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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 31 August

High Energy Astrophysical Phenomena

GRMHD Simulations of Accreting Proto-Magnetars II. Implications for r-process Nucleosynthesis

Tejas Prasanna, Kyle Parfrey, Brian D. Metzger et al. (+3 more)

Newly formed, rapidly spinning, strongly magnetized neutron stars ("millisecond proto-magnetars") can arise in collapsars, neutron star mergers, or white-dwarf accretion-induced collapse, and are often surrounded by compact accretion disks. At accretion rates of ~0.1 Msun/s, these disks can become neutron rich and power outflows capable of rapid neutron-capture (r-process) nucleosynthesis. In Paper I, we presented axisymmetric GRMHD simulations of accretion onto such proto-magnetars and showed how the disk-magnetosphere interaction regulates jet power, variability, and neutron star torques. Here we use the same simulations to study how this interaction regulates the mass, composition, and velocity of the baryon-rich ejecta, comparing proto-magnetar models to otherwise similar black hole accretion. A magnetized neutron star qualitatively changes both the amount and composition of the ejecta. Stronger neutron star magnetic fields suppress accretion and redirect more inflowing material into unbound outflows, even when the magnetosphere remains strongly compressed by the disk. Once the field produces magnetic channeling or centrifugal acceleration, mass loss is enhanced further. Reaction-network calculations show that these magnetically driven outflows can synthesize the full range of r-process nuclei, including the heaviest elements. Moderate neutrino irradiation substantially reduces the third-peak yield, but magnetically accelerated neutron star outflows retain a heavy component more effectively than black hole disk winds; sufficiently strong early-time irradiation suppresses it altogether. Accreting proto-magnetars may therefore be important heavy r-process sources once their neutrino emission has sufficiently declined.
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All authors Tejas Prasanna, Kyle Parfrey, Brian D. Metzger, Ore Gottlieb, Andrei Beloborodov, Koushik Chatterjee

Astrophysics of Galaxies

Local Heavily Obscured Active Galaxies Observed With Chandra (I): Spectral Properties of the Nuclear and Extended X-ray Emission

R. Middei, G. Fabbiano, A. Trindade Falcão et al. (+3 more)

The Chandra X-ray Observatory has revealed that kiloparsec-scale extended X-ray emission is commonly associated with heavily absorbed ($\log (N_{H}$/cm$^{-2})\,>\, 23$) Active Galactic Nuclei (AGN) in the local Universe. We present a homogeneous spatially resolved spectral analysis of a sample of nearby obscured AGN observed with deep ($>100$~ks) Chandra/ACIS exposures and all associated with extra-nuclear extended emission. Exploiting the sub-arcsecond resolution of Chandra, we separate unresolved nuclear emission from physically distinct extended regions and model their spectra using photoionized and thermal plasma components. The extended emission is spectrally complex, requiring a combination of photoionized and collisionally ionized components in most regions. The spectral parameters exhibit systematic radial variations, with nuclear regions typically hosting higher-column and higher-ionization components, while extended regions span similarly broad but overlapping ranges without a simple monotonic radial progression. Hard ($>3$ keV) X-ray emission in excess of nuclear PSF spillover is detected in 19/20 sources, while extended Fe~K$\alpha$ emission is observed in 12/20 systems. These results establish a uniform baseline for the X-ray properties of heavily obscured AGN and provide constraints on the geometry and physical conditions of AGN-driven feedback in the local Universe.
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All authors R. Middei, G. Fabbiano, A. Trindade Falcão, D. Ł. Król, W. P. Maksym, M. Elvis

Cosmology and Nongalactic Astrophysics

TDCOSMO XXVIII. The Hubble constant from the quadruply lensed quasar J1537$-$3010 with precise time delays

A. Galan, A. G. Schweinfurth, S. H. Suyu et al. (+21 more)

We present the first measurement of the Hubble constant ($H_0$) from the quadruply-lensed quasar J1537$-$3010, which has optically-measured time delays at $\sim2 \%$ precision. We combine these delays with multi-band imaging data from the Hubble Space Telescope (HST) and model the system with two independent software and teams. We adopt a mass profile that is maximally degenerate with $H_0$ to fully incorporate the mass-sheet degeneracy in the error budget, with nuisance parameters constrained by spatially resolved stellar kinematics from the Multi Unit Spectroscopic Explorer (MUSE) and a line-of-sight (LoS) analysis using the Euclid Flagship simulation. The entire analysis is performed blindly to $H_0$, distances and mass density slope of the main deflector. After unblinding, we measure $H_0 = 75.5^{+9.3}_{-5.8}\ {\rm km\,s^{-1}\,Mpc^{-1}}$, corresponding to a $10\%$ precision measurement from a single system. This precision is driven by conservative lens modeling assumptions including differences between lens modeling methods and the limited stellar kinematics constraints, from which we infer a total mass-sheet parameter $\lambda\equiv(1-\kappa_{\rm ext})\lambda_{\rm int} = 0.89^{+0.11}_{-0.06}$ ($\lambda_{\rm int}=0.89^{+0.09}_{-0.07}$) that is consistent with current results for elliptical galaxies ($\lambda \approx 1$). Our lensing constraints, stellar kinematic measurements and LoS characterization will be included in subsequent population-level measurements of $H_0$. Moreover, our lens models combined with future near-infrared spectroscopy and imaging from the James Webb Space Telescope will further reduce the uncertainties on $H_0$ from J1537$-$3010 alone, bringing it closer to the few percents precision of the time delays.
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All authors A. Galan, A. G. Schweinfurth, S. H. Suyu, D. P. Johnson, A. Chawla, D. Sluse, G. V. Kharchilava, E. Buckley-Geer, H. Lin, S. Knabel, W. Sheu, S. Ertl, T. Anguita, S. Birrer, F. Courbin, F. Dux, M. Millon, V. Motta, S. Schuldt, T. Treu, D. M. Williams, M. Cappellari, K. C. Wong, D. Eckert

High Energy Astrophysical Phenomena

Portraits of the young and old in X-ray: New millisecond pulsar detections and updated characterization of young neutron stars

