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Research involving Lowell Observatory staff 2025
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    2025

  1. Henault, E., Brunetto, R., Pinilla-Alonso, N., et al., (including Stansberry, J.), 2025, A&A, 694, A126, Irradiation origin and stability of CO on trans-Neptunian objects: Laboratory constraints and observational evidence from JWST/DiSCo-TNOs
    Context. The James Webb Space Telescope large program DiSCo-TNOs has recently shown that CO2 ice is ubiquitous on 54 mediumsize trans-Neptunian objects (TNOs). TNO surfaces are found to define three main spectral and thus compositional groups that are likely linked to their position before planetary migration. CO ice is observed on the spectral type that is richest in CO2 and on the type that is richer in CH3OH and organics. Considerations on the thermal evolution of TNOs predicted the depletion of hypervolatiles such as CO from their surface layers, however. Aims. We investigate a potential irradiation origin of CO as well as its stability by studying the distribution of CO in two TNO compositional types and compared it with irradiation experiments. Methods. We studied the 4.68 m band of CO and the 2.70 m band of CO2 to probe the relation between the two molecules in 33 TNOs. We performed ion irradiation experiments on CO2 and CH3OH ices at 45 and 60 K with 30 keV H+ . We compared the laboratory spectra to TNO observations by focusing on the band areas and positions. Results. We find that the two types of surfaces in which CO is detected are very distinct in terms of their relative abundances and chemical environment. CO that is observed on surfaces that are rich in CO2 are consistent with being produced by CO2 irradiation, specifically, at 45 K. On objects that are rich in CH3OH and complex organics, CO is more likely formed by irradiation of CH3OH. As the CO band areas are only partly related with temperature, the chemical environment plays a major role in the CO retention. Conclusions. We find that the CO that is observed on TNO surfaces is compatible with being a secondary molecule that is entirely formed by late irradiation processes. Its abundance and stability is mostly controlled by the matrix from which it formed.
  2. Thomas, L., Hebrard, G., Kellermann, H., et al., (including Polanski, A.), 2025, A&A, 694, A143, TOI-5108 b and TOI 5786 b: Two transiting sub-Saturns detected and characterized with TESS, MaHPS, and SOPHIE
    We report the discovery and characterization of two sub-Saturns from the Transiting Exoplanet Survey Satellite (TESS) using high- resolution spectroscopic observations from the MaHPS spectrograph at the Wendelstein Observatory and the SOPHIE spectrograph at the Haute-Provence Observatory. Combining photometry from TESS, KeplerCam, LCOGT, and MuSCAT2, along with the radial velocity measurements from MaHPS and SOPHIE, we measured precise radii and masses for both planets. TOI-5108 b is a sub-Saturn, with a radius of 6.6 0.1 R and a mass of 32 5 M. TOI-5786 b is similar to Saturn, with a radius of 8.54 0.13 R and a mass of 73 9 M. The host star for TOI-5108 b is a moderately bright (Vmag 9.75) G-type star. TOI-5786 is a slightly dimmer (Vmag 10.2) F-type star. Both planets are close to their host stars, with periods of 6.75 days and 12.78 days, respectively. This puts TOI-5108 b just within the bounds of the Neptune desert, while TOI-5786 b is right above the upper edge. We estimated hydrogen-helium (H/He) envelope mass fractions of 38% for TOI-5108 b and 74% for TOI-5786 b. However, when using a model for the interior structure that includes tidal effects, the envelope fraction of TOI-5108 b could be much lower (~20%), depending on the obliquity. We estimated mass-loss rates between 1.0 x 109 g/s and 9.8 x 109 g/s for TOI-5108 b and between 3.6 x 108 g/s and 3.5 x 109 g/s for TOI-5786 b. Given their masses, both planets could be stable against photoevaporation. Furthermore, at these mass-loss rates, there is likely no detectable signal in the metastable helium triplet with the James Webb Space Telescope (JWST). We also detected a transit signal for a second planet candidate in the TESS data of TOI-5786, with a period of 6.998 days and a radius of 3.83 0.16 R. Using our RV data and photodynamical modeling, we were able to provide a 3- upper limit of 26.5 M for the mass of the potential inner companion to TOI-5786 b.
  3. Golden-Marx, J., Zhang, Y., Ogando, R., et al., (including Kuehn, K.), 2025, MNRAS, The Hierarchical Growth of Bright Central Galaxies and Intracluster Light as Traced by the Magnitude Gap
    Using a sample of 2800 galaxy clusters identified in the Dark Energy Survey across the redshift range 0.20 < z < 0.60, we characterize the hierarchical assembly of Bright Central Galaxies (BCGs) and the surrounding intracluster light (ICL). To quantify hierarchical formation we use the stellar mass - halo mass (SMHM) relation, comparing the halo mass, estimated via the mass-richness relation, to the stellar mass within the BCG+ICL system. Moreover, we incorporate the magnitude gap (M14), the difference in brightness between the BCG (measured within 30 kpc) and 4th brightest cluster member galaxy within 0.5 R200, c, as a third parameter in this linear relation. The inclusion of M14, which traces BCG hierarchical growth, increases the slope and decreases the intrinsic scatter, highlighting that it is a latent variable within the BCG+ICL SMHM relation. Moreover, the correlation with M14 decreases at large radii. However, the stellar light within the BCG+ICL transition region (30 kpc - 80 kpc) most strongly correlates with halo mass and has a statistically significant correlation with M14. Since the transition region and M14 are independent measurements, the transition region may grow due to the BCG's hierarchical formation. Additionally, as M14 and ICL result from hierarchical growth, we use a stacked sample and find that clusters with large M14 values are characterized by larger ICL and BCG+ICL fractions, which illustrates that the merger processes that build the BCG stellar mass also grow the ICL. Furthermore, this may suggest that M14 combined with the ICL fraction can identify dynamically relaxed clusters.
  4. Dixon, M., Mould, J., Lidman, C., et al., (including Kuehn, K.), 2025, MNRAS, Calibrating the absolute magnitude of type Ia supernovae in nearby galaxies using [OII] and implications for H0
    The present state of cosmology is facing a crisis where there is a fundamental disagreement in measurements of the Hubble constant (H0), with significant tension between the early and late universe methods. Type Ia supernovae (SNe Ia) are important to measuring H0 through the astronomical distance ladder. However, there remains potential to better standardise SN Ia light curves by using known dependencies on host galaxy properties after the standard light curve width and colour corrections have been applied to the peak SN Ia luminosities. To explore this, we use the 5-year photometrically identified SNe Ia sample obtained by the Dark Energy Survey, along with host galaxy spectra obtained by the Australian Dark Energy Survey. Using host galaxy spectroscopy, we find a significant trend with the equivalent width (EW) of the [OII] 3727, 29 doublet, a proxy for specific star formation rate, and Hubble residuals. We find that the correlation with [OII] EW is a powerful alternative to the commonly used mass step after initial light curve corrections. Applying this [OII] EW correction to 20 SNe Ia in calibrator galaxies observed with WiFeS, we examined the impact on SN Ia absolute magnitudes and H0. Our [OII] EW corrections result in H0 values ranging between 73.04 to 73.51kms-1Mpc-1, with a combined statistical and systematic uncertainty of ~1.31kms-1Mpc-1. However, even with this additional correction, the impact of host galaxy properties in standardising SNe Ia appears limited in reducing the current tension (~5) with the CMB result for H0.
