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2026

1. Hoppe, R., Bergemann, M., Eitner, P., Ellwarth, M., Nordlund, A., Leenaarts, J., Plez, B., Serenelli, A., 2026, MNRAS, 546, staf2085, Solar carbon abundance from 3D non-LTE modelling of the diagnostic lines of the CH molecule
   Abstract

   The spectral lines of the CH molecule are a key carbon (C) abundance diagnostic in FGKM-type stars. These lines are detectable in metal-rich and, in contrast to atomic C lines, also in metal-poor late-type stars. However, only 3D LTE analyses of the CH lines have been performed so far. We test the formation of CH lines in the solar spectrum, using for the first time, 3D Non-LTE (NLTE) models. We also aim to derive the solar photospheric abundance of C, using the diagnostic transitions in the optical (4218$4356 \,\rm{\mathring{\rm A}}$) and infrared (33025$37944 \,\rm{\mathring{\rm A}}$). We use the updated NLTE model molecule from S. A. Popa et al. (2023) and different solar 3D radiation-hydrodynamics model atmospheres. The models are contrasted against new spatially resolved optical solar spectra, and the centre-to-limb variation (CLV) of CH lines is studied. We find generally small ($\sim$0.01 dex) NLTE effects in the optical and IR diagnostic CH AX lines in the solar atmosphere. Both 3D NLTE and 3D LTE spectral modelling yield an excellent fit to the solar intensity observations at all viewing angles. The 1D LTE and 1D NLTE models fail to describe the line CLV, and lead to underestimated solar C abundances. The 3D NLTE modelling of diagnostic lines in the optical and IR yields a carbon abundance of A(C) = $8.52\pm 0.07$ dex. The estimate is in agreement with recent results based on neutrino fluxes measured by Borexino. 3D NLTE modelling and tests on spatially resolved solar data are essential to derive robust solar abundances. The analysis presented here focuses on CH, but we expect that similar effects will be present for other molecules of astrophysical interest.

2. Sandford, N., Li, T., Koposov, S., Hayashi, K., Pace, A., Erkal, D., Bovy, J., Da Costa, G., Cullinane, L., Ji, A., Kuehn, K., Lewis, G., Zucker, D., Limberg, G., Medina, G., Simon, J., Yang, Y., (S, 2026, ApJ, 998, 47, Chemodynamics of Bootes I with S⁵: Revised Velocity Gradient, Dark Matter Density, and Galactic Chemical Evolution Constraints
   Abstract

   We combine new spectroscopic observations of the ultrafaint dwarf (UFD) galaxy Bootes I (Boo I) from the Southern Stellar Stream Spectroscopic Survey (S⁵) with 15 yr of archival spectroscopic data to create the largest sample of stellar kinematics and metallicities to date for any Milky Way UFD. Our combined sample includes 148 members extending out to 7 half-light radii (r_h), including 24 newly confirmed members, 18 binary candidates, 15 RR Lyrae stars, and 92 [Fe/H] measurements. Using this larger and more spatially extended sample, we provide updated constraints on Boo I's systemic properties, including its radial population gradients. Properly accounting for perspective rotation effects in a UFD for the first time, we detect a 4 line-of-sight velocity gradient of 1.2 0.3 km s¹ rh1 aligned along Boo I's orbit and discuss its potential tidal origins. We also infer a metallicity gradient of 0.10 0.02 dex rh1 in agreement with previous studies. Using an axisymmetric Jeans model, we provide updated constraints on Boo I's dark matter density profile, which weakly favors a cusped ( =1.00.6+0.5 ) dark matter profile. Lastly, we reanalyze Boo I's metallicity distribution function with a one-zone galactic chemical evolution model and place new constraints on its rapid, inefficient star formation and strong galactic outflows.

