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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 5 December

Earth and Planetary Astrophysics

ExoNAMD: Leveraging the spin-orbit angle to constrain the dynamics of multiplanetary systems

A. Bocchieri, J. Zak and D. Turrini

Multiplanetary systems are excellent laboratories for studying the formation and evolution of exoplanets inside the same stellar environment. The number of known multiplanetary systems is expected to skyrocket with the advent of PLATO and the Roman space telescope. The spin-orbit angle is a key context information for the systems' dynamical history, and in recent years a growing number of planets had their spin-orbit angle measured, revealing a large diversity in orbital configurations, from well-aligned to polar, and even retrograde, orbits. Still, observers lack a robust tool to compare the dynamical state of different systems and to select the most suitable ones for future avenues of exploration, such as investigating the evolutionary pathways and their links to the atmospheric composition. Here, we present ExoNAMD, an open source code aimed at evaluating the dynamical state of multiplanetary systems via the Normalized Angular Momentum Deficit (NAMD) metric. The NAMD measures the deficit in angular momentum with respect to circular, co-planar orbits. It is normalized to compare systems with different architectures and provides a lower limit on the past dynamical excitation of the system. We find that using the spin-orbit angle parameter in the NAMD calculation (A-NAMD) improves the dynamical state's description, compared to using only the relative inclinations (R-NAMD). Comparison of A-NAMD and R-NAMD also yields powerful insights into the interplay between eccentricity and spin-orbit angle. ExoNAMD is a timely tool for easy and fast comparison of the myriad of exoplanetary systems to be discovered by PLATO and Roman, and to optimize the target selection and scientific output for future atmospheric characterization using ELTs, JWST, and Ariel.
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Earth and Planetary Astrophysics

Exploring Exoplanet Dynamics with JWST: Tides, Rotation, Rings, and Moons

Sarah C. Millholland and Joshua N. Winn

Although nearly 6,000 exoplanets are currently known, in most cases our knowledge is limited to a handful of the planet's orbital characteristics and bulk properties such as radius and mass. The James Webb Space Telescope (JWST) can expand our knowledge not only by probing exoplanet atmospheres, but also by measuring additional orbital and physical properties of exoplanets, thanks to its superior light-gathering power and measurement precision. Here, we describe the potential of JWST to unveil dynamical phenomena that were previously beyond our reach, such as tidal distortion and inflation, rotational flattening, planetary rings, and moons.
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Earth and Planetary Astrophysics

Formation of cold giant planets around late M dwarfs via core accretion and the fate of inner rocky worlds

Mariana Sanchez, Nienke van der Marel, Michiel Lambrechts et al. (+2 more)

Modeling the formation of cold giant planets around M dwarfs is difficult because their disks may not contain enough solids to form massive cores and because forming giants are expected to migrate inward through disk interactions. It is also unclear whether inner rocky planets can survive in systems hosting a cold giant, with implications for the habitability of close-in worlds. We investigated the conditions that allow giant planets to form at 1-3 au around a 0.1 M$_\odot$ star and explored when a close-in rocky planet can survive. We perform N-body simulations in which embryos grow through pebble and gas accretion in a disk with a local turbulent viscosity of $\alpha_t = 10^{-4}$. Planet-disk interactions are included using a prescription that triggers outward migration when the planet-to-star mass ratio ($q$) exceeds 0.002. We find that a cold giant can form even in a disk with an initial pebble mass of 6 M$_\oplus$ if the disk gas mass is 10$\%$ of the stellar mass. This requires a compact 20 au disk with a dense inner region set by $\alpha_g = 10^{-4}$, the assembly of a $\sim$5 M$_\oplus$ core within 1 Myr, and a disk lifetime of 10 Myr. A close-in rocky planet can survive if it reaches the inner cavity before the outer body becomes a giant. Thus, giant planet formation around very low-mass stars does not require high dust masses as previously thought. A combination of planet-planet collisions, efficient pebble accretion, and a long disk lifetime plays a key role in enabling the formation of cold giant planets with masses between those of Saturn and Jupiter.
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All authors Mariana Sanchez, Nienke van der Marel, Michiel Lambrechts, Sijme-Jan Paardekooper, Yamila Miguel

Astrophysics of Galaxies

On the Origin of Intracluster Light based on the High-resolution Simulation, NewCluster

Seyoung Jeon, Emanuele Contini, San Han et al. (+11 more)

Intracluster light (ICL) is a key component of galaxy clusters, with the potential to trace their dynamical assembly histories and the underlying dark matter distribution. Despite these prospects, its faint nature makes a consensus on its origin or population properties difficult to achieve, both in observations and simulations. In the hope of finding a breakthrough, we utilize the ongoing high-resolution cluster simulation, NewCluster. By classifying billions of particles in and around the cluster with a rigorous tracking procedure, we find that the majority of the ICL originates from satellites, including surviving and disrupted galaxies. Another notable finding is that the preprocessed component follows the density profile of dark matter better than the other components and has distinctive properties: old age, low metallicity, and enhanced $\alpha$-element abundance. We further investigate the orbital dynamics, and our results demonstrate that the stripped fraction of satellites is primarily determined by the time since infall and the pericenter distance. By linking the demographic, chemical, and orbital properties of ICL stars to their origins, this work proposes a quantitative approach for tracing the assembly history of galaxy clusters from the ICL.
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All authors Seyoung Jeon, Emanuele Contini, San Han, Jinsu Rhee, Garreth Martin, Juhan Kim, Jaehyun Lee, Taysun Kimm, Christophe Pichon, Gyeong-Hwan Byun, Yohan Dubois, Corentin Cadiou, J. K. Jang, Sukyoung K. Yi

Cosmology and Nongalactic Astrophysics

Black hole merger rates for LISA and LGWA from semi-analytical modelling of light seeds

Jasbir Singh, Paola Severgnini, Vieri Cammelli et al. (+10 more)

With the upcoming space- and Moon-based gravitational-wave detectors, LISA and LGWA respectively, a new era of GW astronomy will begin with the possibility of detections of the mergers of intermediate-mass black holes (IMBHs) and supermassive black holes (SMBHs). We generate populations of synthetic black hole (BH) binaries with masses ranging from the intermediate ($10^3-10^5 M_\odot$) to the supermassive regime ($>10^5 M_\odot$), formed from the dynamical processes of merging halos and their residing galaxies, assuming that each galaxy is initially seeded with a single black hole at its centre. The aim is to estimate the rate of these BH mergers which could be detected by LISA and LGWA. Using PINOCCHIO cosmological simulation and a semi-analytical model based on GAEA, we construct a population of merging BHs by implementing a "light" seeding scheme and calculating the merging timescales using the Chandrasekhar prescription. We provide upper and lower limits of dynamical friction timescale by varying the mass of the infalling object to create "pessimistic" and "optimistic" merger rates respectively. We find that for our synthetic population of MBHs, both LGWA and LISA are able to detect more than $15$ binary IMBH mergers per year in the optimistic case, while in the pessimistic case less than $\sim5$ detections would be possible considering the entire lifetime of the detectors. For SMBHs, the rates are slightly lower in both cases. Most mergers below $z\approx4$ are detected in the optimistic case, although mergers beyond $z=8$ are also detectable at a lower rate. We find that LGWA is better suited for high-SNR IMBH detections at higher redshift, while LISA is more sensitive to massive SMBHs. Joint observations will probe the full BH mass spectrum and constrain BH formation and seeding models.
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All authors Jasbir Singh, Paola Severgnini, Vieri Cammelli, Alessandra De Rosa, Cristian Vignali, Fabio Rigamonti, Rosa Valiante, Pierluigi Monaco, Jonathan C. Tan, Lorenzo Battistini, Roberto Della Ceca, Jan Harms, Manali Parvatikar