Wynn C. G. Ho, Patrick H. Wang and Sebastien Guillot

We present analyses of new and archival Chandra and NuSTAR data on two old millisecond pulsars, a young highly-energetic pulsar, and a young neutron star. PSR J1810-0623 is a recently-discovered 4.55 ms radio pulsar in a binary with a possible carbon-oxygen white dwarf companion. We tentatively detect the pulsar for the first time in X-ray using a new short Chandra HRC-I observation. Its faintness suggests a distance more in accord with the further (~1 kpc) of its dispersion measure-inferred distances. PSR J1933-6211 is a 3.54 ms radio pulsar also with a carbon-oxygen white dwarf companion. Our first-time X-ray detection in an archival HRC-S image indicates its X-ray luminosity is similar to that of the 1.9 Msun pulsar PSR J1614-2230. Next, PSR J1813-1749 is a 1-2 kyr pulsar with one of the highest known spin-down luminosities. We measure its spin period of 44.7 ms using 2025 NuSTAR and 2026 Chandra ACIS-S data and update its spin evolution model. We show for the first time the pulse profile of PSR J1813-1749 at 3-79 keV, and we find that the spectra of the pulsar and pulsar wind nebula at these energies did not change significantly between observations in 2018 and 2025. Finally, for the 5-10 kyr neutron star CXOU J182913.1-125113 in the supernova remnant G18.95-1.1, we combine ACIS-I observations from 2009 and 2024 to better measure the neutron star's spectrum.
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High Energy Astrophysical Phenomena

Evidence for a luminosity-class dichotomy in the supergiant donors of persistent high-mass X-ray binaries and supergiant fast X-ray transients

Lara Sidoli and Vito Sguera

We have investigated the properties of the supergiant donors in two types of high-mass X-ray binaries (HMXBs, i.e. the so-called supergiant fast X-ray transients (SFXTs) and the classical X-ray sources), by collecting all available information from the literature. A prevalence of O-type versus B-type supergiant donors in SFXTs was previously suggested in the literature, possibly indicative of faster winds in SFXTs than in classical, persistent sources. Our aim is to investigate whether there is evidence for a dichotomy in the stellar luminosity class, since B-type supergiants are also known to be hosted in SFXTs. Our collection of the relevant literature allowed us to build a robust sample of both types of HMXBs with a secure stellar classification. We have found that the SFXTs showing the most extreme, transient X-ray emission host only O-type or B-type stars with a Ib and Iab luminosity class, whereas classical sources have mostly Ia donors. This is robust evidence that might explain the two different behaviours of HMXBs at X-rays since the stellar luminosity class appears to be linked to the wind properties (the supergiant wind terminal velocity, the mass-loss rate, and the wind strength Q parameter), indicative of faster and less dense winds in SFXTs than in classical sources.
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2609.00175 · 31 Aug · Accepted for publication in Astronomy & Astrophysics (received May 18, 2026; accepted August 11, 2026). The manuscript comprises 11 pages, 5 figures, and 4 tables. The version submitted here also includes all supplementary tables (B.1, C.1, C.2, and D.1), which in the published A&A article are provided exclusively in electronic form via the CDS

Abstract PDF $STAR ×1

High Energy Astrophysical Phenomena

GRMHD Simulations of Accreting Proto-Magnetars I. Implications for Gamma-Ray Burst Jets and Energetic Explosions

Tejas Prasanna, Kyle Parfrey, Brian D. Metzger et al. (+3 more)

Newly formed, rapidly rotating, strongly magnetized neutron stars ("millisecond proto-magnetars") are promising central engines for gamma-ray bursts (GRBs) and luminous supernovae. Although often modeled in isolation, they can be born surrounded by accretion disks in stellar collapse, neutron-star mergers, or accretion-induced collapse. We present axisymmetric GRMHD simulations of hyperaccretion onto such objects, including a physical equation of state and charged-current weak interactions. Holding the weakly magnetized accretion torus fixed, we vary the stellar dipole field strength to span crushed-magnetosphere, magnetically channeled accretion, and centrifugal-propeller regimes, and compare with an otherwise similar accreting black hole. Accretion compresses the stellar magnetosphere and opens additional magnetic flux, producing relativistic jet powers that exceed isolated-dipole spin-down estimates by factors of a few to ~10. Even while the magnetosphere remains compressed against the stellar surface, stronger fields increasingly impede accretion and enhance outflows. Channeled-accretion models show strong jet variability driven by plasmoid eruptions and intermittent magnetospheric accretion, whereas the propeller model produces a steadier, more powerful jet and rapid spin-down. The disk-magnetosphere interaction also regulates how efficiently the neutron star grows and whether it spins up or down; near spin equilibrium, inefficient accretion can delay collapse to a black hole relative to estimates based on the external mass-supply rate. Accreting proto-magnetars can therefore power relativistic jets and baryon-rich outflows with energetics comparable to those inferred for long GRBs and GRB-supernovae. A companion paper explores implications for neutron-rich ejecta and r-process nucleosynthesis.
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All authors Tejas Prasanna, Kyle Parfrey, Brian D. Metzger, Ore Gottlieb, Andrei Beloborodov, Koushik Chatterjee

High Energy Astrophysical Phenomena

Equation of state and neutron star properties with new mass-radius constraints from PSR~J1614–2230, PSR~J2124–3358, and 47~Tuc~X7

Melissa Mendes, Isak Svensson, Hannah Gottling et al. (+9 more)

We study the impact of new mass-radius information from PSR J1614-2230, PSR J2124-3358, and 47 Tuc X7 in a combined equation of state inference based on chiral effective field theory constraints at nuclear densities and using different high-density extensions, including perturbative QCD constraints. The largest impact stems from the heavy-mass PSR J1614-2230 star, which shifts heavy neutron stars to smaller radii by around 0.4 km. Moreover, the combined astrophysical NICER, LIGO/Virgo, and X-ray information drives the radius posterior to a more data-driven distribution, which is less sensitive to the high-density extension. For the equation of state, the new mass-radius information significantly tightens the pressure and speed-of-sound posterior distributions, especially around three times saturation density. Finally, we make predictions for the poorly constrained masses of PSR J2124-3358 and 47 Tuc X7 based on the combined equation of state analysis and the other astrophysical sources.
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All authors Melissa Mendes, Isak Svensson, Hannah Gottling, Kai Hebeler, Achim Schwenk, Nathan Rutherford, Lucien Mauviard, Christine Kazantsev, Yves Kini, Denis Gonzalez-Caniulef, Sebastien Guillot, Anna Watts