3. Webber, K., Hansen, T., Marshall, J., Ji, A., Li, T., Da Costa, G., Cullinane, L., Erkal, D., Koposov, S., Kuehn, K., Lewis, G., Mackey, D., Martell, S., Pace, A., Shipp, N., Simpson, J., Wan, Z., Zucker, D., Alvarado, V., Bland-Hawthorn, J., Limberg, G., Medina, G., Usman, S., 2026, ApJ, 998, 114, Detailed Chemical Abundance Analysis of the Brightest Stars in the Turranburra and Willka Yaku Stellar Streams
   Abstract

   We present a detailed chemical abundance analysis of the three brightest known stars from each of the Turranburra and Willka Yaku stellar streams using high-resolution Magellan/Magellan Inamori Kyocera Echelle spectra. Abundances for 27 elements, ranging from carbon to dysprosium, were derived. Our results support the original classification that Turranburra, with a low average metallicity of [Fe/H] = 2.45 0.07, likely originates from a dwarf galaxy progenitor. Willka Yaku has a low average metallicity of [Fe/H] = 2.35 0.03 with a small scatter in the abundances, consistent with a globular cluster progenitor as suggested by previous studies. Both streams exhibit mild enhancements in neutron-capture elements, with averages of [Eu II/Fe] = 0.47 0.09 for Turranburra and 0.44 0.05 for Willka Yaku, consistent with enrichment from an r-process event. A similar enrichment is observed in other stellar streams, and we further discuss this signature as it relates to the potential enrichment histories of these two streams. *This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

4. Bechtol, K., Sevilla-Noarbe, I., Drlica-Wagner, A., Yanny, B., Gruendl, R., Sheldon, E., Rykoff, E., De Vicente, J., Adamow, M., Anbajagane, D., Becker, M., Bernstein, G., Carnero Rosell, A., Gschwend, J., Gorsuch, M., Hartley, W., Jarvis, M., Jeltema, T., Kron, R., Manning, T., O'Donnell, J., Pieres, A., Rodriguez-Monroy, M., Sanchez Cid, D., Tabbutt, M., Tan, C., Toribio San Cipriano, L., Tucker, D., Weaverdyck, N., Yamamoto, M., Abbott, T., Aguena, M., Alarcon, A., Allam, S., Amon, A., Andrade-Oliveira, F., Avila, S., Bernardinelli, P., Bertin, E., Blazek, J., Brooks, D., Burke, D., Carretero, J., Castander, F., Cawthon, R., Chang, C., Choi, A., Conselice, C., Costanzi, M., Crocce, M., da Costa, L., Davis, T., Desai, S., Diehl, H., Dodelson, S., Doel, P., Doux, C., Ferte, A., Flaugher, B., Fosalba, P., Frieman, J., Garcia-Bellido, J., Gatti, M., Gaztanaga, E., Giannini, G., Gruen, D., Gutierrez, G., Herner, K., Hinton, S., Hollowood, D., Honscheid, K., Huterer, D., Jeffrey, N., Krause, E., Kuehn, K., Lahav, O., Lee, S., Lidman, C., Lima, M., Lin, H., Marshall, J., Mena-Fernandez, J., Miquel, R., Mohr, J., Muir, J., Myles, J., Ogando, R., Palmese, A., Plazas Malagon, A., Porredon, A., Prat, J., Raveri, M., Romer, A., Roodman, A., Samuroff, S., Sanchez, E., Scarpine, V., Smith, M., Soares-Santos, M., Suchyta, E., Tarle, G., Troxel, M., Vikram, V., Walker, A., Weller, J., Wiseman, P., Zhang, Y., DES Collaboration, 2026, ApJS, 282, 62, Dark Energy Survey Year 6 Results: Photometric Dataset for Cosmology
   Abstract

