extracting associated H I emission. A detailed Gaussian decomposition and radiative transfer analysis of the NGC 6822 detections reveals five CNM components, with key properties: a mean spin temperature of 32 6 K, a mean CNM column density of 3.1 10²⁰ cm², and CNM mass fractions of 0.33 and 0.12 for the two sightlines. Stacking nondetections does not reveal low-level signals below our median optical depth sensitivity of 0.05. One detection intercepts a star-forming region, with the H I absorption profile encompassing the CO (21) emission, indicating coincident molecular gas and a depression in high-resolution H I emission. We also analyze a nearby sightline with deep, narrow H I self-absorption dips, where the background warm neutral medium is attenuated by intervening CNM. The association of CNM, CO, and H emissions suggests a close link between the colder, denser H I phase and star formation in NGC 6822.

38. Burris, W., Chandler, C., Trujillo, C., et al., (including Kueny, J.), 2024, DPS, 56, 102.02, A Weight Scheme to Optimize Citizen Science Results from the "Active Asteroids" project
    Abstract

    As part of the NASA Partner Citizen Science project Active Asteroids (Chandler et al. 2024; https://activeasteroids.net), hosted on the Zooniverse website, we analyzed the ability of Citizen Scientists at classifying thumbnail images of small solar system bodies as being active, i.e., showing comet-like comae or tails. Each image is classified by up to 15 users generating a score used to determine which objects warrant further investigation by the science team, roughly 1%. Our analysis shows that person-to-person there is significant variation among users' abilities to correctly identify an object as being active or not, and a given user may improve (the nominal case) or worsen with time. This indicates a need to weight users' classifications and track their weight temporally. We identified three metrics to base a user's weight: (1) the total number of images they classify, (2) their ability to detect activity in training images (which all show activity), and (3) a de-optimism bias (if they see activity far more often than 1% of the time, that indicates optimistic classifying and not necessarily correct classifying). We used this combination of metrics, each of which is individually weighted, to determine a threshold score that helps us discern which images warrant further investigation. The score was chosen to maximize the amount of images likely to contain active objects and minimize the amount unlikely to contain active objects. The weight scheme proved more effective at filtering likely and unlikely active candidates than a naive assessment of the number of users who saw activity versus the number who did not. We believe his approach is undoubtedly useful for other Citizen Science Projects.

39. Barea-Carrion, W., Thieberger, C., Hanley, J., et al., (including Grundy, W.), 2024, DPS, 56, 104.01, The Effect of Propane on Two Liquid Systems in Titan's lakes
    Abstract

    Titan's lakes and seas are predominantly composed of methane, ethane, and dissolved atmospheric nitrogen. Additionally, trace species such as propane may have dissolved from the atmosphere and their effects on the ternary system (CH4-C2H6-N2) are not well-studied. Our research looks to understand what can occur at depth in Titan's seas with these hydrocarbons. Studies suggest that at depth, and therefore a higher pressure, it is possible for Liquid-Liquid-Vapor equilibrium (LLV) to form. To address this, we conducted a series of experiments in the Astrophysical Materials Lab at NAU on the quaternary system (CH4-C2H6-C3H8-N2) with different mixing ratios, varying temperatures, all at 2.0 bar to simulate ~50m depth. Our preliminary results show that in methane rich environments (80:20 CH4:C2H6) and propane rich mixtures (>60%), LLV forms in colder environments (~86 K), where propane poor mixtures form at ~87 K. For equal amounts of methane and ethane, LLV forms at 85 K regardless of the propane concentration. And for ethane rich systems (20:80 CH4:C2H6), LLV tends to form in even colder environments than the other two cases (84 K). This knowledge improves our understanding of Titan's unique hydrocarbon-based hydrological cycle and gives us a picture of the chemical processes that occur in the Titan seas.

    This work was sponsored by NASA SSW grant #80NSSC21K0168, NASA grant NNH19ZDA001N-FINESST, NSF REU grants #1950901 and #2349774, the Lowell Observatory Slipher Society, and a grant from the John and Maureen Hendricks Charitable Foundation.

40. Chernyavskaya, M., Trilling, D., McNeill, A., et al., (including van Belle, G.), 2024, DPS, 56, 105.06, Strength Distribution for Main Belt Asteroids in the Solar System Notification Alert Processing System (SNAPS)
    Abstract

    The Solar System Notification Alert Processing System (SNAPS) is a data processing pipeline and database that ingests asteroid observations from the Zwicky Transient Facility (ZTF). The first data release SNAPShot1 presents measured and derived properties (lightcurve amplitude, rotation period, color, absolute magnitude, etc.) for ~30,000 asteroids. Using these properties, we have modeled the minimum strength required to withstand rotational fission for all SNAPS asteroids. We have previously found 456 candidate asteroids that require non-zero minimum strength, but do not all fall under the canonical 2.2 hour spin barrier typically assigned to Super Fast Rotators (SFRs). In fact, many of these objects have rotational periods greater than 2.2 hours. These results show that the conversation should be shifted from a two-dimensional spin barrier to a three-dimensional strength boundary surface in the space defined by size, elongation, and period. We have performed two cross-validation experiments, using (1) human vetting and (2) additional, dedicated ground-based observations, to understand what percentage of these candidates truly require non-zero strength. We find about 20% of our sample (around 90 objects) require non-zero strength, and we will present this distribution of required strengths. Until this study, most asteroid strength studies report values for single objects; this catalog is the largest sample of asteroid strengths to date, and is derived from a uniform survey. This work is supported by NSF award #2206796.

41. Kareta, T., Moskovitz, N., 2024, DPS, 56, 208.02, The Surface Properties of Two Dark Comets
    Abstract

    The Dark Comets are a recently recognized class of Near-Earth Object which experience non-gravitational accelerations, beyond what can be explained by the Yarkovsky effect, though without an accompanying detection of cometary activity such as the presence of a coma or dust tail. A clearer understanding of what processes drive the Dark Comets to behave the way they do would not just shed light on the orbital evolution of the NEOs and thus the potential risks they might pose but also the nature of the non-gravitational acceleration seen on the first Interstellar Object, 1I/'Oumuamua.

    We present multi-filter photometric observations of two Dark Comets, 1998 KY26 and 2003 RM, taken with the 4.3m Lowell Discovery Telescope throughout 2023 and 2024. The two objects, despite being an order of magnitude different in size and having different kinds of non-gravitational accelerations (e.g. transverse vs. perpendicular to the orbital plane), both have D-type reflectance spectra like some outer main belt asteroids and most cometary nuclei. In other words, the reflectance properties of their surfaces are comet-like, as is their orbital evolution. While the lack of detected cometary mass loss remains puzzling, their properties are broadly consistent with traditional comets approaching dormancy.

    KY26 is also the target of Hayabusa-2's extended mission, so we will also comment on how our observations might help plan for the spacecraft's encounter with the body later in the decade.

42. Hasler, S., Mayorga, L., Grundy, W., et al., 2024, DPS, 56, 210.08, New Horizons Ralph/MVIC Observations of Uranus at High Phase Angles
    Abstract

    The New Horizons spacecraft observed Uranus at a phase angle of 43.9 during September of 2023, as part of a project to image the Solar System ice giants during its second extended mission. The goal of the observations was to obtain high-phase-angle multi-color photometry of the ice giants. In this work, we focus on the Uranus observations. The data from these observations will allow us to better understand Uranus in both the Solar System and in an exoplanet context, and place better constraints on Uranus' global energy balance. Previous high-phase-angle IRIS photometry and imaging system observations of Uranus were taken by the Voyager 1 and 2 spacecraft, at angles between 26-107, but the imaging data were limited in wavelength range. Updated observations from New Horizons provide increased SNR and access to longer wavelengths. We present the results of time-series, multi-color imaging of Uranus across six scans spanning ~14 hours (a full rotation) from the New Horizons Multispectral Visible Imaging Camera (MVIC). We performed aperture photometry on Uranus to obtain its brightness in each photometric band. The photometry suggests that Uranus is darker than predicted by a Lambertian phase curve in the blue and red filters when compared to the spectrum measured by Karkoschka 1998. We also compare the high-phase angle observations to simultaneous low-phase Hubble and ground-based community observations, which indicate a lack of large-scale discrete features at full-phase which would introduce variation in the rotational light curve. Yet, we find potentially significant variation in the I/F in the blue and red MVIC filters. On top of providing new constraints on the reflectivity of Uranus, these results may also serve as "ground-truth" observations to use as a baseline to interpret exoplanet direct-imaging data from future observatories.

43. Verbiscer, A., Porter, S., Fraser, W., et al., (including Grundy, W.), 2024, DPS, 56, 211.05, More Phase Curves from the Kuiper Belt: Photometric Properties of Subaru-Discovered KBOs From New Horizons LORRI and HST Observations
    Abstract

    Since 2020, NASA's New Horizons team has been conducting a ground-based search using Subaru Telescope's Hyper Suprime-Cam dedicated to finding additional targets for the spacecraft's LOng Range Reconnaissance Imager (LORRI) to observe, either via distant or close flybys (Fraser et al. 2024; Yoshida et al. 2024). To date, the search (near RA/Dec 288,-21) has found and reported to the Minor Planet Center over 240 new Kuiper Belt Objects (KBOs). Among these new KBOs, 7 were located close enough to the spacecraft's trajectory that they could be observed by New Horizons' LORRI (V<21); however, LORRI's narrow (0.29 x 0.29) field of view required astrometric refinement provided by Hubble Space Telescope (HST) observations (Programs 16183 and 16924, S. B. Porter, PI) to ensure accurate spacecraft pointing. In addition to their astrometric refinements, these HST images also provide photometric observations at small solar phase angles. Because accurate photometric modeling requires observations that span the widest range possible in solar phase angle, we combine these 'low-phase' HST WFC3 observations with those at 'high-phase' from New Horizons' LORRI to construct disk-integrated solar phase curves that extend their phase curves to phase angles as high as 92 degrees. The Subaru-discovered KBOs already observed by New Horizons sample all but the dynamically coldest populations, and we compare their photometric properties with those of other KBOs already observed by New Horizons to reveal any correlations between surface textural and scattering properties among the dynamical classes. Preliminary results indicate that phase curves of Subaru-discovered KBOs have shallower slopes and therefore different shapes from those of cold classical KBOs. From a heliocentric distance of 60 au in October 2024, New Horizons can no longer observe Classical KBOs, but future LORRI observations can continue to sample Resonant KBOs as well as those from the Scattered Disk. Furthermore, these high-phase LORRI observations can sample objects whose apoapses lie beyond the termination shock and the heliopause, enabling studies of space weathering processes via photometric modeling of surfaces in the outermost regions of the Solar System.

44. Hemmelgarn, S., Moskovitz, N., Pilorz, S., et al., 2024, DPS, 56, 213.07, How Meteor Showers Can Guide the Search for Long Period Comets
    Abstract

    With orbital periods longer than 200 years, most long-period comets (LPCs) remain undiscovered until they are in-bound towards perihelion. The comets that pass close to Earth's orbit are Potentially Hazardous Objects (PHOs). Those with orbital periods up to ~4000 years tend to have passed close to Earth's orbit during a previous perihelion passage and thus may have produced a meteoroid stream dense enough to be detected at Earth as a meteor shower. In anticipation of Rubin Observatory's Legacy Survey of Space and Time (LSST), we investigate how these meteor showers can guide searches for their parent comets. Assuming search parameters (e.g. field of view, limiting magnitude) informed by LSST, we calculated where the 17 known parent bodies of long-period comet meteor showers would have been discovered based on a cloud of synthetic comets generated from the shower properties as measured at Earth. We find that the synthetic comets predict the on-sky location of the parent comets at the time of their discovery. The parent comet's location on average would have been 1.51 1.19 from a line fit through the synthetic comet cloud. The difference between the heliocentric distance of the parent and mean heliocentric distance of synthetic comets on the line was 2.09 1.89 au for comets with unknown absolute nuclear magnitudes and 0.96 0.80 au for comets with known absolute nuclear magnitudes. We applied this method to the -Hydrids, the proposed meteor shower of Comet Nishimura, and found that it successfully matched the pre-covery location of this comet 8 months prior to Nishimura's discovery. The synthetic comets also inform the expected parent's direction and rate of motion, setting bounds which can be used to conduct a shift and stack search for the faintest objects. We found that 96% of the time, synthetic comets inside a 3 x 3 window around the parent comet have a velocity vector 15 and 0.15"/min of the parent. These bounds reduce the number of parameters to be tested when conducting a shift and stack search by >92%, thereby significantly reducing the computational load when carrying out such a search.

45. McGraw, L., Thomas, C., DeMeo, F., et al., (including Burt, B., Moskovitz, N.), 2024, DPS, 56, 303.03, The MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS): Recent Results
    Abstract

    Asteroids formed during the collapse of the solar nebula and remain as relatively unaltered fragments of the primordial Solar System. The near-Earth object (NEO) population is a subset of these widely varying fragments, making them excellent laboratories for testing near-Earth processes that affect airless bodies as well as informing us about Solar System history. The MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS) began in 2004 and has obtained ~1,250 spectral observations of about 1,000 objects using NASA's IRTF's SpeX prism mode. The current phase of the project has three key goals: (1) to improve our understanding of the compositional distribution of NEO spectra with respect to asteroid size via additional IRTF SpeX prism spectra, (2) to examine the distribution of volatiles in the NEO population through an analysis of SpeX LXD 3-micron spectra, and (3) to transition the program from MIT and update our infrastructure (including the website). Our presentation will discuss the current status of MITHNEOS as well as results from target-of-opportunity campaigns and the new 3-micron effort. These two endeavors together have observed nine targets, three of which have a potential 3-micron absorption feature and one that was observed with prism before and after a 0.75LD approach.

46. Joshi, L., Belkhodja, I., Naaman, L., et al., (including Burt, B.), 2024, DPS, 56, 304.03, Using the chi-square test to determine if Mars trojans are fragments of Mars
    Abstract

    Spectroscopy is crucial for understanding the compositional and evolutionary history of asteroids. This study uses Pearson's -square test to analyze the visible and near-infrared reflectance spectra of seven asteroids by comparing their spectra against approximately 11,000 laboratory spectra of meteoritic, terrestrial, synthetic, Apollo, and Luna samples. The chi-square test is initially applied to three well-studied asteroids - (4) Vesta, (6) Hebe, and (19) Fortuna - to validate the technique's reliability and successfully confirms previously predicted spectral matches. Subsequently, the method investigates the spectra of four Mars trojans - (5261) Eureka, (101429) 1998 VF₃₁, (311999) 2007 NS₂, and (385250) 2001 DH₄₇ - due to their undetermined origin and potential relationship with Mars. To account for space weathering, some spectra are de-reddened before the chi-square test is applied. Our results showed significant spectral similarities between the observed Mars Trojans and minerals found on Mars, supporting the hypothesis of a Martian origin for these trojans. However, the possibility that these Mars trojans could be fragments of a disrupted differentiated body or bodies cannot be ruled out. The study underscores the effectiveness of the chi-square test in identifying spectral analogs and providing a robust method for initially analyzing asteroid spectra.

47. Sheppard, S., Tholen, D., Thirouin, A., et al., 2024, DPS, 56, 307.08, Asteroid Twilight Survey
    Abstract

    We are surveying for asteroids in the glare of the Sun using the Blanco 4 meter telescope with the Dark Energy Camera. We cover about 12 square degrees of sky in evening and again in morning twilight near Venus' orbit every third night. A medium to large telescope is ideal for these types of observations in order to overcome the high airmasses, bright sky, poor seeing, and high asteroid phase angles during a short observational window. The best fields reach over 22nd magnitude in the r-band. We have covered over an additional 2000 square degrees of sky since our published paper in 2022 of 624 square degrees (Sheppard et al. 2022, AJ, 164, 168). We have found and recovered several large Near Earth Objects (NEOs) interior to Earth's orbit and the work reported here is an update to our ongoing survey. Through our large area and deep asteroid twilight survey, we put constraints on the asteroid population interior to Earth's orbit. Some of our most recent interesting discoveries include the 600 meter diameter Apollo NEO 2024 AL1 and 500 meter Atira NEO 2023 EL. In addition, we are using the 4.3m Lowell Discovery Telescope to search the sky for asteroids near Mercury's orbit as well as for new Mercury moons. With these telescopes we are able to recover faint asteroids in twilight or in danger of being lost and are happy to observe any asteroids in need of imaging from observing requests.

48. Hanley, J., Thieberger, C., Corlies, P., et al., (including Llama, J.), 2024, DPS, 56, 309.04, Constraining the Variability of Haze and Methane on Titan
    Abstract

    Titan hosts a thick atmosphere with complex organic chemistry resulting from the UV photolysis of methane, forming complex aerosols that obscure Titan's surface. Further, methane acts as the primary absorber in the near-IR, resulting in narrow "windows" that probe to intermediate depths of Titan's atmosphere allowing vertical retrievals of methane and haze abundance. We will present observations from the Lowell Discovery Telescope (LDT) centered across various longitudes in order to get an integrated global picture of these vertical distributions and to look for global scale and temporal differences in these distributions. These observations provide critical insights into the chemical pathways in the upper atmosphere and help constrain the rate of UV photolysis, and by extension the loss-rate of methane, which remains an open question in the Titan community. We use LDT's EXtreme PREcision Spectrometer (EXPRES) observations to study the spectral features of Titan visible spectrum from ~0.4 - 0.75 m at a resolution of R ~ 137,500. This slope is set by absorption of UV and visible light by aerosols, and will lead to constraints on the composition and vertical abundance of hazes in Titan's atmosphere, similar to the photometric analysis conducted with HST. In addition, measuring the shape and strength of the methane absorption feature at 0.62 m at high resolution will allow for sensitive constraints on the vertical distribution of methane in Titan's atmosphere, similar to studies conducted with Keck. To complement the visible wavelengths, we also observe with LDT's Near-Infrared High-Throughput Spectrograph (NIHTS) which is a low-resolution (R ~ 200) near-infrared (NIR) prism spectrograph, covering 0.86 - 2.4 m. NIHTS provides access to the five methane windows (at 0.938, 1.1, 1.3, 1.6, and 2.0 m) that can see down to Titan's surface, permitting us to complete the vertical abundance retrievals through Titan's entire atmosphere. Data from EXPRES shows many features attributed to reflected sunlight, but also the larger methane features expected at ~0.62 and 0.7 m. We use solar data from the Lowell Solar Telescope taken with EXPRES to remove solar features. The high resolution allows for broad features such as UV absorption of hazes, as well as narrow features attributed to specific molecules yet to be determined. NIHTS data is used for correlation with the EXPRES data and permits studies of the longitudinal variability in Titan's methane abundance.

49. Marsset, M., Vernazza, P., Broz, M., et al., (including Burt, B.), 2024, DPS, 56, 311.03, The Massalia asteroid family as the origin of ordinary L chondrites
    Abstract

    Studies of micrometeorites in mid-Ordovician limestones and Earth's impact craters indicate that our planet witnessed a massive infall of ordinary L chondrite material ~466 million years (My) ago (Heck et al. 2017, Schmieder & Kring 2020, Kenkmann 2021) that may have been at the origin of the first major mass extinction event (Schmitz et al. 2019). The breakup of a large asteroid in the main belt is the likely cause of this massive infall. In modern times, material originating from this breakup still dominates meteorite falls (>20% of all falls) (Swindle et al. 2014). We will present spectroscopic observations and dynamical evidence that the Massalia collisional family is the only plausible source of this catastrophic event and of the most abundant class of meteorites falling on Earth today.

50. Naidu, S., Chesley, S., Moskovitz, N., et al., 2024, DPS, 56, 312.04, Orbital and physical characterization of asteroid Dimorphos following the DART impact
    Abstract

    The Double Asteroid Redirection Test (DART) mission struck Dimorphos, the satellite of the binary near-Earth asteroid (65803) Didymos, on September 26, 2022, UTC. By analyzing ground-based photometric and radar data, along with observations from DART's camera, we assessed the changes in the system's orbital and physical characteristics due to the impact. We estimate that the impact instantaneously altered Dimorphos's along-track velocity by -2.63 0.06 mm/s. Initially, this collision induced a change in the orbital period of Dimorphos by -32.7 minutes 16 seconds, resulting in a new period of 11.377 0.004 hours. Subsequently, over several weeks, the orbital period further adjusted by an additional 34 15 seconds, ultimately stabilizing at 11.3674 0.0004 hours. In total, the orbital period changed by -33.25 minutes 1.5 seconds. Post-impact observations revealed an apsidal precession rate of 6.7 0.2 degrees per day. In our model, this rate is influenced by the oblateness parameter of Didymos (J2) and the spherical harmonics coefficients (C20 and C22) of Dimorphos's gravitational field. Assuming that Dimorphos is a triaxial ellipsoid with a uniform density, our C20 and C22 estimates suggest axial ratios of approximately 1.3 for a/b and 1.6 for a/c. Pre-impact imagery from DART showed Dimorphos's shape resembled an oblate spheroid, and thus our results indicate that the impact significantly modified its shape.

51. Rommel, F., Fernandez-Valenzuela, E., Ortiz, J., et al., (including Grundy, W.), 2024, DPS, 56, 313.02, Physical properties of (38628) Huya and its satellite from stellar occultations
    Abstract

    A stellar occultation involves observing a star while an opaque object passes in front of it in the sky plane, briefly blocking its flux for a given observer. This technique has enabled accurate astrometric measurements, size and shape determination, detection of topographic features, and even the discovery of rings around small and distant Solar System objects. Huya is a Trans-Neptunian Object (TNO) located in Neptune's 2:3 mean motion resonance. Its diameter, derived from thermal measurements, agrees with that obtained from a multiple-chord stellar occultation recorded on March 18, 2019 (411 7.3 km). A satellite of 213 km in size was located about 1740 km from Huya in 2012 using Hubble Space Telescope (HST) images. Usually, TNO binaries consist either of a large primary object with a tiny satellite or of two components with equivalent sizes. Huya does not fit neatly into these categories; it lies somewhere in between. Therefore, understanding its physical and dynamical properties may provide fundamental insights into binary formation and evolution in the Solar System. Our international collaboration has monitored this tight binary TNO for occultation events. Here, we report three recently recorded stellar occultations: a single chord of both components acquired on March 28, 2021; a single record of the satellite obtained on February 17, 2023; and multiple positives for Huya along with a single chord of the satellite recorded on June 24, 2023. The satellite chords range from 75 40 km to 179 13 km, providing three astrometric measurements. These were combined with astrometric data from HST and Keck Observatory to derive the secondary's Keplerian orbit. Assuming an equatorial satellite orbit, we constrained the ellipse position angle for Huya's limb determination, obtaining a solution consistent with the previously published one. The unchanged projected limb between both multi-chord stellar occultations and the low amplitude of the published rotational light curve indicates an oblate spheroidal shape for Huya. We have determined Huya's global density by assuming it has a Maclaurin shape with a rotational period of 6.725 hours, observed at an aspect angle equal to the satellite orbit. We also calculated the density using the system mass and Huya's volume. Despite being preliminary, both results seem to disagree, which may indicate that Huya does not have a Maclaurin shape. In this work, we aim to present the physical properties of the Huya system as derived from our data and discuss them in the context of known binaries in the trans-Neptunian region.

52. Thirouin, A., Noll, K., Grundy, W., et al., (including Escarzaga, F.), 2024, DPS, 56, 313.03, Photometric study of the Logos-Zoe system.
    Abstract

    In the trans-Neptunian belt, the dynamically Cold Classical population is located at low inclination and low eccentricity between the 3:2 and 2:1 mean motion resonances with Neptune. The Cold Classical trans-Neptunian objects (TNOs) display specific characteristics compared to the rest of the trans-Neptunian belt; such as a common ultra-red surface color and a large fraction of nearly equal-sized wide binaries.

    One of these nearly equal-sized Cold Classical binary is Logos with its satellite Zoe. The two components orbit a common center of mass with an orbital period of about 310 days in a highly inclined and moderately eccentric orbit. This system is expected to undergo a mutual events season in the upcoming years. Aside from a highly accurate mutual orbit determination, to predict and model the upcoming mutual events, it is crucial to know the rotational period, albedo, shape, size, and density of each component of this system. Unfortunately, the rotational properties of the Logos-Zoe system are mostly unknown.

    Therefore, from 2019 to 2023, we performed a photometric study of this system with the Lowell Discovery Telescope and the Magellan-Baade telescope to retrieve or at least constrain the rotational and physical properties of the Logos-Zoe system. From our ground-based observations, we conclude that Logos is a contact binary with a mass ratio of about 0.7 and a rotational period of 17.43 hours. Such a finding about the primary reveals that the system is more complicated than previously thought and so the upcoming mutual events season will be key to characterize and understand this system. We will present our photometric study of this system as well as some preliminary modeling of the upcoming mutual events season.

    This work is supported by the National Science Foundation (NSF), grants #1734484 and #2109207, and NASA-Solar System Observations grant #80NSSC22K0659.

53. Zhang, Q., Ye, Q., Battams, K., et al., 2024, DPS, 56, 314.04, Comet Detection and Characterization with Diffracted Sunlight: (139359) 2001 ME1, 2P/Encke, and C/2023 A3 (TsuchinshanATLAS)
    Abstract

    Comets passing between the Sun and Earth can become observable in forward scattering geometry, where cometary dust grains efficiently diffract sunlight toward Earth to produce a brief surge in brightness often of many magnitudes. Minor planet (139359) 2001 ME revealed itself to be an active comet through this effect when it unexpectedly appeared with a prominent tail as it crossed the SOHO LASCO coronagraphs' fields of view in 2018 at up to 176 phase angle. We characterized its 7 magnitude forward scattering brightening with simultaneous backscattering observations from 1.5 au away by STEREO-A's HI1 camera, and modeled the brightness surge with a FournierForand phase function to constrain the comet's dust and gas properties. We compared these results and validated this approach with a similar analysis of comet 2P/Encke, which was seen by SOHO and STEREO-A under similar geometry in 2017. The far brighter comet C/2023 A3 (TsuchinshanATLAS) presents similarly favorable forward scattering geometry to observers on Earth during the 2024 AAS/DPS meeting, reaching a peak 173 phase angle on October 9. The corresponding brightness surge will likely drive the comet to negative magnitudes to become the brightest comet of the past decade.

54. Schleicher, D., Bair, A., 2024, DPS, 56, 314.06, A Smorgasbord of Recent Comet Narrowband Photometry: Results from 103P/Hartley 2, 12P/Pons-Brooks, 13P/Olbers, and Tsuchinshan-ATLAS (C/2023 A3).
    Abstract

    We will report on preliminary results of four interesting comets observed at Lowell Observatory in the past year using narrowband filter photometry. Late in 2023, Comet 103P/Hartley 2 made its first good apparition since 2010, when it was visited by the EPOXI spacecraft. We further investigated Hartley 2's secular decrease over several decades (see Knight & Schleicher 2013) and confirm that its gas production continues to significantly decrease with each apparition. Rare appearances of Halley-type dynamical class comets also took place, with both 12P/Pons-Brooks and 13P/Olbers arriving within months of each other. Each last made passages within the inner Solar System in the 1950s, and thus little quantitative data exists. Furthermore, we have fewer comets in the Lowell database from this dynamical class than any other, since most Halley-type objects have only had one opportunity to be studied in the past 48 years. While the orbital circumstances of these two comets was somewhat similar, their behavior was quite different. Pons-Brooks arrived with numerous outbursts, resulting in it often being brighter than expected. In contrast, Olbers has been quite mundane in appearance and activity, and has been fainter than predicted. Both have typical compositions, as expected for long-period objects, and both exhibit moderate dust-to-gas ratios. While Pons-Brooks will not reappear in the north, Olbers will be briefly available in the next two months, when we will attempt to obtain near-perihelion data. The most recent object of interest is Comet Tsuchinshan-ATLAS (C/2023 A3). Currently classified as dynamically new, it very unexpectedly was discovered to exhibit clear depletion of carbon-chain molecules (C2 & C3) as compared to both CN and OH. As was shown by A'Hearn et al. (1995) and more recently with many more objects by Schleicher & Bair (2016), most carbon-chain depleted objects are from the Jupiter-family dynamical class, and only 3 of 162 non-Jupiter family comets have this composition. Tsuchinshan-ATLAS also has a relatively high dust-to-gas ratio. We will resume our observations when it reappears in October, shortly following perihelion. These and additional findings from these four comets will be presented.

55. Bair, A., Knight, M., Battams, K., et al., 2024, DPS, 56, 401.02, Investigating comet dust properties using extreme forward-scattering geometry observations with SOHO and STEREO
    Abstract

    Cometary dust scatters light differently as viewing geometry changes, and these differences can be used to infer properties of the dust grains. Notably, observations at highly "forward-scattering" geometry, when the comet is approximately between the Sun and the observer, can yield large brightness enhancements, with the enhancement exceeding a factor of 100 in extreme cases. This behavior is responsible for greatly increasing the brightness of some historically bright near-Sun comets, but is difficult to quantify since the small solar elongations at which they occur make observations with traditional telescopes difficult or impossible.

    The solar observatories Solar Heliospheric Observatory (SOHO) and Solar Terrestrial RElations Observatory (STEREO) are designed to image the inner heliosphere. Comets which serendipitously pass through these fields of view can, therefore, be observed at extreme forward-scattering geometry. We have identified and measured photometry for all comets reaching phase angles (the Sun-comet-observer angle) greater than 150 degrees in the SOHO or STEREO coronagraphic fields of view. Ten individual comets were successfully measured, including three different apparitions for comet 2P/Encke, while four comets were not detected due, presumably, to low intrinsic quantities of dust or because they had disintegrated (C/2010 X1 Elenin). These comets are at larger phase angles than the highest phase angles used by Marcus (ICQ 29, pp. 39-66, 2007) to derive the current model of comet forward-scattering. Preliminary analysis suggests that the forward-scattering enhancement at these extreme angles is even larger than predicted by the Schleicher-Marcus dust phase model (Schleicher & Bair, AJ 141, 177, 2011), although the effects of sodium emission (cf. Zhang et al., PSJ 4, 70, 2023) and dust tail contamination in the photometric aperture must be considered. Our ongoing results will be presented.

