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2026

1. Boone, K., Ferguson, P., Tabbutt, M., Bechtol, K., Cheng, T., Drlica-Wagner, A., Martinez-Vazquez, C., Mutlu-Pakdil, B., Abbott, T., Aguena, M., Alves, O., Andrade-Oliveira, F., Bacon, D., Bocquet, S., Brooks, D., Camilleri, R., Carnero Rosell, A., da Costa, L., da Silva Pereira, M., Davis, T., De Vicente, J., Desai, S., Doel, P., Everett, S., Flaugher, B., Frieman, J., Garcia-Bellido, J., Gruen, D., Gutierrez, G., Hinton, S., Hollowood, D., Honscheid, K., James, D., Kuehn, K., Marshall, J., Mena-Fernandez, J., Menanteau, F., Miquel, R., Myles, J., Ogando, R., Plazas Malagon, A., Porredon, A., Rodriguez-Monroy, M., Sanchez, E., Sanchez Cid, D., Sevilla-Noarbe, I., Smith, M., Suchyta, E., Swanson, M., Vikram, V., Weaverdyck, N., DES Collaboration, 2026, ApJ, 1001, 208, Robust Measurement of Stellar Streams around the Milky Way: Correcting Spatially Variable Observational Selection Effects in Optical Imaging Surveys
   Abstract

   Observations of density variations in stellar streams are a promising probe of low-mass dark matter substructure in the Milky Way. However, survey systematics such as variations in seeing and sky brightness can also induce artificial fluctuations in the observed densities of known stellar streams. These variations arise because survey conditions affect both object detection and stargalaxy misclassification rates. To mitigate these effects, we use Balrog synthetic source injections in the Dark Energy Survey (DES) Y3 data to calculate detection rate variations and classification rates as functions of survey properties. We show that these rates are nearly separable with respect to survey properties and can be estimated with sufficient statistics from the synthetic catalogs. Applying these corrections reduces the standard deviation of relative detection rates across the DES footprint by a factor of 5, and our corrections significantly change the inferred linear density of the Phoenix stream when including faint objects. Additionally, for artificial streams with DES-like survey properties we are able to recover density power spectra with reduced bias. We also find that uncorrected power-spectrum results for Legacy Survey of Space and Time (LSST)-like data can be around 5 times more biased, highlighting the need for such corrections in future ground-based surveys.

2. Popovic, B., Shah, P., Kenworthy, W., Kessler, R., Davis, T., Goobar, A., Scolnic, D., Vincenzi, M., Wiseman, P., Chen, R., Charleton, E., Acevedo, M., Armstrong, P., Boyd, B., Brout, D., Camilleri, R., Frieman, J., Galbany, L., Grayling, M., Kelsey, L., Rose, B., Sanchez, B., Lee, J., Moller, A., Smith, M., Sullivan, M., Shiamtanis, N., Alarcon, A., Allam, S., Andrade-Oliveira, F., Avila, S., Bacon, D., Blazek, J., Bocquet, S., Brooks, D., Burke, D., Carnero Rosell, A., Carretero, J., Cawthon, R., da Costa, L., da Silva Pereira, M., Diehl, H., Dodelson, S., Doel, P., Everett, S., Frohmaier, C., Garcia-Bellido, J., Gruen, D., Gutierrez, G., Herner, K., Hinton, S., Hollowood, D., Honscheid, K., Huterer, D., James, D., Jeffrey, N., Kuehn, K., Lahav, O., Lee, S., Lidman, C., Marshall, J., Mena-Fernandez, J., Menanteau, F., Miquel, R., Muir, J., Myles, J., Ogando, R., Paterno, M., Plazas Malagon, A., Porredon, A., Prat, J., Nichol, R., Romer, A., Roodman, A., Sanchez, E., Sanchez Cid, D., Sevilla-Noarbe, I., Suchyta, E., Swanson, M., To, C., Tucker, D., Walker, A., Weaverdyck, N., Aguena, M., 2026, MNRAS, The Dark Energy Survey Supernova Program: A Reanalysis Of Cosmology Results And Evidence For Evolving Dark Energy With An Updated Type Ia Supernova Calibration
   Abstract