High Energy Astrophysical Phenomena

A NICER view of PSR J1614$-$2230: a massive and compact millisecond pulsar

Lucien Mauviard, Sebastien Guillot, Lami Suleiman et al. (+17 more)

Using pulse profile modeling, we obtain the mass-radius measurement of a millisecond pulsar (MSP) with data from the Neutron Star Interior Composition ExploreR, XMM-Newton and the Chandra X-ray Observatory. We report here the radius of PSR J1614$-$2230, the second most massive MSP confirmed by radio timing. All of the data sets are well described by a simple model composed of two circular hot spots. The final result yields an equatorial radius of $R_{\rm eq}=10.06 ^{+1.25}_{-0.87}\,$km, and a gravitational mass of $M=1.937^{+0.012}_{-0.013}\,M_{\odot}$ (equally tailed 68% credible intervals). Although a non-thermal component was previously reported at higher energies, we find no sign of it in either our phase-averaged or phase-resolved spectral analyses. Using new relations linking the compactness to oblateness or surface gravity, and tailored to the spin frequency of PSR J1614$-$2230, we infer a configuration with one hot spot near the pole, and another near the equator. The tight mass posterior is essentially informed by radio timing, while the radius constraint is not as tight due to the low source signal (8.5$\sigma$ X-ray pulse significance). However, over all geometries and atmosphere models tested, the radius posterior tends toward low values ($\lesssim12.08\,$km, 90th percentile in all cases).
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All authors Lucien Mauviard, Sebastien Guillot, Lami Suleiman, Yves Kini, Denis González-Caniulef, Christine Kazantsev, Pierre Stammler, Devarshi Choudhury, Bas Dorsman, Mariska Hoogkamer, Daniela Huppenkothen, Tuomo Salmi, Anna L. Watts, Jérôme Novak, Natalie A. Webb, Jean-Francois Olive, Matthew Kerr, Lucas Guillemot, Ismaël Cognard, Gilles Theureau

High Energy Astrophysical Phenomena

Redshift Identifiability from Gamma-Ray Burst Prompt Emission

Shu-Xu Yi

We examine which prompt-emission observables of gamma-ray bursts (GRBs) carry identifiable redshift information in realistic structured-jet scenarios. By examining the photon-level Lorentz and cosmological transformations, we demonstrate any spectral observable reflecting the dominant-patch emission and any temporal observable reflecting the co-moving frame physics in the jet suffers from the same $z$-$\theta_v$ degeneracy. The observable reflecting the absolute flux or count rate will also suffer from this $z$-$\theta_v$ degeneracy in a different form. Due to the large variation of the intrinsic luminosity, combining the observables in the above-mentioned three classes cannot break this degeneracy. However, we demonstrate that two other classes of observables contain the potential to break this degeneracy: (i)~central engine-imprinted time scales, (ii)~emission from out of the dominant patch.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Magnetic field-induced enhancement and quenching of Urca emission in quark matter

William Gyory and Igor A. Shovkovy

Using first-principles field-theoretic methods, we investigate neutrino emission from strongly magnetized dense quark matter under conditions relevant to compact stars. We account for Landau-level quantization of both electron and quark states and show that it strongly modifies the kinematics of Urca processes. In particular, quark quantization restricts the available phase space in which both quark and electron energies can simultaneously lie near their respective Fermi surfaces. At moderately strong magnetic fields, before pronounced quark quantization sets in, the emission rate tends to increase on average with increasing field strength. In the regime of very strong fields, however, the increasingly restricted phase space first gives rise to Shubnikov–de Haas-type oscillations and then to resonance-like spikes near a discrete sequence of Urca-resonant magnetic field values, separated by regions of strong suppression. Finally, the emission rate becomes nearly completely quenched once $|eB| \gtrsim 6\mu_{e}\mu_{u}$, corresponding to approximately $B\gtrsim 1.5\times 10^{19}~\mbox{G}$ for the representative set of model parameters considered. We also find significant anisotropy in the longitudinal momentum emission near the Urca-resonant magnetic field values.
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Cosmology and Nongalactic Astrophysics

Extended radio emission in and around the merging cluster A520 as seen by MeerKAT

S. Giacintucci, W. D. Cotton, M. Markevitch et al. (+3 more)

We present results from a deep MeerKAT 1.28 GHz observation of Abell 520, a galaxy cluster in the middle of a merger and a treasure trove of merger-generated phenomena. MeerKAT's combination of high angular resolution and sensitivity to extended radio emission lets us uncover unprecedented detail of the cluster's giant halo and puzzling features beyond the halo. We find that the main radio halo is sharply bounded along the direction of the NE-SW merger axis by the two X-ray shock fronts. In the perpendicular direction, the halo wings smoothly span over 2 Mpc, with the spectrum steepening in the outskirts. We detect faint radio emission upstream of the main (SW) bow shock; the emissivity jump across this shock can be used to constrain the physical mechanisms at work there. We discover a tail of radio emission extending past the NE shock to the gas-poor, high-entropy “dark subcluster” in the NE outskirts. The tail and subcluster have a higher radio/X-ray brightness ratio than the main halo's, suggesting efficient reacceleration of cosmic rays. We also discover two peripheral radio relics beyond the cluster virial radius, and a faint, $\sim2$ Mpc long, broad radio bridge connecting the dark subcluster to one of the relics along the direction perpendicular to the merger axis. The spectral slopes of the dark subcluster and the bridge are consistent with that of the main halo. This bridge and both relics may be caused by another giant merger-generated shock front at the virial radius.
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All authors S. Giacintucci, W. D. Cotton, M. Markevitch, T. Venturi, T. E. Clarke, H. Bourdin

Instrumentation and Methods for Astrophysics

The promise of self-supervised and active learning for Strong Lens discovery: Astronomaly applied to KiDS

Margherita Grespan, Aprajita Verma, Michelle Lochner et al. (+3 more)