56. Spiro, L., Knight, M., Skiff, B., et al., (including Schleicher, D.), 2024, DPS, 56, 401.07, CN imaging of recent bright comets 12P/Pons-Brooks, 13P/Olbers, C/2021 S3 PanSTARRS, and C/2023 A3 Tsuchinshan-ATLAS
    Abstract

    We report on recent and upcoming CN imaging of four comets obtained from Lowell Observatory, SOAR, and the U.S. Naval Academy (USNA). Halley-type comet 12P/Pons-Brooks was observed on eight epochs between 2024 Jan 31 and 2024 Feb 16 using the Lowell 42in (1.1-m) telescope and USNA's Hopper Hall (0.5-m) telescope. CN imaging revealed two apparently face-on spiral features ~180 deg apart. We used their motion to conclude that the apparent rotation period is 57 1 hr (Knight et al., ATEL 16508, 2024). Post-perihelion observation with SOAR (4.1-m) on 2024 Jul 9 again revealed two jets. A single epoch of CN imaging of returning Oort cloud comet C/2021 S3 PanSTARRS was acquired at SOAR on 2024 Mar 14, revealing a face-on spiral feature. We obtained CN imaging of Halley-type comet 13P/Olbers on four epochs from January through April using the Lowell 42in and SOAR. It exhibited a broad sunward enhancement at each epoch. 13P passed perihelion on 2024 Jun 30 and remains at solar elongations below 40 deg until 2025 making post-perihelion observations challenging. Despite this, we will attempt to obtain additional CN imaging and will present any new observations. Dynamically new comet C/2023 A3 Tsuchinshan-ATLAS reaches perihelion at 0.39 au on 2024 Sep 27, followed by an interval where it may attain naked-eye brightness. We obtained CN imaging on three epochs from 2024 Apr 3 to 2024 Jun 11 using the Lowell 42in. The CN morphology looked similar to broadband-r morphology at all epochs, implying that the morphology was dominated by dust at these epochs. Its solar elongation also remains low until well after perihelion, but we will report on any successful additional observations.

    These observations are part of a larger study utilizing imaging obtained over the past two decades, primarily from Lowell Observatory. Our dataset contains dust and CN data on ~80 comets, which we are using to explore how coma morphology varies with dynamical classification.

    Based in part on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministerio da Ciencia, Tecnologia e Inovacoes (MCTI/LNA) do Brasil, the U.S. National Science Foundation NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

57. Morgan, A., Eduardo, M., Trilling, D., et al., (including Grundy, W.), 2024, DPS, 56, 405.03, Joint JWST and HST Deep Imaging to Characterize Cold Classical TNOs: A Demonstration with 2015 GK56
    Abstract

    We conducted a joint observational survey with the JWST Cycle 1 program 1568 and HST Cycle 29 program 16720 to measure the size and color distribution of cold classical TNOs, aiming to better understand the formation and dynamics of the outer Solar System. We utilized JWST's NIRCam/F150W2 to image a 0.05 deg2 field, anticipating the discovery of approximately 30 TNOs with diameters as small as 10 km. In parallel, HST's WFC3/F350LP and ACS/F814W observed the same fields anticipating measuring the colors of at least 15 TNOs. Our observations included the known TNO 2015 GK56. This object appears in both our JWST and HST data and will serve as a useful testbed for our detection routines. Our presentation will include photometric analysis of GK56, alongside properties of any additional intriguing objects discovered. This study underscores the potential of our approach to yield significant insights into TNO properties.

58. Trilling, D., Eduardo, M., Fraser, W., et al., (including Grundy, W.), 2024, DPS, 56, 405.05, Preliminary results from an ultra-sensitive search for trans-Neptunian objects with JWST
    Abstract

    The size distribution of the cold classical trans-Neptunian objects (TNOs), which can be inferred from their observed magnitude distribution, is crucial for testing theoretical models of planet formation because it reflects the outcomes of accretion, collisional processes, and dynamical evolution over the history of the Solar System. Therefore, comparing the observed size distribution with those predicted by models helps to constrain the proposed physical processes and underlying initial conditions that shaped the current Solar System. However, current streaming instability simulations have yet to completely reproduce the observed size distribution of the planetesimals primarily because of the low number statistics for small TNOs (diameters less than ~50 km), and the relative faintness of TNOs generally limits ground-based searches to magnitudes no fainter than 27. Thus, the faint (small) size distribution of TNOs remains fairly uncertain, significantly hindering detailed modeling and further understanding of Solar System formation.

    In this talk, we will present preliminary results from our pencil beam survey that utilized JWST to search and characterize ultra-faint TNOs to further constrain Solar System formation models. Our JWST cycle 1 program #1568 is a 3-epoch survey that observed 0.05 square degrees of the sky. With the sensitivity of this survey, we expect to detect and characterize TNOs as small as 5 km in diameter. This is the deepest Solar System survey to date, with at least a visible magnitude deeper than the landmark TNO survey by Bernstein et al. (2004).

59. Stansberry, J., Harvison, B., Pinilla-Alonso, N., et al., (including Grundy, W.), 2024, DPS, 56, 405.06, Upper Limits on HDO on Trans-Neptunian Objects from JWST Spectroscopy
    Abstract

    The NIRSpec instrument on the James Webb Space Telescope (JWST) has provided a significant sample of near-IR (~ 1 5 microns) high signal-to-noise ratio spectra of trans-Neptunian objects (TNOs). The spectra for the large majority of the targets fall into one of 3 spectral classes: water ice and silicates for one group, CO2 and CO ices for the second group, and carbon ices and complex organics for the third group (Pinilla-Alonso et al., 2024). However, the largest objects (Emery et al. 2024; Grundy et al. 2024) and Centaurs (Licandro et al. 2024) tend not to fit into those groupings. Approximately 1 out of 4 of the TNOs observed have spectra strongly dominated by absorption features of crystalline water ice. We have analyzed the spectra of 25 water-ice dominated TNOs drawn from the DiSCO-TNOs (program 2418) project, and several guaranteed-time programs (1191, 1231, 1272, 1273), focusing on the 4.13 micron region where HDO has a strong absorption band (e.g. Clark et al., 2019; Hedman et al. 2023). None of the TNO spectra show strong (or even weak) absorption by HDO. We will present initial results for upper limits on the D:H ratio in water ice on TNOs that can be derived from the spectra. Additionally, we will draw conclusions based on a comparison of the derived measurements for TNOs with those of comets and evolved bodies.

60. Steckloff, J., Soderblom, J., Grundy, W., et al., 2024, DPS, 56, 408.05, The Air is Hot Lava! Titan's Atmosphere Makes Methane Ice Unstable.
    Abstract

    Like many planetary bodies with dense atmospheres, ices on Titan likely play vital roles in its climate, weather, and cycling of materials about the climate system. Ice grains in the atmosphere can serve as nucleation sites forming raindrops and/or hailstones. On the surface, the presence of ice and frost can significantly increase a surface's bond albedo, thus reducing the equilibrium surface temperature. Under certain conditions, ices can become buoyant upon an underlying lake or sea, altering exchange between parts of the climate system. As the dominant volatile in Titan's hydrologic cycle, methane-dominated ices in particular have the potential to become abundant, and thus profoundly affect Titan's climate, weather, and surface evolution. Nevertheless, the CRYOCHEM numerical model suggests that methane ice is everywhere unstable under Titan-like conditions near the surface (equilibrium includes only liquid and vapor phases) but survives at altitudes higher than 15 km. Here we use laboratory studies and numerical simulations to explore the stability of methane ices and the kinetics of their melting on Titan across plausible conditions.

    We first formed methane ice in the Astrophysical Ices Laboratory at NAU, before exposing it to a nitrogen atmosphere at 88 K; this is well below the observed surface temperature of 91-94 K. Nevertheless, we find that the N2 atmosphere melted the methane ice almost instantly. Using Molecular Dynamics simulations, we find that this is likely due to atmospheric N2 rapidly attacking methane molecules in the ice lattice, pulling methane molecules into a growing nitrogen-methane liquid layer that ultimately melts the methane ice. We further discuss methane ice's likely instability under conditions thought to exist during theoretical "Slushball Titan" climate regimes.

61. Thieberger, C., Hanley, J., Engle, A., et al., (including Grundy, W.), 2024, DPS, 56, 408.07, Laboratory Studies of Nitrogen-Hydrocarbon Mixtures Relevant to Titan's Lakes and Seas
    Abstract

    Titan is the only extraterrestrial environment known to support bodies of standing liquid on its surface. The Cassini mission provided important composition measurements of a few lakes and seas, which suggest they may contain anywhere from 5 - 80 % methane and 8 - 79 % ethane mixtures, in addition to dissolved nitrogen from the atmosphere. Cassini also measured trace amounts of higher-order hydrocarbons, such as propane, butane, and benzene, in Titan's atmosphere. When these trace species rain down onto the surface and mix with the lakes and seas, they create unique chemical conditions and alter the phase behavior, solubility, and stability of Titan's surface liquids. In an effort to study these environments and map out their extremes, we present our experimental work done in the Astrophysical Materials Lab at NAU. We studied the effects of propane, one of the most abundant of these heavier hydrocarbons, on liquid binary mixtures of methane-nitrogen and ethane-nitrogen. We find that at 90 K and pressures up to 3.0 bar, corresponding to ~ 200 m depths in Titan lakes, methane-propane-nitrogen mixtures do not demonstrate any phase changes and instead continue to grow in volume as nitrogen readily dissolves into the mixture. For the same temperature and pressure regime, ethane-propane-nitrogen mixtures will form a liquid-liquid-vapor (LLV) system at 2.8 bar. When repeating the same experiments at 85 K and pressures up to 3.0 bar, we find that both methane-propane-nitrogen and ethane-propane-nitrogen mixtures will readily form LLV systems. At 85 K, some of these compositions will reach the appropriate pressure to form a four-phase solid-liquid-liquid-vapor (SLLV) system, as we have previously observed in experiments with methane-ethane-nitrogen mixtures (Engle et al., 2024). These experiments have exciting implications for Titan's lakes and seas at depth, demonstrating that there could be compositional stratification of surface liquids, precipitation in nitrogen-hydrocarbon mixtures, or even ice formation when the conditions are right.

62. Cartwright, R., Holler, B., Grundy, W., et al., 2024, DPS, 56, 412.05, The Uranian Moon Ariel, a Carbon Dioxide Wonderland Observed by JWST
    Abstract

    The surface of Ariel exhibits a variety of tectonic and possibly cryovolcanic features that formed in the geologically-recent past. Prior ground-based observations had indicated that Ariel's surface composition includes a large fraction of crystalline CO₂ ice, with hints of NH-bearing species and CO ice that have yet to be confirmed. However, the origin of these volatiles is not well understood. To investigate Ariel's surface composition and the processes that modify it, we analyzed reflectance spectra collected over its leading and trailing hemispheres by the NIRSpec spectrograph on the James Webb Space Telescope (G395M, 2.9 - 5.1 m). These data reveal Ariel's surface composition over the 4 to 5.1 m wavelength range for the first time.

    The NIRSpec spectra show a double-lobed scattering peak centered near 4.20 and 4.25 m, flanked by a 4.27 m absorption band, which are all associated with the ₃ stretching mode of ¹²CO₂ ice. The 4.25 m lobe could represent the largest CO₂ ice Fresnel peak yet observed in the Solar System. Numerous other CO₂ ice features are present, including prominent 4.38 m ¹³CO₂ and 4.90 m ¹²CO₂ bands. The JWST spectra confirm the presence of ¹²CO ice via its 4.67 m ₃ mode (and possibly the 4.78 m ¹³CO ₃ mode). They also reveal a broad 4 m band, potentially resulting from carbonate minerals, as well as other subtle features between 4.4 and 4.6 m that could result from carbon suboxide and nitriles. We see no reliable evidence for NH-bearing species, hydrogen peroxide, or hydrocarbons in these data. Comparison to radiative transfer models suggests that some CO₂ ice deposits could be more than 10 mm thick and segregated from H₂O ice.

    The possible presence of carbonates and concentrated CO₂ ice deposits on both hemispheres suggests that some carbon oxides could originate in Ariel's interior. Carbonates are particularly interesting as they often form over long timescales in aqueous environments, supporting the presence of a subsurface ocean at Ariel, either now or in the past. The surface distribution of these species could be shaped by seasonal migration of CO₂ and CO and perhaps via interactions with Uranus' magnetosphere, albeit the lack of H₂O₂ points to a somewhat quiescent charged particle environment. The non-detection of ammonia and hydrocarbons indicates that they are efficiently oxidized and removed once exposed on Ariel's surface, and/or their spectral signatures are obscured by strong H₂O ice absorption between 2.9 and 3.5 m.

63. DeColibus, R., Cartwright, R., Grundy, W., et al., 2024, DPS, 56, 412.06, Visible-Wavelength Spectral Characteristics of the Large Uranian Satellites
    Abstract

    Exogenic effects such as impact gardening, dust mantling, and magnetospheric irradiation can have a significant impact on the leading and trailing hemispheres of icy satellites, forming leading/trailing asymmetries in surface compositions. These leading and trailing asymmetries in surface composition on the Uranian satellites have been studied thoroughly in the near-IR, but not at visible wavelengths (VIS). Leading/trailing hemispherical asymmetries on the southern hemispheres of the Uranian moons were identified from broadband color imagery from Voyager, but relatively little work has been done on their VIS hemispherical asymmetries and spectral characteristics in the post-Voyager era. In particular, modern studies of the optical spectra of the Uranian satellites are few and far between, and have mostly been limited to narrowband spectrophotometry of their southern hemispheres, obtained during the 1970s-1990s. Ground-based spectroscopic and photometric VIS studies of the Uranian satellites are often difficult due to the substantial scattered light from Uranus, and many prior studies have not distinguished between observations acquired on the leading and trailing hemispheres, so any potential leading/trailing differences in spectral slopes or weak absorption features have not been investigated in detail.

    We present previously unpublished optical spectra of the four largest Uranian satellites obtained at equatorial (4 S - 10 N) and mid-northern (43 - 50 N) subobserver latitudes, with special attention paid to spectral slopes and leading/trailing asymmetries. We also include previously unpublished broadband CCD photometry of Umbriel, Titania, and Oberon, collected in 2005. We confirm that the leading hemispheres of Titania and Oberon are redder than their trailing hemispheres at equatorial and mid-northern latitudes, consistent with prior findings and supporting the hypothesis that an exogenic process such as mantling by dust is primarily responsible for the reddening.

64. Raposa, S., Engle, A., Tan, S., et al., (including Grundy, W., Hanley, J., Thieberger, C.), 2024, JGRE, 129, e2024JE008457, Outbursts Upon Cooling of Low-Temperature Binary Mixtures: Experiments and Their Planetary Implications
    Abstract

    For many binary mixtures, the three-phase solid-liquid-vapor equilibrium curve has intermediate pressures that are higher than the pressure at the two pure triple points. This curve shape results in a negative slope in the high-temperature region near the triple point of the less volatile component. When freezing mixtures in the negative slope regime, fluid trapped below confined ice has latent heat released with more vapor upon cooling, and thus increases in pressure. If the rising pressure of the confined fluid overcomes the strength of the confining solid, which may be its own ice, it can produce an abrupt outburst of material and an increase in the system's overall pressure. Here, we report experimental results of freezing-induced outbursts occurring in the N₂/CH₄, CO/CH₄, and N₂/C₂H₆ systems, and provide insight into the phenomenon through a thermodynamics perspective. We also propose other binary systems that may experience outbursts and explore the geological implications for icy worlds such as Titan, Triton, Pluto and Eris as well as rocky bodies, specifically Earth and Mars.

65. Marsset, M., Vernazza, P., Broz, M., et al., (including Burt, B.), 2024, Natur, 634, 561, The Massalia asteroid family as the origin of ordinary L chondrites
    Abstract

    Studies of micrometeorites in mid-Ordovician limestones and impact craters on Earth indicate that our planet witnessed a massive infall of ordinary L chondrite material about 466 million years ago¹³ that may have been at the origin of an Ordovician ice age and major turnover in biodiversity⁴. The breakup of a large asteroid in the main belt is the likely cause of this massive infall. Currently, material originating from this breakup still dominates meteorite falls (>20% of all falls)⁵. Here we provide spectroscopic observations and dynamical evidence that the Massalia collisional family is the only plausible source of this catastrophic event and the most abundant class of meteorites falling on Earth today. This family of asteroids is suitably located in the inner belt, at low-inclination orbits, which corresponds to the observed distribution of L-chondrite-like near-Earth objects and interplanetary dust concentrated at 1.4 (refs. ^6,7).

66. Ieva, S., Mazzotta Epifani, E., Dotto, E., et al., (including Kareta, T., Moskovitz, N.), 2024, PSJ, 5, 225, Near-infrared Spectral Homogeneity of the Didymos System Before and After the DART Impact
    Abstract

    We spectroscopically characterized the Didymos system, target of the Double Asteroid Redirection Test (DART)/Light Italian Cubesat for Imaging of Asteroids (LICIACube) space mission, close in time to the DART impact event, during six nights between 2022 August and November at Telescopio Nazionale Galileo. Here, we show that near-infrared (NIR) spectra (0.752.25 m) look mostly similar within the same night and between different nights. They are in good agreement with the only spectrum previously available in the literature, observed almost 20 years before those reported in this paper. During one of the observing nights we also obtain spectroscopy information on the ejecta tail induced by the DART impact. The spectrum of the ejecta tail is also very similar to Didymos/Dimorphos itself. All of these aspects seem to suggest that the Didymos system in the NIR looks mostly homogeneous, with very subtle spectral variations. ^* Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundacion Galileo Galilei of the Istituto Nazionale di Astrofisica (INAF) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias (Program AOT45-TAC8 and AOT46-TAC19).

67. Hora, J., Trilling, D., Lopez-Oquendo, A., et al., (including Mommert, M., Moskovitz, N.), 2024, PASP, 136, 105003, Design and Performance of the Upgraded Mid-infrared Spectrometer and Imager (MIRSI) on the NASA Infrared Telescope Facility
    Abstract

    We describe the new design and current performance of the Mid-InfraRed Spectrometer and Imager (MIRSI) on the NASA Infrared Telescope Facility (IRTF). The system has been converted from a liquid nitrogen/liquid helium cryogen system to one that uses a closed-cycle cooler, which allows it to be kept on the telescope at operating temperature and available for observing on short notice, requiring less effort by the telescope operators and day crew to maintain operating temperature. Several other enhancements have been completed, including new detector readout electronics, an IRTF-style standard instrument user interface, new stepper motor driver electronics, and an optical camera that views the same field as the mid-IR instrument using a cold dichroic mirror, allowing for guiding and/or simultaneous optical imaging. The instrument performance is presented, both with an engineering-grade array used from 2021 to 2023, and a science-grade array installed in the fall of 2023. Some sample astronomical results are also shown. The upgraded MIRSI is a facility instrument at the IRTF available to all users.

68. Athanasopoulos, D., Hanus, J., Avdellidou, C., et al., (including van Belle, G.), 2024, A&A, 690, A215, Spin states of X-complex asteroids in the inner main belt: I. Investigating Athor and Zita collisional families
    Abstract

    Context. Based on the V-shape search method, two families, Athor and Zita, have been identified within the X-complex population of asteroids located in the inner main belt. The Athor family is ~3 Gyr old while the Zita family could be as old as the Solar System. Both families were found to be capable of delivering near-Earth asteroids (NEAs). Moreover, the Athor family was linked to the low-iron enstatite (EL) meteorites. Aims. The aim of our study is to characterise the spin states of the members of the Athor and Zita collisional families and test whether these members have a spin distribution consistent with a common origin from the break up of their respective family parent asteroids. Methods. To perform this test, our method is based on the well-established asteroid family evolution, which indicates that there should be a statistical predominance of retrograde-rotating asteroids on the inward side of family's V-shape, and prograde-rotating asteroids on the outward side of family's V-shape. To implement the method, we used photometric data from our campaign and the literature in order to reveal the spin states, and hence their rotation sense (prograde or retrograde), of the asteroids belonging to these families. We combined dense and sparse-in-time photometric data in order to construct asteroid rotational light curves; we performed the light curve inversion method to estimate the sidereal period and 3D convex shape along with the spin axis orientation in space of several family member asteroids. Results. We obtained 34 new asteroid models for Athor family members and 17 for Zita family members. Along with the literature and revised models, the Athor family contains 60% (72% considering only the family's core) of retrograde asteroids on the inward side and, conversely, 76% (77% considering only the family's core) of prograde asteroids on the outward side. We also found that the Zita family exhibits 80% of retrograde asteroids on the inward side. In addition, the Zita family presents an equal amount of prograde and retrograde rotators (50% each) on the outward side. However, when we applied Kernel density estimation (KDE), we also found a clear peak for prograde asteroids on the outward side, as expected from the theory. Conclusions. The spin states of these asteroids validate the existence of both families, with the Athor family exhibiting a stronger signature for the presence of retrograde-rotating and prograde-rotating asteroids on the inner and outer side of the family, respectively. Our work provides an independent confirmation and characterisation of these very old families, whose presence and characteristics offer constraints for theories and models of the Solar System's evolution.

69. Engle, A., Hanley, J., Tan, S., et al., (including Grundy, W., Raposa, S., Thieberger, C.), 2024, PSJ, 5, 224, Ice Formation, Exsolution, and Multiphase Equilibria in the MethaneEthaneNitrogen System at Titan Surface Conditions
    Abstract

    Titan is unique among the icy satellites in that it has a thick atmosphere, stable surficial bodies of liquid, and a precipitation system that promotes interactions between the two. Although Titan's surface conditions are typically assumed to be above the freezing point temperatures of the major constituent species of the climate system (methane, ethane, and nitrogen), conditions may be sufficiently cool across parts of Titan to allow for ice formation alongside known liquid-vapor phases. In this study, we used Raman spectroscopy, visual inspection, and the CRYOCHEM 2.0 equation of state to map the appearance of first ice and to quantify the amount of nitrogen dissolution into liquid in the methaneethanenitrogen system along a 1.5 bar isobaric cooling path in the temperature range 8095 K. This was with the intent of (1) determining the effects nitrogen has on the phase behaviors of the methaneethane binary system, and (2) establishing the temperatures and ternary mixing ratios needed for ice formation on Titan's surface. We found that ethane-rich mixtures enter a three-phase solidliquidvapor equilibrium and are characterized by nitrogen-rich exsolution upon freezing and ice that form at the bottom of the sample. With sufficient methane content, the mixtures cross a univariant four-phase solidliquidliquidvapor boundary, which contributes to a distinct isothermal freezing point profile and ice that forms starting at the liquidliquid interface. Our results generally agree with findings from previous studies of the methaneethanenitrogen system and are intended to add to our current understanding of Titan's geochemical processes.

70. Bocquet, S., Grandis, S., Bleem, L., et al., (including Kuehn, K.), 2024, PhRvD, 110, 083509, SPT clusters with DES and HST weak lensing. I. Cluster lensing and Bayesian population modeling of multiwavelength cluster datasets
    Abstract

    We present a Bayesian population modeling method to analyze the abundance of galaxy clusters identified by the South Pole Telescope (SPT) with a simultaneous mass calibration using weak gravitational lensing data from the Dark Energy Survey (DES) and the Hubble Space Telescope (HST). We discuss and validate the modeling choices with a particular focus on a robust, weak-lensing-based mass calibration using DES data. For the DES Year 3 data, we report a systematic uncertainty in weak-lensing mass calibration that increases from 1% at z=0.25 to 10% at z=0.95, to which we add 2% in quadrature to account for uncertainties in the impact of baryonic effects. We implement an analysis pipeline that joins the cluster abundance likelihood with a multiobservable likelihood for the Sunyaev-Zel'dovich effect, optical richness, and weak-lensing measurements for each individual cluster. We validate that our analysis pipeline can recover unbiased cosmological constraints by analyzing mocks that closely resemble the cluster sample extracted from the SPT-SZ, SPTpol ECS, and SPTpol 500d surveys and the DES Year 3 and HST-39 weak-lensing datasets. This work represents a crucial prerequisite for the subsequent cosmological analysis of the real dataset.

71. Bocquet, S., Grandis, S., Bleem, L., et al., (including Kuehn, K.), 2024, PhRvD, 110, 083510, SPT clusters with DES and HST weak lensing. II. Cosmological constraints from the abundance of massive halos
    Abstract

    We present cosmological constraints from the abundance of galaxy clusters selected via the thermal Sunyaev-Zel'dovich (SZ) effect in South Pole Telescope (SPT) data with a simultaneous mass calibration using weak gravitational lensing data from the Dark Energy Survey (DES) and the Hubble Space Telescope (HST). The cluster sample is constructed from the combined SPT-SZ, SPTpol ECS, and SPTpol 500d surveys, and comprises 1,005 confirmed clusters in the redshift range 0.251.78 over a total sky area of 5200 deg2. We use DES Year 3 weak-lensing data for 688 clusters with redshifts z<0.95 and HST weak-lensing data for 39 clusters with 0.6<z<1.7. The weak-lensing measurements enable robust mass measurements of sample clusters and allow us to empirically constrain the SZ observable-mass relation without having to make strong assumptions about, e.g., the hydrodynamical state of the clusters. For a flat CDM cosmology, and marginalizing over the sum of massive neutrinos, we measure m=0.2860.032, 8=0.8170.026, and the parameter combination 8(m/0.3)0.25=0.8050.016. Our measurement of S88m/0.3=0.7950.029 and the constraint from Planck CMB anisotropies (2018 TT, TE, EE+lowE) differ by 1.1. In combination with that Planck dataset, we place a 95% upper limit on the sum of neutrino masses m<0.18 eV. When additionally allowing the dark energy equation of state parameter w to vary, we obtain w=-1.450.31 from our cluster-based analysis. In combination with Planck data, we measure w=-1.34-0.15+0.22, or a 2.2 difference with a cosmological constant. We use the cluster abundance to measure 8 in five redshift bins between 0.25 and 1.8, and we find the results to be consistent with structure growth as predicted by the CDM model fit to Planck primary CMB data.

72. Bigwood, L., Amon, A., Schneider, A., et al., (including Kuehn, K.), 2024, MNRAS, 534, 655, Weak lensing combined with the kinetic Sunyaev-Zel'dovich effect: a study of baryonic feedback
    Abstract

    Extracting precise cosmology from weak lensing surveys requires modelling the non-linear matter power spectrum, which is suppressed at small scales due to baryonic feedback processes. However, hydrodynamical galaxy formation simulations make widely varying predictions for the amplitude and extent of this effect. We use measurements of Dark Energy Survey Year 3 weak lensing (WL) and Atacama Cosmology Telescope DR5 kinematic Sunyaev-Zel'dovich (kSZ) to jointly constrain cosmological and astrophysical baryonic feedback parameters using a flexible analytical model, 'baryonification'. First, using WL only, we compare the $S_8$ constraints using baryonification to a simulation-calibrated halo model, a simulation-based emulator model, and the approach of discarding WL measurements on small angular scales. We find that model flexibility can shift the value of $S_8$ and degrade the uncertainty. The kSZ provides additional constraints on the astrophysical parameters, with the joint WL + kSZ analysis constraining $S_8=0.823^{+0.019}_{-0.020}$. We measure the suppression of the non-linear matter power spectrum using WL + kSZ and constrain a mean feedback scenario that is more extreme than the predictions from most hydrodynamical simulations. We constrain the baryon fractions and the gas mass fractions and find them to be generally lower than inferred from X-ray observations and simulation predictions. We conclude that the WL + kSZ measurements provide a new and complementary benchmark for building a coherent picture of the impact of gas around galaxies across observations.

73. Barrows, R., Comerford, J., Levine, S., et al., (including West, M.), 2024, hst, 17857, Detecting Stellar Counterparts for a Large Sample of Spatially Offset Active Galactic Nuclei
    Abstract

    Galaxy mergers are predicted to be efficient at triggering active galactic nuclei (AGN) and may play a role in the evolution of the massive black hole population. However, while theory suggests that AGN luminosities are strongly dependent on their host galaxy stellar masses, this dependence has not yet been tested on large samples of AGN in late-stage mergers due to AGN selection methods that are unable to spatially resolve their locations within mergers. To overcome this limitation, we have developed the first systematic, wide-area sample of spatially offset AGN by cross-matching sources from the VLA Sky Survey with galaxies from the Sloan Digital Sky Survey. The selection requires that the AGN be spatially located within the host galaxy and can quantify the merger stage down to small physical separations. Therefore, we propose to use archival HST imaging to detect the individual host galaxies associated with our sample of offset AGN to directly test the merger-AGN connection. The high sensitivity and spatial resolution of HST can detect the faint stellar cores of offset AGN, and the large body of archival HST imaging is expected to identify the galaxies of ~120 offset AGN (~10 times the size of previous samples). We will use this sample to test the role of galaxy mergers for enhancing AGN luminosities, the relative contributions of minor and major mergers, and the dependence on merger stage. This project will also have a larger impact on understanding the role of secular evolution of the massive black hole population and in the identification of precursors to potential binary black holes and hence future gravitational wave sources.