   We present improved cosmological constraints from a re-analysis of the Dark Energy Survey (DES) 5-year sample of Type Ia supernovae (DES-SN5YR). This re-analysis includes an improved photometric cross-calibration, recent white dwarf observations to cross-calibrate between DES and low redshift surveys, retraining the SALT3 light curve model and fixing a numerical approximation in the host galaxy colour law. Our fully recalibrated sample, which we call DES-Dovekie, comprises ~1600 likely Type Ia SNe from DES and ~200 low-redshift SNe from other surveys. With DES-Dovekie, we obtain _m = 0.330 0.015 in Flat CDM which changes _m by -0.022 compared to DES-SN5YR. Combining DES-Dovekie with CMB data from Planck, ACT and SPT and the DESI DR2 measurements in a Flat w₀w_aCDM cosmology, we find w₀ = -0.803 0.054, w_a = -0.72 0.21. Our results hold a significance of 3.2, reduced from 4.2 for DES-SN5YR, to reject the null hypothesis that the data are compatible with the cosmological constant. This significance is equivalent to a Bayesian model preference odds of approximately 5:1 in favour of the Flat w₀w_aCDM model. Using generally accepted thresholds for model preference, our updated data exhibits only a weak preference for evolving dark energy.

3. Thieberger, C., Hanley, J., Tan, S., Grundy, W., Steckloff, J., Lindberg, G., Engle, A., Tegler, S., 2026, PSJ, 7, 81, The Effects of Propane on NitrogenHydrocarbon 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 bulk constituents of these lakes and seas are liquid methane, ethane, and dissolved nitrogen from the atmosphere. However, trace species produced from photochemistry are also expected to be found in these liquid bodies. Propane is one of the most common among these trace species, but its effects on the Titan ternary system are poorly understood. In an effort to study these environments and map out their extremes, we present our experimental work done in the Astrophysical Materials Lab at Northern Arizona University. We studied the effects of propane on liquid binary mixtures of methanenitrogen and ethanenitrogen. This work presents the results of these experiments run at 90 and 85 K at pressures up to 3 bars, which correspond to depths of up to 200 m in Titan lakes. We observed a second liquid emerging at 90 K in liquidliquidvapor (LLV) equilibrium in methane-based mixtures at pressures >2.5 bars. At 85 K, these mixtures would split into LLV at much lower pressures given a sufficient propane molar fraction. In ethane-based mixtures, we observed a second liquid emerging at a consistent pressure of 2.3 bars at 85 K, but in liquidliquid equilibrium, regardless of the relative propane abundance. We also observed chemoclines, bubbles, and ice formation in several of our experiments. These observed phase changes under Titan conditions demonstrate that there could be compositional stratification of surface liquids, nitrogen droplets precipitating out of liquid hydrocarbon mixtures, or even ice formation under certain conditions.

4. Gimar, C., Raut, U., Grundy, W., Teolis, B., Kammer, J., 2026, A&A, 708, L6, Thermal clustering of solid ethane with potential relevance to Charon's Mordor region
   Abstract

   The methane condensed in Charon's winter hemisphere undergoes photolysis by interplanetary medium Lyman- photons, which yields solid ethane as the dominant photoproduct. With the onset of spring, the photolyzed surface experiences increased surface temperatures and solar wind exposure, conditions that promote further structural and chemical modification. We report laboratory measurements that show solid ethane undergoes a marked spectral reddening when thermally processed at Charon's subsolar maximum temperature of 60 K. The reddening follows an Arrhenius temperature dependence, proceeding on hour timescales at 60 K but requiring on the order of 100 years at 45 K. This behavior is consistent with thermally driven diffusion and aggregation of ethane molecules into nanoclusters that preferentially scatter shorter wavelengths. On Charon, simultaneous solar wind radiolysis may convert ethane nanoclusters into higher-order nonvolatile organic nanoclusters that can plausibly account for the observed reddish polar hue of the object.