Strong gravitational lenses (SGLs) are rare systems whose discovery currently relies primarily on supervised machine learning methods trained on large simulated datasets. We present the first application of Astronomaly:PROTEGE to SGL discovery, demonstrating that a human-in-the-loop active learning framework can efficiently identify lenses in large imaging surveys without the need for simulated training data. We consider a sample of 3.7 million bright galaxies from the Kilo-Degree Survey (KiDS) DR4. Feature representations are extracted using a convolutional neural network pre-trained on the ImageNet dataset and subsequently fine-tuned on KiDS data using the self-supervised Bootstrap Your Own Latent (BYOL) framework. Within the embedding of these representations, the active learning loop of Astronomaly iteratively selects the most informative systems for expert inspection. A total of 3,000 objects are inspected across multiple rounds, yielding 34 high-quality (grade A/B) SGL candidates. On the basis that these systems occupy similar regions in the learned feature space, we expand this sample through nearest-neighbour similarity analysis. Including the active learning discoveries, we identify a total of 140 grade A/B candidates and more than 1,000 additional lower-confidence systems (grade C). Among the A/B candidates, 81 are newly identified, while approximately 22% of previously known grade A/B KiDS lenses are recovered. These results demonstrate strong potential for next-generation surveys such as Euclid, Roman, and Rubin's Legacy Survey of Space and Time. With approximately 60% of the high-quality candidates newly reported, this approach complements supervised methods by reducing reliance on simulations and enabling the discovery of a diverse population of SGLs.
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All authors Margherita Grespan, Aprajita Verma, Michelle Lochner, Koketso Mohale, Verlon Etsebeth, Duncan Bowden

Astrophysics of Galaxies

The Halo Gas of Local Spiral Galaxies and the Link to Gaseous Satellites

Yong Zheng, Jingyao Zhu, Ben Wertz et al. (+2 more)

Gaseous satellites orbiting massive host galaxies experience gas stripping and may contribute additional gas to the hosts' circumgalactic medium (CGM). We identify a sample of 21 local spiral galaxies ($<$15 Mpc) and characterize their gaseous satellite populations from existing HI surveys to investigate the connection between host galaxy CGM and satellite gas content. Most of our spiral hosts have $\leq3$ gaseous satellites in their halos with $M_{\rm HI}\gtrsim10^{7}~M_\odot$. Using 26 HST/COS QSO sightlines at impact parameters of 0.1–0.9 $R_{\rm 200c}$, we find that the CGM of $z\sim0$ spiral galaxies show large intrinsic scatters ($\sim1-2$ dex) in ion column densities and harbor a total cool gas mass of $2.5^{+7.5}_{\rm -1.9}\times10^9~(0.3Z_\odot/Z')~M_\odot$, largely consistent with their $z\sim0.2$ counterparts (e.g., COS-Halos). Splitting our sample by the presence of gaseous satellites, we find that galaxy hosts with gaseous satellites have higher detection rates (up to 50%) in metal ion absorbers, including OI, AlII, CII, SiII, SiIII, and SiIV, possibly because their CGM is more metal enriched or has more ionized gas in the cool phase. However, the CGM column densities show no significant correlation with either the number of gaseous satellites or their total HI masses, suggesting that the contribution from the gaseous satellites to the host CGM is likely small compared to the intrinsic scatters in the CGM profiles, and the profile trends are mainly influenced by sightlines' proximity to the hosts. The CGM detection rate becomes elevated when a sightline is within half the virial radius of a massive gaseous satellite (LMC-like or higher mass), likely due to stripped debris.
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All authors Yong Zheng, Jingyao Zhu, Ben Wertz, Yakov Faerman, Mary E. Putman

Earth and Planetary Astrophysics

Self-induced edge rings in protoplanetary disks

Massimiliano Bolchini, Haochang Jiang and Jiaqing Bi

Observations with a high angular resolution by ALMA have revealed that substructures are ubiquitous in protoplanetary disks. Axisymmetric dust rings are the most common morphology. The profiles of some observed disks, including young disks, are smooth overall, with a localized dip or bump near the outer edge of the continuum disk that manifests as an edge ring. While embedded planets might contribute to these structures, their physical origin remains unclear. We investigated the possibility that these edge rings arise purely from radiative transfer effects at the outer edge of a protoplanetary disk. A steep surface density dust gradient at the outer edge of the disk allows stellar irradiation to penetrate more efficiently beyond the disk edge, producing a non-monotonic temperature profile characterized by a dip that is followed by a bump. We tested whether this non-monotonic temperature structure can generate and maintain a localized continuum enhancement. We coupled radiative transfer and dust evolution by iterating between the Monte Carlo radiative transfer code RADMC-3D and the dust evolution code DustPy. This framework self-consistently follows the coupled evolution of temperature, grain growth, and dust dynamics. Thermodynamic feedback at the disk edge can naturally generate and maintain localized dust enhancements resembling the edge rings that are observed in some extremely young disks. Without invoking planets or additional dynamical perturbations, this mechanism offers a plausible explanation for the first-generation ring formation. Our results highlight the importance of coupling thermodynamics and dust evolution when modeling protoplanetary disks, suggesting that thermodynamic feedback probably plays a role in shaping disk substructures.
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Earth and Planetary Astrophysics

The Venus Benchmark: Resolving Degeneracies in Terrestrial Exoplanet Spectra with DAVINCI

Stephen R. Kane, David S. Alexander, Shahid Aslam et al. (+8 more)

The characterization of terrestrial exoplanets with thick, CO$_2$-dominated atmospheres via transmission and emission spectroscopy is limited by degeneracies between atmospheric composition, cloud structure, and surface conditions. These degeneracies are particularly acute for planets in or near the Venus Zone, where sulfuric acid aerosol layers and deep-atmosphere opacity render the lower atmosphere and surface spectroscopically inaccessible via many optical/IR wavelengths. Venus provides the only accessible analog to such worlds, yet current knowledge of its full atmospheric profile relies on decades-old in situ data with known limitations. Here we demonstrate that the forthcoming DAVINCI (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) mission will provide the comprehensive, high-fidelity atmospheric profile data necessary to resolve many of these degeneracies. We quantify how atmospheric profile uncertainties translate into uncertainties in modeled transmission and thermal emission spectra of CO$_2$-dominated terrestrial worlds, and show that the spread in the modeled Venus benchmark spectrum arising from current atmospheric profile uncertainties will decrease by factors of $\sim$4–5 for transmission and $\sim$5–15$\times$ for thermal emission after DAVINCI, providing a correspondingly improved benchmark and prior for the modeling of exoplanets with Venus-like atmospheres. We further demonstrate that these improvement factors are larger for the cloud-free atmospheric case, where the opacity floor is set by gas-phase processes rather than aerosols, because the pre-DAVINCI data are most discrepant in the sub-cloud region. Our results highlight the importance of Venus for the atmospheric characterization of rocky exoplanets in the JWST and HWO era, and demonstrate how DAVINCI measurements will directly improve exoplanet atmospheric modeling.
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All authors Stephen R. Kane, David S. Alexander, Shahid Aslam, Giada N. Arney, James B. Garvin, Stephanie A. Getty, Amy E. Hofmann, Noam R. Izenberg, Natasha M. Johnson, Erika Kohler, Emma L. Miles