  5. Burdanov, A., de Wit, J., Broz, M., et al., (including Grundy, W., Kareta, T., Moskovitz, N., Thirouin, A.), 2025, Natur, 638, 74, JWST sighting of decametre main-belt asteroids and view on meteorite sources
    Asteroid discoveries are essential for planetary-defence efforts aiming to prevent impacts with Earth1, including the more frequent2 megaton explosions from decametre impactors3, 4, 56. Although large asteroids (100 kilometres) have remained in the main belt since their formation7, small asteroids are commonly transported to the near-Earth object (NEO) population8,9. However, owing to the lack of direct observational constraints, their sizefrequency distribution (SFD)which informs our understanding of the NEOs and the delivery of meteorite samples to Earthvaries substantially among models10, 11, 12, 1314. Here we report 138 detections of some of the smallest asteroids (10 metres) ever observed in the main belt, which were enabled by JWST's infrared capabilities covering the emission peaks of the asteroids15 and synthetic tracking techniques16, 1718. Despite small orbital arcs, we constrain the distances and phase angles of the objects using known asteroids as proxies, allowing us to derive sizes through radiometric techniques. Their SFD shows a break at about 100 metres (debiased cumulative slopes of q = 2.66 0.60 and 0.97 0.14 for diameters smaller and larger than roughly 100 metres, respectively), suggestive of a population driven by collisional cascade. These asteroids were sampled from several asteroid familiesmost probably Nysa, Polana and Massaliaaccording to the geometry of pointings considered here. Through further long-stare infrared observations, JWST is poised to serendipitously detect thousands of decametre-scale asteroids across the sky, examining individual asteroid families19 and the source regions of meteorites13,14 'in situ'.
  6. Camilleri, R., Davis, T., Hinton, S., et al., (including Kuehn, K.), 2025, MNRAS, 537, 1818, The Dark Energy Survey Supernova Program: an updated measurement of the Hubble constant using the inverse distance ladder
    We measure the current expansion rate of the Universe, Hubble's constant $H_0$, by calibrating the absolute magnitudes of supernovae to distances measured by baryon acoustic oscillations (BAO). This 'inverse distance ladder' technique provides an alternative to calibrating supernovae using nearby absolute distance measurements, replacing the calibration with a high-redshift anchor. We use the recent release of 1829 supernovae from the Dark Energy Survey spanning $0.01\lt z\lt 1.13$ anchored to the recent baryon acoustic oscillation measurements from Dark Energy Spectroscopic Instrument (DESI) spanning $0.30 \lt z_{\mathrm{eff}}\lt 2.33$. To trace cosmology to $z=0$, we use the third-, fourth-, and fifth-order cosmographic models, which, by design, are agnostic about the energy content and expansion history of the universe. With the inclusion of the higher redshift DESI-BAO data, the third-order model is a poor fit to both data sets, with the fourth-order model being preferred by the Akaike Information Criterion. Using the fourth-order cosmographic model, we find $H_0=67.19^{+0.66}_{-0.64}\mathrm{~km} \mathrm{~s}^{-1} \mathrm{~Mpc}^{-1}$, in agreement with the value found by Planck without the need to assume Flat-$\Lambda$CDM. However, the best-fitting expansion history differs from that of Planck, providing continued motivation to investigate these tensions.
  7. Battle, A., Reddy, V., Sanchez, J., et al., (including Kareta, T.), 2025, PSJ, 6, 31, Long-term Spectral Monitoring of Active Asteroid (6478) Gault: Implications for the H Chondrite Parent Body
    Active asteroid (6478) Gault underwent outbursts between late 2018 and early 2019 with tails morphologically similar to the ejecta from Dimorphous following the Double Asteroid Redirection Test impact. Multiple studies investigated the dust properties, confirmed that Gault is an S-type Phocaea-family asteroid, and obtained a 2.5 hr rotation period consistent with being near the critical rotation period for breakup. We present results from near-infrared spectral monitoring of Gault on one night during a period of activity and five nights across 3 yr after activity ceased in order to understand the evolution of surface mineralogy over time. Spectral band parameters show an average Band I center of 0.920 0.005 m, Band II center of 2.04 0.13 m, and band area ratio of 1.33 0.04. These values correspond to an olivinepyroxene ratio of 0.40, 18.7 mol% fayalite, and 17.2 mol% ferrosiliteall of which are consistent with an H chondrite that has low levels of thermal metamorphism. Three meteorite analogs were identified that are H chondrites with petrologic types between H3.4 and H4. The low-level thermal metamorphism interpretation of Gault's surface suggests that it formed from the outermost portion of the progenitor of the Phocaea family, assuming an "onion shell' structure, which was catastrophically disrupted 1.2 Gyr ago. We discuss implications of Gault's surface composition to better understand this H chondrite parent body, with the suggestion that more dynamical and spectral analyses be performed for members of the Phocaea family.
  8. Corbett, T., Doner, A., Horanyi, M., et al., (including Grundy, W.), 2025, ApJL, 979, L50, Production, Transport, and Destruction of Dust in the Kuiper Belt: The Effects of Refractory and Volatile Grain Compositions
    The Venetia Burney Student Dust Counter (SDC) on board the New Horizons spacecraft measures the spatial and size distributions of dust along its trajectory. Models based on early SDC measurements predicted a peak dust number density at a heliocentric distance of 40 au, followed by a rapid decline. Instead, SDC observed dust fluxes 23 times higher than predicted between 40 and 60 au. One potential explanation for this discrepancy is that SDC may be encountering icy grains with different dynamical behavior than previously modeled silicate grains. Due to ultraviolet photosputtering, waterice grains rapidly erode and migrate outward, significantly contributing to the measured dust number densities only at distances 40 au. We present a model of silicate and ice grain dynamics in the outer solar system, considering gravitational and radiation forces and grain erosion. Using SDC data, we estimate that the mass production rate of ice grains between 0.1 and 10 m in the Kuiper Belt (KB) would need to be 2070 times higher than that of silicate grains. However, KB grains are expected to be refractory/volatile mixtures rather than pure silicate or ice. Thus, we briefly explore simple models of more realistic mixed-grain cases to further gauge the effects of grain composition on the equilibrium dust distribution. Future SDC measurements at greater distances will test the model predictions and further constrain silicate and ice grain production rates in the KB.