74. DES Collaboration, Abbott, T., Acevedo, M., et al., (including Kovacs, E.), 2024, ApJL, 973, L14, The Dark Energy Survey: Cosmology Results with 1500 New High-redshift Type Ia Supernovae Using the Full 5 yr Data Set
    Abstract

    We present cosmological constraints from the sample of Type Ia supernovae (SNe Ia) discovered and measured during the full 5 yr of the Dark Energy Survey (DES) SN program. In contrast to most previous cosmological samples, in which SNe are classified based on their spectra, we classify the DES SNe using a machine learning algorithm applied to their light curves in four photometric bands. Spectroscopic redshifts are acquired from a dedicated follow-up survey of the host galaxies. After accounting for the likelihood of each SN being an SN Ia, we find 1635 DES SNe in the redshift range 0.10 < z < 1.13 that pass quality selection criteria sufficient to constrain cosmological parameters. This quintuples the number of high-quality z > 0.5 SNe compared to the previous leading compilation of Pantheon+ and results in the tightest cosmological constraints achieved by any SN data set to date. To derive cosmological constraints, we combine the DES SN data with a high-quality external low-redshift sample consisting of 194 SNe Ia spanning 0.025 < z < 0.10. Using SN data alone and including systematic uncertainties, we find _M = 0.352 0.017 in flat CDM. SN data alone now require acceleration (q ₀ < 0 in CDM) with over 5 confidence. We find in flat wCDM. For flat w ₀ w _a CDM, we find , consistent with a constant equation of state to within 2. Including Planck cosmic microwave background, Sloan Digital Sky Survey baryon acoustic oscillation, and DES 3 2pt data gives (_M, w) = (0.321 0.007, 0.941 0.026). In all cases, dark energy is consistent with a cosmological constant to within 2. Systematic errors on cosmological parameters are subdominant compared to statistical errors; these results thus pave the way for future photometrically classified SN analyses.

75. Marsset, M., Vernazza, P., Broz, M., et al., (including Burt, B.), 2024, EPSC, EPSC2024-14, The Massalia asteroid family as the origin of ordinary L chondrites
    Abstract

    Studies of micrometeorites in mid-Ordovician limestones and Earth's impact craters indicate that our planet witnessed a massive infall of ordinary L chondrite material ~466 million years (My) ago (Heck et al. 2017, Schmieder & Kring 2020, Kenkmann 2021) that may have been at the origin of the first major mass extinction event (Schmitz et al. 2019). The breakup of a large asteroid in the main belt is the likely cause of this massive infall. In modern times, material originating from this breakup still dominates meteorite falls (>20% of all falls) (Swindle et al. 2014). We will present spectroscopic observations and dynamical evidence that the Massalia collisional family is the only plausible source of this catastrophic event and of the most abundant class of meteorites falling on Earth today.

76. Athanasopoulos, D., Hanus, J., Avdellidou, C., et al., (including van Belle, G.), 2024, EPSC, EPSC2024-359, Spin states of X-complex asteroids in the Inner Main Belt confirm the existence of Athor and Zita collisional families.
    Abstract

    Introduction:Numerous energetic collisions between asteroids in the inner Solar System have led to the creation of groups of fragments, known as asteroid collisional families. These families populate the Main Belt, each family typically originating from a single parent body that was shattered [1]. The fragments of the same collision form a characteristic V-shape in the plane defined by inverse diameter (1/D) and orbital semimajor axis (a), due to the Yarkovsky effect [2, 3]. It is a thermal force, which cause outward drift to prograde rotating asteroids and inward drift to retrograde. A method for the identification of very old and dispersed asteroid families has been developed [4,5] to search for families by their V-shapes. Such families may be invisible with the Hierarchical Clustering Method (HCM) [6, 7]. So far, six asteroid families have been discovered by using the V-shape method: the Eulalia and New Polana families [8], a low-albedo primordial family [5] with nominal age of about 4 Gyr, Athor family, ~3.0 Gyr-old, Zita family, ~4.5 Gyr-old [9] and an S-complex asteroid family, ~4.3 Gyr-old [10].Here, we study the spin states of asteroids that belong to the two X-complex asteroid families in the Inner Main Belt, Athor and Zita [9, 11]. Athor family is detectable also with HCM, conversely, the Zita family is not, as its members have dispersed in orbital elements (ghost family, according to [12]). Methodology:We used shape models that were retrieved from the literature or databases as well as multi-epoch observational datasets. Dense-in-time photometric data were retrieved from the literature and obtained from "Ancient Asteroids"1, our own observing campaign [13]. Specifically, we obtained 366 new lightcurves for 84 asteroids. Sparse-in-time photometric data were retrieved from sky surveys, namely: ASAS-SN, ATLAS, PTF, ZTF, and space missions, Gaia and TESS. Further data were collected from published asteroid models.We reduced and calibrated the photometric data following the same methodology of previous works [14, 15, 16] and using different weights for each dataset based on their accuracy [17]. Then we applied the Convex Inversion (CI) method, developed by Kaasalainen et al. [18, 19], for each asteroid from our sample. The CI reveals the spin axis orientation of asteroids, hence their sense of rotation. Results:Athor family:We obtained 31 new asteroid models for Athor family and 9 revised ones. Including the archival models, the spin state is known for 49 members.Figure 1 shows the spin states of Athor family members distributed in the family's V-shape. We found that the outward side of the family exhibits a statistical predominance of prograde asteroids of 76% and in the inward side retrograde asteroids of 60%. Considering only the family core, the outward side presents similar excess of prograde asteroids (77%) and inward side excess of retrograde asteroids (72%). The Kernel Density Estimation (KDE) visualizes qualitatively the underlying probability distribution for the retrograde and prograde rotators and presents two clear peaks: one for retrograde rotators in the inward side and another for prograde in the outward side.Zita family:Concerning the Zita family, we produced 17 new asteroid models and 7 revised. Including the archival models, the spin state is known for 32 members.Figure 2 shows the spin states of Zita family members distributed in the family's V-shape. We found that the 80% the Zita members in the inward side are retrograde rotators, while the outward side contains same number of prograde and retrograde asteroids. The KDE presents a clear peak for prograde in the outward side, while the maximum for retrograde rotators is around family's V-shape center. Conclusions:The Athor family exhibits a statistical predominance of retrograde asteroids in the inward side and, conversely, predominance of prograde asteroids in the outward side. This result adds evidence that the members are fragments of the same parent body, an EL planetesimal, that was shattered about 3 Gy ago.The Zita family demonstrates an excess of retrograde asteroids in the inward side, but there is absence of asteroids due to orbital resonances. Conversely, the outward side does not present any predominance with an equal distribution of prograde and retrograde rotators. However, KDE exhibits a clear peak for prograde asteroids in the outward side.The spin states of these asteroids, derived from observations and modeling, validate the existence of the Athor and Zita families, with the Athor family exhibiting a stronger signature, which is expected as it is younger and more compact. This research provides independent confirmation and characterisation of these very old families, offering tight constraints for our Solar System's evolution models [10, 20]. References:[1] Zappala et al. (1984). Icarus, 59(2), 261-285.[2] Bottke et al. (2006). Annu. Rev. Earth Planet. Sci., 34, 157-191.[3] Vokrouhlicky et al. (2006). Icarus, 182(1), 118-142.[4] Bolin et al. (2017). Icarus, 282, 290-312.[5] Delbo et al. (2017). Science, 357(6355), 1026-1029.[6] Zappala et al. (1990). Astron.J., 100, 2030-2046.[7] Zappala et al. (1995). Icarus, 116(2), 291-314.[8] Walsh et al. (2013). Icarus, 225(1), 283-297.[9] Delbo et al. (2019). A&A, 624, A69.[10] Ferrone et al. (2023). A&A, 676, A5.[11] Avdellidou et al. (2022). A&A, 665, L9.[12] Dermott et al. (2021). MNRS, 505(2), 1917-1939.[13] Athanasopoulos et al. (2021). EPSC2021-355.[14] Hanus et al. (2011) A&A, 530, A134.[15] Hanus et al. (2013). A&A, 551, A67.[16] Athanasopoulos et al. (2022). A&A, 666, A116.[17] Hanus et al. (2023). A&A, 679, A56.[18] Kaasalainen et al. (2001). Icarus, 153(1), 24-36.[19] Kaasalainen et al. (2001). Icarus, 153(1), 37-51.[20] Avdellidou et al. (2024). Science, eadg8092. Acknowledgments:D.A. acknowledges support from the Academy Complex Systems of the Universite Cote d'Azur under the scheme "Programme de visites doctorales". M.D. and C.A. acknowledge support from ANR "ORIGINS" (ANR-18- 647 CE31-0014). The Czech Science Foundation has supported the research of J.H. through grant 22-17783S. N.T. acknowledge support from the Astronomical station Vidojevica and funding from the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (451-03-47/2023-01/ 200002) and by the European Commission through project BELISSIMA (call FP7-REGPOT-2010-5, No. 256772). 1http://users.uoa.gr/~kgaze/ancient_asteroids.html

77. Protopapa, S., Raut, U., Wong, I., et al., (including Grundy, W.), 2024, EPSC, EPSC2024-1277, Detection of Carbon Dioxide and Hydrogen Peroxide on the Layered Surface of Charon Using the James Webb Space Telescope
    Abstract

    We report the first detection of carbon dioxide (CO2) and hydrogen peroxide (H2O2) on Charon's frozen surface as revealed by JWST NIRSpec instrument. With the extended spectral range of NIRSpec, we have expanded Charon's compositional inventory to include these two new species. Previously, the inventory primarily consisted of water ice (mostly in crystalline form), ammoniated species, and a tholin-like darkening constituent. The synergy of laboratory measurements and modeling analysis reveals a stratified surface rich in crystalline water ice with ammonia diluted in water ice at penetration depths of approximately ~100 micron. Additionally, a layer of pure crystalline CO2 is evident at shallower penetration depths of about ~1 micron. This feature is likely attributable to an endogenous source, unearthed by external impacts. This layering configuration is believed to cause a scattering effect, which may account for the peculiarly strong CO2 absorption band at longer wavelengths. Moreover, the surface is undergoing continuous alteration by photolysis and radiolysis, which are responsible for the presence of H2O2 and amorphous water ice.

78. Kueny, J., Chandler, C., Frissell, M., et al., (including Farrell, K.), 2024, RNAAS, 8, 235, Citizen Scientists Discover "Asteroid in a Cometary Orbit" 2010 MK₄₃ has a Comet Tail
    Abstract

    We present the discovery of a short, diffuse tail on minor planet 2010 MK₄₃ (alternate designation 2010 RA₇₈)an object previously identified as an asteroid in a cometary orbitby volunteers of our Citizen Science program Active Asteroids. Our follow-up investigation revealed eight Dark Energy Camera images showing 2010 MK₄₃ with a tail spanning UT 2024 February 12UT 2024 February 18 when the object was outbound from perihelion. We now classify 2010 MK₄₃ as a Jupiter-family comet based on its Tisserand parameter with respect to Jupiter T _J = 2.888, though our dynamical simulations reveal that, due to frequent close encounters with Jupiter, 2010 MK₄₃ was likely a quasi-Hilda within the last 10 kyr.

79. Hunter, D., Elmegreen, B., Madden, S., 2024, ARA&A, 62, 113, The Interstellar Medium in Dwarf Irregular Galaxies
    Abstract

    Dwarf irregular (dIrr) galaxies are among the most common type of galaxy in the Universe. They typically have gas-rich, low-surface-brightness, metal-poor, and relatively thick disks. Here, we summarize the current state of our knowledge of the interstellar medium (ISM), including atomic, molecular, and ionized gas, along with their dust properties and metals. We also discuss star-formation feedback, gas accretion, and mergers with other dwarfs that connect the ISM to the circumgalactic and intergalactic media. We highlight one of the most persistent mysteries: the nature of pervasive gas that is yet undetected as either molecular or cold hydrogen, the "dark gas." Some highlights include the following: Significant quantities of HI are in far-outer gas disks. Cold HI in dIrrs would be molecular in the Milky Way, making the chemical properties of star-forming clouds significantly different. Stellar feedback has a much larger impact in dIrrs than in spiral galaxies. The escape fraction of ionizing photons is significant, making dIrrs a plausible source for reionization in the early Universe. Observations suggest a significantly higher abundance of hydrogen (H₂ or cold HI) associated with CO in star-forming regions than that traced by the CO alone. Significant quantities of HI are in far-outer gas disks. Cold HI in dIrrs would be molecular in the Milky Way, making the chemical properties of star-forming clouds significantly different. Stellar feedback has a much larger impact in dIrrs than in spiral galaxies. The escape fraction of ionizing photons is significant, making dIrrs a plausible source for reionization in the early Universe. Observations suggest a significantly higher abundance of hydrogen (H₂ or cold HI) associated with CO in star-forming regions than that traced by the CO alone.

80. Liu, D., Forster Schreiber, N., Harrington, K., et al., (including Keller, C.), 2024, NatAs, 8, 1181, Detailed study of a rare hyperluminous rotating disk in an Einstein ring 10 billion years ago
    Abstract

    Hyperluminous infrared galaxies (HyLIRGs) are the rarest and most extreme starbursts and found only in the distant Universe (z 1). They have intrinsic infrared (IR) luminosities L_IR 10¹³ L and are commonly found to be major mergers. Recently, the Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts project (PASSAGES) searched ~10⁴ deg² of the sky and found ~20 HyLIRGs. We describe a detailed study of PJ0116-24, the brightest (L_IR 2.6 10¹⁴ L, magnified with 17) Einstein-ring HyLIRG in the southern sky, at z = 2.125, with observations from the near-IR integral-field spectrograph VLT/ERIS and the submillimetre interferometer ALMA. We detected H, H, [N II] and [S II] lines and obtained an extreme Balmer decrement (H/H 8.73 1.14). We modelled the molecular-gas and ionized-gas kinematics with CO(3-2) and H data at ~100-300 pc and (sub)kiloparsec delensed scales, respectively, finding consistent regular rotation. We found PJ0116-24 to be highly rotationally supported (v_rot/_{0, mol. gas} 9.4) with a richer gaseous substructure than other known HyLIRGs. Our results imply that PJ0116-24 is an intrinsically massive (M_baryon 10^11.3 M) and rare starbursty disk (star-formation rate, SFR = 1,490 M yr¹) probably undergoing secular evolution. This indicates that the maximal SFR (1,000 M yr¹) predicted by simulations could occur during a galaxy's secular evolution, away from major mergers.

81. Elliott, A., Boyajian, T., Ellis, T., et al., (including von Braun, K.), 2024, PASA, 41, e043, Measuring the stellar and planetary parameters of the 51 Eridani system
    Abstract

    In order to study exoplanets, a comprehensive characterisation of the fundamental properties of the host stars such as angular diameter, temperature, luminosity, and age, is essential, as the formation and evolution of exoplanets are directly influenced by the host stars at various points in time. In this paper, we present interferometric observations taken of directly imaged planet host 51 Eridani at the CHARA Array. We measure the limb-darkened angular diameter of 51 Eridani to be $\theta_\mathrm{LD} = 0.450\pm 0.006$ mas and combining with the Gaia zero-point corrected parallax, we get a stellar radius of $1.45 \pm 0.02$ R $_{\odot}$ . We use the PARSEC isochrones to estimate an age of $23.2^{+1.7}_{-2.0}$ Myr and a mass of $1.550^{+0.006}_{-0.005}$ M $_{\odot}$ . The age and mass agree well with values in the literature, determined through a variety of methods ranging from dynamical age trace-backs to lithium depletion boundary methods. We derive a mass of $4.1\pm0.4$ M $_\mathrm{Jup}$ for 51 Eri b using the Sonora Bobcat models, which further supports the possibility of 51 Eri b forming under either the hot-start formation model or the warm-start formation model.

82. Buie, M., Spencer, J., Porter, S., et al., (including Wasserman, L.), 2024, PSJ, 5, 196, The New Horizons Extended Mission Target: Arrokoth Search and Discovery
    Abstract

    Following the Pluto flyby of the New Horizons spacecraft, the mission provided a unique opportunity to explore the Kuiper Belt in situ. The possibility existed to fly by a Kuiper Belt object (KBO), as well as to observe additional objects at distances closer than are feasible from Earth-orbit facilities. However, at the time of launch no KBOs were known about that were accessible by the spacecraft. In this paper we present the results of 10 yr of observations and three uniquely dedicated effortstwo ground-based using the Subaru Suprime Camera, the Magellan MegaCam and IMACS Cameras, and one with the Hubble Space Telescopeto find such KBOs for study. In this paper we overview the search criteria and strategies employed in our work and detail the analysis efforts to locate and track faint objects in the Galactic plane. We also present a summary of all of the KBOs that were discovered as part of our efforts and how spacecraft targetability was assessed, including a detailed description of our astrometric analysis, which included development of an extensive secondary calibration network. Overall, these efforts resulted in the discovery of 85 KBOs, including 11 that became objects for distant observation by New Horizons and (486958) Arrokoth, which became the first post-Pluto flyby destination.

83. Frissell, M., Chandler, C., Oldroyd, W., et al., (including Farrell, K.), 2024, RNAAS, 8, 225, Cometary Activity from Minor Planet 2015 VP₅₁ Discovered with Citizen Science
    Abstract

    We report the discovery of cometary activity emanating from minor planet 2015 VP₅₁ outbound from its recent perihelion passage. The activity, in the form of a diffuse tail, was first identified by volunteers of our Citizen Science program Active Asteroids, a NASA Partner program hosted on the Zooniverse platform. This discovery was aided by the recently implemented TailNet artificial intelligence assistant which filters out images with a low likelihood of showing cometary activity. The tail is present in nine images of 2015 VP₅₁ from the Dark Energy Camera and OmegaCAM between UT 2015 August 2 and UT 2015 October 18. We classify 2015 VP₅₁ as a Jupiter-family comet based on its Tisserand parameter with respect to Jupiter T _J = 2.931.

84. Mena-Fernandez, J., Rodriguez-Monroy, M., Avila, S., et al., (including Kuehn, K.), 2024, PhRvD, 110, 063514, Dark Energy Survey: Galaxy sample for the baryonic acoustic oscillation measurement from the final dataset
    Abstract

    In this paper, we present and validate the galaxy sample used for the analysis of the baryon acoustic oscillation (BAO) signal in the Dark Energy Survey (DES) Y6 data. The definition is based on a color and redshift-dependent magnitude cut optimized to select galaxies at redshifts higher than 0.6, while ensuring a high-quality photo-z determination. The optimization is performed using a Fisher forecast algorithm, finding the optimal i-magnitude cut to be given by i<19.64+2.894zph. For the optimal sample, we forecast an increase in precision in the BAO measurement of 25% with respect to the Y3 analysis. Our BAO sample has a total of 15,937,556 galaxies in the redshift range 0.6<zph<1.2, and its angular mask covers 4,273.42 deg2 to a depth of i=22.5. We validate its redshift distributions with three different methods: directional neighborhood fitting algorithm (DNF), which is our primary photo-z estimation; direct calibration with spectroscopic redshifts from VIPERS, which is a spectroscopic galaxy sample that overlaps with our BAO sample and is complete within our selection cuts; and clustering redshift using SDSS galaxies. The fiducial redshift distribution is a combination of these three techniques performed by modifying the mean and width of the DNF distributions to match those of VIPERS and clustering redshift. In this paper, we also describe the methodology used to mitigate the effect of observational systematics, which is analogous to the one used in the Y3 analysis. This paper is one of the two dedicated to the analysis of the BAO signal in DES Y6. In its companion paper, we present the angular diameter distance constraints obtained through the fitting to the BAO scale.

85. Abbott, T., Adamow, M., Aguena, M., et al., (including Kuehn, K.), 2024, PhRvD, 110, 063515, Dark Energy Survey: A 2.1% measurement of the angular baryonic acoustic oscillation scale at redshift zeff=0.85 from the final dataset
    Abstract

    We present the angular diameter distance measurement obtained with the baryonic acoustic oscillation (BAO) feature from galaxy clustering in the completed Dark Energy Survey, consisting of six years (Y6) of observations. We use the Y6 BAO galaxy sample, optimized for BAO science in the redshift range 0.6<z<1.2, with an effective redshift at zeff=0.85 and split into six tomographic bins. The sample has nearly 16 million galaxies over 4,273 square degrees. Our consensus measurement constrains the ratio of the angular distance to sound horizon scale to DM(zeff)/rd=19.510.41 (at 68.3% confidence interval), resulting from comparing the BAO position in our data to that predicted by PLANCK CDM via the BAO shift parameter =(DM/rd)/(DM/rd)PLANCK. To achieve this, the BAO shift is measured with three different methods, angular correlation function (ACF), angular power spectrum (APS), and projected correlation function (PCF), obtaining =0.9520.023, 0.9620.022, and 0.9550.020, respectively, which we combine to =0.9570.020, including systematic errors. When compared with the CDM model that best fits PLANCK data, this measurement is found to be 4.3% and 2.1 below the angular BAO scale predicted. To date, it represents the most precise angular BAO measurement at z>0.75 from any survey and the most precise measurement at any redshift from photometric surveys. The analysis was performed blinded to the BAO position, and it is shown to be robust against analysis choices, data removal, redshift calibrations, and observational systematics.

86. White, R., Davis, T., Lewis, G., et al., (including Kuehn, K.), 2024, MNRAS, 533, 3365, The Dark Energy Survey Supernova Program: slow supernovae show cosmological time dilation out to z 1.
    Abstract

    We present a precise measurement of cosmological time dilation using the light curves of 1504 Type Ia supernovae from the Dark Energy Survey spanning a redshift range $0.1\lesssim z\lesssim 1.2$. We find that the width of supernova light curves is proportional to $(1+z)$, as expected for time dilation due to the expansion of the Universe. Assuming Type Ia supernovae light curves are emitted with a consistent duration $\Delta t_{\rm em}$, and parametrizing the observed duration as $\Delta t_{\rm obs}=\Delta t_{\rm em}(1+z)^b$, we fit for the form of time dilation using two methods. First, we find that a power of $b \approx 1$ minimizes the flux scatter in stacked subsamples of light curves across different redshifts. Secondly, we fit each target supernova to a stacked light curve (stacking all supernovae with observed bandpasses matching that of the target light curve) and find $b=1.003\pm 0.005$ (stat) $\pm \, 0.010$ (sys). Thanks to the large number of supernovae and large redshift-range of the sample, this analysis gives the most precise measurement of cosmological time dilation to date, ruling out any non-time-dilating cosmological models at very high significance.

87. Jackman, J., Shkolnik, E., Loyd, R., et al., (including Richey-Yowell, T.), 2024, MNRAS, 533, 1894, Optically quiet, but FUV loud: results from comparing the far-ultraviolet predictions of flare models with TESS and HST
    Abstract

    The far-ultraviolet (FUV) flare activity of low-mass stars has become a focus in our understanding of the exoplanet atmospheres and how they evolve. However, direct detection of FUV flares and measurements of their energies and rates are limited by the need for space-based observations. The difficulty of obtaining such observations may push some works to use widely available optical data to calibrate multiwavelength spectral models that describe UV and optical flare emission. These models either use single temperature blackbody curves to describe this emission, or combine a blackbody curve with archival spectra. These calibrated models would then be used to predict the FUV flare rates of low-mass stars of interest. To aid these works, we used TESS optical photometry and archival HST FUV spectroscopy to test the FUV predictions of literature flare models. We tested models for partially (M0-M2) and fully convective (M4-M5) stars, 40 Myr and field age stars, and optically quiet stars. We calculated FUV energy correction factors that can be used to bring the FUV predictions of tested models in line with observations. A flare model combining optical and NUV blackbody emission with FUV emission based on HST observations provided the best estimate of FUV flare activity, where others underestimated the emission at all ages, masses, and activity levels, by up to a factor of 104 for combined FUV continuum and line emission and greater for individual emission lines. We also confirmed previous findings that showed optically quiet low-mass stars exhibit regular FUV flares.

88. Moller, A., Wiseman, P., Smith, M., et al., (including Kuehn, K.), 2024, MNRAS, 533, 2073, The Dark Energy Survey 5-yr photometrically classified type Ia supernovae without host-galaxy redshifts
    Abstract

    Current and future Type Ia Supernova (SN Ia) surveys will need to adopt new approaches to classifying SNe and obtaining their redshifts without spectra if they wish to reach their full potential. We present here a novel approach that uses only photometry to identify SNe Ia in the 5-yr Dark Energy Survey (DES) data set using the SUPERNNOVA classifier. Our approach, which does not rely on any information from the SN host-galaxy, recovers SNe Ia that might otherwise be lost due to a lack of an identifiable host. We select $2{,}298$ high-quality SNe Ia from the DES 5-yr data set an almost complete sample of detected SNe Ia. More than 700 of these have no spectroscopic host redshift and are potentially new SNIa compared to the DES-SN5YR cosmology analysis. To analyse these SNe Ia, we derive their redshifts and properties using only their light curves with a modified version of the SALT2 light-curve fitter. Compared to other DES SN Ia samples with spectroscopic redshifts, our new sample has in average higher redshift, bluer and broader light curves, and fainter host-galaxies. Future surveys such as LSST will also face an additional challenge, the scarcity of spectroscopic resources for follow-up. When applying our novel method to DES data, we reduce the need for follow-up by a factor of four and three for host-galaxy and live SN, respectively, compared to earlier approaches. Our novel method thus leads to better optimization of spectroscopic resources for follow-up.

89. Camilleri, R., Davis, T., Vincenzi, M., et al., (including Kuehn, K.), 2024, MNRAS, 533, 2615, The dark energy survey supernova program: investigating beyond-CDM
    Abstract

    We report constraints on a variety of non-standard cosmological models using the full 5-yr photometrically classified type Ia supernova sample from the Dark Energy Survey (DES-SN5YR). Both Akaike Information Criterion (AIC) and Suspiciousness calculations find no strong evidence for or against any of the non-standard models we explore. When combined with external probes, the AIC and Suspiciousness agree that 11 of the 15 models are moderately preferred over Flat-$\Lambda$CDM suggesting additional flexibility in our cosmological models may be required beyond the cosmological constant. We also provide a detailed discussion of all cosmological assumptions that appear in the DES supernova cosmology analyses, evaluate their impact, and provide guidance on using the DES Hubble diagram to test non-standard models. An approximate cosmological model, used to perform bias corrections to the data holds the biggest potential for harbouring cosmological assumptions. We show that even if the approximate cosmological model is constructed with a matter density shifted by $\Delta \Omega _{\rm m}\sim 0.2$ from the true matter density of a simulated data set the bias that arises is subdominant to statistical uncertainties. Nevertheless, we present and validate a methodology to reduce this bias.

90. Kelly, P., Jobel, J., Eiger, O., et al., (including Kuehn, K.), 2024, MNRAS, 533, 572, Dark energy survey year 3 results: miscentring calibration and X-ray-richness scaling relations in redMaPPer clusters
    Abstract

    We use Dark Energy Survey Year 3 (DES Y3) clusters with archival XMM-Newton and Chandra X-ray data to assess the centring performance of the redMaPPer cluster finder and to measure key richness observable scaling relations. We find that 10-20 per cent of redMaPPer clusters are miscentred, both when comparing to the X-ray peak position and to the visually identified central cluster galaxy. We find no significant difference in miscentring in bins of low versus high richness or redshift. The dominant reasons for miscentring include masked or missing data and the presence of other bright galaxies in the cluster. For half of the miscentred clusters, the correct central was one of the possible centrals identified by redMaPPer, while for ~40 per cent of miscentred clusters, the correct central is not a redMaPPer member mostly due to masking. Additionally, we fit scaling relations of X-ray temperature and luminosity with richness. We find a T_X- scatter of $0.21\pm 0.01$. While the scatter in T_X- is consistent in redshift bins, we find modestly different slopes, with high-redshift clusters displaying a somewhat shallower relation. Splitting based on richness, we find a marginally larger scatter for our lowest richness bin, 20 < < 40. We note that the robustness of the scaling relations at lower richnesses is limited by the unknown selection function, but at > 75, we detect nearly all of the clusters falling within existing X-ray pointings. The X-ray properties of detected, serendipitous clusters are generally consistent with those of targeted clusters.

91. O'Toole, C., Vos, J., Kao, M., et al., 2024, csss, 5, Aurorae, Clouds or Magnetic Spots? Disentangling drivers of variability in three early L-Dwarfs.
    Abstract

    Brown dwarfs provide unique insights into exometeorology - weather on extrasolar objects. They act as powerful analogs to directly imaged exoplanets, due to their similar position on colour-magnitude diagrams. They provide a wealth of information as to how both of these substellar populations form and evolve as they can be observed far easier than directly imaged exoplanets. This study investigates the spectroscopic variability of three early L-type brown dwarfs, 2M0036+18, 2M1721+33 and 2M1906+40, using a novel approach of simultaneous observations from HST/WFC3 at near-IR wavelengths and the VLA in the radio (4-12 GHz). Early L-Dwarfs are especially interesting as they are at the right temperature to allow a number of processes to occur that are not possible at other spectral types including any one of, or a combination of, aurorae, clouds and magnetic spots. This allows different insights into the atmospheric processes in giant extrasolar worlds. We use the HST data to distinguish between the various drivers of variability and potentially detect auroral activity in the near-IR for the first time. 2M0036+18 is a known auroral emitter in the radio, while 2M1721+33's variability is primarily due to condensate clouds. The final case however, 2M1906+40, has ambiguous behaviour. All three objects show significant variability in the HST observations and we aim to disentangle the drivers of variability in each object by analysing their unique signatures of variability.+

92. van Belle, G., Ciardi, D., Hillsberry, D., et al., 2024, SPIE, 13092, 130922N, MoonLITE: a CLPS-delivered NASA Astrophysics Pioneers lunar optical interferometer for sensitive, milliarcsecond observing
    Abstract

    MoonLITE (Lunar InTerferometry Explorer) is an Astrophysics Pioneers proposal to develop, build, fly, and operate the first separated-aperture optical interferometer in space, delivering sub-milliarcsecond science results. MoonLITE will leverage the Pioneers opportunity for utilizing NASA's Commercial Lunar Payload Services (CLPS) to deliver an optical interferometer to the lunar surface, enabling unprecedented discovery power by combining high spatial resolution from optical interferometry with deep sensitivity from the stability of the lunar surface. Following landing, the CLPS-provided rover will deploy the pre-loaded MoonLITE outboard optical telescope 100 meters from the lander's inboard telescope, establishing a two-element interferometric observatory with a single deployment. MoonLITE will observe targets as faint as 17th magnitude in the visible, exceeding ground-based interferometric sensitivity by many magnitudes, and surpassing space-based optical systems resolution by a factor of 50. The capabilities of MoonLITE open a unique discovery space that includes direct size measurements of the smallest, coolest stars and substellar brown dwarfs; searches for close-in stellar companions orbiting exoplanet-hosting stars that could confound our understanding and characterization of the frequency of Earth-like planets; direct size measurements of young stellar objects and characterization of the terrestrial planet-forming regions of these young stars; measurements of the inner regions and binary fraction of active galactic nuclei; and a probe of the very nature of spacetime foam itself. A portion of the observing time will also be made available to the broader community via a guest observer program. MoonLITE takes advantage of the CLPS opportunity to place an interferometer in space on a stable platform - the lunar surface - and delivers an unprecedented combination of sensitivity and angular resolution at the remarkably affordable cost point of Pioneers.