Earth and Planetary Astrophysics

Using Ringed Disks to Determine Fundamental Parameters of Planet Formation

Olivia Wu, Luca Camarra and Eve J. Lee

Two non-dimensional parameters, Stokes number (St) and turbulent $\alpha$, critically control the early stage of planet formation. In spite of their importance, these two numbers are notoriously difficult to obtain and remain largely unconstrained, except in ringed disks. In particular, E. J. Lee (2024) showed that ringed disks can be uniquely leveraged to derive local St and $\alpha$ through a simple model combining dust radial equation of motion with the measured distribution of dust masses in Class 0/I disks. We apply their model to the currently known census of ringed disks, finding 19 viable rings in 10 systems, which more than doubles the previous sample. Similar to previous findings, we obtain generally low St$\sim 10^{-4}$–$10^{-2}$ and $\alpha \sim 10^{-5}$–10$^{-2}$ across a wide range of system parameters, consistent with all the disks that we study to be rich in gas and the dust-to-gas ratio of the rings to be too low to generate planetesimals. Disks around low mass host stars likely have leakier traps, broadly consistent with massive, gap-carving giants to be rare around low mass hosts, if the rings are generated by planets.
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Solar and Stellar Astrophysics

Conspicuous Gas, Cryptic Dust: Spectroscopy and Chromaticity of Complex Periodic Variables

Luke G. Bouma, Facundo Perez Paolino, Lynne A. Hillenbrand et al. (+17 more)

Complex periodic variables (CPVs) are young low-mass stars whose light curves show periodic dips indicative of transiting corotating material. The origin and composition of this material are unclear. Here we present new optical and near-infrared spectroscopy and photometry of four CPVs from Magellan, Keck, Hale, MuSCAT1, MuSCAT2, Tierras, KeplerCam, and TESS. The spectra imply that CPVs host magnetically bound circumstellar plasma clumps, on the basis of sinusoidal-in-time Balmer emission out of transit, and Balmer dimming during transit. Yet large night-to-night changes in circumstellar hydrogen emissivity occur without clear changes in light curve morphology, suggesting that the sharp flux dips are caused not by circumstellar plasma but by dust. Optical chromaticities (depth proportional to $\lambda^{-\beta}$, with $\beta$ = 0.79 $\pm$ 0.16) support this, but the power law breaks in the near-infrared, where a single power law under-predicts the depths observed at 2.1 microns. We therefore favor dips caused by dusty plasma clumps with opaque cores and optically thin halos, though we cannot rule out models in which the dust properties vary per-star or per-epoch. Observations at wavelengths greater than 2 microns and less than 0.4 microns would test this interpretation and clarify the dust's origin.
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All authors Luke G. Bouma, Facundo Perez Paolino, Lynne A. Hillenbrand, Juliana Garcia-Mejia, Allyson Bieryla, Patrick Tamburo, David Charbonneau, John H. Livingston, Keisuke Isogai, Norio Narita, Akihiko Fukui, Enric Palle, Felipe Murgas, Adolfo S. Carvalho, Howard Isaacson, Jessica J. Spake, Luisa M. Rebull, Moira M. Jardine, David R. Ciardi, Jeff A. Valenti

Astrophysics of Galaxies

ACES VII. Compact Continuum Source Catalog of the Central Molecular Zone

Jennifer Wallace, Cara Battersby, Nazar Budaiev et al. (+58 more)

The Central Molecular Zone (CMZ) resides in the inner few hundred parsecs of our Galaxy, and despite being the largest reservoir of dense molecular gas in the Milky Way, it has a relatively low present-day star formation rate (SFR) of $\sim0.08~M_{\odot}~\text{yr}^{-1}$. Continuum and spectral line observations from the Atacama Large Millimeter/submillimeter Array (ALMA) CMZ Exploration Survey (ACES) provide the first full-coverage, high-resolution map of the inner 200 parsecs of the CMZ at 3 mm. In this paper we present the ACES catalog of compact continuum sources, the most complete catalog of potential sites of star formation in the CMZ to date. Using an automated dendrogram-based source extraction procedure in combination with a by-eye morphological classification scheme, we produce a `full' catalog of 1735 detections in total. Additionally, we use spectral index measurements to generate a `filtered' catalog of 567 sources with minimal contamination from non-thermal filaments and extended free-free emission. We find that 359 ($\sim63\%$) of the filtered catalog sources are located at column densities $< 10^{23}$ cm$^{-2}$, outside of the densest molecular cloud regions, 195 of which have not been identified in previous surveys. After cross-referencing with various catalogs generated from data at different wavelengths, we consider it likely that many of these newly discovered detections are produced by pre/protostellar sources or compact HII regions.
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All authors Jennifer Wallace, Cara Battersby, Nazar Budaiev, H Perry Hatchfield, Ashley T. Barnes, Taehwa Yoo, Miriam G. Santa-Maria, Antonio Daley, Q. Daniel Wang, Anika Schmiedeke, Kaitlyn E. Sheriff, Jairo Armijos-Abendaño, Daniel Walker, Gwenllian Williams, Dani R. Lipman, Farideh Mazoochi, Natalie O. Butterfield, Francisco Nogueras-Lara, Yoshiaki Sofue, Ralf S. Klessen, Simon C. O. Glover, Katharina Immer, Savannah R. Gramze, Katarzyna M. Dutkowska, Rojita Buddhacharya, Laura Colzi, Ashley Lieber, Alyssa Bulatek, Michael Wieber, Pablo García, Denise Riquelme-Vásquez, Emad Alkhuja, Yue Hu, Dennis Perlot, Howard A. Smith, Victor M. Rivilla, Wenyu Jiao, Fengwei Xu, Jonathan D. Henshaw, Adam Ginsburg, Elisabeth A. C. Mills, Qizhou Zhang, Steven N. Longmore, Nguyen M. Khang, Galaxy Salo, Jakub Poznanski, Dylan Pare, Maya Petkova, Izaskun Jiménez-Serra, Xing Lu, Sergio Martin, Alvaro Sanchez-Monge, Bijas Najimudeen, Christoph Federrath, Tabassum S. Tanvir, Pei-Ying Hsieh, John Bally, Paul Ho, Mattia C. Sormani, Robin G. Tress, Jaime E. Pineda