  9. Crossfield, I., Polanski, A., Robertson, P., et al., 2025, AJ, 169, 89, OrCAS: Origins, Compositions, and Atmospheres of Sub-Neptunes. I. Survey Definition
    Sub-Neptunesvolatile-rich exoplanets smaller than Neptuneare intrinsically the most common type of planet known. However, the formation and nature of these objects, as well as the distinctions between subclasses (if any), remain unclear. Two powerful tools to tease out the secrets of these worlds are measurements of (i) atmospheric composition and structure revealed by transit and/or eclipse spectroscopy, and (ii) mass, radius, and density revealed by transit photometry and Doppler spectroscopy. Here, we present OrCAS, a survey to better elucidate the origins, compositions, and atmospheres of sub-Neptunes. This radial velocity survey uses a repeatable, quantifiable metric to select targets suitable for subsequent transmission spectroscopy and address key science themes about the atmospheric and internal compositions and architectures of these systems. Our survey targets 26 systems with transiting sub-Neptune planet candidates, with the overarching goal of increasing the sample of such planets suitable for subsequent atmospheric characterization. This paper lays out our survey's science goals, defines our target prioritization metric, and performs light-curve fits and statistical validation using existing TESS photometry and ground-based follow-up observations. Our survey serves to continue expanding the sample of small exoplanets with well-measured properties orbiting nearby bright stars, ensuring fruitful studies of these systems for many years to come.
  10. Menk, A., Zhang, Q., 2025, AAS, 245, 103.04, Investigating the Great September Comet of 1882
    The Great September Comet of 1882 was the brightest known member of the Kreutz family, the only known group of sungrazing comets. We modeled the coma dust surrounding the comet's nucleus to find its physical radius using past observations of the comet between the Earth and the Sun. Measuring the comet "before the disappearance [in front of the Sun] gave 4 arcseconds for the diameter[...]" (Elkin, 1882, p. 22), and another sighting "estimated [the comet] to be still some 5 arcseconds in diameter" (Finlay, 1882, p. 23). The model is based on reports of the comet's observed angular diameters and forward scattering appearance created when the incoming and diffracted sunlight are in the same direction. To account for the reported color of the comet, the average dust size produced needed to be no larger than 1 m in diameter. The calculated dust production rate of 3.87107 1.7107 kg/s and the derived estimate that 4.2[+1.1,-1.0]% of the sunlight reaching the comet was used to sublimate water yielded a comet size of 17.4[+7.3,-3.3] km in radius. Unlike daily visible Kreutz objects, the Great Comet likely resembled the original progenitor, containing a large fraction of the total mass of the family.
  11. Joshi, L., Belkhodja, I., Naaman, L., et al., (including Burt, B.), 2025, AAS, 245, 103.12, Spectral Analysis of Mars Trojans: Is there a Martian Link?
    Understanding the compositions of Mars Trojans is crucial in determining their potential relationship to Mars or other parent bodies. This study employs the Pearson's chi-square () test to compare the visible and near-infrared (VNIR) reflectance spectra of seven asteroids against approximately 11,000 laboratory spectra from meteoritic, terrestrial, synthetic, Apollo, and Luna samples. First, we validate the technique using three well-studied asteroids - (4) Vesta, (6) Hebe, and (19) Fortuna - to confirm previously established spectral matches. To determine spectral analogs, we then apply the test to four Mars Trojans: (5261) Eureka, (101429) 1998 VF31, (311999) 2007 NS2, and (385250) 2001 DH47. For asteroids potentially affected by space weathering, reddening effects are removed. The top matches for the Mars Trojans show notable spectral similarities with Martian meteorites and minerals formed by igneous processes, suggesting a possible Martian origin for the Mars Trojans. However, the possibility that these bodies could be fragments of a disrupted differentiated parent body cannot be ruled out. This study highlights the value of the test as a preliminary tool for identifying spectral analogs and exploring possible surface compositions of asteroids.
  12. Spiro, L., Knight, M., Schleicher, D., et al., (including Skiff, B.), 2025, AAS, 245, 103.21, Analyzing CN Coma Morphology to Investigate Correlations Between Cometary Age and Dynamical Classification
    Comets are considered the most primitive remnants of the solar system's formation. However, little work has been done to analyze comet morphology spanning a large comet imaging database. Almost all research regarding cometary coma morphology has been focused on individual comets. Little large-scale comparative analysis has been done to investigate correlations between coma morphological properties and the overall evolution of comets as they undergo repeated passes through the inner solar system. Our database is one of the largest available to study coma morphology.

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

  13. Smith, N., Beasor, E., Close, L., et al., (including Kueny, J.), 2025, AAS, 245, 163.13, MagAO-X images of the inner core of VY Canis Majoris: A disk and a companion
    We present optical images of VY Canis Majoris obtained with the extreme adaptive-optics system MagAO-X that resolve new detailed structure in the bright core of the nebula around this extreme red supergiant. There are two key results: (1) We detect a separate point source located about 0.12 arcsec away from the central RSG's position. This is plausibly a moderately massive main-sequence star that may be a companion in a binary system. Although the separation is quite wide, this companion may nevertheless cause strong interaction if it has an eccentric orbit, since the radius of the RSG is so large. (2) The central source is not a point source, but instead shows complex resolved asymmetric structure. In particular, the bright central source has a resolved size comparable to the radius where dust forms in the wind, and it appears to be bisected by a dark lane and has elongated structure that may be indicative of an extended circumstellar disk with a radius of 10 R. The orientation of this potential disk (elongated SE/NW) is aligned with larger structures in the nebula, and is perpendicular to a proposed bipolar outflow axis. These two features may be related if the candidate companion star has an eccentric orbit that sweeps through the inner wind/envelope of the RSG. Regardless of the physical origin, this dense asymmetric circumstellar material is emblematic of disks or shells inferred to exist around Type II and Type IIn supernova progenitors, and is vastly different from the winds of normal RSGs.