Astrophysics of Galaxies

SHORES II: Multi-frequency Characterisation of the Sub-mJy Radio Population in FIR-selected Fields

Meriem Behiri, Marcella Massardi, Vincenzo Galluzzi et al. (+4 more)

We present a new deep multi-frequency radio survey of two extragalactic fields observed with the Australia Telescope Compact Array (ATCA) as part of the SHORES project (Serendipitous H-ATLAS fields Observations of Radio Extragalactic Sources). The observations, centred at 2.1, 5.5, and 9 GHz, cover the central 0.5 deg$^2$ of two Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) fields down to rms sensitivities of 9-17 $\mu$Jy$/$beam at 2.1 GHz, 28-39 $\mu$Jy/beam at 5.5 GHz and 38-61 $\mu$Jy/beam at 9 GHz. This setup allows us to investigate the spectral energy distributions (SEDs) of faint radio sources and probe the nature of the sub-mJy population. We extract and validate a robust catalogue of 489 sources at 2.1 GHz, 101 of which are also detected at 5.5 GHz. We perform a multi-frequency analysis of the radio number counts and derive the spectral indices of sources in the deep fields. The spectral index distribution of our sources peaks around $\alpha \sim -0.7$, consistent with synchrotron emission from the faint radio population. The number counts at 2.1 GHz are consistent with previous deep surveys and theoretical models, and provide a lower limit on the star-forming galaxy population, which is expected to dominate the faint end. The 5.5 GHz data offer new, direct constraints on the sub-mJy radio sky at higher frequencies. By cross-matching with the H-ATLAS catalogue, we identify a sample of sources with far-infrared (FIR) counterparts and explore the far-infrared-radio correlation (FIRRC). The sources with $q_{FIR} \geq 1.69$ exhibit radio spectral indices typical of star-forming galaxies. Furthermore, we identify a population of radio-only sources with similar indices that may correspond to high-redshift SFGs, lacking counterparts in the FIR survey due to its limited resolution and sensitivity.
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All authors Meriem Behiri, Marcella Massardi, Vincenzo Galluzzi, Marika Giulietti, Gayathri Gururajan, Isabella Prandoni, Andrea Lapi

Cosmology and Nongalactic Astrophysics

Generalized tension metrics for multiple cosmological datasets

Matías Leizerovich, Susana J. Landau and Claudia G. Scóccola

We introduce a novel estimator to quantify statistical tensions among multiple cosmological datasets simultaneously. This estimator generalizes the Difference-in-Means statistic, $Q_{\rm DM}$, to the multi-dataset regime. Our framework enables the detection of dominant tension directions in the shared parameter space. It further provides a geometric interpretation of the tension for the two- and three-dataset cases in two dimensions. According to this approach, the previously reported increase in tension between DESI and Planck from $1.9\sigma$ (DR1) to $2.3\sigma$(DR2) is reinterpreted as a more modest shift from $1.18\sigma^{\rm eff}$ (DR1) to $1.45\sigma^{\rm eff}$ (DR2). These new tools may also prove valuable across research fields where dataset discrepancies arise.
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Cosmology and Nongalactic Astrophysics

The THESAN project: Lyman-alpha intensity mapping of cosmic reionization

Mouza Almualla, Aaron Smith, Rahul Kannan et al. (+6 more)

Line Intensity Mapping (LIM) has garnered attention as a powerful cosmological probe, with next-generation instruments such as SPHEREx preparing to map the evolution of large-scale structure during the Epoch of Reionization (EoR). Lyman-alpha emission in the EoR is strongly shaped by resonant absorption from neutral hydrogen in the diffuse intergalactic medium (IGM), which transforms galactic sources into a low surface-brightness background. In this work, we leverage the state-of-the-art THESAN cosmological simulations to produce high-resolution theoretical predictions for future Lyman-alpha LIM studies, constructing continuous light cones for line-of-sight cosmological integrations. We assess the contributions of recombination, collisional excitation, and unresolved HII regions to the total Lyman-alpha spectral intensity. In addition, we explore the IGM in absorption at different redshifts using damping wing analysis. We produce channel maps exploring spatial fluctuations across redshift bands probe-able by LIM instruments. We find that the slope of the absorption-included Lyman-alpha fluctuation power spectrum at smaller scales (k > 10^(-2) 1/arcsec) steepens toward lower redshift, and that our emission-only Lyman-alpha power spectrum lies above the SPHEREx sensitivity, whereas the absorption-included signal is ~4 orders of magnitude lower–providing a conservative lower limit on inhomogeneity signatures and highlighting the importance of including resonant scattering in our model in the future. We also find that including outflows in a simple toy model boosts power by four orders of magnitude. We identify limitations in our analysis and propose next steps, including incorporating the effects of resonant Lyman-alpha scattering and line interlopers, as well as larger simulation volumes.
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All authors Mouza Almualla, Aaron Smith, Rahul Kannan, Lars Hernquist, Enrico Garaldi, Adam Lidz, Kevin Lorinc, Jennifer Yik Ham Chan, Mark Vogelsberger

Solar and Stellar Astrophysics

A Test of Substellar Evolutionary Models with High-Precision Ages from Asteroseismology and Gyrochronology for the Benchmark System HR 7672AB

Yaguang Li, Michael C. Liu, Trent J. Dupuy et al. (+35 more)