Solar and Stellar Astrophysics

Modeling Rotation in the Old, Cold Domain: Implications on Gyrochronology and the Stellar Magnetic Wind

Amanda L. Ash, Yuxi Lu and Marc H. Pinsonneault

Gyrochronology ties stellar rotation periods to ages. It is well studied in the young, open cluster age domain, but there are few constraints on gyrochronology in the old field star regime. In this work we use gyro-kinematic ages to explore the spin down of stars in this formerly inaccessible domain. Using forward modeling techniques which relax strict Rossby scaled assumptions, we find evidence for a departure from a standard spin down models. This departure can be explained with a mass-dependent term either in the global strength of the stellar wind or in the relationship between angular velocity and wind strength. Models with this additional mass- dependence help explain prior difficulty in fitting open cluster rotation distributions across the full mass range. Additionally, we use rotation models to identify an mass-dependent age domain over which wind driven stellar spin down can be isolated from other physical effects. For lower mass stars, this age domain is most affected by the core-envelope coupling timescale, where as higher mass stars are more subject to inertial effects late in their main sequence lifetimes. Using simple, analytic models of stellar spin down in this domain is unable to determine whether the stellar wind has a mass-dependence or if the stellar wind is strictly Skumanich-like in nature. In future studies of rotational and dynamo evolution we advocate for a forward modeling approach to gyrochronology over purely empirical approaches due to its superior ability to trace physical effects governing stellar spin down.
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Solar and Stellar Astrophysics

Exploring stellar evolution with Luminous Red Novae and Interacting Gap Transients

Nadejda Blagorodnova

Interacting gap transients encompass several families of astrophysical phenomena where eruptive mass loss and interaction play an important role in shaping the observational properties and energetics of the events. Composed of Luminous Red Novae (LRNe), Intermediate Luminosity Red Transients (ILRTs), Luminous Blue Variable (LBV) giant eruptions, and pre-supernova precursors, interacting gap transients offer crucial insights into unstable mass transfer, extreme stellar mass loss, and binary evolution. In these proceedings, I review the observational signatures, progenitors, physical origin, and classification challenges of these heterogeneous phenomena. Finally, I highlight how ongoing and future wide-field time-domain missions will revolutionize this field by compiling complete volume-limited samples, tracking faint pre-outburst precursors, and establishing statistical links between gap transient families and their progenitor populations.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Dynamics and Frequency Conversion of Accreting Axion Clouds

Ximeng Li, Zhen Zhong, Yifan Chen et al. (+3 more)

Axion fields can form exponentially growing gravitational clouds around compact objects through self-interaction-driven relaxation of ambient axion waves. As the field amplitude approaches the axion decay constant, nonlinear effects become important. We identify two distinct regimes of late-time evolution, determined by the gravitational fine-structure constant and the cloud growth rate: a Bosenova regime, characterized by collapse accompanied by explosive axion bursts, and a saturation regime, in which self-interaction-induced axion emission balances accretion. In the latter regime, the emitted axion radiation exhibits stable discrete spectral lines at odd multiples of the bound-state energy, directly probing the global structure of the axion potential beyond its quadratic minimum. We show that single-cosine potentials and QCD axion-like potentials predict distinct emission spectra, enabling probes of the underlying axion self-interaction structure and its ultraviolet completion through terrestrial detection of relativistic axion fluxes from compact objects.
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All authors Ximeng Li, Zhen Zhong, Yifan Chen, Yue Zhao, Hidetoshi Omiya, Vitor Cardoso

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Solar Spin-Dependent Dark Matter-Neutron Cross Section Constraints: The Lost Case

Thong T.Q. Nguyen, Carlos Blanco and Tim Linden

The Sun has long served as a natural dark matter detector, capturing halo particles that scatter with solar nuclei and electrons and subsequently produce indirect signals from dark matter annihilation that can be probed by either neutrino or $\gamma$-ray instruments. Previous efforts have computed cross-section constraints for dark matter scattering with electrons, as well as spin-independent and spin-dependent dark matter-proton scattering. However, the spin-dependent dark matter-neutron scattering scenario has been neglected, despite its importance in direct detection. For the first time, we compute the capture and evaporation rates for spin-dependent dark matter-neutron scattering in the Sun, including odd-neutron isotope targets in the current standard solar model. Comparing the predicted annihilation signals against current neutrino and $\gamma$-ray observations, and projecting the reach of upcoming detectors, we find that solar constraints exceed direct detection limits for several annihilation channels. For models in which the dark matter annihilates into long-lived mediators, these constraints can extend below the neutrino fog.
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Solar and Stellar Astrophysics

Sinking and spreading of metal pollution in magnetic white dwarfs

Elad Shiftan and Sivan Ginzburg

Observations of magnetic polluted white dwarfs indicate that most of them have higher concentrations of metals near the poles compared to lower latitudes. Maintaining such abundance gradients requires gravitational sinking times $t_\downarrow$ below the convection zone that are shorter than the horizontal spreading time $t_\leftrightarrow$ across the surface by convective eddies. We show analytically that $t_\downarrow/t_\leftrightarrow\propto T^{8/3}$, where $T$ is the temperature at the base of the convection zone, which rises by more than an order of magnitude as convection penetrates deeper into the atmosphere. Correspondingly, $t_\downarrow/t_\leftrightarrow$ jumps by several orders of magnitude, clearly delineating between hot white dwarfs with abundance variations and cold ones with homogenous surfaces. We incorporate magnetic fields self-consistently into the stellar structure and compute for the first time the sinking to spreading time-scale ratio as a function of $B$. Magnetic white dwarfs have shallower convection zones at a given $T_{\rm eff}$, and the inward penetration of convection shifts to lower $T_{\rm eff}$. Quantitatively, $B\sim 10^5\textrm{ G}$ extends the range for enhanced abundance patches from $T_{\rm eff}\gtrsim 30\,000 \textrm{ K}$ ($13\,000\textrm{ K}$) to $T_{\rm eff}\gtrsim 15\,000 \textrm{ K}$ ($6000\textrm{ K}$) for helium (hydrogen) dominated atmospheres, which is insufficient to explain the observed patchy white dwarfs, which are even colder. A possible solution is variability in the accretion rate on a time-scale of a decade, as recently detected in another white dwarf.
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High Energy Astrophysical Phenomena