93. Jensen, L., Gamaunt, J., Scowen, P., et al., (including Llama, J.), 2024, SPIE, 13093, 1309337, Assembly, integration, and testing of the Star-Planet Activity Research CubeSat (SPARCS)
    Abstract

    We discuss the final assembly, integration, and testing of the Star-Planet Activity Research CubeSat. SPARCS is a 6U CubeSat mission designed to monitor the dual-channel, far-UV (153-176 nm) and near-UV (258-308 nm) photometric activity of nearby low mass stars to advance our understanding of their evolution, activity, and the habitability of surrounding exoplanets. This paper details the assembly of the SPARCS instrument and the testing process to characterize and validate the performance of the payload prior to spacecraft integration. To test SPARCS, we have established a customized CubeSat AIT laboratory and thermal vacuum chamber at ASU equipped to handle CubeSats requiring meticulous contamination control for work in the FUV. After a brief overview of these facilities and the testing plan, we will detail the methods and data used to verify the performance of SPARCS and generate calibration products to reduce raw flight data to high-quality science products. The result will be the delivery of the first highly sensitive FUV astrophysics CubeSat which will inform exoplanet environments and future observations of these systems by facilities like the Habitable Worlds Observatory.

94. Ardila, D., Shkolnik, E., Scowen, P., et al., (including Llama, J.), 2024, SPIE, 13093, 1309338, Photometric calibration in the ultraviolet of the Star-Planet Activity Research CubeSat (SPARCS)
    Abstract

    The Start-Planet Activity Research CubeSat (SPARCS) is a NASA-funded mission led by Arizona State University, devoted to characterizing the UV emission of low-mass stars. During its nominal one-year mission, SPARCS will observe close to 20 low-mass stars, with the goal of understanding their short and long-term UV variability. SPARCS will be ready for launch in 2025. SPARCS' payload is a 9-cm telescope paired with two delta-doped charge-coupled devices (CCDs). The data calibration converts the raw instrument counts into an average flux within the two ultraviolet bands (153 - 171 nm, 258 - 308 nm). While the system is only weakly sensitive in the infrared, the target stars are very bright at long wavelengths. This requires careful correction of the data for out-of-band emission. The system is being fully characterized on the ground to provide supporting calibration data. The calibration uses observations of very stable white dwarfs to achieve the 10% photometric accuracy requirement in both bands.

95. Llama, J., Zhao, L., Brewer, J., et al., (including Collins, M., Tiegs, J., Cornelius, F.), 2024, SPIE, 13094, 130942O, The Lowell Observatory Solar Telescope: a fiber feed into the Extreme Precision Spectrometer
    Abstract

    The signal induced by a temperate, terrestrial planet orbiting a Sun-like star is an order of magnitude smaller than the host stars' intrinsic variability. Understanding stellar activity is, therefore, a fundamental obstacle in confirming the smallest exoplanets. We present the Lowell Observatory Solar Telescope (LOST), a solar feed for the EXtreme PREcision Spectrometer (EXPRES) at the 4.3-m Lowell Discovery Telescope (LDT). EXPRES is one of the newest high-resolution spectrographs that accurately measure extreme radial velocity. With LOST/EXPRES, we observe disk-integrated sunlight autonomously throughout the day. In clear conditions, we achieve a R 137, 500 optical spectrum of the Sun with a signal-to-noise of 500 in 150s. Data is reduced using the standard EXPRES pipeline with minimal modification to ensure the data are comparable to the observations of other stars with the LDT. During the first three years of operation, we find a daily RMS of 71cm/s. Additionally, having two EPRV spectrometers located in Arizona gives us an unprecedented opportunity to benchmark the performance of these planet-finders. We find a RMS of just 55cm/s when comparing data taken simultaneously with EXPRES and NEID.

96. Hardesty, B., Bida, T., Collins, M., et al., (including Cornelius, F., Hamilton, R., Kuehn, K., Levine, S.), 2024, SPIE, 13094, 130943X, The Peggy and Eric Johnson 1-meter telescope at Lowell Observatory: converting a historic observatory into a modern research facility
    Abstract

    In 2021 Lowell Observatory began preparations for a new remotely operated 1.0-m class telescope facility. Site studies were conducted and a historic observatory on Anderson Mesa near Flagstaff, Arizona was selected to house a PlaneWave Instruments PW1000 1-meter telescope. This facility previously housed the 13" Pluto Discovery Telescope and the 23" Lowell Observatory Near-Earth-Object Search (LONEOS) telescope. The equatorial piers were modified to accept a custom vibration optimized bridge structure to support the dome-centered Alt/Az telescope mount. Many other updates were installed including network, power, dome repairs, access platforms, and general remodeling. The commissioning instrument selection process resulted in the purchase of the Teledyne-PI SOPHIA 4096B CCD camera. Further custom components were needed to integrate the camera to the Nasmyth port of the telescope including a lightweight filter wheel, detector alignment mechanism, payload support assembly, and cable management/de-rotation limits. Commissioning of the facility started in late 2023 and it has already been used successfully for a number of occultation events. The full SOPHIA instrument assembly, including the custom filter wheel, is on track to be completed in 2025. Future facility plans such as power outage recovery, robotic observing software, and second instrument planning are currently in progress.

97. Anugu, N., ten brummelaar, T., Lanthermann, C., et al., (including van Belle, G.), 2024, SPIE, 13095, 130951B, CHARA/Silmaril instrument software and data reduction pipeline: characterization of the instrument in the lab and on-sky
    Abstract

    The newly installed Silmaril beam combiner at the CHARA array is designed to observe previously inaccessible faint targets, including Active Galactic Nuclei and T-Tauri Young Stellar Objects. Silmaril leverages cuttingedge optical design, low readout noise, and a high-speed C-RED1 camera to realize its sensitivity objectives. In this presentation, we offer a comprehensive overview of the instrument's software, which manages critical functions, including camera data acquisition, fringe tracking, automatic instrument alignment, and observing interfaces, all aimed at optimizing on-sky data collection. Additionally, we offer an outline of the data reduction pipeline, responsible for converting raw instrument data products into the final OIFITS used by the standard interferometry modeling software. Finally, a thorough analysis of the camera and instrument characterization results will be presented, evaluating instrument performance in terms of sensitivity. The purpose of this paper is to provide a solid reference for studies based on Silmaril data.

98. Rau, G., Carpenter, K., Boyajian, T., et al., (including van Belle, G.), 2024, SPIE, 13095, 130951J, Artemis-enabled Stellar Imager (AeSI): a Lunar long-baseline UV/optical imaging interferometer
    Abstract

    NASA's return to the Moon presents unparalleled opportunities to advance high-impact scientific capabilities. At the cutting edge of these possibilities are extremely high-resolution interferometric observations at visible and ultraviolet wavelengths. Such technology can resolve the surfaces of stars, explore the inner accretion disks of nascent stars and black holes, and eventually enable us to observe surface features and weather patterns on nearby exoplanets. We have been awarded Phase 1 support from NASA's Innovative Advanced Concepts (NIAC) program to explore the feasibility of constructing a high-resolution, long-baseline UV/optical imaging interferometer on the lunar surface, in conjunction with the Artemis Program. A 1996 study comparing interferometers on the Moon versus free-flyers in space concluded that, without pre-existing lunar infrastructure, free-flyers were preferable. However, with the advent of the Artemis Program, it is now crucial to revisit the potential of building lunar interferometers. Our objective is to conduct a study with the same level of rigor applied to large baseline, free-flying interferometers during the 2003-2005 NASA Vision Missions Studies. This preparation is essential for timely and effective utilization of the forthcoming lunar infrastructure. In this paper, we highlight the groundbreaking potential of a lunar surface-based interferometer. This concept study will be a huge step forward to larger arrays on both the moon and free-flying in space, over a wide variety of wavelengths and science topics. Our Phase 1 study began in April 2024, and here we present a concise overview of our vision and the progress made so far.

99. van Belle, G., Jorgensen, A., 2024, SPIE, 13095, 130951R, The Big Fringe Telescope
    Abstract

    The Big Fringe Telescope (BFT) is a facility concept under development for a next-generation, kilometer-scale optical interferometer. Observations over the past two decades from routinely operational facilities such as CHARA and VLTI have produced groundbreaking scientific results, reflecting the mature state of the techniques in optical interferometry. However, routine imaging of bright main sequence stars remains a surprisingly unexplored scientific realm. Additionally, the three-plus decade old technology infrastructure of these facilities leads to high operations & maintenance costs, and limits performance. We are developing the BFT, based upon robust, modern, commercially-available, automated technologies with low capital construction and O&M costs, in support of kilometer-scale optical interferometers that will open the door to regular `snapshot' imaging of main sequence stars. Focusing on extreme angular resolution for bright objects leads to substantial reductions in expected costs through use of COTS elements and simplified infrastructure.

100. Ricketti, B., Spencer, L., Leisawitz, D., et al., (including van Belle, G.), 2024, SPIE, 13095, 130951T, Considerations for a next-generation Great Observatory class space-based interferometer for far-infrared astronomy
     Abstract

     Astronomy at far-infrared (far-IR) wavelengths is essential to our understanding of the evolution of the cosmos, from the star formation history of galaxies to how the ice distribution affects the formation of extrasolar planetary systems. The Hubble Space Telescope, James Webb Space Telescope, and the Atacama Large Millimeter Array have already produced ground-breaking astronomical observations with high angular resolution spanning the visible to sub-millimetre wavelength regimes. However, this presents a gap in the far-IR, from roughly 30400m, where ground-based observations are largely intractable due to the opacity of Earth's atmosphere. Indeed, no telescope, observatory, or interferometry array has ever achieved sub-arcsecond angular resolution over this wavelength range. A space-based solution is needed. However, a space-based far-IR telescope capable of subarcsecond angular resolution and high sensitivity, at a cost comparable to the largest space missions to date, presents unique physical, practical, and engineering challenges. In this paper, we envisage what a far-IR Great Observatory class mission might look like in the context of the already-studied Origins Space Telescope (OST) and the Space Infrared Interferometric Telescope (SPIRIT). We begin with a historical reflection of far-IR missions, including OST and the recommendations by the Astro2020 Decadal Survey for a de-scoped mission. We use this to motivate the recommendation of a space-based interferometer as a reasonable path towards sub-arcsecond angular resolution at far-IR wavelengths. Using the SPIRIT mission concept as inspiration, we consider multiple point designs for a two element, structurally connected spatial-spectral space-based far-IR interferometer to understand the implications on achieved angular resolution and estimate total mission cost in context of the Decadal Survey recommended far-IR Great Observatory cost cap. This paper illustrates the unique capabilities only possible through a space-based far-IR double Fourier interferometry mission capable of sub-arcsecond resolution.

101. Kuehn, K., Kelley, T., Kuhlmann, S., et al., 2024, SPIE, 13100, 1310069, Tunable dual-polarization photonic ring resonator filters for OH-suppressed ground-based astronomy
     Abstract

     We seek to advance the capabilities of photonic technologies in support of ground-based infrared astronomy. Currently, observations in the wavelength range 1.0m < < 2.5m suffer from an irreducible background generated by emission from OH (hydroxyl) molecules in the upper atmosphere. Placing instruments in space is one solution, but these are significantly more expensive and much harder (and more dangerous) to maintain and upgrade. Meanwhile, narrow-band notch filters incorporated into the optical path of ground-based astronomical instruments can suppress this background with very little accompanying loss of signal from the astronomical sources of interest. Micron-scale ring resonators are one technology that provides a promising method of generating such notch filters. Building on our previous efforts in astrophotonic technology development, our current goals are 1) to optimize the design of ring resonators so that the notch filters they create provide greatest suppression at the wavelengths of the most prominent OH lines, and 2) to optimize the coupling of the resonator-equipped silicon devices with the input fibers (from the sky) and output fibers (to the spectrograph and detector) such that the throughput losses do not completely eliminate the signal-to-noise improvement gained from the OH suppression. To accomplish the former, we introduce heaters that can actively change the wavelength of the notch filters to match the OH emission lines, as well as mechanisms for polarization-dependent and -independent suppression. To accomplish the latter, we incorporate post-fabrication packaging of fibers to ensure optimal alignment.

102. Sebok, R., Ashmead, F., Diehl, H., et al., (including Kuehn, K.), 2024, SPIE, 13100, 131006A, Small pitch tilting spine optical fiber positioners for massively parallel spectroscopy
     Abstract

     Massively-multiplexed spectroscopic surveys rely on precise optical fiber-positioning technology to match the fiber positions in physical space to targets observed on-sky. Several different technologies have been used for such devices, including Tilting Spines, Twirling Posts, and Walking Bugs; each of these has its own advantages and drawbacks in terms of parallelization, pitch, exclusion radius, and other relevant operational factors. Current instruments using Tilting Spines operate with a pitch (that is, the separation between adjacent spines) of approximately 9 mm. Reducing the pitch to 5 mm allows for observations of many more targets in parallel, as well as (potentially) much denser target fields. Here we describe engineering efforts and progress towards reducing the pitch between adjacent Tilting Spines. We conclude with a brief discussion of the impact an instrument with very densely packed fiber positioners would have on massively-multiplexed astronomical observations.

103. Sickafoose, A., Adams, E., Knieling, B., et al., (including Levine, S.), 2024, IAUGA, 999, Stellar Occultations by Bodies in the Outer Solar System
     Abstract

     Stellar occultations are one of the most accurate, ground-based methods by which to assess physical characteristics of bodies in the outer Solar System. For example, in the trans-Neptunian region, occultation data have been used to determine object sizes and shapes at km-level accuracy, detect or place limits on microbar-level atmospheres, and discover and study rings down to km-level widths. Particularly compelling targets over the next few years include Pluto (which its thin, evolving, global atmosphere) and the trans-Neptunian objects and Centaurs for which rings have been proposed (Chariklo, Chiron, Haumea, and Quaoar). We will present recent results from stellar occultations by bodies in the outer Solar System, and we will consider the implications of large discovery surveys on future occultation efforts as well as how the technique can be used to increase their science return.

104. Pichler, E., Elmegreen, B., Hunter, D., et al., 2024, IAUGA, 2492, HI line properties and relationship to star formation in nearby dwarf galaxy DDO 43
     Abstract

     We describe one of the smallest nearby galaxies, revisiting the LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes, The HI Nearby Galaxy Survey) data. The high-quality HI 21cm VLA spectra provide a resolved view of DDO 43's gas content. We look for gas kinematics traced by HI, and our spectra analysis results reveal the characteristics of local and global neutral gas flows in DDO 43. We report the comparative analysis of the derived HI parameters with available multispectral data tracing gas dynamics, interstellar dust properties and star formation. As stellar winds and supernovae drive interstellar gas and cause turbulent flows, while turbulence affects star formation by compressing and disrupting gas clouds, this feedback process is still awaiting answers. Our highlighted aim is to look for massive star formation areas and provide additional details on the relationship between interstellar gas motions and star formation.

105. Waller, C., Espiritu, R., Tinsman, C., et al., (including Moskovitz, N.), 2024, PSJ, 5, 177, Science Product Pipelines and Archive Architecture for the DART Mission
     Abstract

     On 2022 September 26, the Double Asteroid Redirection Test (DART) mission was the first successful demonstration of a kinetic impactor for planetary defense. The DART mission utilized a novel autonomous data processing pipeline architecture to quickly produce and analyze the quality of raw and calibrated images from the camera mounted on board the spacecraft. Optimization of the data processing pipeline allowed the final 150 images prior to impact to be calibrated and delivered to the Investigation Team and the press within 15 minutes of acquisition. A data quality analysis pipeline allowed for rapid identification of detector misconfigurations, missing data, and other adverse events. DART data products, along with data from LICIACube and data from ground observatories, used common file formats to facilitate the development of analysis and archiving software. This architecture is described for future missions with large volumes of data and an emphasis on quick-turnaround applications such as planetary defense.

106. Cartwright, R., Holler, B., Grundy, W., et al., 2024, ApJL, 970, L29, JWST Reveals CO Ice, Concentrated CO₂ Deposits, and Evidence for Carbonates Potentially Sourced from Ariel's Interior
     Abstract

     The Uranian moon Ariel exhibits a diversity of geologically young landforms, with a surface composition rich in CO₂ ice. The origin of CO₂ and other species, however, remains uncertain. We report observations of Ariel's leading and trailing hemispheres, collected with NIRSpec (2.875.10 m) on the James Webb Space Telescope. These data shed new light on Ariel's spectral properties, revealing a double-lobed CO₂ ice scattering peak centered near 4.20 and 4.25 m, with the 4.25 m lobe possibly representing the largest CO₂ Fresnel peak yet observed in the solar system. A prominent 4.38 m ¹³CO₂ ice feature is also present, as is a 4.90 m band that results from ¹²CO₂ ice. The spectra reveal a 4.67 m ¹²CO ice band and a broad 4.02 m band that might result from carbonate minerals. The data confirm that features associated with CO₂ and CO are notably stronger on Ariel's trailing hemisphere compared to its leading hemisphere. We compared the detected CO₂ features to synthetic spectra of CO₂ ice and mixtures of CO₂ with CO, H₂O, and amorphous carbon, finding that CO₂ could be concentrated in deposits thicker than 10 mm on Ariel's trailing hemisphere. Comparison to laboratory data indicates that CO is likely mixed with CO₂. The evidence for thick CO₂ ice deposits and the possible presence of carbonates on both hemispheres suggests that some carbon oxides could be sourced from Ariel's interior, with their surface distributions modified by charged particle bombardment, sublimation, and seasonal migration of CO and CO₂ from high to low latitudes.

107. Johns-Krull, C., Flagg, L., France, K., et al., (including Prato, L.), 2024, hst, 17700, Separating Accretion and Magnetic Activity in Young Brown Dwarfs
     Abstract

     Several recent studies have begun to explore accretion physics on planetary mass objects orbiting young stars; however, many of these studies highlight uncertainties in the accretion models used to interpret the observations. The models have been developed and calibrated for stellar accretion. Do they apply to planetary mass objects? Young brown dwarfs provide a natural bridge for connecting accretion studies from stars down to planetary mass obejcts. A key difficulty in diagnosing excess emission produced by accretion is to properly account for emission produced by magnetic activity. This is particularly true for line emission. We will study the FUV and blue optical emission of a sample of a dozen young brown dwarfs spanning the mass range from near the stellar limit down to near the planetary mass limit. Half of our sources show evidence for accretion while half do not. We will use these data to separate out the role of accretion and magnetic activity in producing the observed excess emission in order to test the applicability of models of stellar accretion to very low mass objects such as young giant planets.

108. Proudfoot, B., Grundy, W., Ragozzine, D., 2024, hst, 17707, Mutual events of Transneptunian Binaries
     Abstract

     The population of transneptunian objects (TNOs) is a key tracer of the early solar system's formation and evolution. By looking at the binaries within the TNO population, convincing evidence of planetesimal formation by the Streaming Instability has been found. Further study of these bodies is sure to reveal more insights into the earliest moments of our solar system. One ideal way to study binaries at unprecedented resolution is to observe mutual events, periodic dimming events where one binary component occults/eclipses another. Currently, four TNO binaries are (or will soon be) undergoing mutual events. In this proposal, we ask for 8 orbits to precisely determine the times of these mutual events. Current event timing uncertainties are >24 hours, and are impossible to use for planning observations. Our proposed observations will reduce uncertainties to <4 hours, allowing for precise observations from ground-based telescopes. We will also use state-of-the-art non-Keplerian orbit fitting techniques which will allow for far better predictions. Capturing mutual events will provide immense opportunity for discovery, and are impossible without our proposed observations.

109. Lefever, R., Bernini Peron, M., Gonzalez-Tora, G., et al., (including Massey, P.), 2024, hst, 17723, The first UV investigation of a massive stripped-envelope core-collapse progenitor at high metallicity: The WO star WR 102
     Abstract

     The WO-type Wolf-Rayet stars of the oxygen sequence represent the final stage in the life of a massive star. These stars offer a unique window to the evolutionary stages right before going supernovae and collapsing into black holes (BHs). A WO star is dominated by a strong stellar wind that further strips its outer layers. This large mass loss ultimately determines how much mass is left for a BH to form. Given the discrepancy between observed BH masses and final masses from stellar evolution, determining the wind structure and mass-loss rate is paramount. Moreover, the evolution of these stars and their winds is poorly constrained: whether some WO stars will undergo a stripped-envelope supernova (SNIbc) is currently under debate. Optical analyses exist but cannot reveal the whole picture: mayor wind drivers and nucleosynthesis indicators can only be observed in the UV. Yet, UV spectra of WO stars at Galactic metallicities are absent. Looking at the most evolved WO star in the Milky Way, WR 102, we propose to obtain pioneering UV data to understand massive, stripped core-collapse progenitors at high metallicity and shed light on the SNIbc puzzle. Being highly evolved and stripped objects, the abundances of WO stars also yield a unique insight into the highly uncertain C-O nuclear reaction rate. Using stellar atmosphere models with an inherent solution of the hydrodynamic equation, we will further be able to obtain consistent density stratifications for our targets and get a unique handle on the so far uncertain stellar mass. Thereby, we will be able to provide a crucial testbed for the circumstellar emvironment of highly stripped stars undergoing core collapse.

110. Trilling, D., Chandler, C., Grundy, W., et al., (including Kareta, T.), 2024, hst, 17755, An HST Snapshot test of a long-standing mystery in the outer Solar System
     Abstract

     The outermost region in our Solar System retains pristine signatures of planetary system formation and evolution. Centaurs -- objects on dynamically unstable orbits between Neptune and Jupiter -- show, not a continuum of colors, but two distinct surface colors: more red, and less red or "blue." Two rival hypotheses can explain this Centaur color dichotomy. The first hypothesis is that a thermal gradient in the protoplanetary disk led to a compositional gradient for primordial bodies. The second hypothesis is instead that the color dichotomy is a result of recent surface evolution. In this case, for some Centaurs, sublimation of volatile material may have resulted in the accumulation of fresh "blue" material that has buried ancient radiation-reddened surfaces. Here we propose a novel method to test the idea that activity is responsible for the two color groups of Centaurs. We will use the exceptional angular resolution and sensitivity of HST to detect or set stringent upper limits on the presence of activity for Centaurs, far exceeding limits that can be achieved from ground-based telescopes. We will observe up to 62 Centaurs in a snapshot (SNAP) program. If we find activity only among blue Centaurs, we will confirm that activity is responsible for this color. If we find activity among both red and blue Centaurs at approximately the same rate, the interpretation points instead to an explanation relating to cosmochemical formation in the protoplanetary disk. This program will contribute significantly to the total number of known active Centaurs. This project can only be carried out with HST, and SNAP is an ideal mechanism to collect this data.

111. Noonan, J., Kareta, T., 2024, hst, 17795, Active, but at What Cost? Determining Temporary Jupiter Co-orbital Comet P/2023 V6's Size and Probing The Gateway Region
     Abstract

     The discovery of the transient Jupiter co-orbital comet P/2019 LD2 (ATLAS) drew significant interest. Not only will LD2 transition between being a Centaur and a Jupiter Family Comet (JFC) in 2063, the first time this process can be observed as it happens, it is also very active for its large heliocentric distance. We propose HST WFC3 observations of the newly discovered transient Jupiter co-orbital comet P/2023 V6 (PANSTARRS), the second such object known. Despite similar modern orbits, V6 is significantly (15x) less active than LD2 and most JFCs as determined via dust production measurements at the same heliocentric distance. As such, this suggests a correspondinly smaller nucleus size. If the nuclei are similar in size, we interpret these differences in activity as evolutionary, with V6 having lost a significant fraction of its near-surface ice compared to LD2 by previously being warmer. We will observe P/2023 V6 witht F350LP filter for two orbits of HST (a total of 2000s of exposure) to measure the nucleus size using HST's stable PSF and separate the weak dust coma from the nuclear contribution. If our hypothesis about V6's size is proven, this would be more evidence that LD2 is a pristine and ice-rich object, and thus it may display very strong activity when it becomes a JFC. We will use our observattion to delineate the differences between V6 and LD2 to discuss the interpretation of cometary activity at large heliocentric distances. This has significant repercussions for our understanding of the end state of JFCs, as well as the small end of the cratering record of the Galilean Satellites.

112. Gregg, M., Mihos, C., Minniti, D., et al., (including West, M.), 2024, hst, 17844, The Origin of the Virgo Intergalactic Population
     Abstract

     The intracluster light (ICL) is a major component of galaxy clusters, and contains a record of the galaxies destroyed during hierarchical assembly of the cluster. This proposal addresses three issues critical to understanding the origin and evolution of intergalactic populations, using resolved star WFC3/IR photometry of intergalactic fields in the Virgo cluster. Foremost, we will probe the age distribution of Virgo's intracluster stars via the period distribution of bright AGB variable stars, a tool successfully deployed to study stellar populations in elliptical galaxies. By spreading the observations over 8 epochs and two HST cycles (4+4), we can determine periods and reveal the age spread of the intracluster stars, opening a new window on their origin and evolution. Second, IR color magnitude diagrams from the stacked imaging will establish the metallicity distribution function of the ICL, constraining the luminosity function and abundances of the galaxies that have been dismembered in assembling the intracluster population. Third, by observing five fields around the core of the cluster, we will trace how spatially well-mixed the ICL population is and how its age and metallicity vary across diverse environments, and thus measure its evolutionary state. While JWST will extend photometric work on the Virgo ICL, period determination of LPVs with JWST is very difficult because of its restricted visibility window in Virgo. It is therefore critical to begin these multi-cycle observations while time permits before the end of HST's lifetime.

113. Carleton, T., Willner, S., Ellsworth-Bowers, T., et al., (including Archer, H.), 2024, RNAAS, 8, 181, New Spectroscopic Redshift Places PEARLSDG in a Group at 124 Mpc
     Abstract

     PEARLSDG was previously reported as an isolated dwarf galaxy with a TRGB distance of 30 Mpc. New data show this to not be the case. We report a new spectroscopic redshift of 0.02809, which argues for an association with a group of galaxies at 124 Mpc.

114. Shah, P., Davis, T., Bacon, D., et al., (including Kuehn, K.), 2024, MNRAS, 532, 932, The dark energy survey: detection of weak lensing magnification of supernovae and constraints on dark matter haloes
     Abstract

     The residuals of the distance moduli of Type Ia supernovae (SNe Ia) relative to a Hubble diagram fit contain information about the inhomogeneity of the Universe, due to weak lensing magnification by foreground matter. By correlating the residuals of the Dark Energy Survey Year 5 SN Ia sample (DES-SN5YR) with extragalactic foregrounds from the DES Y3 Gold catalogue, we detect the presence of lensing at $6.0 \sigma$ significance. This is the first detection with a significance level above $5\sigma$. Constraints on the effective mass-to-light ratios and radial profiles of dark matter haloes surrounding individual galaxies are also obtained. We show that the scatter of SNe Ia around the Hubble diagram is reduced by modifying the standardization of the distance moduli to include an easily calculable de-lensing (i.e. environmental) term. We use the de-lensed distance moduli to recompute cosmological parameters derived from SN Ia, finding in Flat wcold dark matter a difference of $\Delta \Omega _{\rm M} = +0.036$ and $\Delta w = -0.056$ compared to the unmodified distance moduli, a change of $\sim 0.3\sigma$. We argue that our modelling of SN Ia lensing will lower systematics on future surveys with higher statistical power. We use the observed dispersion of lensing in DES-SN5YR to constrain $\sigma _8$, but caution that the fit is sensitive to uncertainties at small scales. Nevertheless, our detection of SN Ia lensing opens a new pathway to study matter inhomogeneity that complements galaxy-galaxy lensing surveys and has unrelated systematics.

115. Jenniskens, P., Pilorz, S., Gural, P., et al., (including Avner, D., Blomquist, S., Gialluca, M., Hemmelgarn, S., Moskovitz, N.), 2024, Icar, 415, 116034, Lifetime of cm-sized zodiacal dust from the physical and dynamical evolution of meteoroid streams
     Abstract

     While comets eject mass mostly at cm-sizes and larger, that size range of particles is mostly absent from the interplanetary medium. Such particles are thought to be lost from the solar system by grain-grain collisions. Here, we investigate the lifetime of cm-sized meteoroids from their abundance in meteoroid streams of different age. For 487 streams, we measured the orbital element dispersions, the magnitude size distribution index, the ratio of fluffy and dense materials in the stream and their bulk densities, and the meteor light curve shape-parameter. We find that older long-period comet meteoroid streams tend to be more dispersed and evolve towards smaller semi-major axis, higher magnitude size distribution index, and contain relatively more high-density material. Meteoroids that approach the Sun closer than 0.20.3 AU are mostly young and composed of denser materials poor in sodium. We compare the observed properties of the streams to age estimates from the literature and to a set of new age estimates for long-period comet streams based on observed dispersions. We find that streams broaden with age inversely proportional to the perihelion distance (q). By selecting narrow ranges of age, we find that their magnitude distribution index changes proportional to 1/q, less steep than expected from meteoroid destruction by collisions. Instead, this shallow dependence suggests a lifetime inversely proportional to the peak grain temperature along its orbit, with the lifetime limited by thermal stresses if 0.3 < q < 1.02 AU and by sublimation if q < 0.2 AU.