We present high-precision measurements for HR~7672AB, composed of a Sun-like (G0V) star and an L~dwarf companion. Three nights of precise (70 cm/s) radial velocity (RV) asteroseismology with the Keck Planet Finder clearly detect 5-minute oscillations from the primary HR~7672A, and modeling of the frequency spectrum yields an asteroseismic age of $1.87\pm0.65$~Gyr. We also determine a gyrochronological age of $2.58\pm0.47$~Gyr, and we combine these two results for a final age of $2.26\pm0.40$~Gyr. In addition, we obtained new RVs for HR~7672A and new astrometry for the companion HR~7672B. From a joint orbit fit, we measured a dynamical mass of $1.111\pm0.017$~$\text{M}_\odot$ for HR~7672A and $75.39\pm0.67$~$\text{M}_{\text{Jup}}$ for HR~7672B. This places the companion near the stellar/substellar boundary and thus particularly sensitive to differences in model predictions. The joint precision in host star age (18% uncertainty) and companion mass (0.9% uncertainty) makes HR~7672AB an exceptional substellar benchmark. Combined with the companion's luminosity, we use these measurements to test predictions from six brown dwarf cooling models. The best agreement occurs with the Chabrier et al. (2023) models, which incorporate a new equation of state, resulting in predictions that agree within $<$0.3$\sigma$ with all the observations. The other 5 sets of models agree at the 1–3$\sigma$ level depending on the particular test, and some models struggle to predict a sufficient low luminosity for HR~7672B at any age given its dynamical mass. We also detected a weak seismic signal in near-simultaneous TESS photometry of HR~7672A, with the resulting RV-to-photometry oscillation amplitude ratio consistent with solar values.
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All authors Yaguang Li, Michael C. Liu, Trent J. Dupuy, Daniel Huber, Jingwen Zhang, Daniel Hey, R.R. Costa, Jens Reersted Larsen, J. M. Joel Ong, Sarbani Basu, Travis S. Metcalfe, Yixiao Zhou, Jennifer van Saders, Timothy R. Bedding, Marc Hon, Hans Kjeldsen, Tiago L. Campante, Mário J. P. F. G. Monteiro, Mia Sloth Lundkvist, Mark Lykke Winther, Ashley Chontos, Nicholas Saunders, Theron W. Carmichael, Antonin Bouchez, Carlos Alvarez, Samuel A. U. Walker, Aldo G. Sepulveda, Howard Isaacson, Andrew W. Howard, Steven R. Gibson, Samuel Halverson, Kodi Rider, Arpita Roy, Ashley D. Baker, Jerry Edelstein, Chris Smith, Benjamin J. Fulton, Josh Walawender

Astrophysics of Galaxies

Globular clusters in OrbIT: complete dynamical characterisation of the globular cluster population of the Milky Way through updated orbital reconstruction

Michele De Leo, Manuela Zoccali, Julio Olivares-Carvajal et al. (+3 more)

In hierarchical structure formation, the content of a galaxy is determined both by its in-situ processes and by material added via accretions. Globular clusters in particular represent a window for the study of the different merger events that a galaxy underwent. Establishing the correct classification of in-situ and accreted tracers, and distinguishing the various different progenitors that contributed to the accreted population are important tools to deepen our understanding of galactic formation and evolution. Our aim is to refine our knowledge of the assembly history of the Milky Way by studying the dynamics of its globular cluster population and establishing an updated classification among in-situ objects and the different merger events identified. We used a custom built orbit integrator to derive precise orbital parameters, integrals of motions and adiabatic invariants for the globular cluster sample studied. By properly accounting for the rotating bar, which transforms the underlying model in a time-varying potential, we proceeded to a complete dynamical characterisation of the globular clusters. We present a new catalogue of clear associations between globular clusters and structures (both in-situ and accreted) in the Milky Way, and a full table of derived parameters. By using all dynamical information available, we were able to attribute previously unassociated or misclassified globular clusters to the different progenitors, including those responsible for the Aleph, Antaeus, Cetus, Elqui, and Typhon merger events. By using a custom built orbit integrator and properly accounting for the time-varying nature of the Milky Way potential, we have shown the depth of information that can be extracted from a purely dynamical analysis of the globular clusters of our Galaxy.
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All authors Michele De Leo, Manuela Zoccali, Julio Olivares-Carvajal, Belén Acosta-Tripailao, Felipe Gran, Rodrigo Contreras-Ramos

High Energy Astrophysical Phenomena

A Song of Lines and Winds: Tracing the Signatures of AGN Outflows in X-rays

M. Laurenti, F. Tombesi, P. Condò et al. (+14 more)

Ultra-fast outflows (UFOs) are highly ionized, mildly relativistic winds seen in the X-ray spectra of active galactic nuclei (AGN) and are thought to contribute to AGN feedback and galaxy evolution. We investigate UFO signatures by analyzing a broad collection of published detections. Our final sample comprises 122 robust (> 2$\sigma$) UFO detections in 57 AGN, spanning wide ranges in redshift, luminosity, black hole mass, and Eddington ratio. By combining phenomenological and photoionization modeling of the absorption features, we characterize empirical correlations among UFO properties. We find that line width, equivalent width, and outflow velocity are positively correlated, indicating that the broadest and strongest absorption lines trace the fastest winds, although the $\upsilon_\mathrm{out} - \sigma$ trend is comparatively weak. The large inferred velocity dispersions, often exceeding the uncertainty on the centroid velocity, must be included when estimating wind energetics and scaling relations. From the velocity constraints we derive lower limits on the launching radii, finding a minimum distance consistent with the innermost stable circular orbit of a weakly or non-rotating Schwarzschild black hole. We also assess for the first time how UFO properties depend on AGN class: differences between Seyferts and quasars, bridged by narrow-line Seyfert 1 galaxies, appear to be driven mainly by black hole mass and luminosity. The observed co-variation of velocity, width, and equivalent width supports a picture of clumpy, multi-component winds propagating through a thermally unstable multiphase medium within the chaotic cold accretion (CCA) cycle, and is consistent with both magnetically and line-driven acceleration. High-resolution X-ray spectroscopy with missions such as XRISM and NewAthena will be crucial to resolve the structure, kinematics, and physical origin of these flows.
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All authors M. Laurenti, F. Tombesi, P. Condò, M. Gaspari, F. Nicastro, E. Torresi, A. Luminari, E. Piconcelli, L. Zappacosta, K. Fukumura, G. Lanzuisi, R. Serafinelli, M. Dadina, M. Cappi, R. Middei, F. Arevalo Gonzalez, F. Di Salvo

Astrophysics of Galaxies

A Galactic Transformation – Understanding the SMC's Structural and Kinematic Disequilibrium

Himansh Rathore, Gurtina Besla, Roeland P. van der Marel et al. (+1 more)