Causal self-consistency of the Blandford–McKee self-similar solution

Gilad Sadeh, Tamar Faran, Doron Kushnir et al. (+1 more)

The Blandford–McKee (BM) solution describes the ultra-relativistic self-similar flow behind a strong spherical blast wave propagating into an external density profile $\propto r^{-k}$, where $k<4$ and $r$ is the distance from the center, but it applies only to the hot shell adjacent to the shock, sufficiently deep behind it, the fluid leaves the BM regime. Since the similarity profiles are determined solely by the shock conditions, with no conditions imposed at the inner end, the validity of the solution near the shock depends on whether the flow beyond the BM regime can imprint on this hot shell. For shallow density profiles, $k<k_g\simeq 2.062$, the characteristic structure of the BM solution already prevents forward-going acoustic information from the non-BM interior from reaching the shock during the ultra-relativistic stage. For steeper profiles, $k_g<k<4$, the hot equation of state fails while the flow is still relativistic and shock-connected. There, we derive a new self-similar solution for the cooling relativistic flow, which has its own similarity scale, equations, and characteristic structure. It overlaps with the hot BM solution toward the shock, and reaches a sonic point beyond this overlap. This critical point separates the shock-connected BM-plus-cooling composite from the deeper downstream region, so acoustic signals generated beyond it cannot propagate toward the shock. The mechanism is explicit at $k=7/2$, for which the cooling solution is obtained analytically. This causal structure is therefore what enables the BM solution, which remains self-consistent near the shock even though it does not globally describe the full downstream flow.
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All authors Gilad Sadeh, Tamar Faran, Doron Kushnir, Eli Waxman

Astrophysics of Galaxies

Early Supermassive Black Holes and Little Red Dots Require Free-Fall Growth

Junehyoung Jeon, Volker Bromm, Michael Boylan-Kolchin et al. (+1 more)

Supermassive black holes/active galactic nuclei (SMBHs/AGN), forming only a few hundred million years after the Big Bang as observed with the James Webb Space Telescope (JWST), challenge theoretical understanding. How could they grow so massive $(M_{\rm BH} > 10^6 {\rm \,M}_\odot)$ so quickly after initial seeding? Is this rapid growth related to the numerous and enigmatic Little Red Dots (LRDs), compact sources with AGN-like characteristics, discovered by JWST? To address these mysteries, we consider the first-order constraint on SMBH growth: enough baryonic material has to reach the vicinity of the SMBH seed, located near the bottom of the gravitational potential well of the host dark matter halo. We specifically examine cold-mode accretion, where gas from the cosmic environment flows into the virialized halo in cold streams without being shock-heated, efficiently reaching the center on a free-fall timescale. We find that cold mode accretion is necessary to supply material for the SMBHs to reach the observed masses, whereas for shock-heated gas inflow the required amount could only be supplied by implausibly rare halos. Moreover, cold-mode inflow in rare $(\sim1$ Gpc$^{-3}$) halos matches the mass and number of the massive quasars, and halos able to support super-Eddington accretion for massive SMBHs ($\sim10^7$ M$_\odot$) match LRD number densities. The decreasing LRD abundance at lower redshifts may then reflect the termination of cold-mode accretion in the growing host halos. The populations of massive SMBHs and LRDs at early times may thus arise naturally from cosmological structure formation, based on the abundance of halos capable of supplying sufficient material through cold accretion.
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All authors Junehyoung Jeon, Volker Bromm, Michael Boylan-Kolchin, Julian B. Muñoz

Astrophysics of Galaxies

Reconciling Galactic rotation curve constraints with stellar stream modeling

Mingyu Chang, Francois Hammer and Yanbin Yang

Recent Gaia-based measurements of the Milky Way rotation curve and stellar-stream modeling give significantly different estimates of the Galactic dynamical mass beyond Galactocentric radii of 15 kpc. The stream-based model predicts an outer halo five times more massive than that predicted by the Gaia rotation curve. We aim to test the impact of analytic assumptions used in stream modeling and to assess whether the currently available stream constraints can distinguish between low- and high-mass Galactic potentials. We first compared globular-cluster disruption in analytic and N-body Milky Way potentials. We then modeled Palomar~5 and ATLAS–Aliqa Uma, which are unique in probing the outer region beyond $R_{GC}$=15 kpc and are the most relevant to understanding the mass discrepancy. Both streams have usable constraints on sky position, proper motion, line-of-sight velocity, and RR~Lyrae distance. They were modeled for both a rotation-curve-based and a stream-based Galactic potential. In the N-body simulations, tidal shocks have a stronger effect on the closer orbit than on the more distant orbit, and therefore do not naturally explain the outer-Galaxy mass discrepancy. For the streams Palomar 5 and ATLAS–Aliqa Uma, simulations performed for both low- and high-mass Galactic potentials provide comparably good fits of their morphologies and kinematics. Neither potential provides a uniformly better match to all observables, and their differences are comparable to the present observational and modeling uncertainties. Current stream data do not discriminate between the low- and high-mass Milky Way models over the radial range probed by Palomar~5 and ATLAS–Aliqa Uma. This resolves the apparent tension between the rotation-curve- and stream-based constraints over this radial range.
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Astrophysics of Galaxies

Weighing Little Red Dots with Transient Events

Vinh Tran, Xuejian Shen, Oliver Zier et al. (+3 more)