  14. Park, N., Shkolnik, E., Llama, J., 2025, AAS, 245, 172.05, Correlating Solar Coronal Mass Ejections (CMEs) with Far-Ultraviolet (FUV) Flares to better understand the space weather of exoplanets around Sun-like Stars
    Stellar coronal mass ejections (CMEs) affect planetary habitability by disrupting the stability of planetary atmospheres. While stellar flares have been characterized at a wide range of wavelengths, the physical properties of stellar CMEs remain completely unconstrained due to the lack of conclusive stellar CME detections. In this context, our Sun is critical for CMEs from solar-type stars. Using three different space missions detecting CMEs, X-ray flares and far-ultraviolet (FUV), where the stellar flares are and will be routinely observed (CME rate and mass from LASCO/SOHO, X-ray flare information from XRS/GOES, and far-ultraviolet flare peak flux from AIA1600/SDO), we present a peak flare flux-CME mass correlation that builds upon results from Aarnio et al. (2011). The solar data used in this study covers two entire Solar Cycles (Cycle 23 and 24; 1996-2019). These correlations can predict the extent of CME mass release from associated flare observations for other Sun-like stars. Our result can aid in characterizing stellar mass-loss rates and in assessing the impact on exoplanet atmospheric evolution that affects the potential habitability of exoplanets.
  15. Richey-Yowell, T., Shkolnik, E., Llama, J., et al., (including Sikora, J.), 2025, AAS, 245, 172.06, In Search of Exoplanet Infrared Aurorae: Constraints from Two Hot Jupiters
    Infrared (IR) H3+ aurorae are dynamic probes of star-planet interactions. Aurorae can provide detections of the planetary magnetic fields, constrain host-star wind properties, and deliver information on the thermal structures of planets. Decades of work towards understanding the IR aurorae of Jupiter, Saturn, and Uranus prepared us for applying similar methods to exoplanets. We will present the history of IR auroral searches on exoplanets and our team's own recent work with Keck NIRSPEC to search for molecular H3+ auroral signatures on the hot Jupiters WASP-69b and WASP-80b. While we do not detect H3+ from these planets, we place the most stringent upper limits on H3+ emission to date and approach the regime of emission suspected from theoretical models. Finally, we will discuss the future of H3+ searches and how next-generation observatories may open the path to potentially numerous detections of IR aurorae.
  16. Spencer, L., Benson, C., Bonato, M., et al., (including van Belle, G.), 2025, AAS, 245, 209.22, Sub-arcsecond Far-infrared space-based double Fourier interferometer simulations and simulation tools
    Sub-arcsecond angular resolution hyperspectral observations are significant future milestones in the Far-Infrared (far-IR) region of the electromagnetic spectrum. Such observations require a space-based interferometer observatory with baselines of at least tens of meters in length. While end-to-end demonstration of such technology from a space-based platform has yet to be done, many of the instrument subsystems are already at a flight-ready TRL level. Furthermore, such mission concepts have been considered in design studies and related activities in the past. The Space Infrared Interferometric Telescope (SPIRIT) and the Far Infrared Interferometer (FIRI) are two such examples of two-element, structurally connected spatial-spectral far-IR space-based interferometers that have been previously considered by NASA and ESA as mission concepts. Building on this groundwork, the Far Infrared Space Interferometer Critical Assessment (FISICA) studied FIRI in detail, and to this end, developed both the Far-infrared Interferometer Instrument Simulator (FIInS), and an open-source Python based version (pyFIInS). This software functions as a simulation tool for modeling a FIRI-like interferometer and simulating the output hyperspectral datacubes of double-Fourier interferometer (DFI) astronomical observations.

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

  17. Marin, L., Massey, P., Skiff, B., et al., 2025, AAS, 245, 211.04, The Discovery of Three Galactic Wolf-Rayet Stars
    Wolf-Rayet stars (WRs) are evolved massive stars in the brief, evolved stage before they undergo core collapse. Not only are they rare, but they also can be particularly difficult to find in the Milky Way due to the high extinction in the Galactic plane. We found three new Galactic WRs that were previously classified as H emission stars. Thanks to Gaia spectra, we were able to identify the broad, strong emission lines that characterize WRs. Using the Lowell Discovery Telescope and the DeVeny spectrograph, we obtained spectra for each star. Two are WC9s, and the third is a WN6 + O6.5 V binary. The latter is a known eclipsing system with a 4.4 day period from ASAS-SN data. We found the absolute visual magnitudes for all three stars to be between -7 and -6, which is consistent with our expectations of these subtypes. These discoveries highlight the incompleteness of the WR census in our local volume of the Milky Way and suggest the potential for future Galactic WR discoveries from Gaia low-dispersion spectra. Furthermore, radial velocity studies of the newly found binary will provide direct mass estimates and orbital parameters, providing insight into the role that binarity plays in massive star evolution.

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

  18. van Belle, G., Creech-Eakman, M., Baylis-Aguirre, D., 2025, AAS, 245, 211.06, A "Wonderful" Reference Data Set for Mira Variables
    Mira variable atmospheres are excellent laboratories to study stellar physics, included molecule and grain formation, dust production, stellar winds, mass-loss, opacity driven pulsation, and shocks. Using a decade of observations from the Palomar Testbed Interferometer (PTI), our team has been generating a Reference Data Set for 106 Mira variables, including M, S, and C-types, over a variety of pulsation periods. The measured K-band angular diameters allow us to establish effective temperatures, radial size. Supplemental observations include ongoing period-dependent bolometric flux measurements, as well as previous Spitzer IRS measurements. All the data produced for the Reference Data Set will be hosted on a public website for researchers to exploit this "wonderful" data set.
  19. Beaumont, C., Massey, P., Hillier, D., et al., 2025, AAS, 245, 233.01, The Physical Parameters of a WN3 Wolf-Rayet Star in the LMC
    The goal of this project is to answer the longstanding question in massive star evolution of what effect binarity has on the formation of Wolf-Rayet stars. By understanding the processes involved in the formation of these massive stars, we can gain a greater understanding of the role they play in the evolution of galaxies and create tools that will allow us to better understand the spectra of distant galaxies. We have been using the radiative transfer program CMFGEN to determine the physical parameters of early-type WN stars in the LMC in order to compare their properties with those of single-star and binary-star evolutionary models. At this meeting, we will give the results for our first star, BAT99-15. The UV spectrum of BAT99-15 was measured using NASA's International Ultraviolet explorer, while the optical and NIR spectra were taken with MagE and FIRE on the Baade 6.5-meter telescope. At the culmination of this project, we will be able to report on fundamental properties of a large sample of WN stars, such as the luminosity, temperature, element abundances, etc. This work was supported by the National Science Foundation through grant AST 2307594.