   We describe the photometric dataset assembled from the full 6 yr of observations by the Dark Energy Survey (DES) in support of static-sky cosmology analyses. DES Y6 Gold is a curated dataset derived from DES Data Release 2 (DR2) that incorporates improved measurement, photometric calibration, object classification and value-added information. Y6 Gold comprises nearly 5000 deg² of grizY imaging in the south Galactic cap and includes 669 million objects with a depth of i_AB 23.4 mag at a signal-to-noise ratio 10 for extended objects and a top-of-the-atmosphere photometric uniformity <2 mmag. Y6 Gold augments DES DR2 with simultaneous fits to multiepoch photometry for more robust galaxy shapes, colors, and photometric redshift estimates. Y6 Gold features improved morphological stargalaxy classification with an efficiency of 98.6% and a contamination of 0.8% for galaxies with 17.5 < i_AB < 22.5. Additionally, it includes per-object quality information, and accompanying maps of the footprint coverage, masked regions, imaging depth, survey conditions, and astrophysical foregrounds that are used for cosmology analyses. After quality selections, benchmark samples contain 448 million galaxies and 120 million stars. This publication is complemented by data access and documentation.

5. Hang, Q., Jeffrey, N., Whiteway, L., Lahav, O., Williamson, J., Gatti, M., DeRose, J., Kovacs, A., Alarcon, A., Amon, A., Bechtol, K., Becker, M., Bernstein, G., Campos, A., Rosell, A., Kind, M., Chang, C., Chen, R., Choi, A., Dodelson, S., Doux, C., Drlica-Wagner, A., Elvin-Poole, J., Everett, S., Ferte, A., Gruen, D., Gruendl, R., Harrison, I., Jarvis, M., MacCrann, N., McCullough, J., Myles, J., Navarro-Alsina, A., Pandey, S., Prat, J., Raveri, M., Rollins, R., Rykoff, E., Sanchez, C., Secco, L., Sevilla-Noarbe, I., Sheldon, E., Shin, T., Troxel, M., Tutusaus, I., Wechsler, R., Yanny, B., Yin, B., Aguena, M., Alves, O., Andrade-Oliveira, F., Bacon, D., Blazek, J., Bocquet, S., Brooks, D., Carretero, J., Cawthon, R., Crocce, M., da Costa, L., Pereira, M., Davis, T., Desai, S., Diehl, H., Doel, P., Flaugher, B., Frieman, J., Gutierrez, G., Hinton, S., Hollowood, D., Honscheid, K., Kuehn, K., Lee, S., Marshall, J., Mena-Fernandez, J., Miquel, R., Malagon, A., Porredon, A., Roodman, A., Samuroff, S., Sanchez, E., Cid, D., Smith, M., Suchyta, E., Swanson, M., To, C., Vikram, V., 2026, MNRAS, 546, stag006, Biasing from galaxy trough and peak profiles with the DES Y3 redMaGiC galaxies and the weak lensing mass map
   Abstract

   We measure the correspondence between the distribution of galaxies and matter around troughs and peaks in the projected galaxy density, by comparing redMaGiC galaxies ($0.15< z<0.65$) to weak lensing mass maps from the Dark Energy Survey (DES) Y3 data release. We obtain stacked profiles, as a function of angle $\theta$, of the galaxy density contrast $\delta _{\rm g}$ and the weak lensing convergence $\kappa$, in the vicinity of these identified troughs and peaks, referred to as 'void' and 'cluster' superstructures. The ratio of the profiles depend mildly on $\theta$, indicating good consistency between the profile shapes. We model the amplitude of this ratio using a function $F(\boldsymbol{\eta }, \theta)$ that depends on cosmological parameters $\boldsymbol{\eta }$, scaled by the galaxy bias. We construct templates of $F(\boldsymbol{\eta }, \theta)$ using a suite of N-body (Gower Street) simulations forward-modelled with DES Y3-like noise and systematics. We discuss and quantify the caveats of using a linear bias model to create galaxy maps from the simulation dark matter shells. We measure the galaxy bias in three lens tomographic bins (near to far): $2.32^{+0.86}_{-0.27}, 2.18^{+0.86}_{-0.23}, 1.86^{+0.82}_{-0.23}$ for voids, and $2.46^{+0.73}_{-0.27}, 3.55^{+0.96}_{-0.55}, 4.27^{+0.36}_{-1.14}$ for clusters, assuming the best-fitting Planck cosmology. Similar values with $\sim 0.1\sigma$ shifts are obtained assuming the mean DES Y3 cosmology. The biases from troughs and peaks are broadly consistent, although a larger bias is derived for peaks, which is also larger than those measured from the DES Y3 $3\times 2$-point analysis. This method shows an interesting avenue for measuring field-level bias that can be applied to future lensing surveys.