Recent JWST observations have revealed a large population of compact red sources at $z \gtrsim 4$, known as Little Red Dots (LRDs), many of which show signatures of accreting massive black holes (BHs). The physical nature of these sources and their connection to host galaxies are under debate. We propose an independent avenue for constraining their nature through transient phenomena, such as tidal disruption events (TDEs) and quasi-periodic eruptions (QPEs), arising from interactions between a star and the gas envelope surrounding the BH. These event rates depend sensitively on BH mass and provide a way to "weigh" LRDs. We calculate the expected TDE and QPE rates in LRDs under three distinct scenarios: (1) LRDs are truly overmassive BHs, (2) LRDs have BH masses following the classical local scaling relations (and the reported BH masses in observations are overestimated), and (3) the currently observed LRDs are only the tip of the iceberg of a larger population of low-mass BHs. We find that the predicted TDE and QPE rates differ dramatically across scenarios, especially in the presence of steep stellar cusps. The expected TDE rates per degree-square, assuming a Hernquist stellar distribution with a Bahcall-Wolf cusp embedded, are $2.78 \times 10^{-3}$, $1.96 \times 10^{-3}$, and $3.37 \times 10^{-2} \, {\rm yr}^{-1} \, {\rm deg}^{-2}$ for the three scenarios, respectively, while the QPE rates are $1.64 \times 10^{-2}$, $4.72 \times 10^{-2}$, and $4.96 \times 10^{-1} \, {\rm yr}^{-1} \, {\rm deg}^{-2}$. Upcoming wide-field surveys with Euclid, Roman, and LSST may be capable of detecting these high-redshift transient events and obtaining light curves, which encode additional information about the BH mass and the gas structure of LRDs. Stellar transient events will provide valuable insight into the early assembly of massive BHs.
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All authors Vinh Tran, Xuejian Shen, Oliver Zier, Anna de Graaff, Rohan P. Naidu, Mark Vogelsberger

Astrophysics of Galaxies

Skyfire: A Spectroscopic Census of Little Red Dots and Broad-Line AGN in the CEERS Field

Dale D. Kocevski, Anthony J. Taylor, Masafusa Onoue et al. (+24 more)

We present the Skyfire program, a 21-hour Cycle 3 JWST/NIRSpec survey with the G395M medium-resolution grating covering five pointings in the Extended Groth Strip. The survey is designed to carry out a systematic census of faint, broad-line AGN candidates with a range of rest-optical colors identified at z > 3 by the Cosmic Evolution Early Release Science (CEERS) Survey. Our primary targets include photometrically-selected Little Red Dots (LRDs), blue extreme emission line galaxies (EELGs), and X-ray-detected AGN. We present spectroscopic redshifts for 178 sources observed by Skyfire, as well as a catalog of 34 sources with broad emission lines in the redshift range 2.7 < z < 6.5. Our broad-line sample includes 18 LRDs, which brings the spectroscopic completeness of LRDs with $\beta_{\rm opt}>-0.02$ in the CEERS field to 73%. We explore the prevalence of broad emission lines in photometrically-selected LRDs as a function of their rest-frame continuum slope and observed color distributions. We find the broad-line detection fraction in LRDs remains high at relatively blue rest-optical colors and extends smoothly into the bluer regime occupied by Little Blue Dots (LBDs). We discuss the implications of this finding for LRD-LBD unification scenarios. We also find that only 18% (3/17) of EELGs selected primarily for their high-equivalent-width emission lines and compact morphologies exhibit broad emission lines, suggesting these criteria alone are poor predictors of broad-line activity. We present a revised set of LRD selection criteria that captures bluer sources by extending down to $\beta_{\rm opt}=-0.52$. Using this new threshold, we find that $80.9^{+4.6}_{-7.5}\%$ of photometrically-selected LRDs brighter than 26.5 in F444W show broad emission lines and that LRDs make up 54% of the overall broad-line population identified in the CEERS field.
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All authors Dale D. Kocevski, Anthony J. Taylor, Masafusa Onoue, Kohei Inayoshi, Steven L. Finkelstein, Guillermo Barro, Jingsong Guo, Pablo Arrabal Haro, Jonathan R. Trump, Rebecca L. Larson, Mark Dickinson, Casey Papovich, Fabio Pacucci, Pablo G. Perez-Gonzalez, Michaela Hirschmann, Elizabeth J. McGrath, Brenda L. Jones, Nikko J. Cleri, Kelcey Davis, Mauro Giavalisco, Norman A. Grogin, Taylor A. Hutchison, Jeyhan S. Kartaltepe, Allison Kirkpatrick, Gene C. K. Leung, Rachel S. Somerville, Stephen M. Wilkins

Instrumentation and Methods for Astrophysics

Detectability-Aware Screening of Post-Merger Gravitational-Wave Damping Anomalies in Real Detector Noise: A Graph-Spectral Approach with Empirical Null Calibration

Ruslan Alaskarov

A two-stage methodological proof of concept for screening simplified post-merger gravitational-wave damping anomalies in real LIGO Livingston noise is presented. The injected signal is a controlled damped-sinusoid proxy rather than a physically complete binary-neutron-star post-merger waveform; it is used to test statistical detectability and damping-time scoring under real-noise calibration. Stage 1 constructs a local time-frequency graph from Constant-Q representations of whitened candidate windows and uses the leading eigenvalue as a detectability statistic, with its null distribution calibrated empirically on real detector noise. Stage 2 estimates an effective damping-time score for Stage-1-passing candidates using nonlinear least squares and an interpretable ridge/energy-decay estimator, with thresholds fixed before final held-out evaluation. The matched-filter SNR convention is checked with synthetic Gaussian noise, while the graph statistic is assessed through power-comparison and tile-shuffling tests. On a held-out real-noise test block, the nonlinear least-squares Stage-2 score gives AUC = 0.943 and TPR = 0.879 at FPR = 0.012, outperforming a calibrated power-only baseline.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Evolution of Cosmic String Loops under Gravitational Backreaction

Lasse Gerblich, Richard A. Battye and E.P.S. Shellard

Nambu-Goto cosmic string loops generically develop cusps, points where the string momentarily reaches the speed of light. These cusps produce strong gravitational wave bursts with a characteristic strain spectrum $\tilde{h}(\omega)\propto (G\mu)\,\omega^{-4/3}$, making them prime targets for gravitational wave searches, where $\mu$ is the string mass per unit length. However, this picture is modified when one accounts for gravitational backreaction. Using a convenient gauge, we reformulate the Nambu-Goto equations of motion for a loop moving in its own dynamically sourced gravitational field, enabling the first continuous numerical evolution of loops under this backreaction. A key finding is that locally cusps survive backreaction. Nevertheless, the gravitational waveform calculated in this formalism is significantly modified, weakening the cusp burst and introducing a high-frequency cutoff at $f_c\propto(G\mu)^{-3/2}$. This suppression above $f_c$ reduces the expected signal-to-noise ratio in current and near-future detectors relative to unperturbed waveform predictions.
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