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2025

1. Henault, E., Brunetto, R., Pinilla-Alonso, N., Baklouti, D., Djouadi, Z., Guilbert-Lepoutre, A., Muller, T., Cryan, S., de Souza-Feliciano, A., Holler, B., de Pra, M., Emery, J., McClure, L., Schambeau, C., Pendleton, Y., Harvison, B., Licandro, J., Lorenzi, V., Cruikshank, D., Peixinho, N., Bannister, M., Stansberry, J., 2025, A&A, 694, A126, Irradiation origin and stability of CO on trans-Neptunian objects: Laboratory constraints and observational evidence from JWST/DiSCo-TNOs
   Abstract

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

2. Thomas, L., Hebrard, G., Kellermann, H., Korth, J., Heidari, N., Forveille, T., Sousa, S., Scholler, L., Riffeser, A., Gossl, C., Serrano Bell, J., Kiefer, F., Hara, N., Grupp, F., Ehrhardt, J., Murgas, F., Collins, K., Bieryla, A., Parviainen, H., Belinski, A., Esparza-Borges, E., Ciardi, D., Clark, C., Fukui, A., Gilbert, E., Hopp, U., Ikuta, K., Jenkins, J., Latham, D., Narita, N., Nielsen, L., Quinn, S., Palle, E., Pippert, J., Polanski, A., Ries, C., Schmidt, M., Schwarz, R., Seager, S., Strakhov, I., Striegel, S., van Eyken, J., Watanabe, N., Watkins, C., Winn, J., Ziegler, C., Zoller, R., 2025, A&A, 694, A143, TOI-5108 b and TOI 5786 b: Two transiting sub-Saturns detected and characterized with TESS, MaHPS, and SOPHIE
   Abstract

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

3. Golden-Marx, J., Zhang, Y., Ogando, R., Yanny, B., Pereira, M., Hilton, M., Aguena, M., Allam, S., Andrade-Oliveira, F., Bacon, D., Brooks, D., Carnero Rosell, A., Carretero, J., Cheng, T., da Costa, L., De Vicente, J., Desai, S., Doel, P., Everett, S., Ferrero, I., Frieman, J., Garcia-Bellido, J., Gatti, M., Giannini, G., Gruen, D., Gruendl, R., Gutierrez, G., Hinton, S., Hollowood, D., Honscheid, K., James, D., Kuehn, K., Lee, S., Mena-Fernandez, J., Menanteau, F., Miquel, R., Mohr, J., Palmese, A., Pieres, A., Plazas Malagon, A., Samuroff, S., Sanchez, E., Schubnell, M., Sevilla-Noarbe, I., Smith, M., Suchyta, E., Tarle, G., Vikram, V., Walker, A., Weaverdyck, N., Wiseman, P., 2025, MNRAS, The Hierarchical Growth of Bright Central Galaxies and Intracluster Light as Traced by the Magnitude Gap
   Abstract

   Using a sample of 2800 galaxy clusters identified in the Dark Energy Survey across the redshift range 0.20 < 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 R_{200, c}, as a third parameter in this linear relation. The inclusion of M14, which traces BCG hierarchical growth, increases the slope and decreases the intrinsic scatter, highlighting that it is a latent variable within the BCG+ICL SMHM relation. Moreover, the correlation with M14 decreases at large radii. However, the stellar light within the BCG+ICL transition region (30 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., Taylor, E., Flynn, C., Duffy, A., Galbany, L., Scolnic, D., Davis, T., Moller, A., Kelsey, L., Lee, J., Wiseman, P., Vincenzi, M., Shah, P., Aguena, M., Allam, S., Alves, O., Bacon, D., Bocquet, S., Brooks, D., Burke, D., Carnero Rosell, A., Carollo, D., Carretero, J., Conselice, C., da Costa, L., Pereira, M., Diehl, H., Doel, P., Everett, S., Ferrero, I., Flaugher, B., Frieman, J., Garcia-Bellido, J., Gatti, M., Gaztanaga, E., Giannini, G., Gruen, D., Gruendl, R., Gutierrez, G., Herner, K., Hinton, S., Hollowood, D., Honscheid, K., James, D., Kuehn, K., Lima, M., Marshall, J., Mena-Fernandez, J., Menanteau, F., Miquel, R., Myles, J., Nichol, R., Ogando, R., Palmese, A., Pieres, A., Plazas Malagon, A., Samuroff, S., Sanchez, E., Sanchez Cid, D., Sevilla-Noarbe, I., Smith, M., Sobreira, F., Suchyta, E., Swanson, M., Tarle, G., To, C., Tucker, B., Tucker, D., Vikram, V., Walker, A., Weaverdyck, N., 2025, MNRAS, Calibrating the absolute magnitude of type Ia supernovae in nearby galaxies using [OII] and implications for H₀
   Abstract