6. Elmegreen, B., Hunter, D., Corbelli, E., 2026, ApJ, 997, 235, Pressure and Star Formation in LITTLE THINGS Dwarf Irregular Galaxies
   Abstract

   The surface densities of star formation, _SFR, in 24 dwarf irregular (dIrr) galaxies from the LITTLE THINGS survey are combined with gas surface densities and midplane pressures to examine the correlations found previously for spiral galaxies. The pressure is the weight of the disk inside the gas layer, including gas, stars, and dark matter, which usually dominates disk gravity in dIrrs. We compare the results to the outer part of M33, which has similar local properties but a slightly higher metallicity, enabling the detection of CO. All the data are convolved to the H I beam, but to study the effects of resolution, the galaxies are examined first with average radial profiles, and then with maps having 1 . 5 pixels and 244 pc pixels. The correlations are found to be independent of resolution from 24 to 424 pc. The average ratio of molecular to atomic surface density is estimated to be 0.23 0.1, from the H₂ surface density in M33 compared to the H I surface density at the same _SFR in the dIrrs. With this ratio, the average star formation rate per molecule is about the same for all the dIrrs, and a factor of 2 less than the rate in M33. The pressure in dIrrs is so low that CO is essentially a dense gas tracer, with the same surface density threshold at the low metallicities of dIrrs as HCN has in spiral galaxies. As a result, CO regions in dIrrs should be strongly self-gravitating.

7. Farrah, D., Ejercito, K., Efstathiou, A., Leisawitz, D., Engholm, A., Shivaei, I., Bonato, M., Clements, D., Petty, S., Pitchford, L., Varnava, C., Afonso, J., Gruppioni, C., Hatziminaoglou, E., Hoffman, A., Lacy, M., Matthews, B., Nixon, C., Pearson, C., Ricketti, B., Rigopoulou, D., Robinson, L., Spencer, L., Wang, L., Sanders, D., van Belle, G., 2026, ApJ, 997, 150, How Accurately Can Obscured Galaxy Luminosities Be Measured Using Spectral Energy Distribution Fitting of Near- through Far-infrared Observations?
   Abstract

   Infrared-luminous galaxies are important sites of stellar and black hole mass assembly at most redshifts. Their luminosities are often estimated by fitting spectral energy distribution (SED) models to near- to far-infrared data, but the dependence of these estimates on the data used is not well understood. Here, using observations simulated from a well-studied local sample, we compare the effects of wavelength coverage, signal-to-noise ratio, flux calibration, angular resolution, and redshift on the recovery of starburst, active galactic nucleus (AGN), and host luminosities. We show that the most important factors are wavelength coverage that spans the peak in a SED, and dense wavelength sampling. Such observations recover starburst and AGN infrared luminosities with systematic bias below 20%. Starburst luminosities are best recovered with far-infrared observations, while AGN luminosities are best recovered with near- and mid-infrared observations, though the recovery of both are enhanced with near/mid-infrared and far-infrared observations, respectively. Host luminosities are best recovered with near/far-infrared observations, but are usually biased low, by 20%. The recovery of starburst and AGN luminosity is enhanced by observing at high angular resolution. Starburst-dominated systems show more biased recovery of luminosities than do AGN-dominated systems. As redshift increases, far-infrared observations become more capable and mid-infrared observations less capable at recovering luminosities. Our results highlight the transformative power of a far-infrared instrument with dense wavelength coverage, from tens to hundreds of microns, for studying infrared-luminous galaxies. We tabulate estimates of systematic bias and random error for use with JWST and other observatories.