The SMC is in disequilibrium. Gas line-of-sight (LoS) velocity maps show a gradient of $60-100$ km s$^{-1}$, generally interpreted as a rotating gas disk consistent with the Tully-Fisher relation. Yet, the stars don't show rotation. Despite a small on-sky extent ($\sim4$ kpc), the SMC exhibits a large ($\sim10$ kpc) LoS depth, and the stellar photometric center is offset from the HI kinematic center by $\sim$1 kpc. With N-body hydrodynamical simulations, we show that a recent ($\sim$100 Myr ago) SMC-LMC collision (impact parameter $\sim2$ kpc) explains the observed SMC's internal structure and kinematics. The simulated SMC is initialized with rotating stellar and gaseous disks. Post-collision, the SMC's tidal tail accounts for the large LoS depth. The SMC's stellar kinematics become dispersion dominated ($v/\sigma\approx0.2$), with radially outward motions at $R>2$ kpc, and a small ($<10$ km s$^{-1}$) remnant rotation at $R<2$ kpc, consistent with observations. Post-collision gas kinematics are also dominated by radially outward motions, without remnant rotation. Hence, the observed SMC's gas LoS velocity gradient is due to radial motions as opposed to disk rotation. Ram pressure from the LMC's gas disk during the collision imparts $\approx30$ km s$^{-1}$ kick to the SMC's gas, sufficient to destroy gas rotation and offset the SMC's stellar and gas centers. Our work highlights the critical role of group processing through galaxy collisions in driving dIrr to dE/dSph transformation, including the removal of gas. Consequently, frameworks that treat the SMC as a galaxy in transformation are required to effectively use its observational data to constrain interstellar medium and dark matter physics.
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All authors Himansh Rathore, Gurtina Besla, Roeland P. van der Marel, Nitya Kallivayalil

Astrophysics of Galaxies

Lyman-$\alpha$ Visibility During the Epoch of Reionization: Combining JWST FRESCO Grism Data with Keck Archival Spectroscopy

Ecaterina Leonova, Rohan P. Naidu, Pascal A. Oesch et al. (+5 more)

The visibility of Lyman-$\alpha$ emission at $z>7$ provides crucial insights into the reionization process and the role of galaxies in shaping the ionized intergalactic medium. Using JWST FRESCO data, we investigate the environments of Lyman-$\alpha$ emitters (LAEs) in the GOODS-N and GOODS-S fields by identifying [OIII] emitters and analyzing their large-scale distribution. Using the FRESCO redshifts, we recover eight new LAEs from archival Keck/MOSFIRE observations at $z=7.0-7.7$, including a potential AGN candidate at $z \sim 7.2$. Complemented by six literature LAEs, our sample consists of 14 LAEs in total, all of which are [OIII] emitters except for one very faint source not detected by FRESCO. We define seven groups of [OIII] emitters centered around the brightest LAEs and find that these bright LAEs do not reside in more overdense environments than the average galaxy population. The overdensity parameters for LAEs and [OIII] emitters without Lyman-$\alpha$, calculated for sources with $\mathrm{M_{UV}<-19.5}$ to ensure completeness, are similar, indicating that overdensities alone cannot fully explain Lyman-$\alpha$ visibility. While LAEs have slightly higher recent star formation (SFR$_{10}$/SFR$_{50} \approx 1.3\times$) and [OIII] EW ($\approx1.5\times$), they show no significant differences from [OIII] emitters in UV slope ($\beta$), UV magnitude ($\mathrm{M_{UV}}$), or stellar mass ($\log_{\mathrm{M}_{\star}}$). Our results suggest that other factors may contribute to the observability of Lyman-$\alpha$ emission. Future spectroscopic surveys with broader wavelength coverage and more complete sampling will be crucial for refining our understanding of reionization.
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All authors Ecaterina Leonova, Rohan P. Naidu, Pascal A. Oesch, Gabriel Brammer, Jorryt Matthee, Romain A. Meyer, Daniel Schaerer, Mengyuan Xiao

Astrophysics of Galaxies

The quenched fraction of satellites around simulated Milky Way-mass galaxies

Francisco J. Mercado, Devontae C. Baxter, M. Katy Rodriguez Wimberly et al. (+7 more)

We compare satellite quenched fractions across three cosmological simulation suites (FIREbox, the FIRE-2 zoom-ins, and IllustrisTNG50) and observational datasets from SAGA, ELVES, and the combined satellite population of the Milky Way and M31. To enable consistent comparisons, we select Milky Way-mass hosts with $M_{\rm halo} = 10^{11.9}$ - $10^{12.2} \, M_{\odot}$ and satellites with stellar masses of $10^7$ - $10^{10} \, M_{\odot}$, applying nearly uniform radial selections and a common quenching definition. All three simulations reproduce the strong observed trend that lower-mass satellites are more likely to be quenched, closely matching the stellar mass dependence seen in SAGA, ELVES, and the Milky Way and M31 system. This agreement indicates that the mass dependence of satellite quenching is a robust outcome of contemporary galaxy formation models. Radial trends, however, show greater diversity. SAGA and ELVES exhibit gently declining quenched fractions with projected distance, consistent with stronger quenching at small radii. TNG50 most closely matches this behavior, while FIREbox remains broadly consistent with a weak radial trend within uncertainties. The FIRE-2 zoom-ins show suppressed quenched fractions at small projected distances, driven primarily by their paired MW-M31 analogs. We show that this discrepancy is not explained by host environment alone, but instead reflects atypical satellite populations in the paired systems, where star-forming and quenched satellites occupy distinct spatial distributions. Overall, our results demonstrate that stellar mass-quenched fraction trends are robust across simulations and observations, while radial trends are more sensitive to the detailed properties and distributions of satellite populations
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All authors Francisco J. Mercado, Devontae C. Baxter, M. Katy Rodriguez Wimberly, Jorge Moreno, Coral Wheeler, Pratik Gandhi, Andrew Wetzel, Robert Feldmann, Lucas Tortora, Jenna Samuel

Earth and Planetary Astrophysics

An Ancient Brown Dwarf Transiting a Metal-Poor Thick Disk Star

Jéa Adams Redai, Vedant Chandra, Samuel W. Yee et al. (+20 more)

We report the discovery of TOI-7019b, the first transiting brown dwarf (BD) known to orbit a star that is part of the Milky Way's ancient thick disk, as defined chemically ([Fe/H] $= -0.79 \pm 0.05$ dex, [$\alpha$/Fe] $= +0.26 \pm 0.05$ dex, [M/H] $= -0.59 \pm 0.06$ dex) and kinematically ($v_{\perp} \approx 150 \pm 1$ km s$^{-1}$). We estimate a system age $\tau = 12 \pm 2$ Gyr by fitting the host star's spectrum and spectral energy distribution to alpha-enhanced isochrones, and independently using the age-metallicity relation of the thick disk. This makes TOI-7019 by far the most metal-poor and ancient BD host known to date. We measure a BD mass of $61.3 \pm 2.1$ $M_{\rm J}$ and radius of $0.82 \pm 0.02$ $R_{\rm J}$ from a joint analysis of transit photometry and radial velocity measurements, along with an orbital period of $48.2592 \pm 0.0001$ days and an orbital eccentricity of $0.403 \pm 0.002$. The measured radius appears $12.3\% \pm 2.8\%$ larger than predicted relative to standard evolutionary models for old, metal-poor brown dwarfs, hinting at missing physics like the magnetic inhibition of convection. TOI-7019b lowers the probed metallicity regime for transiting BDs by over a factor of two, making it a benchmark system to test evolutionary models in the low-metallicity regime. Future measurements of TOI-7019b's atmosphere will test whether a brown dwarf's atmospheric composition tracks its host star's abundances, as expected for binary-like co-formation.
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All authors Jéa Adams Redai, Vedant Chandra, Samuel W. Yee, Victoria DiTomasso, Sean Andrews, Karin Öberg, Rebecca Woody, David W. Latham, Allyson Bieryla, Samuel N. Quinn, David Charbonneau, Theron W. Carmichael, Chih-Chun Hsu, Noah Vowell, Jason J. Wang, Sebastian Zieba, Paul Benni, Karen A. Collins, David R. Ciardi, Julian van Eyken, William Fong, Michael B. Lund, Andrei M. Tatarnikov

Astrophysics of Galaxies

Do Low-Mass, Low-Luminosity AGNs Deviate from the Quasar Main Sequence?