5. Cocke, B., Massey, P., Morrell, N., Penny, L., Neugent, K., Eldridge, J., Szymanski, M., Udalski, A., Marin, L., 2026, ApJ, 1001, 116, An Orbit for a Massive WolfRayet Binary in the LMC: An Example of Binary Evolution
   Abstract

   WolfRayet (WR) stars are helium-burning, evolved massive stars which have had most of their hydrogen-rich outer layers removed, either through stellar winds and/or binary stripping. Here, we report on LMC 173-1, a WN3+O binary located in the Large Magellanic Cloud (LMC). Using spectra obtained from the Magellan and Gemini-S telescopes, we have derived system parameters for this intriguing binary. The WR star's mass is only 43% that of its companion, and we argue that this requires binary evolution rather than mass loss by stellar winds alone, given the metallicity of the LMC. The stars are close enough to each other with their 3.52 days period that the O star is actually orbiting within the wind of the WR star, as is the case for other well-known WR+O systems, such as V444 Cyg. As a result, high precision OGLE photometry reveals a WR atmospheric eclipse, as well as a 78 millimag ellipsoidal modulation, due primarily to the tidal distortion of the O star. Modeling the light curve allows us to estimate the orbital inclination. Derivation of stellar parameters suggests neither component is filling its Roche-lobe surface today. The O star is spinning much faster than synchronous rotation. Using BPASS v2.2 binary models, we discuss the probable evolutionary history of the system. The WR progenitor likely underwent Case A Roche-lobe overflow (RLOF) before leaving the main sequence. As it lost its H-rich envelope, it became a WN-type WR. The resulting system is a binary with similar luminosities but very different radii, representing a post-RLOF phase. *This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. It also utilizes observations from the International Gemini Observatory, a program of NSF NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the U.S. National Science Foundation (NSF) on behalf of the Gemini Observatory partnership: the NSF (United States), National Research Council (Canada), Agencia Nacional de Investigacion y Desarrollo (Chile), Ministerio de Ciencia, Tecnologiia e Innovacion (Argentina), Ministerio da Ciencia, Tecnologia, Inovacoes e Comunicacoes (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea).

6. Yang, Y., Lewis, G., Li, T., Martell, S., Erkal, D., Ji, A., Koposov, S., Zucker, D., Pace, A., Cullinane, L., Da Costa, G., Kuehn, K., Limberg, G., Medina, G., 2026, MNRAS, 547, stag488, Epicyclic density variations in the Indus stellar stream
   Abstract

   Longitudinal density fluctuations observed in stellar streams can result from gravitational interactions with massive perturbers in the Milky Way, such as dark matter subhaloes. Analysing these density variations provides a powerful probe of properties (motion, mass, size, etc.) of the perturbing objects. However, caution is needed because density variations may arise naturally from internal dynamics of streams, namely epicycles. In this work, we focus on the Indus stellar stream, a remnant of an ancient dwarf satellite of the Galaxy. An Indus stream spanning $\sim 90^{\circ }$ is revealed in the southern Galactic sky using a comprehensive matched-filter analysis utilizing data from the Gaia mission. A spatial density model is fitted to the filtered map to quantitatively characterize the morphology, which demonstrates episodic density peaks and gaps in the stream. Through N-body simulations, we show that there are strong epicyclic motions of stars happening during tidal disruptions. The present-day longitudinal densities from simulations are comparable to the measurement from data, with similar numbers and locations of peaks and gaps, suggesting that the observed density should mainly be caused by epicycles. We also find that a cuspy dark matter halo for the Indus dwarf is likely to produce milder stellar epicyclic peaks compared to a cored halo, which results in steeper peaks. This arises from different instantaneous mass-loss due to distinct central mass distributions of haloes, where a cored halo usually leads to severer tidal stripping. The observed density exhibits moderate peak sharpness, implying that Indus may have originally possessed a cuspy halo.

