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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 19 May

Cosmology and Nongalactic Astrophysics

Recombination Thickness as an Uncertainty in Inflationary Observables

V.K. Oikonomou

Standard CMB analysis assumes a direct deterministic mapping between the multipole probed by the CMB $\ell$ and the primordial wavenumber $k$. Since the recombination era has a finite duration, this mapping is probabilistic by construction. We elevate the power spectrum of the primordial perturbations to a probability distribution caused by the finite duration of the recombination era. We show that a finite recombination width introduces a Gaussian smoothing scale in $\ln k$ with $\sigma_{\ln k} \sim \sigma_\eta / D_*$, leading to a probabilistic mapping from multipoles to inflationary e-folds. This effect is zero in standard power-law inflationary scenarios, but it may become relevant for scenarios with exotic oscillating features of the primordial power spectrum, which will be probed by the future CMB experiments. The observed effective power spectrum is the true primordial spectrum blurred by the uncertainty in scale reconstruction, which is mathematically identical to a Bayesian marginalization over a latent variable, and thus there is a propagation of the measurement error in the independent variable, which is another more formal way to view the smoothing effect. Our results indicate that the smoothing has quantifiable effects on the spectral index and its running, but more importantly the difference between the TT and EE inferred spectral indices, $n_s^{TT}-n_s^{EE}$, is non-trivial, in contrast to standard inflation without smoothing, and might become observable by future cosmic microwave background experiments. Any tension in $n_s^{TT}-n_s^{EE}$ could indicate oscillations in the primordial spectrum and the effects of the power spectrum smoothing. Finally, a minimal Fisher matrix analysis is performed to investigate the observability prospects of the smoothing effect.
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Solar and Stellar Astrophysics

A Systematic NLTE Study of Very Metal-Poor Stars with Metallicity Down to $-4.3$ dex. II. Lithium Abundance and New Insight to the Lithium Plateau

Hong-Liang Yan, Jinxiao Qin, Shuai Liu et al. (+12 more)

Metal-poor stars are crucially important for understanding the early Galaxy, first stars, and the Universe. In this series of papers, we present a homogeneous non-local thermodynamic equilibrium (NLTE) abundances analysis of 12 elements for 103 very/extremely metal-poor (VMP/EMP) stars with metallicity down to $-4.3$ dex. The sample was selected from the LAMOST survey and observed by the high-resolution spectroscopy of Subaru. In this paper, we present the NLTE abundances and evolution of lithium in these stars. We report different lithium behaviors corresponding to different evolutionary stages and their signatures: 1) The Spite Plateau shows a slightly positive slope, indicating increasing lithium abundance with increasing metallicity. Most significantly, it appears to extend to lower metallicities as previously suggested, calling into question the reality of the so-called 'meltdown' at low metallicity; 2) We confirm a lithium plateau for lower red giant branch (LRGB) stars with A(Li) $= 1.13$ dex in our sample, while lithium abundance drops rapidly to A(Li)$<0.5$ as stars continue to evolve to higher stage. 3) We identify four Li-rich stars in our sample across different evolutionary stages, showing complex and multiple lithium production mechanisms in VMP/EMP stars. These findings suggest that early Galactic lithium enrichment results from a complex interplay between depletion and production processes.
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All authors Hong-Liang Yan, Jinxiao Qin, Shuai Liu, Zeming Zhou, Gang Zhao, Jianrong Shi, Sofya Alexeeva, Huawei Zhang, Haining Li, Huiling Chen, Junbo Zhang, Yufu Shen, Wako Aoki, Tadafumi Matsuno, Jingkun Zhao

Astrophysics of Galaxies

AMPM I. A Targeted Search for Asteroid Mass Primordial Black Hole Microlenses

Renee Key, Edward N. Taylor, Ken C. Freeman et al. (+5 more)