  20. Hunter, D., Zhang, H., Elmegreen, B., et al., (including Castelloe, E., Ledford, H., Nisley, I., Hatano, R.), 2025, AAS, 245, 251.05, Star Formation in the Extreme Far Outer Disk of a Dwarf Irregular Galaxy
    We have obtained ultra-deep UBVI imaging of nearby non-interacting dwarf irregular galaxies in order to examine their far outer stellar disks (out to 29 mag/arcsec2). Photometry of distinct objects in the far outer disks is used to determine ages of the objects in order to look for those that are young. We present the results for one galaxy - DDO 43. We find five objects with high-confidence ages 3-10 Myrs. These objects are too young to have scattered into the far outer disk from the central regions. Therefore, they likely formed in situ. This leaves us with the question of how star-forming gas clouds could form in the extreme environment of the far outer stellar disks of dwarfs. We are grateful to NSF for funding for the building of the camera on the Lowell Discovery Telescope that was used for these observations (NSF AST-1005313).
  21. Kutra, T., Prato, L., Tofflemire, B., et al., (including Tang, S.), 2025, AAS, 245, 268.04, An ALMA Survey of Circumstellar Disks in Young Binaries
    Young binary systems offer a unique opportunity to study the fragility of circumstellar disks in dynamically tumultuous environments. In this talk, I will present preliminary ALMA continuum and 12CO emission for several systems, including the puzzling DF Tau. DF Tau is a close visual binary with a semi-major axis of only 14 AU; we find circumstellar disks around both the primary and secondary star. Other disk signatures, i.e. accretion measurements and H-band veiling, indicate only a disk around the primary star. Because the two stars likely formed together, with the same composition, in the same environment, and at the same time, we expect their disks to be co-eval. However the absence of an inner disk around the secondary suggests uneven dissipation. We resolve this contradiction by proposing that the inner disk of DF Tau B is, at minimum, beyond ~0.06 AU and consider several processes which have the potential to accelerate inner disk evolution.
  22. Ayala, C., Escapa, I., Wade, E., et al., 2025, AAS, 245, 354.19, A Study of the Irregular Variable BH Lac via Observations from the Yerkes Astronomical Glass Plate Collection
    We present results from a study of the stellar variability of the Ross variable star BH Lac using photometric magnitude estimates obtained from the digitization of glass plates containing it. The Ross variable star catalog consists of 379 variable stars identified by Yerkes astronomer Frank Elmore Ross upon comparing glass plates he took between 1924 to 1930 with those taken by Yerkes astronomer E.E Barnard between 1904 to 1915. Today, the 180,000 glass plates of the Yerkes Glass Plate Collection represent the second largest glass plate collection in the world, and the largest collection which has not been fully digitized. The irregular variable BH Lac, identified as R 93 in the Ross variable star catalog, was found to contain a total of 39 glass plates dating between 1907-1929 by the Yerkes Astronomical Plate Search System (YAPSS). Upon performing plate solving methods and aperture photometry on these 39 plates, we were able to estimate the changes in the photometric magnitude of BH Lac from 1907 to 1929 and produce a light curve. We compare our results with light curves generated using the digitized Harvard College Observatory's Astronomical Photographic Glass Plate Collection, as well as with TESS light curves. Additional stellar measurements, acquired via crossmatching our observations with multiwavelength catalogs including Gaia, 2MASS, and WISE, further helped us deduce the potential nature of the star and the processes responsible for its irregular variability, suggesting that stellar youth could possibly be responsible for it. Even in the age of large ground-based optical telescopes, the application of modern tools and techniques towards the Yerkes Glass Plate Collection suggests that its century-long historical astronomical data retains a potential critical role in furthering studies such as identifying changes in stellar proper motion, estimating the periods of binary star systems, and characterizing the stellar variability of long period variables.
  23. Speckert, M., Rector, T., Prato, L., 2025, AAS, 245, 357.05, High-Sensitivity Detections of New Herbig Haro Objects in the Ophiuchus Star Forming Region
    Herbig-Haro objects are tracers of early star formation. By studying them, we can get a better grasp of the presence of young stars with ages of ~1 Myr. Herbig-Haro objects form when jets of gas, ejected from these young protostars, interact with the surrounding medium and create observable shocks. We have imaged numerous star forming regions to facilitate comparisons of Herbig-Haro frequency and morphology across different environments, shedding light on the conditions influencing molecular cloud evolution. Our highly sensitive approach is to use multi-filter (g', i', and H) imaging from the Dark Energy Camera on the Blanco 4-meter telescope and to follow up with confirmation observations in the [SII] N673 filter. This process yields detections of some of the faintest Herbig-Haro objects ever identified. We have discovered ~50 new Herbig-Haro objects in the Ophiuchus region. Herbig-Haro objects are important because their presence indicates ongoing protostar formation within a young region, even when the protostars themselves are not directly visible because they are still embedded in the dark cloud cores. By studying these phenomena we can improve our understanding of the connections between molecular cloud environments of early star formation.
  24. Knowlton, P., Hyden, J., Speckert, M., et al., (including Prato, L., Kutra, T.), 2025, AAS, 245, 357.11, Young Stellar Inclinations Derived from Photometric and Spectroscopic Data
    Understanding the inclinations of stellar spin axes is fundamental for studying planet formation and young binary star evolution. Obliquities between exoplanet orbits and their host stars can be traced to the misalignment of circumstellar disks and stellar rotation. In both single and binary systems, these misalignments can impact disk lifetimes and hinder the formation of planets altogether. Our goal is to derive the inclinations for single and binary systems in the Taurus star-forming region using a unique method that relies on estimates of stellar radii. We first identify rotation periods from TESS and K2 light curves for over a hundred sources. In order to test that these periods reflect the stellar rotation of CTTSs, we model the impact of accretion and other activity on our ability to extract the underlying sinusoidal signal we expect from rotation. We combine these data with projected stellar rotation velocities and effective temperatures derived by fitting a synthetic model grid to IGRINS spectra of our sources. Alongside all of these parameters, we use stellar ages and evolutionary track models from the literature to determine inclination. We present the details of this novel approach and the results from our derived distribution of stellar inclinations.
  25. Tang, S., Johns-Krull, C., Prato, L., 2025, AAS, 245, 367.01D, Searching for the Youngest Hot Jupiters Around T Tauri Stars using Spectroscopic Data
    Characterizing the spot-induced variability of T Tauri Stars (TTSs) is essential for discovering planets orbiting them. Spot activity significantly affects radial velocity (RV) measurements, often overwhelming or mimicking planetary signalsespecially in young, active stars where stellar activity-induced RV variations can be several times larger than those induced by planets. Large cool spots covering up to 80% of the stellar disk complicate the detection and can even mask signals from hot Jupiters (HJs), planets with large sizes but short orbital periods. Over the past two decades, our team has collected hundreds of high-resolution optical and near-infrared spectra in our Young Exoplanet Spectroscopic Survey. Analyzing temperature-sensitive spectral lines, I developed an empirical equivalent width ratio (EWR)-effective temperature (Teff) relationship for late K and M-dwarfs with interferometrically determined Teff, spanning 3400 to 5000 K. This relationship allows me to study the short-term average surface Teff variations of TTSs, serving as a new stellar activity index. My findings reveal temperature variations exceeding 150 K in individual TTSs, confirming substantial stellar activity beyond measurement scatter. Our team observed a correlation between average surface magnetic field strengths and Teff variations, consistent with the interplay between magnetic fields and stellar surface features. Notably, a quarter-phase delay between EWR and RV phase curves points to spot-driven RV modulation. In contrast, CI Tau's zero phase delay suggests more complex dynamics, possibly of planetary origin, and V830 Tau's three-quarter-phase delay hints at a hot spot's involvement. I will also present simulation results, including fits to our observations, and explore how spot sizes and spot-to-photosphere temperature contrast affect the RV and EWR signal strength as functions of wavelength.