116. Prato, L., Kutra, T., Tofflemire, B., et al., (including Knowlton, P., Hyden, J.), 2024, AAS, 244, 202.05, Should I Stay or Should I Go: What Governs Circumstellar Disk Lifetimes
     Abstract

     Primordial disks around young stars are the demonstrated sites of planet formation, yet the qualities supporting disk longevity and the triggers driving disk dissipation are poorly understood. Circumstellar disks in pre-main sequence binary systems provide ideal environments within which to analyze disk properties as a function of stellar characteristics. We present early results from our unique high-angular resolution program which combines (1) millimeter imaging of circumstellar disks with ALMA and (2) near-infrared, component-resolved, R=30,000 spectroscopy of the young stars with Keck+NIRSPEC for binaries with at least partially determined orbits. By controlling for orbital parameters, we highlight the relationships between the properties of circumstellar disks (e.g., radial extent, substructure, inclination) and stars (e.g., veiling, rotation period, magnetic field strength). In the eccentric, 0.1" quasi-twin DF Tau binary, two circumstellar disks are detected with ALMA but one disk is actively accreting while the other appears to have decoupled from a rapidly rotating central star. Another twin system, the 0.2" low-eccentricity FO Tau binary, shows well-aligned orbital and disk inclinations, and modest stellar rotation and near-infrared excess veiling in both components. This research was supported in part by NSF awards AST-1313399 and AST-2109179.

117. Horch, E., Wolf, M., Smith, M., et al., (including van Belle, G.), 2024, AAS, 244, 204.02, Introducing IFUSI: the Integral Field Unit Speckle Imager
     Abstract

     We discuss preliminary design work and prototyping for IFUSI, the Integral Field Unit Speckle Imager. This instrument, planned as a visitor instrument at the 4.3-m Lowell Discovery Telescope, will use a ~2500-fiber integral field unit to record spectra over a highly-magnified ~1.1x1.1-arcsecond field of view. From these spectra, it will be possible to reconstruct speckle patterns at all wavelengths through the visible range, after which the patterns can be reduced and analyzed in the standard way to produce diffraction-limited images. This will make IFUSI the first truly pan-chromatic speckle imager to be built. In addition to discussing the progress on the project to date, we will detail the data reduction philosophy we plan to employ, and also educational and public outreach activities associated with the project. Finally, the science enabled with the instrument at Lowell will be outlined, including definitive determinations of which star an exoplanet obits in close binary systems that host exoplanets.

     We gratefully acknowledge support from National Science Foundation grants AST-2206099 and AST-2206100 in the completion of this work.

118. Levine, S., 2024, AAS, 244, 318.04, Lowell Observatory, 130 Years Young
     Abstract

     Lowell Observatory is a private, independent non-profit institution. Its mission today, as it was when it was founded in 1894, is to pursue the study of astronomy and to bring the results of astronomical research to the general public. Over the years, Lowell has gone through several cycles of change. This talk will focus on how the continuity of mission aims has enabled Lowell to productively repurpose older research equipment (like the Clark 24inch telescope, and the glass plate archive) in support of outreach and unforeseen research ideas. At the same time, Lowell is also integrating modern tools in the all aspects of the research (the 4.3-m Lowell Discovery Telescope) and outreach mission (the Giovale Open Deck Observatory and the coming Astronomy Discovery Center); Lowell remains a vibrant center of both research and outreach.

119. Hunter, D., 2024, AAS, 244, 321.01, HI and star formation in nearby dwarf irregular galaxies
     Abstract

     Dwarf irregular (dIrr) galaxies are not just small versions of spiral galaxies. They are gas-dominated but with low gas density overall and with thick disk structure and high gas porosity. These properties have consequences for the formation of clouds that produce new stars. Yet, young stars can be found not only in the central regions of dIrrs, but in their far outer disks where gas densities are very low. I will discuss four possible drivers for cloud formation in dIrrs and the complications with each in explaining the star formation found in typical, isolated dIrrs.

120. Burgasser, A., Brooks, H., Alvarado, E., et al., 2024, AAS, 244, 406.01, A Hypervelocity L Subdwarf Passing Through the Solar Neighborhood
     Abstract

     We report the discovery of a very high velocity metal-poor L subdwarf whose kinematics indicate that it is escaping the Milky Way. The source, CWISE J1249+3621, was discovered by citizen scientists as part of the Backyard Worlds: Planet 9 program as a high proper motion ( = 1.03 arcsec/yr) faint red source. Moderate resolution spectroscopy obtained with Keck/NIRES reveals it to be a metal-poor early L subdwarf with a high radial velocity (-103 km/s). With an estimated distance of 140 pc, CWISE J1249+3621 has a total speed of at least 600 km/s, exceeding the local Galactic escape velocity. Remarkably, the source is moving radially inward, suggesting it was ejected from a globular cluster located in outer Galactic plane in the past 10-30 Myr. CWISE J1249+3621 is the first very low mass star - and the nearest system - found to have an extragalactic trajectory, and may represent a broader population of high-velocity, low-mass ejections from dense cluster systems.

121. Alvarado, E., Gerasimov, R., Burgasser, A., et al., (including Brooks, H.), 2024, AAS, 244, 406.04, Probing the Early History of the Milky Way with New Models of Metal-poor Brown Dwarfs
     Abstract

     Ultracool Dwarfs (UCDs) are stars and brown dwarfs with surface temperatures 3000K and masses 0.1 solar. The atmospheres of UCDs are dominated by molecular opacity and chemistry, rendering their spectra highly sensitive to element abundances. In combination with appropriate stellar models with non-solar chemistry, UCDs may be used as chemical tracers of stellar populations.

     Metal-poor UCDs are particularly interesting, as they represent the poorly understood early phases of the chemical evolution of the Milky Way. However, few metal-poor UCD stellar models are available in the literature. We present a new grid of evolutionary models and model atmospheres for metal-poor UCDs. Our models were calculated using the PHOENIX code, version 15, and include the Allard & Homeier treatment of clouds with gravitational settling. The atmosphere grid extends down to 700 K in effective temperature, and spans metallicities ([Fe/H]) from -2.4 to 0.3 dex for multiple values of -enhancement. The corresponding evolutionary models and synthetic isochrones were calculated with the MESA code, using our model atmospheres as atmosphere-interior boundary conditions.

     These new models will support studies of metal-poor UCDs discovered by deep surveys with the James Webb Space Telescope, the Nancy Grace Roman Space Telescope, and the Vera Rubin Observatory, as well as new photometric surveys of UCDs in globular clusters.

122. Porter, S., Benecchi, S., Verbiscer, A., et al., (including Grundy, W.), 2024, PSJ, 5, 143, Detection of Close Kuiper Belt Binaries with HST WFC3
     Abstract

     Binaries in the Kuiper Belt are common. Here we present our analysis of the Solar System Origins Legacy Survey (SSOLS) to show that using a point-spread function (PSF)-fitting method can roughly double the number of binaries identified in that data set. Out of 198 Kuiper Belt objects (KBOs) observed by SSOLS, we find 23 to be visually separated binaries, while a further 19 are blended PSF binaries detectable with the method we present here. This is an overall binary fraction of 21% for the SSOLS data set of cold classical KBOs. In addition, we tested our fitting methods on synthetic data, and while we were able to show them to be very effective at detecting certain blended-PSF binary KBOs, fainter or closer binary KBOs may easily be missed, suggesting that the close binary KBO fraction could be even higher. These results strongly support the idea that most (if not all) KBOs were formed through the streaming instability process, and as a consequence, most KBOs were formed as near-equal mass binaries.

123. Kawata, D., Kawahara, H., Gouda, N., et al., (including Levine, S.), 2024, PASJ, 76, 386, JASMINE: Near-infrared astrometry and time-series photometry science
     Abstract

     The Japan Astrometry Satellite Mission for INfrared Exploration (JASMINE) is a planned M-class science space mission by the Institute of Space and Astronautical Science, the Japan Aerospace Exploration Agency. JASMINE has two main science goals. One is Galactic archaeology with a Galactic Center survey, which aims to reveal the Milky Way's central core structure and formation history from Gaia-level (~25 ${\mu} $as) astrometry in the near-infrared (NIR) H_w band (1.0-1.6 ${\mu} $m). The other is an exoplanet survey, which aims to discover transiting Earth-like exoplanets in the habitable zone from NIR time-series photometry of M dwarfs when the Galactic Center is not accessible. We introduce the mission, review many science objectives, and present the instrument concept. JASMINE will be the first dedicated NIR astrometry space mission and provide precise astrometric information on the stars in the Galactic Center, taking advantage of the significantly lower extinction in the NIR. The precise astrometry is obtained by taking many short-exposure images. Hence, the JASMINE Galactic Center survey data will be valuable for studies of exoplanet transits, asteroseismology, variable stars, and microlensing studies, including discovery of (intermediate-mass) black holes. We highlight a swath of such potential science, and also describe synergies with other missions.

124. Reddy, V., Kelley, M., Benner, L., et al., (including Burt, B.), 2024, PSJ, 5, 141, 2023 DZ2 Planetary Defense Campaign
     Abstract

     We present the results of a fourth planetary defense exercise, focused this time on the small near-Earth asteroid (NEA) 2023 DZ2 and conducted during its close approach to the Earth in 2023 March. The International Asteroid Warning Network (IAWN), with support from NASA's Planetary Defense Coordination Office (PDCO), has been coordinating planetary defense observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. The last campaign focused on the NEA Apophis, and an outcome of that exercise was the need for a short burst campaign to replicate a real-life near-Earth object impact hazard scenario. The goal of the 2023 DZ2 campaign was to characterize the small NEA as a potential impactor and exercise the planetary defense system including observations, hypothetical risk assessment and risk prediction, and hazard communication with a short notice of just 24 hr. The entire campaign lasted about 10 days. The campaign team was divided into several working groups based on the characterization method: photometry, spectroscopy, thermal IR photometry and optical polarimetry, radar, and risk assessment. Science results from the campaign show that 2023 DZ2 has a rotation period of 6.2745 0.0030 minutes; visible wavelength color photometry/spectroscopy/polarimetry and near-IR spectroscopy all point to an E-type taxonomic classification with surface composition analogous to aubrite meteorites; and radar observations show that the object has a diameter of 30 10 m, consistent with the high albedo (0.49) derived from polarimetric and thermal IR observations.

125. Sanchez, J., Reddy, V., Thirouin, A., et al., (including Kareta, T.), 2024, PSJ, 5, 131, The Population of Small Near-Earth Objects: Composition, Source Regions, and Rotational Properties
     Abstract

     The study of small (<300 m) near-Earth objects (NEOs) is important because they are more closely related than larger objects to the precursors of meteorites that fall on Earth. Collisions of these bodies with Earth are also more frequent. Although such collisions cannot produce massive extinction events, they can still produce significant local damage. Here we present the results of a photometric and spectroscopic survey of small NEOs that include near-infrared spectra of 84 objects with a mean diameter of 126 m and photometric data of 59 objects with a mean diameter of 87 m. We found that S-complex asteroids are the most abundant among the NEOs, comprising 66% of the sample. Most asteroids in the S-complex were found to have compositions consistent with LL-chondrites. Our study revealed the existence of NEOs with spectral characteristics similar to those in the S-complex but that could be hidden within the C- or X-complex due to their weak absorption bands. We suggest that the presence of metal or shock darkening could be responsible for the attenuation of the absorption bands. These objects have been grouped into a new subclass within the S-complex called Sx-types. The dynamical modeling showed that 83% of the NEOs escaped from the ₆ resonance, 16% from the 3:1, and just 1% from the 5:2 resonance. Lightcurves and rotational periods were derived from the photometric data. No clear trend between the axis ratio and the absolute magnitude or rotational period of the NEOs was found.

126. Toribio San Cipriano, L., De Vicente, J., Sevilla-Noarbe, I., et al., (including Kuehn, K.), 2024, A&A, 686, A38, Dark Energy Survey Deep Field photometric redshift performance and training incompleteness assessment
     Abstract

     Context. The determination of accurate photometric redshifts (photo-zs) in large imaging galaxy surveys is key for cosmological studies. One of the most common approaches is machine learning techniques. These methods require a spectroscopic or reference sample to train the algorithms. Attention has to be paid to the quality and properties of these samples since they are key factors in the estimation of reliable photo-zs.
     Aims: The goal of this work is to calculate the photo-zs for the Year 3 (Y3) Dark Energy Survey (DES) Deep Fields catalogue using the Directional Neighborhood Fitting (DNF) machine learning algorithm. Moreover, we want to develop techniques to assess the incompleteness of the training sample and metrics to study how incompleteness affects the quality of photometric redshifts. Finally, we are interested in comparing the performance obtained by DNF on the Y3 DES Deep Fields catalogue with that of the EAzY template fitting approach.
     Methods: We emulated - at a brighter magnitude - the training incompleteness with a spectroscopic sample whose redshifts are known to have a measurable view of the problem. We used a principal component analysis to graphically assess the incompleteness and relate it with the performance parameters provided by DNF. Finally, we applied the results on the incompleteness to the photo-z computation on the Y3 DES Deep Fields with DNF and estimated its performance.
     Results: The photo-zs of the galaxies in the DES deep fields were computed with the DNF algorithm and added to the Y3 DES Deep Fields catalogue. We have developed some techniques to evaluate the performance in the absence of "true" redshift and to assess the completeness. We have studied the tradeoff in the training sample between the highest spectroscopic redshift quality versus completeness. We found some advantages in relaxing the highest-quality spectroscopic redshift requirements at fainter magnitudes in favour of completeness. The results achieved by DNF on the Y3 Deep Fields are competitive with the ones provided by EAzY, showing notable stability at high redshifts. It should be noted that the good results obtained by DNF in the estimation of photo-zs in deep field catalogues make DNF suitable for the future Legacy Survey of Space and Time (LSST) and Euclid data, which will have similar depths to the Y3 DES Deep Fields.

     The data are available at https://des.ncsa.illinois.edu/releases/y3a2/Y3deepfields

127. Archer, H., Hunter, D., Elmegreen, B., et al., 2024, AJ, 167, 274, Probing the Relationship Between Early Star Formation and CO in the Dwarf Irregular Galaxy WLM with JWST
     Abstract

     WolfLundmarkMelotte (WLM) is a Local Group dwarf irregular (dIrr) galaxy with a metallicity 13% of solar. At 1 Mpc, the relative isolation of WLM provides a unique opportunity to investigate the internal mechanisms of star formation at low metallicities. The earliest stages of star formation in larger spirals occur in embedded clusters within molecular clouds, but dIrrs lack the dust, heavy metals, and organized structure of spirals believed necessary to collapse the molecular clouds into stars. Despite actively forming stars, the early stages of star formation in dIrrs is not well understood. We examine the relationship between early star formation and molecular clouds at low metallicities. We utilize ALMA-detected CO cores, JWST near-infrared (NIR) images (F090W, F150W, F250M, and F430M), and GALEX far-ultraviolet (FUV) images of WLM to trace molecular clouds, early star formation, and longer star formation timescales respectively. We compare clumps of NIR-bright sources (referred to as objects) categorized into three types based on their proximity to FUV sources and CO cores. We find objects, independent of their location, have similar colors and magnitudes and no discernible difference in temperature. However, we find that objects near CO have higher masses than objects away from CO, independent of proximity to FUV. Additionally, objects near CO are coincident with Spitzer 8 m sources at a higher frequency than objects elsewhere in WLM. This suggests objects near CO may be embedded star clusters at an earlier stage of star formation, but accurate age estimates for all objects are required for confirmation.

128. Speckert, M., Massey, P., Skiff, B., 2024, AJ, 167, 262, The Stellar Content of the Young Open Cluster Berkeley 50 (IC 1310)
     Abstract

     We observed the Galactic open cluster Berkeley 50 in order to determine its stellar content, distance, and age. We obtained UBV photometry of 1145 stars in a 12.'3 12.'3 field, and used Gaia proper motions and parallaxes to identify 64 members, of which we obtained spectra of the 17 brightest members. The majority of the observed population we classified as B dwarfs, with the exception of a newly identified red supergiant star, which our spectroscopy shows has a B-type companion. Our study establishes the distance as 3.8 kpc, with an average color-excess E(B V) = 0.9. Comparison of the physical properties of the cluster with the Geneva evolutionary tracks places the age of the cluster as 5060 Myr, with its most massive members being 7M

129. Malik, U., Sharp, R., Penton, A., et al., (including Kuehn, K.), 2024, MNRAS, 531, 163, OzDES Reverberation Mapping Program: Stacking analysis with H, Mg II, and C IV
     Abstract

     Reverberation mapping is the leading technique used to measure direct black hole masses outside of the local Universe. Additionally, reverberation measurements calibrate secondary mass-scaling relations used to estimate single-epoch virial black hole masses. The Australian Dark Energy Survey (OzDES) conducted one of the first multi-object reverberation mapping surveys, monitoring 735 AGN up to z ~ 4, over 6 years. The limited temporal coverage of the OzDES data has hindered recovery of individual measurements for some classes of sources, particularly those with shorter reverberation lags or lags that fall within campaign season gaps. To alleviate this limitation, we perform a stacking analysis of the cross-correlation functions of sources with similar intrinsic properties to recover average composite reverberation lags. This analysis leads to the recovery of average lags in each redshift-luminosity bin across our sample. We present the average lags recovered for the H, Mg II, and C IV samples, as well as multiline measurements for redshift bins where two lines are accessible. The stacking analysis is consistent with the Radius-Luminosity relations for each line. Our results for the H sample demonstrate that stacking has the potential to improve upon constraints on the R-L relation, which have been derived only from individual source measurements until now.

130. Zhang, Y., Golden-Marx, J., Ogando, R., et al., (including Kuehn, K.), 2024, MNRAS, 531, 510, Dark Energy Survey Year 6 results: Intra-cluster light from redshift 0.2 to 0.5
     Abstract

     Using the full 6 years of imaging data from the Dark Energy Survey, we study the surface brightness profiles of galaxy cluster central galaxies and intra-cluster light. We apply a 'stacking' method to over 4000 galaxy clusters identified by the redMaPPer cluster finder in the redshift range of 0.2-0.5. This yields high-signal-to-noise circularly averaged profile measurements of the central galaxy and intra-cluster light out to 1 Mpc from the cluster centre. Using redMaPPer richness as a cluster mass indicator, we find that the brightness of the intra-cluster light has a strong mass dependence throughout the 0.2-0.5 redshift range, and this dependence grows stronger at a larger radius. In terms of redshift evolution, we find some evidence that the central galaxy, as well as the diffuse light within the transition region between the cluster central galaxy and intra-cluster light within 80 kpc from the centre, may be growing over time. At larger radii, more than 80 kpc away from the cluster centre, we do not detect evidence of additional redshift evolution beyond the cluster mass dependence, consistent with the findings from the IllustrisTNG hydrodynamic simulation. We speculate that the major driver of intra-cluster light growth, especially at large radii, is associated with cluster mass growth. Finally, we find that the colour of the cluster central galaxy and intra-cluster light displays a radial gradient that becomes bluer at a larger radius, which is consistent with a stellar stripping and disruption origin of intra-cluster light as suggested by simulation studies.

131. Brozovic, M., Benner, L., Naidu, S., et al., (including Moskovitz, N.), 2024, PSJ, 5, 123, Radar and Optical Observations and Physical Modeling of Binary Near-Earth Asteroid 2018 EB
     Abstract

     We report radar, photometric, and visible-wavelength spectrophotometry observations of NEA 2018 EB obtained in 2018. The radar campaign started at Goldstone (8560 MHz, 3.5 cm) on April 7, and it was followed by more extensive observations from October 5 to 9 by both Arecibo (2380 MHz, 12.6 cm) and Goldstone. 2018 EB was observed optically on April 5, 8, and 9 and again on October 18. Spectrophotometry was obtained on October 19 with the SOAR telescope, and the data suggest that 2018 EB is an Xk-class object. The echo power spectra and delay-Doppler radar images revealed that 2018 EB is a binary system. Radar images constrained the satellite's diameter to km, but the data were not sufficient for shape modeling. Shape modeling of lightcurves and radar data yielded an oblate primary with an effective diameter D = 0.30 0.04 km and a sidereal rotation period of hr. Measurements of delay-Doppler separations between the centers of mass of the primary and the satellite, along with the timing of a radar eclipse observed on October 9, resulted in an orbit fit for the satellite with a semimajor axis of km, an eccentricity of 0.15 0.04, a period of hr, and an orbit pole constrained to the ecliptic longitudes and latitudes of and . The system mass was estimated to be kg, which yielded a bulk density of g cm³. Our analysis suggests that 2018 EB has a low optical albedo of p _V = 0.028 0.016 and a relatively high radar albedo of _OC = 0.29 0.11 at Arecibo and = 0.22 0.10 at Goldstone.

132. Levison, H., Marchi, S., Noll, K., et al., (including Grundy, W.), 2024, Natur, 629, 1015, A contact binary satellite of the asteroid (152830) Dinkinesh
     Abstract

     Asteroids with diameters less than about 5 km have complex histories because they are small enough for radiative torques (that is, YORP, short for the YarkovskyO'KeefeRadzievskiiPaddack effect)¹ to be a notable factor in their evolution². (152830) Dinkinesh is a small asteroid orbiting the Sun near the inner edge of the main asteroid belt with a heliocentric semimajor axis of 2.19 AU; its S-type spectrum^3,4 is typical of bodies in this part of the main belt⁵. Here we report observations by the Lucy spacecraft^6,7 as it passed within 431 km of Dinkinesh. Lucy revealed Dinkinesh, which has an effective diameter of only 720 m, to be unexpectedly complex. Of particular note is the presence of a prominent longitudinal trough overlain by a substantial equatorial ridge and the discovery of the first confirmed contact binary satellite, now named (152830) Dinkinesh I Selam. Selam consists of two near-equal-sized lobes with diameters of 210 m and 230 m. It orbits Dinkinesh at a distance of 3.1 km with an orbital period of about 52.7 h and is tidally locked. The dynamical state, angular momentum and geomorphologic observations of the system lead us to infer that the ridge and trough of Dinkinesh are probably the result of mass failure resulting from spin-up by YORP followed by the partial reaccretion of the shed material. Selam probably accreted from material shed by this event.

133. Kareta, T., Noonan, J., Volk, K., et al., 2024, ApJL, 967, L5, Jupiter Co-Orbital Comet P/2023 V6 (PANSTARRS): Orbital History and Modern Activity State
     Abstract

     The discovery of the transient Jupiter co-orbital comet P/2019 LD2 (ATLAS) drew significant interest. Not only will LD2 transition between being a Centaur and a Jupiter-family comet (JFC) in 2063, the first time this process can be observed as it happens, it is also very active for its large heliocentric distance. We present observations and orbital integrations of the newly discovered transient Jupiter co-orbital comet P/2023 V6 (PANSTARRS), the second such object known. Despite similar modern orbits, V6 is significantly (15) less active than LD2 and most JFCs as determined via Af measurements at the same R _H . We find that V6 is co-orbital between 2020 and 2044, twice the duration of LD2, but it will not become a JFC soon. We interpret these differences in activity as evolutionary, with V6 having lost a significant fraction of its near-surface ice compared to LD2 by previously being warmer. While V6's pre-encounter orbit was somewhat warmer than LD2's, future thermal modeling will be needed to understand if this can explain their differences or if a more significant difference further into the past is required. This is more evidence that LD2 is a pristine and ice-rich object, and thus it may display very strong activity when it becomes a JFC. We use the differences between V6 and LD2 to discuss the interpretation of cometary activity at large heliocentric distances as well as the small end of the cratering record of the Galilean satellites. Continuing observations of both objects are highly encouraged.

134. Pang, X., Liao, S., Li, J., et al., (including Tang, S.), 2024, ApJ, 966, 169, The Present-day Mass Function of Star Clusters in the Solar Neighborhood
     Abstract

     This work analyzes the present-day mass function (PDMF) of 93 star clusters utilizing Gaia Data Release 3 data, with membership determined by the StarGo machine-learning algorithm. The impact of unresolved binary systems on mass estimation is rigorously assessed, adopting three mass ratio profiles for correction. The PDMF is characterized by the power-law index, , derived through a robust maximum likelihood method that avoids biases associated with data binning. The value of for stars between the completeness limited mass of Gaia (with a mean 0.3 M for our cluster samples) and 2 M exhibits stability for clusters younger than 200 Myr, decreasing for older clusters, particularly when considering stars within the half-mass radius. The PDMF of these star clusters is consistent with a dynamically evolved Kroupa initial mass function via the loss of low-mass stars. Cluster morphology shows a correlation with , as values exhibit a decreasing trend from filamentary to tidal-tail clusters, mirroring the sequence of increasing cluster age. The dependence of on the total cluster mass is weak, with a subtle increase for higher-mass clusters, especially outside the half-mass radius. We do not observe a correlation between and the mean metallicity of the clusters. Younger clusters have lower metallicity compared to their older counterparts, which indicates that the older clusters might have migrated to the solar neighborhood from the inner disk. A comparison with numerical models incorporating a black hole population suggests the need for observations of distant, older, massive open clusters to determine whether or not they contain black holes.

135. Eisner, N., Grunblatt, S., Barragan, O., et al., (including Llama, J.), 2024, AJ, 167, 241, Planet Hunters TESS. V. A Planetary System Around a Binary Star, Including a Mini-Neptune in the Habitable Zone
     Abstract

     We report on the discovery and validation of a transiting long-period mini-Neptune orbiting a bright (V = 9.0 mag) G dwarf (TOI 4633; R = 1.05 R , M = 1.10 M ). The planet was identified in data from the Transiting Exoplanet Survey Satellite by citizen scientists taking part in the Planet Hunters TESS project. Modelling of the transit events yields an orbital period of 271.9445 0.0040 days and radius of 3.2 0.20 R . The Earth-like orbital period and an incident flux of ${1.56}_{-0.16}^{+0.20}$ F places it in the optimistic habitable zone around the star. Doppler spectroscopy of the system allowed us to place an upper mass limit on the transiting planet and revealed a non-transiting planet candidate in the system with a period of 34.15 0.15 days. Furthermore, the combination of archival data dating back to 1905 with new high angular resolution imaging revealed a stellar companion orbiting the primary star with an orbital period of around 230 yr and an eccentricity of about 0.9. The long period of the transiting planet, combined with the high eccentricity and close approach of the companion star makes this a valuable system for testing the formation and stability of planets in binary systems.

136. Tofflemire, B., Prato, L., Kraus, A., et al., 2024, AJ, 167, 232, Sites of Planet Formation in Binary Systems. I. Evidence for DiskOrbit Alignment in the Close Binary FO Tau
     Abstract

     Close binary systems present challenges to planet formation. As binary separations decrease, so do the occurrence rates of protoplanetary disks in young systems and planets in mature systems. For systems that do retain disks, their disk masses and sizes are altered by the presence of the binary companion. Through the study of protoplanetary disks in binary systems with known orbital parameters, we seek to determine the properties that promote disk retention and therefore planet formation. In this work, we characterize the young binarydisk system FO Tau. We determine the first full orbital solution for the system, finding masses of ${0.35}_{-0.05}^{+0.06}\ {M}_{\odot }$ and 0.34 0.05 M for the stellar components, a semimajor axis of $22{\,(}_{-1}^{+2})$ au, and an eccentricity of $0.21{\,(}_{-0.03}^{+0.04})$ . With long-baseline Atacama Large Millimeter/submillimeter Array interferometry, we detect 1.3 mm continuum and ¹²CO (J = 21) line emission toward each of the binary components; no circumbinary emission is detected. The protoplanetary disks are compact, consistent with being truncated by the binary orbit. The dust disks are unresolved in the image plane, and the more extended gas disks are only marginally resolved. Fitting the continuum and CO visibilities, we determine the inclination of each disk, finding evidence for alignment of the disk and binary orbital planes. This study is the first of its kind linking the properties of circumstellar protoplanetary disks to a precisely known binary orbit. In the case of FO Tau, we find a dynamically placid environment (coplanar, low eccentricity), which may foster its potential for planet formation.

137. Goksu, O., Kutra, T., Wu, Y., 2024, AJ, 167, 236, On the Rigidly Precessing, Eccentric Gas Disk Orbiting the White Dwarf SDSS J1228+1040
     Abstract

     Metal pollution onto white dwarfs is a widespread phenomenon that remains puzzling. Some of these white dwarfs also harbor gaseous debris disks. Emission lines from these disks open a unique window to the physical properties of the polluting material, lending insights into their origin. We model the emission line kinematics for the gas disk around SDSS J1228+1040, a system that has been monitored for over two decades. We show that the disk mass is strongly peaked at 1 R (modulo the unknown inclination), and the disk eccentricity decreases from a value of 0.44 at the inner edge, to nearly zero at the outer edge. This eccentricity profile is exactly what one expects if the disk is in a global eccentric mode, precessing rigidly under general relativity and gas pressure. The precession period is about two decades. We infer that the mass of the gas disk is roughly equivalent to that of a 50 km rocky body, while the mass of the accompanying dust disk is likely insignificant. The disk eccentricity confirms an origin in tidal disruption, while the short disk diffusion time suggests that the disruption event happened a few centuries ago. Moreover, we argue that the initial orbit for the disrupted body, and that of its putative planetary perturber, fall within an astronomical unit around the white dwarf. The total mass of the source population is likely orders of magnitude more massive than our own Asteroid belt and does not seem to exist around main-sequence stars.

138. Hasegawa, S., Marsset, M., DeMeo, F., et al., (including Burt, B.), 2024, AJ, 167, 224, Candidate Main-belt Asteroids for Surface Heterogeneity
     Abstract

     Large terrestrial bodies in our solar system like the Earth, Mars, Mercury, and the Moon exhibit geologically complex surfaces with compositional heterogeneity. From past studies using large telescopes and spacecraft, it was shown that asteroids with diameters larger than 100 km also show surface heterogeneity at hemispheric scales, while on smaller objects, such features remain to be detected. Here, we investigate candidates for surface heterogeneity in a sample of 130 main-belt asteroids using multiepoch spectroscopic data from the MITHawaii Near-Earth Object Spectroscopic Survey, which has been observing asteroids for about 20 yr using a self-consistent observation technique. Twelve conservative candidates with spectra more than 3 apart from each other at 2.4 m and 52 optimistic candidates for surface heterogeneity are detected. These candidates include eight objects already reported as being heterogeneous. Our study suggests that the size boundary between small homogeneous asteroids and larger heterogeneous objects, if it exists, is lower than 100 km. A-type asteroids have a higher proportion of heterogeneous candidates than other asteroids. This may be because olivine, which is the main surface constituent of these objects, reacts more efficiently to space weathering with respect to pyroxene, such that a similar range of surface ages will translate into a wider range of optical-to-near-infrared spectral slopes in the case of A-type bodies.