Himanshu Sharma, Vivek Kumar Jha, Hum Chand et al. (+1 more)

We present a comprehensive spectroscopic and variability-based characterisation of a sample of low-luminosity active galactic nuclei (AGNs) hosting low mass black holes, identified by $H\beta$ full width at half maximum (FWHM) $< 2200$ km s$^{-1}$. While the narrow line widths are consistent with the formal definition of narrow-line Seyfert 1 (NLSy1) galaxies, the broader accretion and emission properties reveal key distinctions. The sample exhibits sub-Eddington accretion rates (median $\log R_{Edd} \approx -0.68$) and comparatively weak FeII emission (median $R_{FeII} \approx 0.61$), in contrast to the strong FeII strengths and high Eddington ratios characteristic of classical NLSy1s. Optical variability amplitudes, derived from Zwicky Transient Facility (ZTF) light curves, are similar to those typically seen in Seyfert 1 galaxies, with a median $\log(\sigma) \approx -0.68$, suggesting the AGN component's significant contribution to variability. In the optical plane of the 4D Eigenvector 1 (4DE1) parameter space, these sources occupy a distinct locus in the low-$R_{FeII}$, low-$R_{Edd}$ regime, suggesting a physically distinct accretion state. Our findings indicate that this population may represent a low-accretion analogue within the broader narrow-line AGN family, offering new insights into black hole growth at low mass scales.
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All authors Himanshu Sharma, Vivek Kumar Jha, Hum Chand, Swayamtrupta Panda

Solar and Stellar Astrophysics

SN 2024afav: A Superluminous Supernova with Multiple Light Curve Bumps and Spectroscopic Signatures of Circumstellar Interaction

Harsh Kumar, Peter K. Blanchard, Edo Berger et al. (+8 more)

We present a comprehensive optical and near-infrared spectroscopic study of SN 2024afav - a hydrogen-poor superluminous supernova (SLSN-I) that peaks at $\approx$ -20.7 mag and exhibits an unusual multi-bumped light curve. Our spectroscopic observations, spanning phases of -14 to +160 d, reveal several unusual features: (i) a narrow (1,800 km s$^{-1}$) and blueshifted (11,000 km s$^{-1}$) absorption from H$\alpha$ starting at +20 d; (ii) persistent optical and NIR He I lines at all available phases, showing double absorption structure in NIR spectra at +23 d, with a high velocity component at a similar velocity to H$\alpha$; (iii) early appearance of nebular [O III] emission starting at $\approx$ +50 d; and (iv) strong [O II] + [Ca II] 7300 Å emission complex starting at $\approx$ +110 d. These unusual features, and their onset at the time of the light curve bumps, provide compelling evidence of circumstellar interaction between the SN ejecta and a nearby hydrogen-rich shell, as well as the presence of helium in both the outer layers of the progenitor star and in the circumstellar medium. A comparison of SN 2024afav to other SLSNe-I showing bumpy light curves and similar spectral properties (PTF10hgi, SN 2017egm, SN 2019hge), points to a rare sub-group of SLSNe-I in which CSM interaction provides an important modulation to the energy input.
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All authors Harsh Kumar, Peter K. Blanchard, Edo Berger, Wasundara Athukoralalage, Daichi Hiramatsu, Sebastian Gomez, Moira Andrews, K. Azalee Bostroem, Joseph R. Farah, D. Andrew Howell, Curtis McCully

High Energy Astrophysical Phenomena

Revealing the accelerating wind in the inner region of the colliding-wind binary WR 112

John D. Monnier, Yinuo Han, Michael F. Corcoran et al. (+17 more)

Colliding winds in massive binaries generate X-ray-bright shocks, synchrotron radio emission, and sometimes even dusty "pinwheel" spirals. We report the first X-ray detections of the dusty WC+O binary system WR 112 from Chandra and Swift, alongside 27 years of VLA/ATCA radio monitoring and new diffraction-limited Keck images. Because we view the nearly circular orbit almost edge-on, the colliding-wind zone alternates between heavy Wolf-Rayet wind self-absorption and a near-transparent O-star wind foreground each 20-yr orbit, producing phase-locked radio and X-ray variability. This scenario leads to a prediction that the radio spectral index is flatter from a larger non-thermal contribution around the radio intensity maximum, which is indeed observed. Existing models that assume a single dust-expansion speed fail to reproduce the combined infrared geometry and radio light curve. Instead, we require an accelerating post-shock flow that climbs from near-stationary to ~1350 km/s in about one orbital cycle, naturally matching the infrared spiral from about 5" down to within 0.1", while also fitting the phase of the radio brightening. These kinematic constraints supply critical boundary conditions for future hydrodynamic simulations, which can link hot-plasma cooling, non-thermal radio emission, X-ray spectra, and dust formation in a self-consistent framework. WR 112 thus joins WR 140, WR 104, and WR 70-16 (Apep) as a benchmark system for testing colliding-wind physics under an increasingly diverse range of orbital architectures and physical conditions.
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All authors John D. Monnier, Yinuo Han, Michael F. Corcoran, Sanne Bloot, Joseph R. Callingham, William Danchi, Philip G. Edwards, Lincoln Greenhill, Kenji Hamaguchi, Matthew J. Hankins, Ryan Lau, Jon M. Miller, Anthony F. J. Moffat, Garreth Ruane, Christopher M. P. Russell, Anthony Soulain, Samaporn Tinyanont, Peter Tuthill, Jason J. Wang, Peredur M. Williams

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Investigating all-sky Frequency Hough performances for neutron stars

Martina Di Cesare, Pia Astone, Rosario De Rosa et al. (+3 more)