  26. Moreland, J., Clark, C., van Belle, G., et al., (including von Braun, K.), 2025, AAS, 245, 403.02, The POKEMON Speckle Survey of Nearby M-Dwarfs. An Analysis of Stellar Multiplicity, Orbital Period, and Mass Ratio Distributions Based on Fitted Spectral Data
    M dwarfs are strong candidate planet hosts due to their abundance, longevity, small sizes, and low luminosities. Yet stellar multiples can induce false positives and overall complicate the process of exoplanet detection and characterization. We have therefore carried out the Pervasive Overview of Kompanions of Every M dwarfs in Our Neighborhood (POKEMON) survey. Using high-angular-resolution speckle imaging, we have characterized the stellar multiplicity of 455 M dwarfs within 15 pc. In this continuation of the study, we are using sedFit to compare photometry from Gaia, 2MASS, and the Titan Monitor facility at Lowell Observatory with the PHOENIX spectral library, allowing us to infer stellar attributes such as effective temperature, luminosity class, and spectral type for each M dwarf primary and secondary in the sample. In addition to a stellar multiplicity rate as a function of spectral subtype, this analysis will allow us to establish updated mass ratio and orbital period distributions down to the bottom of the Main Sequence, revealing the nature of our low-mass neighbors.
  27. Fernandez, N., Richey-Yowell, T., 2025, AAS, 245, 418.04, Characterizing Ultraviolet Flaring Behavior in K-Type Stars
    To better understand the environment of exoplanets, it is essential to first characterize the behavior of their host stars. The flare activity of these stars, particularly in ultraviolet (UV) light, is a critical factor in assessing the potential for exoplanets to develop and sustain life. UV flares can significantly alter the photochemistry of exoplanetary atmospheres, and over time, may even lead to atmospheric loss, rendering exoplanets uninhabitable. While the UV flare behavior of M-type stars has been extensively studied, K-type stars remain less understood. Using Hubble Space Telescope observations of more than a dozen K-type stars across various age groups, we aim to analyze their UV flare activity and compare the results to those of M-type stars. This comparison will help determine whether K-type stars warrant increased attention in the search for potentially habitable exoplanetary systems.
  28. Burgasser, A., Gerasimov, R., Alvarado, E., et al., (including Brooks, H.), 2025, AAS, 245, 464.06, Arcana of the Ancients: First Results from a JWST Spectral Survey of Metal-poor Ultracool Dwarfs
    Elemental composition guides the formation, evolution, and atmosphere processes of the lowest-mass stars and brown dwarfs, or ultracool dwarfs (UCDs). While the vast majority of known UCDs are solar-metallicity objects in the Milky Way's thin disk, a rare subsample of metal-poor stellar and substellar subdwarfs are known in the Solar Neighborhood. We report the first results from our 0.6-14 m spectroscopic survey of 32 L and T dwarfs and subdwarfs, including 11 wide companions to FGK stars, aimed at investigating the influence of metallicity on chemistry, condensation, and disequilibrium mixing in the coolest atmospheres. We show the first temperature and metallicity spectral grid for ultracool dwarfs spanning 0.6-14 m, and identify key metallicity-sensitive features in this regime including evidence of PH3 absorption in the moderate-resolution spectrum of the metal-poor companion T dwarf Wolf 1130C. We demonstrate robust fits to these data to select model grids, including the first self-consistent fits to the extreme T subdwarfs J1810-1010 and J0414-5854 with the SAND model grid, and report preliminary atmosphere parameters from NIRSpec+MIRI low-resolution spectra and radial velocities from moderate-resolution NIRSpec spectra. This program is supported by NASA through program JWST-GO-04688.
  29. Kareta, T., Fuentes-Munoz, O., Moskovitz, N., et al., 2025, ApJL, 979, L8, On the Lunar Origin of Near-Earth Asteroid 2024 PT5
    The near-Earth asteroid (NEA) 2024 PT5 is on an Earth-like orbit that remained in Earth's immediate vicinity for several months at the end of 2024. PT5's orbit is challenging to populate with asteroids originating from the main belt and is more commonly associated with rocket bodies mistakenly identified as natural objects or with debris ejected from impacts on the Moon. We obtained visible and near-infrared reflectance spectra of PT5 with the Lowell Discovery Telescope and NASA Infrared Telescope Facility on 2024 August 16. The combined reflectance spectrum matches lunar samples but does not match any known asteroid typesit is pyroxene-rich, while asteroids of comparable spectral redness are olivine-rich. Moreover, the amount of solar radiation pressure observed on the PT5 trajectory is orders of magnitude lower than what would be expected for an artificial object. We therefore conclude that 2024 PT5 is ejecta from an impact on the Moon, thus making PT5 the second NEA suggested to be sourced from the surface of the Moon. While one object might be an outlier, two suggest that there is an underlying population to be characterized. Long-term predictions of the position of 2024 PT5 are challenging due to the slow Earth encounters characteristic of objects in these orbits. A population of near-Earth objects that are sourced by the Moon would be important to characterize for understanding how impacts work on our nearest neighbor and for identifying the source regions of asteroids and meteorites from this understudied population of objects on very Earth-like orbits.
  30. Tang, S., Johns-Krull, C., Prato, L., et al., 2025, ApJ, 978, 119, Erratum: "Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines" (2024, ApJ, 973, 124)
    No abstract found.