139. Blakley, B., Grundy, W., Steckloff, J., et al., (including Hanley, J., Koga, K.), 2024, P&SS, 244, 105863, The equilibrium vapor pressures of ammonia and oxygen ices at outer solar system temperatures
     Abstract

     Few laboratory studies have investigated the vapor pressures of the volatiles that may be present as ices in the outer solar system; even fewer studies have investigated these species at the temperatures and pressures suitable to the surfaces of icy bodies in the Saturnian and Uranian systems (<100 K, <10^-9 bar). This study adds to the work of Grundy et al. (2024) in extending the known equilibrium vapor pressures of outer solar system ices through laboratory investigations at very low temperatures. Our experiments with ammonia and oxygen ices provide new thermodynamic models for these species' respective enthalpies of sublimation. We find that ammonia ice, and to a lesser degree oxygen ice, are stable at higher temperatures than extrapolations in previous literature have predicted. Our results show that these ices should be retained over longer periods of time than previous extrapolations would predict, and a greater amount of these solids is required to support observation in exospheres of airless bodies in the outer solar system.

140. Emery, J., Wong, I., Brunetto, R., et al., (including Grundy, W.), 2024, Icar, 414, 116017, A tale of 3 dwarf planets: Ices and organics on Sedna, Gonggong, and Quaoar from JWST spectroscopy
     Abstract

     The dwarf planets Sedna, Gonggong, and Quaoar are interesting in being somewhat smaller than the methane-rich bodies of the Kuiper Belt (Pluto, Eris, Makemake), yet large enough to be spherical and to have possibly undergone interior melting and differentiation. They also reside on very different orbits, making them an ideal suite of bodies for untangling effects of size and orbit on present day surface composition. We observed Sedna, Gonggong, and Quaoar with the NIRSpec instrument on the James Webb Space Telescope (JWST). All three bodies were observed in the low-resolution prism mode at wavelengths spanning 0.7 to 5.2 m. Quaoar was additionally observed at 10 higher spectral resolution from 0.97 to 3.16 m using medium-resolution gratings. Sedna's spectrum shows a large number of absorption features due to ethane (C₂H₆), as well as acetylene (C₂H₂), ethylene (C₂H₄), H₂O, and possibly CO₂. Gonggong's spectrum also shows several, but fewer and weaker, ethane features, along with stronger and cleaner H₂O features and CO₂ complexed with other molecules. Quaoar's prism spectrum shows even fewer and weaker ethane features, the deepest and cleanest H₂O features, a feature at 3.2 m possibly due to HCN, and CO₂ ice. The higher-resolution medium grating spectrum of Quaoar reveals several overtone and combination bands of ethane and methane (CH₄). Spectra of all three objects show steep red spectral slopes and strong, broad absorptions between 2.7 and 3.6 m indicative of complex organic molecules. The suite of light hydrocarbons and complex organic molecules are interpreted as the products of irradiation of methane. We infer that the differences in apparent abundances of irradiation products among these three similarly-sized bodies are likely due to their distinctive orbits, which lead to different timescales of methane retention and to different charged particle irradiation environments. In all cases, however, the continued presence of light hydrocarbons implies a resupply of methane to the surface. We suggest that these three bodies have undergone internal melting and geochemical evolution similar to the larger dwarf planets and distinct from all smaller KBOs. The feature identification presented in this paper is the first step of analysis, and additional insight into the relative abundances and mixing states of materials on these surfaces will come from future spectral modeling of these data.

141. Clark, C., van Belle, G., Horch, E., et al., (including von Braun, K., Skiff, B., Llama, J.), 2024, AJ, 167, 174, The POKEMON Speckle Survey of Nearby M Dwarfs. III. The Stellar Multiplicity Rate of M Dwarfs within 15 pc
     Abstract

     M dwarfs are ubiquitous in our Galaxy, and the rate at which they host stellar companions, and the properties of these companions, provide a window into the formation and evolution of the star(s), and of any planets that they may host. The Pervasive Overview of "Kompanions" of Every M dwarf in Our Neighborhood (POKEMON) speckle survey of nearby M dwarfs is volume limited from M0V through M9V out to 15 pc, with additional targets at larger distances. In total, 1125 stars were observed, and 455 of these are within the volume-limited, 15 pc sample of M-dwarf primaries. When we combine the speckle observations with known companions from the literature, we find that the stellar multiplicity rate of M dwarfs within 15 pc is 23.5% 2.0%, and that the companion rate is 28.8% 2.1%. We also find that the projected separation distribution for multiples that are known to host planets peaks at 198 au, while the distribution for multiples that are not yet known to host planets peaks at 5.57 au. This result suggests that the presence of close-in stellar companions inhibits the formation of M-dwarf planetary systems, similar to what has been found for FGK stars.

142. Knieling, B., Schindler, K., Sickafoose, A., et al., (including Levine, S.), 2024, PSJ, 5, 104, Stellar Occultations in the Era of Data Mining and Modern Regression Models: Using Gaussian Processes to Analyze Light Curves and Improve Predictions
     Abstract

     Gaussian process (GP) regression is a nonparametric Bayesian approach that has been used successfully in various astronomical domains, especially in time-domain astronomy. The most common applications are the smoothing of data for interpolation and the detection of periodicities. The ability to create unbiased data-driven models without a predefined physical model can be a major advantage over conventional regression methods. Prior knowledge can be included by setting boundary conditions or constraining hyperparameter values, while unknown hyperparameters are optimized during the conditioning of the model. We have adapted and transformed previous approaches of GP regression and introduce three new applications for this regression method, especially in the context of stellar occultations: the modeling of occultation light curves, the correction of public JPL ephemerides of minor planets based on publicly available image data of the Zwicky Transient Facility, and the detection of natural satellites. We used data from observations of stellar occultations to validate the models and achieved promising results in all cases, and thus we confirmed the flexibility of GP regression models. Considering various existing use cases in addition to our novel applications, GP regression can be used to model diverse data sets addressing a wide range of problems. The accuracy of the model depends on the input data and on the set boundary conditions. Generally, high-quality data allow the usage of loose boundary conditions, while low-quality data require more restrictive boundary conditions to avoid overfitting.

143. Zhao, L., Dumusque, X., Ford, E., et al., (including Llama, J.), 2024, ESS, 56, 200.02, The Extreme Stellar Signals Project
     Abstract

     The Extreme Stellar Signals Project (ESSP) is an international research network of scientists developing methods for mitigating stellar signals. With our first round of work, we established the current state of the field through a self-consistent comparison of 21 different methods implemented on the same extreme-precision spectroscopic data from the EXPRES instrument. This talk will introduce the second round of comparisons, which makes use of contemporaneous Sun-as-a-star observations taken by HARPS, HARPS-N, EXPRES, and NEID. I will share lessons learned from comparing contemporaneous data across instruments and discuss strategies for combining data from different instruments. I will conclude with the potential and limitations of this combined data set for testing mitigation methods.

144. Shkolnik, E., Park, N., Llama, J., 2024, ESS, 56, 203.02, Understanding Space Weather in Exoplanetary Systems: Learning from the Sun through Solar Flare and Coronal Mass Ejection Studies
     Abstract

     Eruptive events such as stellar flares and coronal mass ejections (CMEs; energetic and highly magnetized plasma) affect the evolution, chemistry, and habitability of planets, especially of tightly-orbiting planets. Consequently, the particle environment of the Sun, a.k.a. space weather, is continuously monitored. However, data on other stars remains limited, with no conclusively detected stellar CMEs. Our work aims to bridge this gap by correlating solar X-ray and UV flare fluxes with the mass of corresponding CMEs, observed over more than two solar cycles (23 years). We uncover a log-linear correlation between flare peak flux and CME mass, which could extend to Sun-like stars, aiding in predicting CME plasma mass. These predictions are vital for models assessing the impact of energetic particles on planetary atmospheres, thus contributing to a better understanding of planet habitability in different stellar environments.

145. Llama, J., Brewer, J., Zhao, L., et al., 2024, ESS, 56, 601.04, Disentangling planetary and stellar signals by observing the Sun with the EXtreme PREcision Spectrograph (EXPRES)
     Abstract

     The signal induced by a temperate, terrestrial planet orbiting a Sun-like star is an order of magnitude smaller than the host stars' intrinsic variability. Understanding stellar activity is, therefore, a fundamental obstacle in confirming the smallest exoplanets. The EXtreme PREcision Spectrograph (EXPRES) has been obtaining EPRV measurements of stars to search for Earth-sized exoplanets since 2019. Recently, we integrated a solar feed into EXPRES to observe the Sun during the day in an analogous way to the stars at night. The Lowell Observatory Solar Telescope (LOST) is a 70-mm aperture lens that is fiber-fed into EXPRES. In clear conditions, the EXPRES solar observations have a cadence of approximately 300-s and single measurement uncertainty of just 35 cm/s. Since first light in late 2020, we have obtained over 35,000 RV measurements of the Sun. In this presentation, I will present our first results including comparisons with other solar telescopes, comparisons with disk-resolved data from NASA's Solar Dynamics Observatory, and prospects for correcting the RV variability induced by stellar activity.

146. Clark, C., van Belle, G., Horch, E., et al., (including von Braun, K., Skiff, B., Llama, J.), 2024, ESS, 56, 614.01, Planet-Hosting M Dwarfs Have Fewer Close-In Stellar Companions
     Abstract

     Stellar companions are known to affect multiple facets of exoplanet formation, evolution, detection, and characterization. In particular, recent studies of FGK stars from Kepler, K2, and TESS have shown that stellar companions to planet-hosting stars have a projected separation distribution that peaks at a larger value than what is expected from non-planet-hosting field stars. This is likely the result of close-in companions affecting and perhaps inhibiting the planet formation process. To test if this is true for the lowest-mass stars as well, we have conducted a volume-limited, high-resolution imaging survey of M dwarfs out to 15 pc. The 15-pc POKEMON sample consists of 455 M dwarfs from M0V through M9V, making it one of the most complete surveys across the broad range of M-dwarf masses. We find a stellar multiplicity rate of 24.02.0%, and a projected separation distribution that peaks at 6.81 au, which is consistent with previous studies of M-dwarf multiplicity. However, the projected separation distribution of the planet-hosting stars in the sample is shifted significantly out to 198 au similar to what has been found for the FGK stars. These results indicate that the presence of a stellar companion impacts the formation and evolution of any planets around our low-mass neighbors.

147. Kutra, T., 2024, ESS, 56, 622.04, A New Steady State of Irradiated Disks: the Staircase
     Abstract

     Much of a protoplanetary disk is thermally controlled by the central irradiation. Such a disk, thought to have a flaring shape, is likely unstable to the so-called 'irradiation instability'. But what's the outcome of such an instability? In particular, is it possible that such a disk settle into a shape that is immune to the instability? We combine Athena++ with a simplified thermal treatment to show that passively heated disks settle into a staircase-like steady state. The steady state is punctuated by bright rings and dark gaps, with the bright rings intercepting the lion's share of stellar illumination, and the dark gaps lying in shadows. The optical surface of such a disk (height at which starlight is absorbed) resembles a staircase. We use the RADMC3d code to show that the steady state we find is also in good thermal equilibrium. The novel staircase state, if confirmed by more sophisticated radiative hydrodynamic simulations, has a range of implications for disk evolution and planet formation.

148. Richey-Yowell, T., Shkolnik, E., Llama, J., et al., 2024, ESS, 56, 624.42, In Search of Exoplanet Infrared Aurorae: Constraints from Two Hot Jupiters
     Abstract

     Infrared (IR) aurorae on exoplanets are dynamic probes of star-planet interactions, with strong aurorae providing detections of the planetary magnetic fields, constraining host-star wind properties, and delivering 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 present the history of IR auroral searches 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. We further discuss the need for improved modeling work and advancements in technology to find these elusive auroral signatures on exoplanets.

149. Thieberger, C., Robinson, T., Hanley, J., 2024, ESS, 56, 627.05, Characterization of Hazy Planetary Atmospheres
     Abstract

     The Habitable Worlds Observatory (HWO) is an under-development NASA space telescope mission concept that will observe exoplanets by direct imaging to study their atmospheres. Exoplanets that have been observed thus far, mainly with transit spectroscopy, have shown a ubiquitous presence of hazes in clouds in their atmospheres. Characterization of these atmospheres relies on modeling for interpretation of the observed spectra. However, current atmospheric models for exoplanets generally adopt untested, low-complexity treatments for hazes and clouds, thus limiting the analysis of the data. In order to prepare an accurate model ahead of the HWO data collection, we must turn to analog environments in order to test and fit our haze parameterizations. Objects within our Solar System make for excellent candidates to develop this model since they are ground-truthed, thus enabling identification of biases that occur when aerosols are treated in a simplified manner. Within our Solar System, Titan is likely the best analog to hazy exoplanets. The Cassini-Huygens mission and numerous ground-based telescope campaigns provide essential ground truth observations of Titan, allowing us to check model retrievals against measured values to ensure accuracy. We developed a haze parameterization model with wavelength-dependent expressions for absorption and scattering efficiencies, as well as single-scattering albedo. We apply our atmospheric retrieval model to visible-wavelength observations of Titan's geometric albedo from Karkoschka (1998). Preliminary results demonstrate a significant improvement from past models that do not incorporate the wavelength-dependence of atmospheric haze. We are also in the process of fitting the model to our own spectra from the Lowell Discovery Telescope's EXtreme PREcision Spectrometer (EXPRES) and Near-Infrared High-Throughput Spectrometer (NIHTS) to monitor Titan's haze and methane abundances (see Hanley et al, this conference, for more information on the observations).

150. van Belle, G., Ciardi, D., Hillsberry, D., et al., 2024, ESS, 56, 628.18, MoonLITE: the Extreme Instrument for Extreme Solar Systems
     Abstract

     The MoonLITE (Lunar InTerferometry Explorer) project is a 2023 NASA Astrophysics Pioneers proposal to develop, build, fly, and operate the first separated-aperture optical interferometer in space. MoonLITE is proposed fly as a payload hosted aboard one of NASA's Commercial Lunar Payload Services (CLPS) landers, to deliver an optical interferometer to the lunar surface. Recent lunar surface operations by other telescope facilities have significantly retired the perceived risk of lunar dust contamination, and the stability of the moon's surface markedly simplifies interferometer pointing and stationkeeping requirements relative to orbital concepts. The combination of high spatial resolution from optical interferometry, with deep sensitivity from the stability of the lunar surface, would open up unprecedented discovery space for exoplanet science. After landing on the lunar surface, the CLPS rover will deploy the pre-loaded MoonLITE outboard optical element 100 meters from the lander, establishing a interferometric observatory with a single deployment. MoonLITE combines a 110 microarcsecond limiting spatial resolution with enough sensitivity to observe targets fainter than 17th magnitude in the visible. The capabilities of MoonLITE open a unique discovery space that includes direct size measurements of the smallest, coolest stellar and substellar exoplanet hosts. MoonLITE will also conduct searches for close-in stellar companions orbiting exoplanet-hosting stars that could confound future HWO observations of Earth-like planets, as well as extragalactic science at extreme levels of angular resolution. MoonLITE will open up the lunar landscape for potential SMEX and MIDEX class facilities that will measure the masses of exoplanets via astrometric surveys. Twenty percent of the observing time of this revolutionary observatory will be also made available to the broader community via a guest observer program.

151. Hanley, J., Thieberger, C., Corlies, P., et al., (including Llama, J.), 2024, ESS, 56, 632.03, Identifying Clouds and the Vertical Abundances of Haze and Methane on Titan with Applications to Exoplanets
     Abstract

     Saturn's largest moon, Titan, is an excellent candidate for observational analogs of exoplanets. Titan hosts a thick atmosphere with complex organic chemistry resulting from the UV photolysis of methane and nitrogen, resulting in the formation of complex aerosols that obscure Titan's surface. Haze and clouds are expected to occur on exoplanets, potentially limiting the ability to probe the full atmosphere. Our observations demonstrate a technique for not only identifying haze and methane clouds, but also their vertical distributions (see Thieberger et al, this conference). We will present observations centered across various longitudes in order to get an integrated picture of these vertical distributions and to look for global scale and temporal differences. We use the Lowell Discovery Telescope (LDT) EXtreme PREcision Spectrometer (EXPRES) to study Titan's spectrum from ~0.4 - 0.75-m at resolution R~135,000. This slope is set by absorption and scattering of UV and visible light by aerosols, and will lead to constraints on the composition and vertical abundance of hazes in Titan's atmosphere. The high resolution also allows identification of narrow features attributed to specific molecules yet to be determined. Observations with EXPRES are sensitive to Titan's middle and upper atmosphere; we also observe with LDT's Near-Infrared High-Throughput Spectrograph (NIHTS) which is low-resolution (R~200), covering 0.86-2.4 m. Using both instruments allows access to the methane windows that can see down to Titan's surface, permitting us to complete the vertical abundance retrievals through Titan's entire atmosphere. Also, by comparing the brightness at specific wavelengths, we can monitor for any changes that might indicate cloud formation. Data from EXPRES show many features attributed to reflected sunlight, but one challenge that arises from the high spectral resolution is the issue of dividing by a reference star. Typical Solar System observations use a G2 star as a solar analog. Due to variations in composition and rotation rates between these stars and the Sun, they are not compatible with our observations. Thus we have started using the Lowell Observatory Solar Telescope (LOST) which collects EXPRES spectra of the Sun daily to divide by (see Llama et al, this conference). Our results demonstrate that probing various depths of the atmosphere is possible for exoplanets.

152. Jackman, J., Shkolnik, E., Loyd, R., et al., (including Richey-Yowell, T., Llama, J.), 2024, MNRAS, 529, 4354, A dragon's flame of many colours: multiwavelength observations of flares from the active M binary CR Draconis
     Abstract

     We present the results of a multiwavelength Professional-Amateur campaign to study the behaviour of flares from the active M1.5V star binary CR Draconis. CR Dra was observed with Transiting Exoplanet Survey Satellite (TESS) 20-s photometry, Swift near-ultraviolet (NUV) grism spectroscopy and with ground-based optical photometry and spectroscopy from a global collaboration of amateur astronomers. We detected 14 flares with TESS and Swift simultaneously, one of which also had simultaneous ground-based photometry and spectroscopy. We used the simultaneous two-colour optical and NUV observations to characterize the temperature evolution of the flare and test the accuracy of using optical data to predict NUV emission. We measured a peak temperature of $7100^{+150}_{-130}$ K for this flare, cooler than the typically assumed 9000 K blackbody model used by flare studies. We also found that the 9000 K blackbody overestimated the NUV flux for other flares in our sample, which we attributed to our Swift observations occurring during flare decays, highlighting the phase-dependence for the accuracy of flare models.

153. Thirouin, A., Sheppard, S., 2024, PSJ, 5, 84, Rotational Study of 5:3 and 7:4 Resonant Objects within the Main Classical Trans-Neptunian Belt
     Abstract

     The 5:3 and 7:4 mean motion resonances of Neptune are at 42.3 and 43.7 au, respectively, and overlap with objects in the classical trans-Neptunian belt (Kuiper Belt). We report the complete/partial lightcurves of 13 and 14 trans-Neptunian objects (TNOs) in the 5:3 and 7:4 resonances, respectively. We report a most likely contact binary in the 7:4 resonance, 2013 FR₂₈, with a periodicity of 13.97 0.04 hr and a lightcurve amplitude of 0.94 0.02 mag. With a V-/U-shaped lightcurve, 2013 FR₂₈ has one of the largest well-sampled TNO amplitudes observed with ground-based observations, comparable to the well-determined contact binary 2001 QG₂₉₈. 2013 FR₂₈ has a mass ratio q 1 with a density 1 g cm³. We find several objects with large amplitudes and classify 2004 SC₆₀, 2006 CJ₆₉, and 2013 BN₈₂ as likely contact binaries and 2001 QF₃₃₁, 2003 YW₁₇₉, and 2015 FP₃₄₅ as likely elongated objects. We observe the 17:9 resonant or classical object 2003 SP₃₁₇ that we classify as a likely contact binary. A lower estimate of 10%50% and 20%55% for the fraction of (nearly) equal-sized contact binaries is calculated in the 5:3 and 7:4 resonances, respectively. Surface colors of 2004 SC₆₀, 2013 BN₈₂, 2014 OL₃₉₄, and 2015 FP₃₄₅ have been obtained. Including these colors with ones from the literature reveals that elongated objects and contact binaries share the same ultrared surface color, except ManweThorondor and 2004 SC₆₀. Not only are the colors of the 7:4 and 5:3 TNOs similar to the cold classicals, but we demonstrate that the rotational properties of the 5:3 and 7:4 resonants are similar to those of the cold classicals, inferring a clear link between these subpopulations.

154. Wong, I., Brown, M., Emery, J., et al., (including Grundy, W.), 2024, PSJ, 5, 87, JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO₂
     Abstract

     We present observations obtained with the Near Infrared Spectrograph on JWST of the five Jupiter Trojans that will be visited by the Lucy spacecraftthe PatroclusMenoetius binary, Eurybates, Orus, Leucus, and Polymele. The measured 1.75.3 m reflectance spectra, which provide increased wavelength coverage, spatial resolution, and signal-to-noise ratio over previous ground-based spectroscopy, reveal several distinct absorption features. We detect a broad OH band centered at 3 m that is most prominent on the less-red objects Eurybates, PatroclusMenoetius, and Polymele. An additional absorption feature at 3.33.6 m, indicative of aliphatic organics, is systematically deeper on the red objects Orus and Leucus. The collisional fragment Eurybates is unique in displaying an absorption band at 4.25 m that we attribute to bound or trapped CO₂. Comparisons with other solar system small bodies reveal broad similarities in the 2.73.6 m bands with analogous features on Centaurs, Kuiper Belt objects (KBOs), and the active asteroid 238P. In the context of recent solar system evolution models, which posit that the Trojans initially formed in the outer solar system, the significant attenuation of the 2.73.6 m absorption features on Trojans relative to KBOs may be the result of secondary thermal processing of the Trojans' surfaces at the higher temperatures of the Jupiter region. The CO₂ band manifested on the surface of Eurybates suggests that CO₂ may be a major constituent in the bulk composition of Trojans, but resides in the subsurface or deeper interior and is largely obscured by refractory material that formed from the thermophysical processes that were activated during their inward migration.

155. Loyd, R., Schneider, P., Jackman, J., et al., (including Llama, J.), 2024, AJ, 167, 185, Erratum: "Flares, Rotation, Activity Cycles, and a Magnetic StarPlanet Interaction Hypothesis for the Far-ultraviolet Emission of GJ 436" (2023, AJ, 165, 146)
     Abstract

     No abstract found.

156. Qu, H., Sako, M., Vincenzi, M., et al., (including Kuehn, K.), 2024, ApJ, 964, 134, The Dark Energy Survey Supernova Program: Cosmological Biases from Host Galaxy Mismatch of Type Ia Supernovae
     Abstract

     Redshift measurements, primarily obtained from host galaxies, are essential for inferring cosmological parameters from type Ia supernovae (SNe Ia). Matching SNe to host galaxies using images is nontrivial, resulting in a subset of SNe with mismatched hosts and thus incorrect redshifts. We evaluate the host galaxy mismatch rate and resulting biases on cosmological parameters from simulations modeled after the Dark Energy Survey 5 Yr (DES-SN5YR) photometric sample. For both DES-SN5YR data and simulations, we employ the directional light radius method for host galaxy matching. In our SN Ia simulations, we find that 1.7% of SNe are matched to the wrong host galaxy, with redshift differences between the true and matched hosts of up to 0.6. Using our analysis pipeline, we determine the shift in the dark energy equation of state parameter (w) due to including SNe with incorrect host galaxy matches. For SN Iaonly simulations, we find w = 0.0013 0.0026 with constraints from the cosmic microwave background. Including core-collapse SNe and peculiar SNe Ia in the simulation, we find that w ranges from 0.0009 to 0.0032, depending on the photometric classifier used. This bias is an order of magnitude smaller than the expected total uncertainty on w from the DES-SN5YR sample of 0.03. We conclude that the bias on w from host galaxy mismatch is much smaller than the uncertainties expected from the DES-SN5YR sample, but we encourage further studies to reduce this bias through better host-matching algorithms or selection cuts.

157. Navarro-Meza, S., Trilling, D., Mommert, M., et al., 2024, AJ, 167, 163, Taxonomy of Subkilometer Near-Earth Objects from Multiwavelength Photometry with RATIR
     Abstract

     We present results from observations of 238 near-Earth objects (NEOs) obtained with the RATIR instrument on the 1.5 m robotic telescope at San Pedro Martir's National Observatory in Mexico, in the frame of our multiobservatory, multifilter campaign. Our project is focused on rapid response photometric observations of NEOs with absolute magnitudes in the range 18.127.1 (diameter 600 and 10 m, respectively). Data with coverage in the near-infrared and visible range were analyzed with a nonparametric classification algorithm, while visible-only data were independently analyzed via Monte Carlo simulations and a 1-Nearest Neighbor method. The rapid response and the use of spectrophotometry allows us to obtain taxonomic classifications of subkilometer objects with small telescopes, representing a convenient characterization strategy. We present taxonomic classifications of the 87 objects observed in the visible and near-infrared. We also present the taxonomic distribution of an additional 151 objects observed in the visible. Our most accurate method suggests a nonfeatured-to-featured ratio of 0.75, which is consistent with the value found by the Mission Accessible Near-Earth Object Survey, which conducted a similar study using a spectral analysis. The results from the Monte Carlo method suggest a ratio of 0.8, although this method has some limitations. The 1-Nearest Neighbor method showed to be not suitable for NEO classifications.

158. Proudfoot, B., Ragozzine, D., Thatcher, M., et al., (including Grundy, W.), 2024, AJ, 167, 144, Beyond Point Masses. II. Non-Keplerian Shape Effects Are Detectable in Several TNO Binaries
     Abstract

     About 40 trans-Neptunian binaries (TNBs) have fully determined orbits with about 10 others being solved except for breaking the mirror ambiguity. Despite decades of study, almost all TNBs have only ever been analyzed with a model that assumes perfect Keplerian motion (e.g., two point masses). In reality, all TNB systems are non-Keplerian due to nonspherical shapes, possible presence of undetected system components, and/or solar perturbations. In this work, we focus on identifying candidates for detectable non-Keplerian motion based on sample of 45 well-characterized binaries. We use MultiMoon, a non-Keplerian Bayesian inference tool, to analyze published relative astrometry allowing for nonspherical shapes of each TNB system's primary. We first reproduce the results of previous Keplerian fitting efforts with MultiMoon, which serves as a comparison for the non-Keplerian fits and confirms that these fits are not biased by the assumption of a Keplerian orbit. We unambiguously detect non-Keplerian motion in eight TNB systems across a range of primary radii, mutual orbit separations, and system masses. As a proof of concept for non-Keplerian fitting, we perform detailed fits for (66652) Borasisi-Pabu, possibly revealing a J ₂ 0.44, implying Borasisi (and/or Pabu) may be a contact binary or an unresolved compact binary. However, full confirmation of this result will require new observations. This work begins the next generation of TNB analyses that go beyond the point mass assumption to provide unique and valuable information on the physical properties of TNBs with implications for their formation and evolution.

159. Chandler, C., Trujillo, C., Oldroyd, W., et al., (including Kueny, J.), 2024, AJ, 167, 156, The Active Asteroids Citizen Science Program: Overview and First Results
     Abstract

     We present the Citizen Science program Active Asteroids and describe discoveries stemming from our ongoing project. Our NASA Partner program is hosted on the Zooniverse online platform and launched on 2021 August 31, with the goal of engaging the community in the search for active asteroidsasteroids with comet-like tails or comae. We also set out to identify other unusual active solar system objects, such as active Centaurs, active quasi-Hilda asteroids (QHAs), and Jupiter-family comets (JFCs). Active objects are rare in large part because they are difficult to identify, so we ask volunteers to assist us in searching for active bodies in our collection of millions of images of known minor planets. We produced these cutout images with our project pipeline that makes use of publicly available Dark Energy Camera data. Since the project launch, roughly 8300 volunteers have scrutinized some 430,000 images to great effect, which we describe in this work. In total, we have identified previously unknown activity on 15 asteroids, plus one Centaur, that were thought to be asteroidal (i.e., inactive). Of the asteroids, we classify four as active QHAs, seven as JFCs, and four as active asteroids, consisting of one main-belt comet (MBC) and three MBC candidates. We also include our findings concerning known active objects that our program facilitated, an unanticipated avenue of scientific discovery. These include discovering activity occurring during an orbital epoch for which objects were not known to be active, and the reclassification of objects based on our dynamical analyses.

160. Glein, C., Grundy, W., Lunine, J., et al., 2024, Icar, 412, 115999, Moderate D/H ratios in methane ice on Eris and Makemake as evidence of hydrothermal or metamorphic processes in their interiors: Geochemical analysis
     Abstract

     Dwarf planets Eris and Makemake have surfaces bearing methane ice of unknown origin. This ice can provide important insights into the origin and evolution of volatiles in the outer solar system. Deuterium/hydrogen (D/H) ratios were recently determined from James Webb Space Telescope (JWST) observations of Eris and Makemake (Grundy et al., 2024b), giving us new clues to decipher the origin of methane. Here, we develop geochemical models to test if the origin of methane could be primordial, derived from CO₂ or CO ("abiotic"), or sourced by organics ("thermogenic"). We find that primordial methane (as currently understood) is inconsistent with the observational data, whereas both abiotic and thermogenic methane can have D/H ratios that overlap the observed ranges. This suggests that Eris and Makemake either never acquired much methane during their formation, or their original inventories were removed and then replaced by internally produced methane. Because producing abiotic or thermogenic methane likely requires temperatures above 150 C, we infer that Eris and Makemake have rocky cores that underwent substantial radiogenic heating. Their cores may still be warm/hot enough to make methane. This heating could have driven hydrothermal circulation at the bottom of an ice-covered ocean to generate abiotic methane, and/or metamorphic reactions involving accreted organic matter could have occurred in response to heating in the deeper interior, generating thermogenic methane. Additional analyses of relevant thermal evolution model results and theoretical predictions of the D/H ratio of methane in the solar nebula support our findings of elevated subsurface temperatures and an apparent lack of primordial methane on Eris and Makemake. It remains an open question whether their D/H ratios may have evolved subsequent to methane outgassing. We also suggest that lower-than-expected D/H and ⁸⁴Kr/CH₄ ratios in Titan's atmosphere disfavor a primordial origin of methane there as well. Recommendations are given for future activities to further test proposed scenarios of abiotic and thermogenic methane production on Eris and Makemake, and to explore these worlds up close so that we can see if they bear additional evidence of endogenic processes.