Between the estimated population of Neutron Stars (NSs) and the actual number present in the catalogs, there is a huge gap: O(10$^{8-9}$) vs O(10$^3$). Among the different search techniques for Continuous gravitational waves (CWs), the all-sky could help to reduce the discrepancy. We focus on the all-sky CW pipeline Frequency Hough (FH), which operates without prior knowledge of the source parameters ($f,\dot{f}, \lambda, \beta$). Here, we present a Machine Learning strategy, diverging from the standard follow-up(FU) of the FH pipeline. We study the performance with real interferometer data, until reaching $h$ value subthreshold for the standard FU procedure ($CR_{thr}=5$), with encouraging classification results.
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All authors Martina Di Cesare, Pia Astone, Rosario De Rosa, David Keitel, Cristiano Palomba, Marco Serra

Instrumentation and Methods for Astrophysics

Removing correlated noise stripes from the Nancy Grace Roman Space Telescope survey images

Katherine Laliotis, Christopher M. Hirata, Emily Macbeth et al. (+1 more)

Weak gravitational lensing has emerged as a powerful tool for investigating the matter distribution in the Universe and how it has evolved over cosmic time. The Wide Field Instrument (WFI) on the Nancy Grace Roman Space Telescope (Roman) will deliver some of the highest precision measurements of weak lensing ever made. Since weak lensing is based on statistics of faint sources, it can be biased by even tiny instrument systematics, including correlated read noise. Previous works have shown the infrared detectors used in the Roman WFI show correlations in their noise fields at a level significant for weak lensing measurements, even after application of standard reference pixel corrections; of particular concern is 1/f noise, which appears as horizontal banding in the detector frame. In this paper, we present imDestripe: a new Python module utilizing the multiple roll angles in Roman's observing strategy and linear algebra techniques to remove correlated noise stripes from observed images. We test imDestripe in a hybrid simulation by combining real noise realizations (from darks taken during ground testing) with simulated images of the astronomical scene, and find that the power spectrum of the banding can be suppressed by factors of 10–30 on large scales. We briefly discuss plans for further development of imDestripe in the context of the WFI pipeline.
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All authors Katherine Laliotis, Christopher M. Hirata, Emily Macbeth, Kaili Cao

Solar and Stellar Astrophysics · Cross-listed from nucl-ex

Constraining r-process nucleosynthesis via enhanced accuracy neutron-capture experiments

C. Domingo-Pardo, C. Lederer-Woods and A. Mengoni

The isotopic abundances of r-process elements in the solar system are traditionally derived as residuals from the subtraction of s-process contributions from total solar abundances. However, the uncertainties in s-process nucleosynthesis – particularly those arising from Maxwellian Averaged Cross Sections (MACS) – propagate directly into the r-process residuals, affecting their reliability. Building upon the seminal work of Goriely (1999), who introduced a multi-event s-process model to quantify these uncertainties, we revisit the problem using a simplified yet effective approach. By assuming that the relative uncertainty in s-process isotopic abundances scales linearly with the MACS uncertainties from data libraries (KADoNiS), we identify a subset of isotopes for which the r-process residuals remain significantly uncertain. Using updated solar abundances (Lodders 2025) and s-process contributions from Bisterzo et al. (2014), we present a short list of isotopes that are prime candidates for improved (n,g) measurements at CERN n_TOF in the near future. Our analysis provides a practical framework for prioritizing future experimental efforts that will profit from upgrades and enhancements of the n_TOF facility. It also highlights the need to revisit key neutron-capture cross sections to refine our understanding of the r-process isotopic abundance pattern, commonly used as a benchmark in stellar models of explosive nucleosynthesis.
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Earth and Planetary Astrophysics

Transformation of orientation and rotation angles of synchronous satellites: Application to the Galilean moons

Marie Yseboodt and Rose-Marie Baland

The orientation and rotation of a synchronous satellite can be referred to both its Laplace plane and the ICRF equatorial plane, in terms of Euler angles or spin axis Cartesian coordinates and Earth equatorial coordinates, respectively. We computed second-order analytical expressions to make the transformation between the two systems and applied them to the Galilean satellites (Io, Europa, Ganymede, and Callisto). If one term of the spin axis Cartesian coordinates series is dominant, trigonometric series can be generated for the inertial and orbital obliquities, node longitude and offset with respect to the Cassini plane. Since the transformation does not require any fit of amplitudes and frequencies on numerical series, the physical meaning of the frequencies is preserved from the input series and the amplitudes can be directly related to the geophysical parameters of interest. We provide tables for the coordinates and angles' series assuming that the satellites are entirely solid, and considering two different orbital theories. The possible amplitude ranges for the main terms are also examined in the case where a liquid layer is assumed in the interior model. We use our transformation method to propose an updated IAU WG solution which would result in an improvement with respect to zero obliquity models used so far. This method will also be useful for the interpretation of future Earth-based radar observations or JUICE data.
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Astrophysics of Galaxies

ALMAGAL VI. The spatial distribution of dense cores during the evolution of cluster-forming massive clump

E.Schisano, S.Molinari, A.Coletta et al. (+51 more)

High-mass stars and star clusters form from the fragmentation of massive dense clumps driven by gravity, turbulence, and magnetic fields. The ALMAGAL project observed $\sim1000$ clumps at $\sim$1000\,au resolution, enabling a statistically significant characterization of this process across a large range of clump physical parameters and evolutionary stages. In this work, we investigated the spatial distribution of dense cores in the 514 massive, potentially cluster-forming, clumps hosting at least 4 cores, to trace fragmentation's initial conditions and early evolution. We used quantitative descriptors, evaluated against the clump bolometric luminosity-to-mass ratio as an indicator of evolution. Core separations were measured with the minimum spanning tree method (MST) and compared with the Jeans gravitational fragmentation theory. We used the $Q$ parameter and the mass segregation ratio, $\Lambda_{MSR}$, to evaluate whether cores have specific arrangements or differences depending on their masses. ALMAGAL cores are usually arranged in elliptical groups with an axis ratio $e\sim2.2$, but $e\geq$5 is also observed. A single characteristic core separation per clump is found in $\sim76$% of cases, but signatures of multiple fragmentation lengths not rare. Typical core separations are compatible with the clump-averaged thermal Jeans length, $\lambda^{th}_{J}$, though a population, typical of low-fragmented/young clumps, has wider separations with $l\approx3\times\lambda^{th}_{J}$. The core separation decreases on average from $l\sim22000$ au in younger systems to $l\sim7000$ au in more evolved ones. Cores are typically distributed in fractal-type subclusters, with centrally concentrated patterns appearing only at later stages, but without a progressive evolutionary transition. Finally, mass segregation is found in 110 systems, with its occurrence increasing with evolution.
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All authors E.Schisano, S.Molinari, A.Coletta, D.Elia, P.Schilke, A.Traficante, Á.Sanchez-Monge, H.Beuther, M.Benedettini, C.Mininni, R.S.Klessen, J.D.Soler, A.Nucara, S.Pezzuto, F.van der Tak, P.Hennebelle, M.T.Beltrán, L.Moscadelli, K.L.J.Rygl, P.Sanhueza, P.M.Koch, D.C.Lis, R.Kuiper, G.A.Fuller, A.Avison, L.Bronfman, U.Lebreuilly, T.Möller, T.Liu, V.-M.Pelkonen, L.Testi, Q.Zhang, T.Zhang, A.Ahmadi, J.Allande, C.Battersby, J.Wallace, C.L.Brogan, S.Clarke, F.De Angelis, F.Fontani, P.T.P.Ho, T.R.Hunter, B.Jones, K.G.Johnston, P.D.Klaassen, S.J.Liu, S.-Y.Liu, Y.Maruccia, A.J.Rigby, Y.-N.Su, Y.Tang, S.Walch, H.Zinnecker