   The present state of cosmology is facing a crisis where there is a fundamental disagreement in measurements of the Hubble constant (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., Muller, T., Hoffmann, T., Ferrais, M., Micheli, M., Jehin, E., Parrott, D., Hasler, S., Binzel, R., Ducrot, E., Kreidberg, L., Gillon, M., Greene, T., Grundy, W., Kareta, T., Lagage, P., Moskovitz, N., Thirouin, A., Thomas, C., Zieba, S., 2025, Natur, 638, 74, JWST sighting of decametre main-belt asteroids and view on meteorite sources
   Abstract

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

6. Camilleri, R., Davis, T., Hinton, S., Armstrong, P., Brout, D., Galbany, L., Glazebrook, K., Lee, J., Lidman, C., Moller, A., Nichol, R., Sako, M., Scolnic, D., Shah, P., Smith, M., Sullivan, M., Sanchez, B., Vincenzi, M., Wiseman, P., Allam, S., Abbott, T., Aguena, M., Andrade-Oliveira, F., Asorey, J., Avila, S., Bacon, D., Bechtol, K., Bocquet, S., Brooks, D., Buckley-Geer, E., Burke, D., Rosell, A., Carollo, D., Carretero, J., Castander, F., Conselice, C., da Costa, L., Pereira, M., Desai, S., Diehl, H., Everett, S., Ferrero, I., Flaugher, B., Frieman, J., Garcia-Bellido, J., Gaztanaga, E., Giannini, G., Gruendl, R., Herner, K., Hollowood, D., Honscheid, K., Huterer, D., James, D., Kent, S., Kuehn, K., Lahav, O., Lee, S., Lewis, G., Lima, M., Marshall, J., Mena-Fernandez, J., Miquel, R., Myles, J., Ogando, R., Palmese, A., Pieres, A., Plazas Malagon, A., Romer, A., Roodman, A., Samuroff, S., Sanchez, E., Sanchez Cid, D., Schubnell, M., Sevilla-Noarbe, I., Suchyta, E., Suntzeff, N., Swanson, M., Tarle, G., Tucker, B., Walker, A., Weaverdyck, N., DES Collaboration, 2025, MNRAS, 537, 1818, The Dark Energy Survey Supernova Program: an updated measurement of the Hubble constant using the inverse distance ladder
   Abstract

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

7. Battle, A., Reddy, V., Sanchez, J., Pearson, N., Sharkey, B., Kareta, T., 2025, PSJ, 6, 31, Long-term Spectral Monitoring of Active Asteroid (6478) Gault: Implications for the H Chondrite Parent Body
   Abstract

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

8. Corbett, T., Doner, A., Horanyi, M., Brandt, P., Grundy, W., Lisse, C., Parker, J., Peltier, L., Poppe, A., Singer, K., Stern, S., Verbiscer, A., 2025, ApJL, 979, L50, Production, Transport, and Destruction of Dust in the Kuiper Belt: The Effects of Refractory and Volatile Grain Compositions
   Abstract

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

9. Crossfield, I., Polanski, A., Robertson, P., Murphy, J., Turtelboom, E., Luque, R., Beatty, T., Daylan, T., Isaacson, H., Brande, J., Kreidberg, L., Batalha, N., Huber, D., Rhem, M., Dressing, C., Kane, S., Bossett, M., Gagnebin, A., Kroft, M., Premnath, P., Rogers, C., Collins, K., Latham, D., Watkins, C., Ciardi, D., Howell, S., Savel, A., Berlind, P., Calkins, M., Esquerdo, G., Mink, J., Clark, C., Lund, M., Matson, R., Everett, M., Schlieder, J., Matthews, E., Giacalone, S., Barclay, T., Zambelli, R., Plavchan, P., Ellingson, T., Bowen, M., Srdoc, G., McLeod, K., Schwarz, R., Barkaoui, K., Kamler, J., Murgas, F., Palle, E., Narita, N., Fukui, A., Relles, H., Bieryla, A., Girardin, E., Massey, B., Stockdale, C., Lewin, P., Papini, R., Guerra, P., Conti, D., Yalcinkaya, S., Basturk, O., Mourad, G., 2025, AJ, 169, 89, OrCAS: Origins, Compositions, and Atmospheres of Sub-Neptunes. I. Survey Definition
   Abstract

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

9 publications and 22 citations in 2025.

9 publications and 22 citations total.