161. Gatti, M., Jeffrey, N., Whiteway, L., et al., (including Kuehn, K.), 2024, PhRvD, 109, 063534, Dark Energy Survey Year 3 results: Simulation-based cosmological inference with wavelet harmonics, scattering transforms, and moments of weak lensing mass maps. Validation on simulations
     Abstract

     Beyond-two-point statistics contain additional information on cosmological as well as astrophysical and observational (systematics) parameters. In this methodology paper we provide an end-to-end simulation-based analysis of a set of Gaussian and non-Gaussian weak lensing statistics using detailed mock catalogs of the Dark Energy Survey (DES). We implement: 1) second and third moments; 2) wavelet phase harmonics (WPH); 3) the scattering transform (ST). Our analysis is fully based on simulations, it spans a space of seven w CDM cosmological parameters, and it forward models the most relevant sources of systematics of 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 likelihood-free-inference approach. We validate the pipeline extensively, and we find that WPH exhibits the strongest performance when combined with second moments, followed by ST, and then by third moments. The combination of all the different statistics further enhances constraints with respect to second moments, up to 25 percent, 15 percent, and 90 percent for S₈ , _m, and the figure-of-merit FoM_S8,m , respectively. We further find that non-Gaussian statistics improve constraints on w and on the amplitude of intrinsic alignment with respect to second moments constraints. The methodological advances presented here are suitable for application to Stage IV surveys from Euclid, Rubin-LSST, and Roman with additional validation on mock catalogs for each survey. In a companion paper we present an application to DES Year 3 data.

162. Naidu, S., Chesley, S., Moskovitz, N., et al., 2024, PSJ, 5, 74, Orbital and Physical Characterization of Asteroid Dimorphos Following the DART Impact
     Abstract

     The Double Asteroid Redirection Test (DART) mission impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos, on 2022 September 26 UTC. We estimate the changes in the orbital and physical properties of the system due to the impact using ground-based photometric and radar observations, as well as DART camera observations. Under the assumption that Didymos is an oblate spheroid, we estimate that its equatorial and polar radii are 394 11 m and 290 16 m, respectively. We estimate that the DART impact instantaneously changed the along-track velocity of Dimorphos by 2.63 0.06 mm s¹. Initially, after the impact, Dimorphos's orbital period had changed by 32.7 minutes 16 s to 11.377 0.004 hr. We find that over the subsequent several weeks the orbital period changed by an additional 34 15 s, eventually stabilizing at 11.3674 0.0004 hr. The total change in the orbital period was 33.25 minutes 1.5 s. The postimpact orbit exhibits an apsidal precession rate of 6.7 0.2 day¹. Under our model, this rate is driven by the oblateness parameter of Didymos, J ₂, as well as the spherical harmonics coefficients, C ₂₀ and C ₂₂, of Dimorphos's gravity. Under the assumption that Dimorphos is a triaxial ellipsoid with a uniform density, its C ₂₀ and C ₂₂ estimates imply axial ratios, a/b and a/c, of about 1.3 and 1.6, respectively. Preimpact images from DART indicate Dimorphos's shape was close to that of an oblate spheroid, and thus our results indicate that the DART impact significantly altered the shape of Dimorphos.

163. Proudfoot, B., Ragozzine, D., Giforos, W., et al., (including Grundy, W.), 2024, PSJ, 5, 69, Beyond Point Masses. III. Detecting Haumea's Nonspherical Gravitational Field
     Abstract

     The dwarf planet Haumea is one of the most compelling trans-Neptunian objects to study, hosting two small, dynamically interacting satellites, a family of nearby spectrally unique objects, and a ring system. Haumea itself is extremely oblate due to its 3.9 hr rotation period. Understanding the orbits of Haumea's satellites, named Hi'iaka and Namaka, requires detailed modeling of both satellitesatellite gravitational interactions and satellite interactions with Haumea's nonspherical gravitational field (parameterized here as J ₂). Understanding both of these effects allows for a detailed probe of the satellites' masses and Haumea's J ₂ and spin pole. Measuring Haumea's J ₂ provides information about Haumea's interior, possibly determining the extent of past differentation. In an effort to understand the Haumea system, we have performed detailed non-Keplerian orbit fitting of Haumea's satellites using a decade of new, ultra-precise observations. Our fits detect Haumea's J ₂ and spin pole at 2.5 confidence. Degeneracies present in the dynamics prevent us from precisely measuring Haumea's J ₂ with the current data, but future observations should enable a precise measurement. Our dynamically determined spin pole shows excellent agreement with past results, illustrating the strength of non-Keplerian orbit fitting. We also explore the spinorbit dynamics of Haumea and its satellites, showing that axial precession of Hi'iaka may be detectable over decadal timescales. Finally, we present an ephemeris of the Haumea system over the coming decade, enabling high-quality observations of Haumea and its satellites for years to come.

164. Cross, D., Thoron, G., Jeltema, T., et al., (including Kuehn, K.), 2024, MNRAS, 529, 52, Examining the self-interaction of dark matter through central cluster galaxy offsets
     Abstract

     While collisionless cold dark matter models have been largely successful in explaining a wide range of observational data, some tensions still exist, and it remains possible that dark matter possesses a non-negligible level of self-interactions. In this paper, we investigate a possible observable consequence of self-interacting dark matter: offsets between the central galaxy and the centre of mass of its parent halo. We examine 23 relaxed galaxy clusters in a redshift range of 0.1-0.3 drawn from clusters in the Dark Energy Survey and the Sloan Digital Sky Survey which have archival Chandra X-ray data of sufficient depth for centre and relaxation determination. We find that most clusters in our sample show non-zero offsets between the X-ray centre, taken to be the centroid within the cluster core, and the central galaxy position. All of the measured offsets are larger, typically by an order of magnitude, than the uncertainty in the X-ray position due to Poisson noise. In all but six clusters, the measured offsets are also larger than the estimated, combined astrometric uncertainties in the X-ray and optical positions. A more conservative cut on concentration to select relaxed clusters marginally reduces but does not eliminate the observed offset. With our more conservative sample, we find an estimated median X-ray to central galaxy offset of $\mu = 6.0 ^{+ 1.4}_{- 1.5}$ kpc. Comparing to recent simulations, this distribution of offsets is consistent with some level of dark matter self-interaction, though further simulation work is needed to place constraints.

165. Grundy, W., Tegler, S., Steckloff, J., et al., (including Koga, K., Hanley, J.), 2024, Icar, 410, 115767, Laboratory measurement of volatile ice vapor pressures with a quartz crystal microbalance
     Abstract

     Nitrogen, carbon monoxide, and methane are key materials in the far outer Solar System where their high volatility enables them to sublimate, potentially driving activity at very low temperatures. Knowledge of their vapor pressures and latent heats of sublimation at relevant temperatures is needed to model the processes involved. We describe a method for using a quartz crystal microbalance to measure the sublimation flux of these volatile ices in the free molecular flow regime, accounting for the simultaneous sublimation from and condensation onto the quartz crystal to derive vapor pressures and latent heats of sublimation. We find vapor pressures to be somewhat lower than previous estimates in literature, with carbon monoxide being the most discrepant of the three species, almost an order of magnitude lower than had been thought. These results have important implications across a variety of astrophysical and planetary environments.

166. Grundy, W., Wong, I., Glein, C., et al., 2024, Icar, 411, 115923, Measurement of D/H and ¹³C/¹²C ratios in methane ice on Eris and Makemake: Evidence for internal activity
     Abstract

     James Webb Space Telescope's NIRSpec infrared imaging spectrometer observed the outer solar system dwarf planets Eris and Makemake in reflected sunlight at wavelengths spanning 1 through 5 m. Both objects have high albedo surfaces that are rich in methane ice, with a texture that permits long optical path lengths through the ice for solar photons. There is evidence for N₂ ice absorption around 4.2 m on Eris, though not on Makemake. No CO ice absorption is seen at 4.67 m on either body. For the first time, absorption bands of two heavy isotopologues of methane are observed at 2.615 m (¹³CH₄), 4.33 m (¹²CH₃D), and 4.57 m (¹²CH₃D). These bands enable us to measure D/H ratios of (2.5 0.5) 10^-4 and (2.9 0.6) 10^-4, along with ¹³C/¹²C ratios of 0.012 0.002 and 0.010 0.003 in the surface methane ices of Eris and Makemake, respectively. The measured D/H ratios are much lower than that of presumably primordial methane in comet 67P/Churyumov-Gerasimenko, but they are similar to D/H ratios in water in many comets and larger outer solar system objects. This similarity suggests that the hydrogen atoms in methane on Eris and Makemake originated from water, indicative of geochemical processes in past or even ongoing hot environments in their deep interiors. The ¹³C/¹²C ratios are consistent with commonly observed solar system values, suggesting no substantial enrichment in ¹³C as could happen if the methane currently on their surfaces was the residue of a much larger inventory that had mostly been lost to space. Possible explanations include geologically recent outgassing from the interiors as well as processes that cycle the surface methane inventory to keep the uppermost surfaces refreshed.

167. Clark, C., van Belle, G., Horch, E., et al., (including von Braun, K., Llama, J.), 2024, AJ, 167, 56, The POKEMON Speckle Survey of Nearby M Dwarfs. II. Observations of 1125 Targets
     Abstract

     Stellar multiplicity is correlated with many stellar properties, yet multiplicity measurements have proven difficult for the M dwarfsthe most common type of star in our galaxydue to their faintness and the fact that a reasonably complete inventory of later M dwarfs did not exist until recently. We have therefore carried out the Pervasive Overview of "Kompanions" of Every M dwarf in Our Neighborhood (POKEMON) survey, which made use of the Differential Speckle Survey Instrument on the 4.3 m Lowell Discovery Telescope, along with the NN-EXPLORE Exoplanet Stellar Speckle Imager on the 3.5 m WIYN telescope. The POKEMON sample is volume limited from M0V through M9V out to 15 pc, with additional brighter targets at larger distances. In total, 1125 targets were observed. New discoveries were presented in the first paper in the series. In this second paper in the series, we present all detected companions, gauge our astrometric and photometric precision, and compare our filtered and filterless speckle observations. We find that the majority (58.9%) of the companions we detect in our speckle images are not resolved in Gaia, demonstrating the need for high-resolution imaging in addition to long-term astrometric monitoring. Additionally, we find that the majority (73.2%) of simulated stellar companions would be detectable by our speckle observations. Specifically within 100 au, we find that 70.3% of simulated companions are recovered. Finally, we discuss future directions of the POKEMON survey.

168. Ly, K., Grundy, W., 2024, CBET, 5351, 1, 2009 YK_32
     Abstract

     K. Ly, University of California at Los Angeles, writes that he has detected an apparent companion to the transneptunian object 2009 YK_32 in six archival 30-s exposure r-band images taken on 2016 Jan. 6.31-6.55 UT with the 8.2-m Subaru telescope's Hyper-Suprime Cam on Mauna Kea (observer R. Jedicke). The following information was measured by W. M. Grundy (Lowell Observatory) and Ly: The two components were nearly resolved in all images with a mean separation of 0".64 +/- 0".06, corresponding to a projected separation distance of 20000 +/- 2000 km. The mean brightnesses of the two components were almost identical, although the northwestern component appeared fainter by 0.2 +/- 0.1 mag in four of the six images. The fainter northwestern component was positioned at p.a. 323 +/- 4 deg from the primary component. The following astrometry and r-band magnitudes are for the center of light and the combined fluxes.

     2016 UT R.A. (2000) Decl. Mag. Observer

     Jan. 6.31407 7 28 20.44 +21 54 31.9 22.1 Jedicke

     6.55432 7 28 19.18 +21 54 34.7 22.1 "

169. Ly, K., Grundy, W., 2024, CBET, 5352, 1, (534625) 2014 UQ_224
     Abstract

     K. Ly, University of California at Los Angeles, reports that six archival images taken on 2015 Nov. 17.61 and 18.54 UT with the 8.2-m Subaru telescope's Hyper-Suprime Cam (HSC) on Mauna Kea indicate that the transneptunian object (534625) is binary. Three 110-s i-band exposures were taken on 2015 Nov. 17, and three 130-s r-band exposures were taken on 2015 Nov. 18. There were also Subaru/HSC z-band images of (534625) taken on 2015 Nov. 16, but the resolution was too low to discern the binary nature. Later 30-s r-band Subaru/HSC observations on 2016 Jan. 6 and 100-s z-band exposures taken on 2016 Nov. 24 did not show obvious signs of a companion. W. M. Grundy (Lowell Observatory) helped with measuring the binary system's separation and magnitude difference in the 2015 Nov. 17 and 18 images. The mean separation of the two components on both dates was 0".4 +/- 0".1, corresponding to a projected separation distance of 13000 +/- 3000 km. The secondary component was 1.0 +/- 0.5 mag fainter and was positioned at p.a. 305 +/- 15 deg from the primary. The following astrometry and magnitudes are for the center of light and the combined fluxes.

     2015 UT R.A. (2000) Decl. Mag.

     Nov. 17.60752 4 32 24.10 +23 31 04.0 21.9

     18.53933 4 32 19.74 +23 30 55.7 22.0

170. de Souza Feliciano, A., Alvarez-Candal, A., Brunetto, R., et al., (including Grundy, W.), 2024, jwst, 6064, Constraining the dynamical evolution of the outer solar system with trans-Neptunian binaries
     Abstract

     Trans-Neptunian objects (TNOs) are icy remnants of the planetary formation that orbit the Sun in the region beyond Neptune. We propose to resolve a sample of 10 trans-Neptunian binaries (TNBs) of similar and different sizes with tight and wide separations using three sets of NIRCAM filters. The combination of the physical and the compositional properties of the binary systems in our sample could constrain the formation scenario cases due to impact, or streaming instabilit in the early trans-Neptunain region. One portion of our sample is not explained by the current binary formation models since they have similar size (that could be compatible with the streaming instability) but tight separation (as the satellites of the larger TNOs, that could have been formed by impacts). The characterization of the surface composition of both components is crucial to address that matter. Due to their spatial separation, NIRSpec is not suitable for this task. Through the combination of the short and long filters of NIRCAM with the compositional map of the trans-Neptunian region done in the first cycle of JWST, this proposal has potential to constrain proposed formation models and provide an initial input for the expansion of dynamic and evolution theories for some TNBs.

171. Rector, T., Prato, L., 2024, AAS, 243, 128.01, Caught in the Act: Dozens of New Herbig-Haro Objects Reveal Waves of Star Formation in the Aquila Rift
     Abstract

     The extensive Aquila Rift dark cloud complex stretches across the northern hemisphere summer Milky Way. It contains at least 100,000 solar masses of molecular gas, yet only a handful or two of young stars had been identified in the Rift, raising questions about the apparent paucity of star forming activity. Although the Herschel mission detected several hundred embedded cores, an in-between generation of young protostars has not been previously seen. We have surveyed Aquila for Herbig-Haro outflows using the Blanco 4-meter telescope with DECam, a unique facility+instrument combination that offers high sensitivity, wide (3 square degrees) field of view, and arcsecond resolution. Observations with H-alpha, [SII], g' and i' narrow and broad band filters have yielded 45 new HH object detections, allowing us to map the distribution of over 100 embedded young stars in the Rift cloud cores. We compare the distribution of molecular and atomic gas in Aquila to the location of the HH objects in order to understand the broad context for star formation in a giant cloud complex. Differences between the Galactic location of the Rift and other similar regions with more evolved young star populations may provide clues to the chronology of star formation in our Galactic region.

172. Hyden, J., Prato, L., Knowlton, P., et al., (including Kutra, T., Skiff, B.), 2024, AAS, 243, 176.01, A Database for Young Binary Stars
     Abstract

     Circumstellar disks are the sites of planet formation. Most solar analogs are found in binary systems; therefore, understanding how these systems influence circumstellar disk evolution is important. The occurrence of planet formation around binaries is low but not zero, raising the question of what drives or inhibits planet formation in these systems. Our goal is to identify which stellar or system properties influence planet formation via disk dissipation. Our dataset will combine state-of-the-art observations and archival data of approximately 100 binary systems from Keck, the VLT and ALMA, providing years of high-quality spectra for analysis. With the Young Binary Star Database, we will provide a comprehensive archive of high-resolution infrared data, including uniformly derived stellar parameters and reduced spectra, to the community. The database is meticulously maintained using MySQL and JavaScript, while incorporating automated Python scripts for seamless updates, providing a significant and up-to-date resource for the scientific community. The finalized database will illuminate how the interplay between stellar and system properties in binaries impacts disk formation, evolution, and planet formation.

173. Knowlton, P., Prato, L., Kutra, T., et al., (including Hyden, J.), 2024, AAS, 243, 176.07, Stars and Circumstellar Disks in Close Young Binary Systems
     Abstract

     Most stars are located in binary/multiple systems, therefore a complete picture of planet formation requires incorporating the impact of binary systems. Although fewer planets form around stars in multiple systems, astronomers have discovered hundreds of circumstellar exoplanets in binaries. Theoretical and observational evidence suggests that close binaries, with separations <50 AU, have smaller and shorter-lived disks than their single-star or wide binary counterparts. We aim to correlate well-determined stellar properties with circumstellar disk characteristics in order to understand their influence on the formation of planets. Using the Keck II and VLT telescopes, we have collected high-resolution (R=30,000), near-infrared spectra of the individual components in 100 young binary systems with separations from ~10 to several hundred AU. Our analyses focus on absorption lines highly sensitive to stellar and disk parameters such as effective temperature, veiling, surface gravity, surface-averaged magnetic field strength, and projected rotational velocity, extracted by fitting the observed spectra to synthetic models. Statistical tests will reveal how stellar properties impact circumstellar material and either permit or impede the formation of planets. Uniformly-derived disk and stellar parameters and the observed spectra will be made publicly available on the Young Binary Star Database.

174. Prato, L., Knowlton, P., Hyden, J., et al., (including Kutra, T.), 2024, AAS, 243, 176.09, Extreme Veiling Variability and Circumstellar Disk Evolution in the UY Aur Infrared Companion
     Abstract

     Historically the UY Aur system has varied in optical light by many magnitudes; in the early 1990s, the 0.9 arcsecond binary component was identified as an infrared companion (IRC). The stars have similar spectral types, K7 and M1 for the A and B components, respectively. Adaptive optics imaging has not revealed any additional visual components in the system. Over the past 20 years, a dozen high-resolution (R=30,000 or higher), infrared spectra have demonstrated stable and consistent results for the primary component but extreme variability in the IRC: at times the spectrum manifests normal absorption lines and in some cases within months the absorption lines disappear completely. We interpret this behavior as extreme veiling variability and in this contribution we explore the implications for accretion and inner disk structure and evolution in the IRC. This research was supported in part by NSF awards AST-1313399 and AST-2109179.

175. Brown, C., Richey-Yowell, T., 2024, AAS, 243, 259.14, Assessing Mg I Activity with Rotation and Age for FGK Stars
     Abstract

     A thorough understanding of how stellar activity, age, and rotation are connected is crucial for accurately modeling and predicting the underlying physical processes present in all types of stars. In general, we observe that a star's rotation slows down as it ages due to magnetic braking. This spin down relationship is relatively predictable for certain classes of stars (e.g. F and G stars), but K stars have an interesting stalling period where they rotate at a constant rate for up to 1.4 Gyr before resuming their spin down. To better understand age-activity-rotation relations and how this unique K star behavior contributes, we build on previous observational work focused on measuring the activity of the corona, transition region, and upper chromosphere of K stars by examining the activity of the lower chromosphere. We accomplished this by analyzing the Mg I line at 8809.2 angstroms of 49 K star targets; we then compared our results to the measured Mg I activity of young F and G stars found in a similar observational study by Yamashita et al. (2022). We found that while the Mg I emission line is a good activity marker in young F and G stars, it is an absorption feature and therefore a poor activity marker in older K star targets. We plan to observe young K star targets to see if a trend exists between lower chromospheric activity and age. If not, this may suggest that K stars have a less-active lower chromosphere than other types of stars.

176. Nelsen, M., Ragozzine, D., Proudfoot, B., et al., (including Grundy, W.), 2024, AAS, 243, 340.04, Altjira: A Potential Hierarchical Triple Trans-Neptunian Object Discovered through non-Keplerian Motion
     Abstract

     At the edge of the solar system is a region of icy small bodies called the Kuiper Belt. Some of these objects are binaries and when we observe and track their motion, we can then measure many qualities of the objects dynamically, such as mass, orbit, density, and shape. Most of the known objects appear to have only two components, but there is a single known hierarchical triple system with three nearly-equal mass components called (47171) Lempo (Benecchi et al. 2010). A hierarchical triple is so called because when there are three nearly-equal size objects, the only stable configuration is two objects orbiting closely with a third object orbiting further away. Lempo was originally thought to be a binary, but a detailed analysis of the very highest-resolution Hubble Space Telescope images was barely able to resolve the inner binary. So far, no other hierarchical triples have been found in the solar system, due to their rarity and the resolution capabilities of telescopes. Discovering more hierarchical triples will help constrain the streaming instability model of planet formation (Nesvorny et al. 2022). We present evidence for a new hierarchical triple, (148780) Altjira (2001 UQ18), based on non-Keplerian dynamical modeling of the two observed components. Our non-Keplerian analysis includes data over 17 years (including data from ongoing HST Program 17206) which can detect the orbital precession caused by non-spherical shapes and/or unresolved inner binaries. Our analysis shows that Altjira has very strong and statistically significant oblateness (J2), which is best explained as an inner binary. We also find an excellent fit with a hierarchical triple model where the inner binary is unresolved. This potential discovery of the second hierarchical triple in the solar system will help provide new insights into planet formation from these primordial objects.

177. Brewer, J., Zhao, L., Llama, J., 2024, AAS, 243, 352.01, What do Planetary Architectures Really Look Like? New Insights from EXPRES.
     Abstract

     Our view of planetary system architectures is heavily influenced by the biases in our detection methods. Transit survey statistics tell us that there are plenty of small planets, between the radius of Earth and Neptune, at least on orbits shorter than about 40 days. RV surveys have identified a handful of these interior planets, but their small size has limited their detection, even at these close-in orbits. The long time baselines of RV surveys have allowed us to identify many longer period planets, but they are typically larger than Neptune. This leaves large gaps in our knowledge, even in well studied systems. Extreme Precision RV instruments are starting to fill in those gaps. The EXtreme PREcision Spectrometer (EXPRES) and the high cadence 100 Earths Survey has been searching for these missing planets since August 2019. We have found new planets in systems that have been observed for 30 years. I will present our latest results including new planet detections and our plans to reach even smaller signals.

178. Moreland, J., Clark, C., van Belle, G., et al., (including von Braun, K.), 2024, AAS, 243, 355.07, The POKEMON Speckle Survey of Nearby M dwarfs. The Stellar Multiplicity Rate of M Dwarfs by Spectral Subtype
     Abstract

     M type stars are strong candidate exoplanet hosts due to their abundance, longevity, small sizes, and low luminosities. Yet stellar multiples involving these M type stars, specifically M type dwarfs, 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) speckle survey. The purpose of this study is to investigate the stellar multiplicity rate of nearby M dwarfs and how stellar multiplicity relates to the changes as a function of spectral subtype spectral subtype at the low mass end of the main sequence, using photometric data from M type dwarf stars to classify them. In this study, we use the sedFit code, a code designed to read in photometric data and fit it to a list of given template photometric data sets of stars of varying spectral type and luminosity class. Using this code, in conjunction with photometric data collected by 2MASS, Gaia, and the Lowell Observatory's Titan Monitor, we have accurately classified the spectral subtypes of 852 targets from the POKEMON survey. Using this information, in conjunction with the known multicity of the stars in the POKEMON survey, we were able to accurately describe the relationship between stellar multiplicity stars and spectral type for the M dwarfs. We also plan to use these spectral types to update the mass ratio and orbital period distributions for M-dwarf multiples within 15 parsecs to gain additional understanding of M-dwarf formation and evolution, and of the relationship between the properties of stellar multiples and any planets that they host.

179. Villa, K., Knight, M., Schleicher, D., et al., (including Skiff, B.), 2024, AAS, 243, 363.05, Morphological Comparison of CN and OH in Comet Comae
     Abstract

     While comet morphology has been analyzed for individual comets in the past (such as 103P/Hartley 2, 46P/Wirtanen, and 41P/Tuttle-Giacobini-Kresak), in this work we attempt to make the first large-scale comparison of CN and OH gas morphology across a range of comets. Recent data have shown unexpected differences in CN and OH morphology in some instances, with OH often appearing to originate from an extended coma source, e.g., icy grains. However, not enough comets have yet been analyzed collectively to form a general assessment of the correlation, or lack thereof, between CN and OH morphology. Our project attempts to do so by analyzing data from the past two decades at the same time and in a uniform manner. We have identified nearly 50 comets for which images were acquired with the comet narrowband CN and OH filters in our archive of data taken using various telescopes, primarily the Lowell Discovery Telescope (4.3-m) and Lowell 42in Hall Telescope. Using standard image enhancement techniques, we are analyzing the spatial distribution of CN and OH and attempting to correlate these with orbital parameters (to include perihelion distance q, orbit eccentricity e, inclination i, and Tisserand parameter T_J ) as well as inherent comet characteristics (i.e. chemical composition). We are comparing CN and OH imagery both visually and quantitatively to identify trends. Further analysis and image refinement will be completed to demonstrate correlations that may be indicative of a comet's dynamical or physical properties, as well as potentially trace gases to source regions on the nucleus or in the tail. This work tests the classical picture of comet activity as driven by the sublimation of water ice when heated bythe Sun inside the snow line; we will also investigate whether ices other than water (e.g., CO and CO₂ ) are more significant to comet activity than previously thought.

180. Archer, H., Hunter, D., Elmegreen, B., et al., 2024, AAS, 243, 404.11, Probing the Relationship Between Early Star Formation and CO in the Dwarf Irregular Galaxy WLM with JWST
     Abstract

     Dwarf irregular (dIrr) galaxies in the local universe offer a unique window into low-metallicity star formation. These low-metallicity environments strongly affect the formation and structure of molecular clouds, which are primarily composed of H₂ but often traced using low rotational transitions of CO, compared to those in higher-metallicity galaxies. In a pioneering study, Rubio et al. (2015) mapped 10 CO cores with ALMA in the dIrr galaxy WLM, which has an oxygen abundance only 13% of solar. Archer et al. (2022) then examined the environments and star-forming regions surrounding the 10 CO cores, plus an additional 47 subsequently detected, in WLM but found no clear properties driving the formation of the cores. Now, thanks to JWST's exceptional resolution and sensitivity, we can investigate the role of resolved CO cores in WLM's young star-forming regions. In this study, we analyze images of WLM in the JWST F090W, F150W, F250M, and F430M filters from the ERS Program #1334 to examine the relationship between early star formation and the presence of CO cores. We compare properties, including temperature and mass, of the embedded star-forming regions near CO cores with those in other parts of the galaxy. We find shared characteristics in embedded clusters across diverse environments, regardless of proximity to FUV emission indicative of recent star formation or presence of CO cores. Any link between CO core location and early star formation at low metallicities therefore remains elusive. Funding for this work was provided by NSF to D.H. through grant AST-1907492.

181. Kutra, T., 2024, AAS, 243, 413.04D, A New Steady State of Irradiated Disks: the Staircase
     Abstract

     Much of a protoplanetary disk is thermally controlled by the central irradiation. Such a disk, thought to have a flaring shape, is likely unstable to the so-called 'irradiation instability'. But what's the outcome of such an instability? In particular, is it possible that such a disk settle into a shape that is immune to the instability? We combine Athena++ with a simplified thermal treatment to show that passively heated disks settle into a staircase-like steady state. The steady state is punctuated by bright rings and dark gaps, with the bright rings intercepting the lion's share of stellar illumination, and the dark gaps lying in shadows. The optical surface of such a disk (height at which starlight is absorbed) resembles a staircase. We use the RADMC3d code to show that the steady state we find is also in good thermal equilibrium. The novel staircase state, if confirmed by more sophisticated radiative hydrodynamic simulations, has a range of implications for disk evolution and planet formation.

182. Clark, C., van Belle, G., Horch, E., et al., (including von Braun, K., Skiff, B.), 2024, AAS, 243, 447.01, Planet-Hosting M Dwarfs Have Fewer Close-In Stellar Companions
     Abstract

     Stellar companions are known to affect multiple facets of exoplanet formation, evolution, detection, and characterization. In particular, recent studies of FGK stars from Kepler, K2, and TESS have shown that stellar companions to planet-hosting stars have a projected separation distribution that peaks at a larger value than what is expected from non-plant-hosting field stars. This is likely the result of close-in companions affecting and perhaps inhibiting the planet formation process. To test if this is true for the lowest-mass stars as well, we have conducted a volume-limited, high-resolution imaging survey of M dwarfs out to 15 pc. The 15-pc POKEMON sample consists of 454 M dwarfs from M0V through M9V, making it one of the most complete surveys across the broad range of M-dwarf masses. We find a stellar multiplicity rate of 25.12.0%, and a projected separation distribution that peaks at 14.6 au, which is consistent with previous studies of M-dwarf multiplicity. However, the projected separation distribution of the planet-hosting stars in the sample is shifted significantly - out to 305 au similar to what has been found for the FGK stars. These results indicate that the presence of a stellar companion impacts the formation and evolution of any planets around our low-mass neighbors.