7. Thomsen, A., Bucko, J., Kacprzak, T., Ajani, V., Fluri, J., Refregier, A., Anbajagane, D., Castander, F., Ferte, A., Gatti, M., Jeffrey, N., Alarcon, A., Amon, A., Bechtol, K., Becker, M., Bernstein, G., Campos, A., Carnero Rosell, A., Chang, C., Chen, R., Choi, A., Crocce, M., Davis, C., DeRose, J., Dodelson, S., Doux, C., Eckert, K., Elvin-Poole, J., Everett, S., Fosalba, P., Gruen, D., Harrison, I., Herner, K., Huff, E., Jarvis, M., Kuropatkin, N., Leget, P., MacCrann, N., McCullough, J., Myles, J., Navarro-Alsina, A., Pandey, S., Porredon, A., Prat, J., Raveri, M., Rodriguez-Monroy, M., Rollins, R., Roodman, A., Rykoff, E., Sanchez, C., Secco, L., Sheldon, E., Shin, T., Troxel, M., Tutusaus, I., Varga, T., Weaverdyck, N., Wechsler, R., Yanny, B., Yin, B., Zhang, Y., Zuntz, J., Aguena, M., Allam, S., Andrade-Oliveira, F., Bacon, D., Blazek, J., Brooks, D., Camilleri, R., Carretero, J., Cawthon, R., da Costa, L., da Silva Pereira, M., Davis, T., De Vicente, J., Desai, S., Doel, P., Garcia-Bellido, J., Gutierrez, G., Hinton, S., Hollowood, D., Honscheid, K., James, D., Kuehn, K., Lahav, O., Lee, S., Marshall, J., Mena-Fernandez, J., Menanteau, F., Miquel, R., Muir, J., Ogando, R., Plazas Malagon, A., Sanchez, E., Sanchez Cid, D., Sevilla-Noarbe, I., Smith, M., Suchyta, E., Swanson, M., Thomas, D., To, C., Tucker, D., DES Collaboration, 2026, PhRvD, 113, 083501, Dark Energy Survey Year 3 results: Simulation-based wCDM inference from weak lensing and galaxy clustering maps with deep learning: Analysis design
   Abstract

   Data-driven approaches using deep learning are emerging as powerful techniques to extract non-Gaussian information from cosmological large-scale structure. This work presents the first simulation-based inference (SBI) pipeline that combines weak lensing and galaxy clustering maps in a realistic Dark Energy Survey Year 3 (DES Y3) configuration and serves as preparation for a forthcoming analysis of the survey data. We develop a scalable forward model based on the COSMOGRIDV1 suite of N-body simulations to generate over one million self-consistent mock realizations of DES Y3 at the map level. Leveraging this large dataset, we train deep graph convolutional neural networks on the full survey footprint in spherical geometry to learn low-dimensional features that approximately maximize mutual information with target parameters. These learned compressions enable neural density estimation of the implicit likelihood via normalizing flows in a ten-dimensional parameter space spanning cosmological wCDM, intrinsic alignment, and linear galaxy bias parameters, while marginalizing over baryonic, photometric redshift, and shear bias nuisances. To ensure robustness, we extensively validate our inference pipeline using synthetic observations derived from both systematic contaminations in our forward model and independent BUZZARD galaxy catalogs. Our forecasts yield significant improvements in cosmological parameter constraints, achieving 23 higher figures of merit in the m-S8 plane relative to our implementation of baseline two-point statistics and effectively breaking parameter degeneracies through probe combination. These results demonstrate the potential of SBI analyses powered by deep learning for upcoming stage-IV wide-field imaging surveys.

8. Proudfoot, B., Grundy, W., Ragozzine, D., 2026, ApJL, 1001, L4, Trans-Neptunian Binary Mutual Events in the 2020s and 2030s
   Abstract

   Mutual events of trans-Neptunian binaries (TNBs) provide rare opportunities to measure the physical and orbital properties of small bodies in the outer solar system. However, successful observations of these events have been limited by uncertain predictions. Here, we present probabilistic predictions of TNB mutual events occurring through the 2030s, using high-precision non-Keplerian orbit solutions from the Beyond Point Masses project combined with a Bayesian framework that propagates orbital and size uncertainties. Our methods generate distributions of event timing, duration, depth, and probability of occurrence, enabling direct assessment of observability. We provide predictions for five systems with ongoing or imminent mutual event seasons, including (38628) Huya, (58534) LogosZoe, (148780) Altjira, (469705) Kagara-!Haunu, and (524366) 2001 XR₂₅₄. Preparing for upcoming events with long-baseline light-curve monitoring is vital, as events may be difficult to distinguish from a regular rotational light curve. Rapid dissemination of event detections will benefit the entire community, allowing predictions to be updated, ensuring that these rare mutual event opportunities can be fully exploited.

8 publications and 69 citations in 2026.

8 publications and 69 citations total.