Astrophysics of Galaxies

Learning the Cosmic Web: Graph-based Classification of Simulated Galaxies by their Dark Matter Environments

Dakshesh Kololgi, Krishna Naidoo, Amelie Saintonge et al. (+1 more)

We present a novel graph-based machine learning classifier for identifying the dark matter cosmic web environments of galaxies. Large galaxy surveys offer comprehensive statistical views of how galaxy properties are shaped by large-scale structure, but this requires robust classifications of galaxies' cosmic web environments. Using stellar mass-selected IllustrisTNG-300 galaxies, we apply a three-stage, simulation-based framework to link galaxies to the total (mainly dark) underlying matter distribution. Here, we apply the following three steps: First, we assign the positions of simulated galaxies to a void, wall, filament, or cluster environment using the T-Web classification of the underlying matter distribution. Second, we construct a Delaunay triangulation of the galaxy distribution to summarise the local geometric structure with ten graph metrics for each galaxy. Third, we train a graph attention network (GAT) on each galaxy's graph metrics to predict its cosmic web environment. For galaxies with stellar mass $\mathrm{>10^9 M_{\odot}}$, our GAT+ model achieves an accuracy of $85\,\%$, outperforming graph-agnostic multilayer perceptrons and graph convolutional networks. Our results demonstrate that graph-based representations of galaxy positions provide a powerful and physically meaningful way to infer dark matter environments. We plan to apply this simulation-based graph modelling to investigate how the properties of observed galaxies from the Dark Energy Spectroscopic Instrument (DESI) survey are influenced by their dark matter environments.
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All authors Dakshesh Kololgi, Krishna Naidoo, Amelie Saintonge, Ofer Lahav

Instrumentation and Methods for Astrophysics

Euclid Quick Data Release (Q1). From simulations to sky: Advancing machine-learning lens detection with real Euclid data

Euclid Collaboration: N. E. P. Lines, T. E. Collett, P. Holloway et al. (+300 more)

In the era of large-scale surveys like Euclid, machine learning has become an essential tool for identifying rare yet scientifically valuable objects, such as strong gravitational lenses. However, supervised machine-learning approaches require large quantities of labelled examples to train on, and the limited number of known strong lenses has lead to a reliance on simulations for training. A well-known challenge is that machine-learning models trained on one data domain often underperform when applied to a different domain: in the context of lens finding, this means that strong performance on simulated lenses does not necessarily translate into equally good performance on real observations. In Euclid's Quick Data Release 1 (Q1), covering 63 deg2, 500 strong lens candidates were discovered through a synergy of machine learning, citizen science, and expert visual inspection. These discoveries now allow us to quantify this performance gap and investigate the impact of training on real data. We find that a network trained only on simulations recovers up to 92% of simulated lenses with 100% purity, but only achieves 50% completeness with 24% purity on real Euclid data. By augmenting training data with real Euclid lenses and non-lenses, completeness improves by 25-30% in terms of the expected yield of discoverable lenses in Euclid DR1 and the full Euclid Wide Survey. Roughly 20% of this improvement comes from the inclusion of real lenses in the training data, while 5-10% comes from exposure to a more diverse set of non-lenses and false-positives from Q1. We show that the most effective lens-finding strategy for real-world performance combines the diversity of simulations with the fidelity of real lenses. This hybrid approach establishes a clear methodology for maximising lens discoveries in future data releases from Euclid, and will likely also be applicable to other surveys such as LSST.
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All authors Euclid Collaboration: N. E. P. Lines, T. E. Collett, P. Holloway, K. Rojas, S. Schuldt, R. B. Metcalf, T. Li, A. Verma, G. Despali, F. Courbin, R. Gavazzi, C. Tortora, B. Clément, N. Aghanim, B. Altieri, L. Amendola, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, H. M. Courtois, M. Cropper, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, X. Dupac, S. Dusini, A. Ealet, S. Escoffier, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, F. Finelli, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, E. Keihänen, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, M. Melchior, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, R. Nakajima, C. Neissner, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, C. Rosset, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, J. A. Schewtschenko, P. Schneider, T. Schrabback, A. Secroun, G. Seidel, S. Serrano, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, G. Zamorani, F. M. Zerbi, E. Zucca, M. Ballardini, M. Bolzonella, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, T. Castro, J. A. Escartin Vigo, L. Gabarra, J. García-Bellido, V. Gautard, S. Hemmati, M. Huertas-Company, J. Macias-Perez, R. Maoli, J. Martín-Fleitas, M. Maturi, N. Mauri, P. Monaco, M. Pöntinen, C. Porciani, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, G. Angora, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, E. Aubourg, L. Bazzanini, D. Bertacca, M. Bethermin, F. Beutler, A. Blanchard, L. Blot, M. Bonici, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, S. Conseil, A. R. Cooray, O. Cucciati, S. Davini, F. De Paolis, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, P.-A. Duc, V. Duret, M. Y. Elkhashab, A. Enia, Y. Fang, P. G. Ferreira, A. Finoguenov, A. Fontana, A. Franco, K. Ganga, T. Gasparetto, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, A. Gruppuso, M. Guidi, C. M. Gutierrez, A. Hall, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, M. Lattanzi, L. Legrand, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, M. Magliocchetti, A. Manjón-García, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, A. Montoro, C. Moretti, G. Morgante, S. Nadathur, K. Naidoo, P. Natoli, S. Nesseris, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, G. W. Pratt, S. Quai, M. Radovich, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, C. Tao, F. Tarsitano, G. Testera, R. Teyssier, S. Tosi, A. Troja, A. Venhola, D. Vergani, G. Vernardos, G. Verza, S. Vinciguerra, M. Walmsley, N. A. Walton, A. H. Wright

High Energy Astrophysical Phenomena

Differentially rotating neutron stars with dark matter cores

Lorenzo Cipriani, Violetta Sagun, Kalin V. Staykov et al. (+2 more)