8. Zhang, Q., Battams, K., 2026, PASP, 138, 014403, Rapid Brightening of 3I/ATLAS Ahead of Perihelion
   Abstract

   Interstellar comet 3I/ATLAS has been approaching its 2025 October 29 perihelion while opposite the Sun from Earth, hindering ground-based optical observations over the preceding month. However, this geometry placed the comet within the fields of view of several space-based solar coronagraphs and heliospheric imagers, enabling its continued observation during its final approach toward perihelion. We report photometry from STEREO-A's SECCHI HI1 and COR2, SOHO's LASCO C3, and GOES-19's CCOR-1 instruments in 2025 SeptemberOctober, which show a rapid rise in the comet's brightness scaling with heliocentric distance r as r^7.51.0. CCOR-1 also resolves the comet as an extended source with an apparent coma of 4' in diameter. Furthermore, LASCO/CCOR-1 color photometry shows the comet to be distinctly bluer than the Sun, consistent with gas emission contributing a substantial fraction of the visible brightness near perihelion.

9. Micheli, M., Devogele, M., Denneau, L., Ryan, E., Ryan, W., Pravec, P., Hornoch, K., Kucakova, H., Fatka, P., Brucker, M., Lejoly, C., Moskovitz, N., Granvik, M., Gray, Z., Fedorets, G., Djupvik, A., Fuls, C., Rankin, D., Wierzchos, K., Gray, B., Lister, T., Wainscoat, R., Weryk, R., Hainaut, O., Spoto, F., Veres, P., Rivkin, A., Holler, B., Burdanov, A., de Wit, J., Farnocchia, D., Rudawska, R., Alonso Peleato, E., Ocana, F., Tonry, J., Audenaert, J., Faggioli, L., Gianotto, F., Fenucci, M., Conversi, L., Moissl, R., 2026, JAnSc, 73, 8, Astrometric Follow-up of Near-Earth Asteroid 2024 YR₄ During a Torino Scale Level 3 Alert
   Abstract

   The discovery of 2024 YR₄ presented the planetary defense community with the most significant impact threat in almost two decades, reaching level 3 on the Torino scale. The community, now mature and well-organized, responded with a global observational effort. Astrometric measurements, forming the basis for orbital refinement and impact prediction, were a central component of this response. In this paper, we present the astrometric data collected by the international community, from the time of discovery until the object became too faint for all existing observational assets, including JWST. We also discuss the coordination role played by the International Asteroid Warning Network, and the importance of publicly available image archives to enable precovery searches.

10. Brasseur, C., Jardine, M., Daley-Yates, S., Donati, J., Morin, J., 2026, MNRAS, Electron Cyclotron Maser Emission from Ejected Stellar Prominences on V374 Peg
    Abstract

    We investigate a possible origin for bursty radio emission observed on the active M dwarf V374 Peg, combining data-driven magnetic field modelling with archival radio light curves. We examine whether stellar prominence ejection can plausibly account for the observed radio bursts that have been attributed to electron cyclotron maser (ECM) emission. Our analysis shows that ejected prominences can produce the required energy range to drive the emission, and that modelled ECM visibility exhibits a rotational phase dependence consistent with the limited observational data (four observed bursts). The results support prominence ejection as a viable mechanism for ECM generation on V374 Peg and motivate further observational campaigns to constrain this process.