  31. Esteves, J., Pereira, M., Soares-Santos, M., et al., (including Kuehn, K.), 2025, MNRAS, 536, 931, Copacabana: a probabilistic membership assignment method for galaxy clusters
    Cosmological analyses using galaxy clusters in optical/near-infrared photometric surveys require robust characterization of their galaxy content. Precisely determining which galaxies belong to a cluster is crucial. In this paper, we present the COlor Probabilistic Assignment of Clusters And BAyesiaN Analysis (Copacabana) algorithm. Copacabana computes membership probabilities for all galaxies within an aperture centred on the cluster using photometric redshifts, colours, and projected radial probability density functions. We use simulations to validate Copacabana and we show that it achieves up to 89 per cent membership accuracy with a mild dependence on photometric redshift uncertainties and choice of aperture size. We find that the precision of the photometric redshifts has the largest impact on the determination of the membership probabilities followed by the choice of the cluster aperture size. We also quantify how much these uncertainties in the membership probabilities affect the stellar mass-cluster mass scaling relation, a relation that directly impacts cosmology. Using the sum of the stellar masses weighted by membership probabilities ($\rm \mu _{\star }$) as the observable, we find that Copacabana can reach an accuracy of 0.06 dex in the measurement of the scaling relation at low redshift for a Legacy Survey of Space and Time type survey. These results indicate the potential of Copacabana and $\rm \mu _{\star }$ to be used in cosmological analyses of optically selected clusters in the future.
  32. Simon, A., Kaplan, H., Reuter, D., et al., (including Grundy, W.), 2025, PSJ, 6, 7, Lucy L'Ralph In-flight Calibration and Results at (152830) Dinkinesh
    The L'Ralph instrument is a key component of NASA's Lucy mission, intended to provide spectral image data of multiple Jupiter Trojans. The instrument operates from 0.35 to 4 m using two focal plane assemblies: a 350950 nm multispectral imager, Multi-spectral Visible Imaging Camera (MVIC), and a 0.974 m imaging spectrometer, Linear Etalon Imaging Spectral Array (LEISA). Instrument calibration was established through ground testing before launch and has been monitored during cruise utilizing internal calibration sources and stellar targets. In-flight data have shown that the instrument thermal performance is exceeding expectations, allowing for early updates to LEISA radiometric and pointing calibrations. MVIC radiometric performance remains stable more than 3 yr since launch. The serendipitous identification of a new flyby target, (152830) Dinkinesh, allowed testing of instrument performance and interleaved LEISA and MVIC acquisitions on an asteroid target. Both MVIC and LEISA obtained data of Dinkinesh and its moon, Selam, demonstrating that they show good spectral agreement with an S- or Sq-type asteroid, along with evidence of a 3 m absorption feature.
  33. Chandler, C., Sedaghat, N., Oldroyd, W., et al., (including Farrell, K.), 2025, RNAAS, 9, 3, AI-enhanced Citizen Science Discovers Cometary Activity on Near-Earth Object (523822) 2012 DG61
    We report the discovery of cometary activity in the form of a pronounced tail emanating from Near-Earth Object (523822) 2012 DG61, identified in UT 2024 April 18 Dark Energy Camera images by our AI assistant TailNet. TailNet is an AI designed to filter out images unlikely to show activity for volunteers of our NASA Partner "Active Asteroids" Citizen Science campaign, from which our AI is trained. Subsequently, our archival investigation revealed 2012 DG61 is recurrently active after we found it displaying a pronounced tail in a UT 2018 April 16 Steward Observatory Bart Bok 2.3 m telescope image and UT 2018 May 14 observations by G. Borisov with the 0.3 m telescope at MARGO Observatory. Our dynamical integrations reveal that 2012 DG61, an Apollo dynamical class member, is likely in 2:1 mean-motion resonance with Jupiter. We encourage additional observations to help characterize the activity morphology of this near-Earth comet.
  34. Jenniskens, P., Johannink, C., Moskovitz, N., et al., 2025, eMetN, 10, 20, Short note on what appears to have been a 2024 outburst of epsilon-Ursae-Minorids (IAU#1044)
    A meteor outburst with a radiant in Ursa Minor was detected by low-light level video cameras of the Global Meteor Network and by Belarusian and Ukranian meteor camera networks on September 2325, 2024. Here, we report on the results from the CAMS network and discuss the possible association with the epsilon-Ursae-Minorids outburst observed in 2019. If this is the same stream, a return of the shower is expected in 2025, and again in 2030/2031.
  35. Awad, P., Li, T., Erkal, D., et al., (including Kuehn, K.), 2025, A&A, 693, A69, S5: New insights from deep spectroscopic observations of the tidal tails of the globular clusters NGC 1261 and NGC 1904
    As globular clusters (GCs) orbit the Milky Way, their stars are tidally stripped and form tidal tails that follow the orbit of the cluster around the Galaxy. The morphology of these tails is complex and shows correlations with the phase of orbit and the orbital angular velocity, especially for GCs on eccentric orbits. Here we focus on two GCs, NGC 1261 and NGC 1904, that were potentially accreted alongside Gaia-Enceladus and that have shown signatures of having, in addition to tidal tails, structures formed by distributions of extra-tidal stars that are misaligned with the general direction of the clusters' respective orbits. To provide an explanation for the formation of these structures, we made use of spectroscopic measurements from the Southern Stellar Stream Spectroscopic Survey (S5) as well as proper motion measurements from Gaia's third data release (DR3), and applied a Bayesian mixture modelling approach to isolate high-probability member stars. We recovered extra-tidal features surrounding each cluster matching findings from previous work. We then conducted N-body simulations and compared the expected spatial distribution and variation in the dynamical parameters along the orbit with those of our potential member sample. Furthermore, we used Dark Energy Camera (DECam) photometry to inspect the distribution of the member stars in the colour-magnitude diagram (CMD). We find that potential members agree reasonably with the N-body simulations, and that the majority follow a simple stellar population distribution in the CMD, which is characteristic of GCs. We link the extra-tidal features with their orbital properties and find that the presence of the tails agrees well with the theory of stellar stream formation through tidal disruption. In the case of NGC 1904, we clearly detect the tidal debris escaping the inner and outer Lagrange points, which are expected to be prominent when at or close to the apocentre of its orbit. Our analysis allows for further exploration of other GCs in the Milky Way that exhibit similar extra-tidal features.
  36. Hsieh, H., Noonan, J., Kelley, M., et al., (including Thirouin, A., Moskovitz, N.), 2025, PSJ, 6, 3, The Volatile Composition and Activity Evolution of Main-belt Comet 358P/PANSTARRS
    We report the detection of water vapor associated with main-belt comet 358P/PANSTARRS on UT 2024 January 89 using the NIRSPEC instrument on board JWST. We derive a water production rate of molecules s1, marking only the second direct detection of sublimation products of any kind from a main-belt comet, after 238P/Read. Similar to 238P, we find a remarkable absence of hypervolatile species, finding molecules s1, corresponding to %. Upper limits on CH3OH and CO emission are also estimated. Photometry from ground-based observations shows that the dust coma brightened and faded slowly over 250 days in 20232024, consistent with photometric behavior observed in 20122013, but also indicates a 2.5 decline in the dust production rate between these two periods. Dynamical dust modeling shows that the coma's morphology as imaged by JWST's NIRCam instrument on 2023 November 22 can be reproduced by asymmetric dust emission from a nucleus with a midrange obliquity ( 80) with a steady-state mass-loss rate of 0.8 kg s1. Finally, we find similar Af -to-gas ratios of for 358P and for 238P, suggesting that Af could serve as an effective proxy for estimating water production rates in other active main-belt comets. The confirmation of water vapor outgassing in both main-belt comets observed by JWST to date reinforces the use of recurrent activity near perihelion as an indicator of sublimation-driven activity in active asteroids.