Dark matter is expected to accumulate inside neutron stars, modifying the structure of isolated stars and influencing both the dynamics of binary mergers and the evolution of the resulting hypermassive remnants. Since differential rotation is the primary mechanism delaying the collapse of these remnants, understanding its behavior is crucial when assessing the impact of an embedded dark component. In this work, we extend the numerical code RNS to describe two gravitationally coupled fluids in differential rotation, with baryonic matter modeled by a realistic nuclear equation of state and dark matter represented as a self-interacting bosonic condensate. Within this framework, we construct equilibrium sequences for a representative differential rotation law, providing a basis to explore how dark matter may influence the global properties and rotational dynamics of binary neutron star remnants.
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All authors Lorenzo Cipriani, Violetta Sagun, Kalin V. Staykov, Daniela D. Doneva, Stoytcho S. Yazadjiev

Solar and Stellar Astrophysics

Asteroseismology of SPB stars: a comparison of forward asteroseismic modelling results from Kepler and TESS

L. J. A. Scott and D. M. Bowman

The slowly pulsating B (SPB) stars are a class of variable star with masses between about 3 and 8 M$_{\odot}$. Their gravity-mode pulsation frequencies are sensitive to the near-core structure, which makes them useful probes of rotation and mixing in the deep stellar interior. Time series photometry, such as from the Kepler and TESS space telescopes, allows the extraction of their pulsation frequencies and construction of period spacing patterns. Previously, samples of slowly pulsating B stars were observed by the Kepler mission and underwent forward asteroseismic modelling to retrieve stellar parameters such as mass, age and core mass. However, all of these stars have since been re-observed by the ongoing TESS mission with light curves that are usually shorter and non-continuous, resulting in more difficult frequency extraction and interpretation in terms of constructing period spacing patterns. In this paper we compare the results of forward asteroseismic modelling of a sample of SPB stars using intermittent TESS light curve data to those based on long-duration Kepler light curves. We show how in some cases that the masses and core masses derived from only a few sectors of TESS data agree well with the 4-yr Kepler mission results, despite the stars having far fewer significant pulsation frequencies in their TESS light curves. However, some stars yield incompatible results, emphasising the complexities in forward asteroseismic modelling of gravity-mode pulsators with sparsely sampled or short duration TESS light curves.
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Solar and Stellar Astrophysics

High-contrast L-band Integral Field Spectroscopy of HD 33632 Ab

Jordan M. Stone, Steve Ertel, Travis Barman et al. (+5 more)

We present LBTI/ALES 3.07-4.08 micron spectroscopic observations of HD~33632~Ab, a ~53 M_Jup directly imaged companion to an F8 star. Spectroscopic measurements of HD 33632 Ab now span 1-4 micron, and we perform the first spectroscopic analysis covering this full range. The data are compared to isolated brown dwarf template spectra, indicating that HD 33632 Ab is similar to L8/9 field brown dwarfs. Synthetic atmosphere model spectra from multiple model families are fit, with cloudy models providing the best fits, consistent with expectations for an L-dwarf. Evolutionary model predictions for the bulk properties of HD 33632 Ab are highly constrained by the precise dynamical mass found for the object. In particular, predictions for surface gravity are narrowly peaked, log(g)=5.21+/-0.05, and not dependent on the effects of clouds or cloud dispersion. We find significant tension between the surface gravities and object radii inferred from atmosphere model fits and those predicted by evolutionary models. We conclude with a comparison to the spectra of the HR 8799 c, d, and e, and emphasize the case that HD 33632 Ab, and other L/T transition directly imaged companions with constrained masses, will serve an essential role in understanding the complex physical processes governing the appearance of clouds in planetary atmospheres.
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All authors Jordan M. Stone, Steve Ertel, Travis Barman, Andrew J. I. Skemer, Jarron M. Leisenring, Philip M. Hinz, Charles E. Woodward, Michael F. Skrutskie

Astrophysics of Galaxies

A new Gaia census of OB associations within 1 kpc

Alexis L. Quintana, Nicholas J. Wright, Lilly A. Kormann et al. (+6 more)

OB associations are primordial tracers of star formation and Galactic structure. Originally defined about 80 years ago, their historical membership lists have been superseded thanks to the precise astrometry from ESA's Gaia's satellite. Recent studies have however been mostly focused on individual OB associations or limited by the coverage of spectroscopic surveys. In this paper, we exploit a complete census of $\sim$25,000 O- and B-type stars within 1 kpc of the Sun to produce a highly-reliable catalogue of 56 OB associations using the HDBSCAN clustering algorithm, increasing the number of known OB associations by a factor of two within this volume. We assess the validity of this catalogue by crossmatching our OB association members with other catalogues of OB associations, star clusters and young stellar groups, confirming the high-confidence of our census of OB associations. We characterize these OB associations physically (total initial stellar mass, number of OB stars, ...) and kinematically (velocity dispersion, linear expansion ages, ...). The majority of the OB associations (38 out of 56) exhibit a significant expansion pattern in at least one direction, including 12 in both plane-of-the-sky directions, though differences in expansion velocity suggest anisotropical expansion patterns. We compare the locations of these OB associations with superclouds and features in the local Milky Way such as the Radcliffe Wave and discuss the implications for star formation in the solar neighbourhood.
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All authors Alexis L. Quintana, Nicholas J. Wright, Lilly A. Kormann, João Alves, David Katz, Laia Casamiquela, Paola Di Matteo, Misha Haywood, Chervin Laporte

Cosmology and Nongalactic Astrophysics

A redshift-independent theoretical halo mass function validated with Uchuu simulations

Elena Fernández-García, Juan E. Betancort-Rijo, Francisco Prada et al. (+3 more)

We present a new theoretical framework for the halo mass function (HMF) that accurately predicts the abundance of dark matter haloes across an exceptionally wide range in mass and redshift. Building on a generalised Press & Schechter model and triaxial collapse (GPS+), we predict the HMF in terms of the variance of the linear density field, with only a weak explicit dependence on halo mass and no explicit dependence on redshift. The GPS+ model naturally provides the correct normalization and high-mass behaviour without requiring empirical fitting. We calibrate and validate the GPS+ model using the Uchuu N-body simulation suite, which combines large cosmological volume and high mass resolution under Planck cosmology. Using six simulations with up to 300 realizations, we obtain precision HMF measurements spanning halo masses in the range 6.5 < log($M_{\rm 200m}$/[h$^{-1}$ $M_{\odot}$]) <16 over 0 < z < 20, with reduced cosmic variance. Across this full domain, the GPS+ model reproduces the simulated HMF with deviations typically below 10-20%. Comparison with the Sheth-Tormen (ST) model shows similar performance at z < 2, but markedly improved agreement at higher redshifts, where ST can deviate by 70-80% while our model remains within ~20%. Finally, we assess the impact of the halo mass definition: adopting the evolving virial overdensity of Bryan & Norman (1998) worsens agreement at low redshift and high masses, whereas M200m yields a more universal, nearly redshift-independent HMF.
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All authors Elena Fernández-García, Juan E. Betancort-Rijo, Francisco Prada, Tomoaki Ishiyama, Anatoly Klypin, José Ruedas