11. Hsieh, H., Usher, H., Lister, T., Chandler, C., Frissell, M., Thirouin, A., Sheppard, S., Micheli, M., Kelley, M., Holt, C., Gomez, E., Chatelain, J., Greenstreet, S., 2026, RNAAS, 10, 1, Early Observations of New Active Asteroid 2025 VZ₈
    Abstract

    We report observations of main-belt asteroid 2025 VZ₈ using multiple telescopes from UT 2025 November 24 to UT 2025 December 23 that confirm the presence of visible comet-like activity. These observations were motivated by online reports that an abrupt brightening event may have led to the object's discovery on UT 2025 November 9. In all observations reported here, the object displays a tapered tail approximately 3 long aligned with the antisolar direction. The object has an asteroidal Tisserand parameter value with respect to Jupiter (T_J = 3.371), and is thus considered an active asteroid. We measure an average apparent r' -band magnitude of m_r 21.6 mag over the reported observing period. Due to the sudden appearance of activity far from perihelion, we suggest that the activity is more likely due to an impact or rotational destabilization, rather than sublimation.

12. Prat, J., Gatti, M., Doux, C., Pranav, P., Chang, C., Jeffrey, N., Whiteway, L., Anbajagane, D., Sugiyama, S., Thomsen, A., Alarcon, A., Amon, A., Bechtol, K., Bernstein, G., Campos, A., Chen, R., Choi, A., Davis, C., DeRose, J., Dodelson, S., Eckert, K., Elvin-Poole, J., Everett, S., Ferte, A., Gruen, D., Huff, E., Harrison, I., Herner, K., Jarvis, M., Kuropatkin, N., Leget, P., MacCrann, N., McCullough, J., Myles, J., Navarro-Alsina, A., Pandey, S., Raveri, M., Rollins, R., Roodman, A., Sanchez, C., Secco, L., Sheldon, E., Shin, T., Troxel, M., Tutusaus, I., Varga, T., Yanny, B., Yin, B., Zhang, Y., Zuntz, J., Abbott, T., Aguena, M., Allam, S., Andrade-Oliveira, F., Blazek, J., Bocquet, S., Brooks, D., Carretero, J., Carnero Rosell, A., Cawthon, R., De Vicente, J., Desai, S., da Silva Pereira, M., Diehl, H., Flaugher, B., Frieman, J., Garcia-Bellido, J., Gruendl, R., Gutierrez, G., Hinton, S., Hollowood, D., Honscheid, K., James, D., Kuehn, K., da Costa, L., Lahav, O., Lee, S., Marshall, J., Mena-Fernandez, J., Miquel, R., Mohr, J., Ogando, R., Plazas Malagon, A., Porredon, A., Samuroff, S., Sanchez, E., Santiago, B., Sevilla-Noarbe, I., Smith, M., Suchyta, E., Swanson, M., Thomas, D., To, C., Vikram, V., Walker, A., Weaverdyck, N., Weller, J., 2026, MNRAS, 545, staf2152, Dark Energy Survey Year 3 results: wCDM cosmology from simulation-based inference with persistent homology on the sphere
    Abstract

    We present cosmological constraints from Dark Energy Survey Year 3 (DES Y3) weak lensing data using persistent homology, a topological data analysis technique that tracks how features like clusters and voids evolve across density thresholds. For the first time, we apply spherical persistent homology to galaxy survey data through the algorithm TOPOS2, which is optimized for curved-sky analyses and HEALPIX compatibility. Employing a simulation-based inference framework with the Gower Street simulation suite specifically designed to mimic DES Y3 data properties we extract topological summary statistics from convergence maps across multiple smoothing scales and redshift bins. After neural network compression of these statistics, we estimate the likelihood function and validate our analysis against baryonic feedback effects, finding minimal biases (under $0.3\sigma$) in the $\Omega _\mathrm{m}-S_8$ plane. Assuming the wCold Dark Matter model, our combined Betti numbers and second moments analysis yields $S_8 = 0.821 \pm 0.018$ and $\Omega _\mathrm{m} = 0.304\pm 0.037$ constraints 70 per cent tighter than those from cosmic shear two-point statistics in the same parameter plane. Our results demonstrate that topological methods provide a powerful and robust framework for extracting cosmological information, with our spherical methodology readily applicable to upcoming Stage IV wide-field galaxy surveys.

12 publications and 49 citations in 2026.

12 publications and 49 citations total.