  37. Faga, L., Andrade-Oliveira, F., Camacho, H., et al., (including Kuehn, K.), 2025, MNRAS, 536, 1586, Dark energy survey year 3 results: cosmology from galaxy clustering and galaxy-galaxy lensing in harmonic space
    We present the joint tomographic analysis of galaxy-galaxy lensing and galaxy clustering in harmonic space (HS), using galaxy catalogues from the first three years of observations by the Dark Energy Survey (DES Y3). We utilize the REDMAGIC and MAGLIM catalogues as lens galaxies and the METACALIBRATION catalogue as source galaxies. The measurements of angular power spectra are performed using the pseudo-$C_\ell$ method, and our theoretical modelling follows the fiducial analyses performed by DES Y3 in configuration space, accounting for galaxy bias, intrinsic alignments, magnification bias, shear magnification bias and photometric redshift uncertainties. We explore different approaches for scale cuts based on non-linear galaxy bias and baryonic effects contamination. Our fiducial covariance matrix is computed analytically, accounting for mask geometry in the Gaussian term, and including non-Gaussian contributions and super-sample covariance terms. To validate our HS pipelines and covariance matrix, we used a suite of 1800 log-normal simulations. We also perform a series of stress tests to gauge the robustness of our HS analysis. In the $\Lambda$CDM model, the clustering amplitude $S_8 =\sigma _8(\Omega _m/0.3)^{0.5}$ is constrained to $S_8 = 0.704\pm 0.029$ and $S_8 = 0.753\pm 0.024$ (68 per cent C.L.) for the REDMAGIC and MAGLIM catalogues, respectively. For the wCDM, the dark energy equation of state is constrained to $w = -1.28 \pm 0.29$ and $w = -1.26^{+0.34}_{-0.27}$, for REDMAGIC and MAGLIM catalogues, respectively. These results are compatible with the corresponding DES Y3 results in configuration space and pave the way for HS analyses using the DES Y6 data.
  38. Chen, R., Scolnic, D., Vincenzi, M., et al., (including Kuehn, K.), 2025, MNRAS, 536, 1948, Evaluating cosmological biases using photometric redshifts for Type Ia Supernova cosmology with the Dark Energy Survey Supernova Program
    Cosmological analyses with Type Ia Supernovae (SNe Ia) have traditionally been reliant on spectroscopy for both classifying the type of supernova and obtaining reliable redshifts to measure the distance-redshift relation. While obtaining a host-galaxy spectroscopic redshift for most SNe is feasible for small-area transient surveys, it will be too resource intensive for upcoming large-area surveys such as the Vera Rubin Observatory Legacy Survey of Space and Time, which will observe on the order of millions of SNe. Here, we use data from the Dark Energy Survey (DES) to address this problem with photometric redshifts (photo-z) inferred directly from the SN light curve in combination with Gaussian and full $p(z)$ priors from host-galaxy photo-z estimates. Using the DES 5-yr photometrically classified SN sample, we consider several photo-z algorithms as host-galaxy photo-z priors, including the Self-Organizing Map redshifts (SOMPZ), Bayesian Photometric Redshifts (BPZ), and Directional-Neighbourhood Fitting (DNF) redshift estimates employed in the DES 3 2 point analyses. With detailed catalogue-level simulations of the DES 5-yr sample, we find that the simulated w can be recovered within $\pm 0.02$ when using SN+SOMPZ or DNF prior photo-z, smaller than the average statistical uncertainty for these samples of 0.03. With data, we obtain biases in w consistent with simulations within ${\sim} 1\sigma$ for three of the five photo-z variants. We further evaluate how photo-z systematics interplay with photometric classification and find classification introduces a subdominant systematic component. This work lays the foundation for next-generation fully photometric SNe Ia cosmological analyses.
  39. Kutra, T., Prato, L., Tofflemire, B., et al., (including Tang, S.), 2025, AJ, 169, 20, Sites of Planet Formation in Binary Systems. II. Double the Disks in DF Tau
    This article presents the latest results of our Atacama Large Millimeter/submillimeter Array (ALMA) program to study circumstellar disk characteristics as a function of orbital and stellar properties in a sample of young binary star systems known to host at least one disk. Optical and infrared observations of the eccentric, 48 yr period binary DF Tau indicated the presence of only one disk around the brighter component. However, our 1.3 mm ALMA thermal continuum maps show two nearly equal-brightness components in this system. We present these observations within the context of updated stellar and orbital properties, which indicate that the inner disk of the secondary is absent. Because the two stars likely formed together, with the same composition, in the same environment, and at the same time, we expect their disks to be co-eval. However the absence of an inner disk around the secondary suggests uneven dissipation. We consider several processes that have the potential to accelerate inner disk evolution. Rapid inner disk dissipation has important implications for planet formation, particularly in the terrestrial-planet-forming region.
  40. Shah, P., Davis, T., Vincenzi, M., et al., (including Kuehn, K.), 2025, MNRAS, 536, 946, Constraints on compact objects from the Dark Energy Survey 5-yr supernova sample
    Gravitational lensing magnification of Type Ia supernovae (SNe Ia) allows information to be obtained about the distribution of matter on small scales. In this paper, we derive limits on the fraction $\alpha$ of the total matter density in compact objects (which comprise stars, stellar remnants, small stellar groupings, and primordial black holes) of mass M > 0.03 ${\rm M}_{\odot }$ over cosmological distances. Using 1532 SNe Ia from the Dark Energy Survey Year 5 sample (DES-SN5YR) combined with a Bayesian prior for the absolute magnitude M, we obtain < 0.12 at the 95 per cent confidence level after marginalization over cosmological parameters, lensing due to large-scale structure, and intrinsic non-Gaussianity. Similar results are obtained using priors from the cosmic microwave background, baryon acoustic oscillations, and galaxy weak lensing, indicating our results do not depend on the background cosmology. We argue our constraints are likely to be conservative (in the sense of the values we quote being higher than the truth), but discuss scenarios in which they could be weakened by systematics of the order of $\Delta \alpha \sim 0.04$.

    41. 40 publications and 44 citations in 2025.

40 publications and 44 citations total.

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