183. van Belle, G., Ciardi, D., Hillsberry, D., et al., 2024, AAS, 243, 450.08, MoonLITE: the Lunar InTerferometry Explorer
     Abstract

     The MoonLITE (Lunar InTerferometry Explorer) project is a 2023 NASA Astrophysics Pioneers proposal to develop, build, fly, and operate the first separated-aperture optical interferometer in space, delivering faint, sub-milliarcsecond science results. MoonLITE is proposed fly as a Pioneers hosted payload aboard one of NASA's Commercial Lunar Payload Services (CLPS) landers, to deliver an optical interferometer to the lunar surface. The combination of high spatial resolution from optical interferometry, with deep sensitivity from the stability of the lunar surface, would open up unprecedented discovery space. After landing on the lunar surface, the CLPS rover will deploy the pre-loaded MoonLITE outboard optical element 100 meters from the lander, establishing a interferometric observatory with a single deployment. MoonLITE combines a 110 microarcsecond limiting spatial resolution with enough sensitivity to observe targets fainter than 17th magnitude in the visible. The capabilities of MoonLITE open a unique discovery space that includes direct size measurements of the smallest, coolest stars and substellar brown dwarfs; searches for close-in stellar companions orbiting exoplanet-hosting stars that could confound our understanding and characterization of the frequency of earth-like planets; direct size measurements of young stellar objects and characterization of the terrestrial planet forming regions of these young stars; measurements of the inner regions and binary fraction of active galactic nuclei; and probing the very nature of spacetime foam itself. Twenty percent of the observing time of this revolutionary observatory will be also made available to the broader community via a guest observer program. MoonLITE takes advantage of the CLPS opportunity to place an interferometer in space, on a stable lunar surface, and delivers an unprecedented combination of sensitivity and angular resolution, at the remarkably affordable cost point of Pioneers.

184. Chabot, N., Rivkin, A., Cheng, A., et al., (including Moskovitz, N.), 2024, PSJ, 5, 49, Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission
     Abstract

     NASA's Double Asteroid Redirection Test (DART) mission was the first to demonstrate asteroid deflection, and the mission's Level 1 requirements guided its planetary defense investigations. Here, we summarize DART's achievement of those requirements. On 2022 September 26, the DART spacecraft impacted Dimorphos, the secondary member of the Didymos near-Earth asteroid binary system, demonstrating an autonomously navigated kinetic impact into an asteroid with limited prior knowledge for planetary defense. Months of subsequent Earth-based observations showed that the binary orbital period was changed by 33.24 minutes, with two independent analysis methods each reporting a 1 uncertainty of 1.4 s. Dynamical models determined that the momentum enhancement factor, , resulting from DART's kinetic impact test is between 2.4 and 4.9, depending on the mass of Dimorphos, which remains the largest source of uncertainty. Over five dozen telescopes across the globe and in space, along with the Light Italian CubeSat for Imaging of Asteroids, have contributed to DART's investigations. These combined investigations have addressed topics related to the ejecta, dynamics, impact event, and properties of both asteroids in the binary system. A year following DART's successful impact into Dimorphos, the mission has achieved its planetary defense requirements, although work to further understand DART's kinetic impact test and the Didymos system will continue. In particular, ESA's Hera mission is planned to perform extensive measurements in 2027 during its rendezvous with the DidymosDimorphos system, building on DART to advance our knowledge and continue the ongoing international collaboration for planetary defense.

185. Weaver, H., Sunshine, J., Ernst, C., et al., (including Moskovitz, N.), 2024, PSJ, 5, 43, Lucy Observations of the DART Impact Event
     Abstract

     The Lucy LOng Range Reconnaissance Imager (L'LORRI) took 1549 images of the DidymosDimorphos binary system, starting 12 hr before the Double Asteroid Redirection Test (DART) impact event on 2022 September 26 and ending 24 hr after it. The Lucy imaging campaign provided pre-impact monitoring of the baseline brightness of the Didymos system, as well as intensive 1 s cadence imaging starting 3 minutes prior to impact and extending until 4 minutes after impact, and then continued monitoring at increasing cadences and image exposure times to measure the Didymos system brightness changes produced by ejecta released during the impact. One of the L'LORRI images encompassed the exact time when the DART spacecraft impacted Dimorphos, but there is no evidence of a thermally generated optical flash in the image. L'LORRI observed a shell of fast-moving ejecta, and we derive a range of projected speeds (0.263.6 km s¹) for that material. The much slower moving ejecta (1 m s¹) stayed within a single L'LORRI pixel for the entire duration of the Lucy-DART program. We find that the slow ejecta were responsible for 57.4% 2.2% of the total post-impact brightness increase measured by L'LORRI, while the fast ejecta were responsible for 42.6% 2.3% of the post-impact brightness increase. The initial brightness increase relative to the pre-impact Didymos system brightness was significantly smaller for L'LORRI compared to that measured by some ground-based observers, which is plausibly explained by differences in phase angles and different responses to sodium emission depending on the camera spectral bandwidths.

186. Devogele, M., McGilvray, A., MacLennan, E., et al., (including Kareta, T., Skiff, B.), 2024, PSJ, 5, 44, Surface Heterogeneity, Physical, and Shape Model of Near-Earth Asteroid (52768) 1998 OR2
     Abstract

     On 2020 April 29, the near-Earth object (52768) 1998 OR2 experienced a close approach to Earth at a distance of 16.4 lunar distances (LD). 1998 OR2 is a potentially hazardous asteroid of absolute magnitude H = 16.04 that can currently come as close to Earth as 3.4 LD. We report here observations of this object in polarimetry, photometry, and radar. Our observations show that the physical characteristics of 1998 OR2 are similar to those of both M- and S-type asteroids. Arecibo's radar observations provide a high radar albedo of ${\hat{\sigma }}_{\mathrm{OC}}\,=$ 0.29 0.08, suggesting that metals are present in 1998 OR2 near-surface. We find a circular polarization ratio of _c = 0.291 0.012, and the delay-Doppler images show that the surface of 1998 OR2 is a top-shape asteroid with large-scale structures such as large craters and concavities. The polarimetric observations display a consistent variation of the polarimetric response as a function of the rotational phase, suggesting that the surface of 1998 OR2 is heterogeneous. Color observations suggest an X-complex taxonomy in the BusDeMeo classification. Combining optical polarization, radar, and two epochs from the NEOWISE satellite observations, we derived an equivalent diameter of D = 1.80 0.1 km and a visual albedo p _v = 0.21 0.02. Photometric and radar data provide a sidereal rotation period of P = 4.10872 0.00001 hr, a pole orientation of (332.3 5, 20.7 5), and a shape model with dimensions of

     $({2.08}_{-0.10}^{+0.10},{1.93}_{-0.10}^{+0.10},{1.60}_{-0.05}^{+0.05})$ km.

187. Bourdelle de Micas, J., Fornasier, S., Delbo, M., et al., (including van Belle, G.), 2024, A&A, 682, A64, Compositional characterization of a primordial S-type asteroid family of the inner main belt
     Abstract

     Context. Recently, a primordial family of moderate-albedo asteroid fragments was discovered in the inner main belt. Its age was estimated to be 4.4 1.7 Gyr. However, there is a lack of compositional characterization, which is important to the study of the earliest collisions in the main belt.
     Aims: In addition to the previously identified members and the parameters that define the family's borders (V shape), we expanded the list of family members to include asteroids located within the central region of the V shape. These additional potential members were selected based on their diameter (larger than 7 km) and their geometric visible albedo (greater than or equal to 12%). Subsequently, we conducted a spectroscopic survey to determine the dominant taxonomy and composition of this family. This allowed us to further refine the list of family members by removing interlopers.
     Methods: From an initial list of 263 asteroids that are considered to be potential members of the aforementioned primordial family, we retrieved their spectra in the visible and near-infrared range from the literature and from the Gala DR3 spectral catalog of Solar System objects. For asteroids with no or poor signal-to-noise ratio spectra in the literature, we carried out new ground-based observations. We obtained new spectra for 33 members of the family using the 1.82 m Asiago Telescope for the visible spectroscopy, while for near-infrared spectroscopy, we used the 3.58 m Telescopio Nazionale Galileo (TNG) and the 4.30 m Lowell Discovery Telescope (LDT).
     Results: In total, we collected spectra for 261 potential members of the primordial S-type family out of 263. We determined their spectral taxonomy and properties, such as spectral slopes and absorption band parameters, when existing. Using the taxonomical characterization and the orbital space parameters, we identified and removed 71 interlopers from the potential members list. The final list of the primordial S-type family members includes 190 asteroids. The family is dominated by S-complex (~71%) asteroids with a mineralogy similar to ordinary chondrites and pyroxene-rich minerals. The family also contains members classified as L-types and V-types. (~15% and ~9%, respectively).
     Conclusions: The mean albedo of the family is ~23%, and its largest probable remnant is the asteroid (30) Urania. The estimated size of the family parent body ranges between 110 and 210 km. This size range is compatible with the progenitor of H and L chondrites.

     New spectra are available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/682/A64

188. Carleton, T., Ellsworth-Bowers, T., Windhorst, R., et al., (including Archer, H.), 2024, ApJL, 961, L37, PEARLS: A Potentially Isolated Quiescent Dwarf Galaxy with a Tip of the Red Giant Branch Distance of 30 Mpc
     Abstract

     A wealth of observations have long suggested that the vast majority of isolated classical dwarf galaxies (M _* = 10⁷10⁹ M ) are currently star forming. However, recent observations of the large abundance of "ultra-diffuse galaxies" beyond the reach of previous large spectroscopic surveys suggest that our understanding of the dwarf galaxy population may be incomplete. Here we report the serendipitous discovery of an isolated quiescent dwarf galaxy in the nearby Universe, which was imaged as part of the JWST PEARLS Guaranteed Time Observation program. Remarkably, individual red-giant branch stars are visible in this near-IR imaging, suggesting a distance of 30 4 Mpc, and a wealth of archival photometry point to an sSFR of 2 10¹¹ yr¹ and star formation rate of 4 10⁴ M yr¹. Spectra obtained with the Lowell Discovery Telescope find a recessional velocity consistent with the Hubble Flow and >1500 km s¹ separated from the nearest massive galaxy in Sloan Digital Sky Survey suggesting that this galaxy was either quenched from internal mechanisms or had a very high-velocity (1000 km s¹) interaction with a nearby massive galaxy in the past. This analysis highlights the possibility that many nearby quiescent dwarf galaxies are waiting to be discovered and that JWST has the potential to resolve them.

189. Tegler, S., Grundy, W., Loeffler, M., et al., (including Hanley, J.), 2024, PSJ, 5, 31, Optical Constants of Ices Important to Planetary Science from Laboratory Reflectance Spectroscopy
     Abstract

     Laboratory-derived optical constants are essential for identifying ices and measuring their relative abundances on solar system objects. Almost all optical constants of ices important to planetary science come from experiments with transmission geometries. Here we describe our new experimental setup and the modification of an iterative algorithm in the literature to measure the optical constants of ices from experiments with reflectance geometries. We apply our techniques to CH₄ ice and H₂O ice samples and find good agreement between our values and those in the literature, except for one CH₄ band in the literature that likely suffers from saturation. The work we present here demonstrates that labs with reflectance geometries can generate optical constants essential for the proper analysis of near- and mid-infrared spectra of outer solar system objects such as those obtained with the James Webb Space Telescope.

190. Moskovitz, N., Thomas, C., Pravec, P., et al., (including Polakis, T., Kareta, T., Skiff, B., Burt, B., Thirouin, A.), 2024, PSJ, 5, 35, Photometry of the Didymos System across the DART Impact Apparition
     Abstract

     On 2022 September 26, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes. Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite's orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from 2022 July to 2023 February. We focus here on decomposable lightcurves, i.e., those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the postimpact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first 1 day after impact and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days postimpact. This bulk photometric behavior was not well represented by an HG photometric model. An HG ₁ G ₂ model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least 2023 March. Its persistence implied ongoing escape of ejecta from the system many months after DART impact.

191. Doner, A., Horanyi, M., Bagenal, F., et al., (including Grundy, W.), 2024, ApJL, 961, L38, New Horizons Venetia Burney Student Dust Counter Observes Higher than Expected Fluxes Approaching 60 au
     Abstract

     The NASA New Horizons Venetia Burney Student Dust Counter (SDC) measures dust particle impacts along the spacecraft's flight path for grains with mass 10¹² g, mapping out their spatial density distribution. We present the latest SDC dust density, size distribution, and flux measurements through 55 au and compare them to numerical model predictions. Kuiper Belt objects (KBOs) are thought to be the dominant source of interplanetary dust particles in the outer solar system due to both collisions between KBOs and their continual bombardment by interstellar dust particles. Continued measurements through 55 au show higher than model-predicted dust fluxes as New Horizons approaches the putative outer edge of the Kuiper Belt (KB). We discuss potential explanations for the growing deviation: radiation pressure stretches the dust distribution to further heliocentric distances than its parent body distribution; icy dust grains undergo photosputtering that rapidly increases their response to radiation pressure forces and pushes them further away from the Sun; and the distribution of KBOs may extend much further than existing observations suggest. Ongoing SDC measurements at even larger heliocentric distances will continue to constrain the contributions of dust production in the KB. Continued SDC measurements remain crucial for understanding the Kuiper Belt and the interpretation of dust disks around other stars.

192. McNanna, M., Bechtol, K., Mau, S., et al., (including Kuehn, K.), 2024, ApJ, 961, 126, A Search for Faint Resolved Galaxies Beyond the Milky Way in DES Year 6: A New Faint, Diffuse Dwarf Satellite of NGC 55
     Abstract

     We report results from a systematic wide-area search for faint dwarf galaxies at heliocentric distances from 0.3 to 2 Mpc using the full 6 yr of data from the Dark Energy Survey (DES). Unlike previous searches over the DES data, this search specifically targeted a field population of faint galaxies located beyond the Milky Way virial radius. We derive our detection efficiency for faint, resolved dwarf galaxies in the Local Volume with a set of synthetic galaxies and expect our search to be complete to M _V (7, 10) mag for galaxies at D = (0.3, 2.0) Mpc. We find no new field dwarfs in the DES footprint, but we report the discovery of one high-significance candidate dwarf galaxy at a distance of ${2.2}_{-0.12}^{+0.05}\,\mathrm{Mpc}$ , a potential satellite of the Local Volume galaxy NGC 55, separated by 47' (physical separation as small as 30 kpc). We estimate this dwarf galaxy to have an absolute V-band magnitude of $-{8.0}_{-0.3}^{+0.5}\,\mathrm{mag}$ and an azimuthally averaged physical half-light radius of ${2.2}_{-0.4}^{+0.5}\,\mathrm{kpc}$ , making this one of the lowest surface brightness galaxies ever found with $\mu =32.3\,\mathrm{mag}\,{\mathrm{arcsec}}^{-2}$ . This is the largest, most diffuse galaxy known at this luminosity, suggesting possible tidal interactions with its host.

193. Souza-Feliciano, A., Holler, B., Pinilla-Alonso, N., et al., (including Stansberry, J.), 2024, A&A, 681, L17, Spectroscopy of the binary TNO Mors-Somnus with the JWST and its relationship to the cold classical and plutino subpopulations observed in the DiSCo-TNO project
     Abstract

     Context. Trans-Neptunian objects (TNOs) are remnants of small icy bodies from planetary formation that orbit in the region beyond Neptune. Within the population of TNOs, Trans-Neptunian binaries (TNBs) provide a valuable opportunity to test the models of the formation and evolution of planetesimals in the trans-Neptunian region. Various theories have been proposed to describe the observed separations between binary components, their relative sizes, and other orbital parameters. The colors of TNOs have been used to trace the dynamical history of the outer Solar System and the colors of TNB components provide tests for formation theories. However, spectral information for the components of small TNBs, crucial information that could validate formation mechanisms, has until now remained elusive.
     Aims: The main goal of this work is to characterize the near-infrared spectral properties of the TNB plutino (341520) Mors-Somnus, the only TNB with resolved components in the James Webb Space Telescope (JWST) Large Cycle 1 General Observer program "DiSCo-TNOs" (PID 2418; PI: Pinilla-Alonso). The secondary goal is to use the surface compositions of the individual components of the Mors-Somnus system to probe formation and dynamical evolution in the outer Solar System through comparison to the surface properties of the cold classical and plutino (3:2 resonant) dynamical groups.
     Methods: To achieve these goals, we measured the spectral slope of the continuum and identified absorption bands in the individual spectra of Mors and Somnus, as well as in those of the cold classicals and plutinos obtained with the NIRSpec Integral Field Unit (IFU) and the PRISM/CLEAR disperser (0.6-5.3 m), and compared these results to shed light on the dynamical evolution of the Mors-Somnus binary.
     Results: The spectra of Mors and Somnus are similar and indicate the presence of complex organic materials, CO₂, CO, OH-compounds, and tentative nitrogen-rich materials. We find a high degree of compositional diversity in the plutino population, a group of TNOs that likely formed elsewhere and moved to their current orbits during the migration of Neptune, while the cold classical TNOs, which likely formed in situ, appear more homogeneous.
     Conclusions: The very wide separation between the components, their nearly equal sizes, and the high orbital inclination of the system suggest this plutino binary is a survivor of the primordial population of objects beyond 30 au. The similarities found between the spectral features of the plutinos Mors and Somnus and those of all of the cold classical TNOs in the DiSCo-TNOs sample as well as the high degree of compositional heterogeneity found in the plutino population provide compositional evidence for evaluation of Neptune's migration in the trans-Neptunian region early on in the history of the Solar System.

194. Scheirich, P., Pravec, P., Meyer, A., et al., (including Moskovitz, N.), 2024, PSJ, 5, 17, Dimorphos Orbit Determination from Mutual Events Photometry
     Abstract

     The NASA Double Asteroid Redirection Test spacecraft successfully impacted the DidymosDimorphos binary asteroid system on 2022 September 26 UTC. We provide an update to its preimpact mutual orbit and estimate the postimpact physical and orbital parameters, derived using ground-based photometric observations taken from 2022 July to 2023 February. We found that the total change of the orbital period was 33.240 0.072 minutes (all uncertainties are 3). We obtained the eccentricity of the postimpact orbit to be 0.028 0.016 and the apsidal precession rate was 7.3 2.0 degrees day¹ from the impact to 2022 December 2. The data taken later in 2022 December to 2023 February suggest that the eccentricity dropped close to zero or the orbit became chaotic approximately 70 days after the impact. Most of the period change took place immediately after the impact, but in the few weeks following the impact it was followed by an additional change of $-{27}_{-58}^{+19}$ s or 19 18 s (the two values depend on the approach we used to describe the evolution of the orbital period after the impactan exponentially decreasing angular acceleration or the assumption of a constant orbital period, which changed abruptly some time after the impact, respectively). We estimate the preimpact DimorphosDidymos size ratio was 0.223 0.012 and the postimpact is 0.202 0.018, which indicate a marginally significant reduction of Dimorphos' volume by (9 9)% as the result of the impact.

195. Marques, G., Madhavacheril, M., Darwish, O., et al., (including Kuehn, K.), 2024, JCAP, 2024, 033, Cosmological constraints from the tomography of DES-Y3 galaxies with CMB lensing from ACT DR4
     Abstract

     We present a measurement of the cross-correlation between the MAGLIM galaxies selected from the Dark Energy Survey (DES) first three years of observations (Y3) and cosmic microwave background (CMB) lensing from the Atacama Cosmology Telescope (ACT) Data Release 4 (DR4), reconstructed over ~ 436 deg² of the sky. Our galaxy sample, which covers ~ 4143 deg², is divided into six redshift bins spanning the redshift range of 0.20<z<1.05. We adopt a blinding procedure until passing all consistency and systematics tests. After imposing scale cuts for the cross-power spectrum measurement, we reject the null hypothesis of no correlation at 9.1. We constrain cosmological parameters from a joint analysis of galaxy and CMB lensing-galaxy power spectra considering a flat CDM model, marginalized over 23 astrophysical and systematic nuisance parameters. We find the clustering amplitude S _{8 8}( _m /0.3)^0.5 = 0.75^+0.04 _-0.05. In addition, we constrain the linear growth of cosmic structure as a function of redshift. Our results are consistent with recent DES Y3 analyses and suggest a preference for a lower S ₈ compared to results from measurements of CMB anisotropies by the Planck satellite, although at a mild level (< 2) of statistical significance.

196. Bom, C., Annis, J., Garcia, A., et al., (including Kuehn, K.), 2024, ApJ, 960, 122, Designing an Optimal Kilonova Search Using DECam for Gravitational-wave Events
     Abstract

     We address the problem of optimally identifying all kilonovae detected via gravitational-wave emission in the upcoming LIGO/Virgo/KAGRA observing run, O4, which is expected to be sensitive to a factor of ~7 more binary neutron star (BNS) alerts than previously. Electromagnetic follow-up of all but the brightest of these new events will require >1 m telescopes, for which limited time is available. We present an optimized observing strategy for the DECam during O4. We base our study on simulations of gravitational-wave events expected for O4 and wide-prior kilonova simulations. We derive the detectabilities of events for realistic observing conditions. We optimize our strategy for confirming a kilonova while minimizing telescope time. For a wide range of kilonova parameters, corresponding to a fainter kilonova compared to GW170817/AT 2017gfo, we find that, with this optimal strategy, the discovery probability for electromagnetic counterparts with the DECam is ~80% at the nominal BNS gravitational-wave detection limit for O4 (190 Mpc), which corresponds to an ~30% improvement compared to the strategy adopted during the previous observing run. For more distant events (~330 Mpc), we reach an ~60% probability of detection, a factor of ~2 increase. For a brighter kilonova model dominated by the blue component that reproduces the observations of GW170817/AT 2017gfo, we find that we can reach ~90% probability of detection out to 330 Mpc, representing an increase of ~20%, while also reducing the total telescope time required to follow up events by ~20%.

197. Deming, D., Llama, J., Fu, G., 2024, AJ, 167, 34, Precise Radial Velocities Using Line Bisectors
     Abstract

     We study the properties of line bisectors in the spectrum of the Sun-as-a-star, as observed using the Integrated Sunlight Spectrometer (ISS) of the SOLIS project. Our motivation is to determine whether changes in line shape due to magnetic modulation of photospheric convection can be separated from the 9 cm s^-1 Doppler reflex of the Earth's orbit. Measuring bisectors of 21 lines over a full solar cycle, our results overwhelmingly indicate that solar magnetic activity modulates photospheric convection so as to reduce the asymmetries of line profiles in the spectrum of the Sun-as-a-star (having both C-shaped and reversed-C-shaped bisectors). However, some lines are constant or have variations in shape that are too small to measure. We inject a 9 cm s^-1 radial velocity signal with a 1 yr period into the ISS spectra. Informed by a principal component analysis of the bisectors, we fit the most significant components to the bisectors of each line by linear regression, including a zero-point offset in velocity that is intended to capture the injected radial velocity signal. Averaging over lines, we are able to recover that signal to solid statistical significance in the presence of much larger changes in the line shapes. Although our work has limitations (that we discuss), we establish that changes in absorption line shapes do not in themselves prevent the detection of an Earth-like planet orbiting a Sun-like star using precise radial velocity techniques.

198. Anbajagane, D., Chang, C., Baxter, E., et al., (including Kuehn, K.), 2024, MNRAS, 527, 9378, Cosmological shocks around galaxy clusters: a coherent investigation with DES, SPT, and ACT
     Abstract

     We search for signatures of cosmological shocks in gas pressure profiles of galaxy clusters using the cluster catalogues from three surveys: the Dark Energy Survey (DES) Year 3, the South Pole Telescope (SPT) SZ survey, and the Atacama Cosmology Telescope (ACT) data releases 4, 5, and 6, and using thermal Sunyaev-Zeldovich (SZ) maps from SPT and ACT. The combined cluster sample contains around 10⁵ clusters with mass and redshift ranges $10^{13.7} \lt M_{\rm 200m}/\, {\rm M}_\odot \lt 10^{15.5}$ and 0.1 < z < 2, and the total sky coverage of the maps is $\approx 15\, 000 \deg ^2$. We find a clear pressure deficit at R/R_200m 1.1 in SZ profiles around both ACT and SPT clusters, estimated at 6 significance, which is qualitatively consistent with a shock-induced thermal non-equilibrium between electrons and ions. The feature is not as clearly determined in profiles around DES clusters. We verify that measurements using SPT or ACT maps are consistent across all scales, including in the deficit feature. The SZ profiles of optically selected and SZ-selected clusters are also consistent for higher mass clusters. Those of less massive, optically selected clusters are suppressed on small scales by factors of 2-5 compared to predictions, and we discuss possible interpretations of this behaviour. An oriented stacking of clusters - where the orientation is inferred from the SZ image, the brightest cluster galaxy, or the surrounding large-scale structure measured using galaxy catalogues - shows the normalization of the one-halo and two-halo terms vary with orientation. Finally, the location of the pressure deficit feature is statistically consistent with existing estimates of the splashback radius.

199. Carruba, V., Camargo, J., Aljbaae, S., et al., (including Kuehn, K.), 2024, MNRAS, 527, 6495, Main belt asteroids taxonomical information from dark energy survey data
     Abstract

     While proper orbital elements are currently available for more than 1 million asteroids, taxonomical information is still lagging behind. Surveys like SDSS-MOC4 provided preliminary information for more than 100 000 objects, but many asteroids still lack even a basic taxonomy. In this study, we use Dark Energy Survey (DES) data to provide new information on asteroid physical properties. By cross-correlating the new DES data base with other data bases, we investigate how asteroid taxonomy is reflected in DES data. While the resolution of DES data is not sufficient to distinguish between different asteroid taxonomies within the complexes, except for V-type objects, it can provide information on whether an asteroid belongs to the C- or S-complex. Here, machine learning methods optimized through the use of genetic algorithms were used to predict the labels of more than 68 000 asteroids with no prior taxonomic information. Using a high-quality, limited set of asteroids with data on gri slopes and i - z colours, we detected 409 new possible V-type asteroids. Their orbital distribution is highly consistent with that of other known V-type objects.

200. Gatti, M., Jeffrey, N., Whiteway, L., et al., (including Kuehn, K.), 2024, MNRAS, 527, L115, Detection of the significant impact of source clustering on higher order statistics with DES Year 3 weak gravitational lensing data
     Abstract

     We measure the impact of source galaxy clustering on higher order summary statistics of weak gravitational lensing data. By comparing simulated data with galaxies that either trace or do not trace the underlying density field, we show that this effect can exceed measurement uncertainties for common higher order statistics for certain analysis choices. We evaluate the impact on different weak lensing observables, finding that third moments and wavelet phase harmonics are more affected than peak count statistics. Using Dark Energy Survey (DES) Year 3 (Y3) data, we construct null tests for the source-clustering-free case, finding a p-value of p = 4 10^-3 (2.6) using third-order map moments and p = 3 10^-11 (6.5) using wavelet phase harmonics. The impact of source clustering on cosmological inference can be either included in the model or minimized through ad hoc procedures (e.g. scale cuts). We verify that the procedures adopted in existing DES Y3 cosmological analyses were sufficient to render this effect negligible. Failing to account for source clustering can significantly impact cosmological inference from higher order gravitational lensing statistics, e.g. higher order N-point functions, wavelet-moment observables, and deep learning or field-level summary statistics of weak lensing maps.

201. Giannini, G., Alarcon, A., Gatti, M., et al., (including Kuehn, K.), 2024, MNRAS, 527, 2010, Dark Energy Survey Year 3 results: redshift calibration of the MAGLIM lens sample from the combination of SOMPZ and clustering and its impact on cosmology
     Abstract

     We present an alternative calibration of the MAGLIM lens sample redshift distributions from the Dark Energy Survey (DES) first 3 yr of data (Y3). The new calibration is based on a combination of a self-organizing-map-based scheme and clustering redshifts to estimate redshift distributions and inherent uncertainties, which is expected to be more accurate than the original DES Y3 redshift calibration of the lens sample. We describe in detail the methodology, and validate it on simulations and discuss the main effects dominating our error budget. The new calibration is in fair agreement with the fiducial DES Y3 n(z) calibration, with only mild differences (<3) in the means and widths of the distributions. We study the impact of this new calibration on cosmological constraints, analysing DES Y3 galaxy clustering and galaxy-galaxy lensing measurements, assuming a Lambda cold dark matter cosmology. We obtain _m = 0.30 0.04, ₈ = 0.81 0.07, and S₈ = 0.81 0.04, which implies a ~0.4 shift in the - S₈ plane compared to the fiducial DES Y3 results, highlighting the importance of the redshift calibration of the lens sample in multiprobe cosmological analyses.

202. Whitten, K., Boegen, L., Levine, S., et al., 2024, ISTL, 106, 1, Astronomy's Photographic Glass Plates: Demonstrating Value Through Use Cases
     Abstract

     Astronomy's extensive collections of photographic glass plates contain historical images and spectra of celestial objects, documenting more than a century of the observable cosmos. Many reveal changes, both sudden (explosive), periodic, or gradual (evolutionary), which is material of immense interest for time-domain studies because of the long time-base they cover. Those early photographic observations also furnished all the basic data which supported our early understanding of the universe, and from which modern stellar classifications have been derived. Once the ubiquitous workhorse detector, plates or film are now replaced by electronic detectors, and systems are modified to take advantage of advances in telescope technology. This change poses challenges of preservation and accessibility for the plates, leading administrators to question the usefulness of the older materials in relation to the cost of their care and preservation. The following paper details many examples of reusing or re-purposing those plates, demonstrates their unique value to modern astronomy and the history of science, and makes a strong case for committing resources towards their long-term preservation and ultimately their comprehensive digitization.

202 publications and 1151 citations in 2024.

202 publications and 1151 citations total.