Gravitational microlensing is a powerful technique for constraining the abundance of dark matter in asteroid mass to supermassive primordial black holes at masses of $-11 \lesssim \log M/\mathrm{M}_\odot \lesssim 5$. In this work, we introduce a new high-cadence stellar microlensing survey in the Large Magellanic Cloud, AMPM. The primary goal of AMPM is to place constraints in the asteroid-to-planetary-mass regime of primordial black hole dark matter. We present the five nights of survey data, the microlensing detection pipeline, and the microlensing efficiency of AMPM. We explore the impact of the stellar distribution in the Large Magellanic Cloud on the microlensing detection efficiency and conduct a detailed analysis of second-order microlensing effects and the impact on the primordial black hole dark matter constraints. Our findings indicate that these second-order effects shift the maximum sensitivity of AMPM toward the lunar-mass black hole regime at $10^{-8} - 10^{-6} \, M_{\odot}$. From the five nights of data, we detect a single microlensing candidate and find that AMPM can constrain at the 95% C.L up to 30% of the Galactic primordial black hole dark matter distribution.
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All authors Renee Key, Edward N. Taylor, Ken C. Freeman, Jeremy Mould, Abhijit Saha, Anais Möller, Timothy M. C. Abbott, Alan R. Duffy

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Locality in effective field theory for inflationary soft modes

Takahiro Tanaka and Yuko Urakawa

The gradient expansion and the separate universe approach provide an effective description of inflationary soft modes after coarse-graining shorter-wavelength degrees of freedom. We formulate a locality condition on the quantum state, requiring that the hard-mode state in each local universe depend on the soft modes only through the local soft-mode values in the same patch. When this condition is satisfied, the coarse-grained soft-mode dynamics remains local, and loop corrections from hard modes to superhorizon correlators of the adiabatic curvature perturbation are perturbatively suppressed. This provides a model-independent diagnosis of when enhanced corrections due to hard modes can invalidate the gradient expansion. We further show that the same locality condition implies a generalized soft theorem, from which the standard consistency relations follow under additional assumptions. This formulation clarifies the origin of possible deviations from the standard consistency relations in multi-field systems or in a non-attractor background. We also show that the locality condition guarantees the absence of infrared divergences for the correlators of operators invariant under a large gauge transformation. Thus, locality of the hard-mode state provides a unified criterion for the effective description of inflationary soft modes, generalized soft theorems, the suppression of hard-mode loop corrections, and the infrared regularity of observable correlators.
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Earth and Planetary Astrophysics

Constraints on the Crystallinity of Water Ice in Planet-forming Disks from Infrared Scattered-Light Spectra

Kanon Nakazawa and Ryo Tazaki

The crystallinity of water ice not only records the thermal history experienced by an astronomical body, but also affects the composition of forming planets by controlling the trapping of volatile materials in amorphous ice and their subsequent transport. An additional structure within the 3~$\rm \mu m$ water-ice absorption band, known as the Fresnel feature, may serve as a diagnostic of ice crystallinity. Recent observations with the James Webb Space Telescope have detected a Fresnel peak in a debris disk and in Trans-Neptunian Objects (TNOs). Here, we propose a portable expression that translates the observed Fresnel peak strength into the degree of crystallinity of icy grains in debris disks. Our formula targets scattered light at around 90$^{\circ}$ angles, which are easily accessible for spatially resolved debris disks regardless of the inclination angle. Applying this expression, we derive the degree of crystallinity of a debris disk around HD 181327 to be 10-20%. We also study the Fresnel feature in protoplanetary disks and find that it is generally weaker than in debris disks even for the same crystallinity. We then analyzed a scattered light spectrum of the protoplanetary disk around d216-0939, which shows a weak crystalline feature, and inferred a crystallinity of $\sim$50%. We conclude that the Fresnel feature is a reliable observational tracer for ice crystallinity, and future near-IR spectroscopic observations will be crucial to elucidate the crystalline ice evolution.
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Astrophysics of Galaxies

Correlation between baryonic process and galaxy assembly bias

Zilan Xiao, Junyu Hua, Zhongxu Zhai et al. (+2 more)

Galaxy assembly bias (GAB) is the dependence of galaxy clustering on secondary properties beyond halo mass. In this work, we study the connections between GAB and baryonic processes using the Galacticus semianalytic model (SAM) for galaxy formation and evolution applied to the UNIT simulation. By generating hundreds of galaxy mocks with varying parameters governing gas cooling, star formation, stellar feedback, and active galactic nucleus (AGN) feedback, we quantify the GAB signal using a shuffling technique that compares the clustering of the original galaxy samples with that of shuffled samples, in which galaxies are randomly reassigned among halos of the same mass. We then compare the GAB signals associated with halo concentration and smoothed environmental density, and use the random forest (RF) algorithm to identify which baryonic processes are most correlated with GAB within the explored SAM parameter space. We find that for stellar-mass-selected galaxies, the dominant baryonic processes are gas cooling and stellar feedback, and the result does not change significantly with the number density; for star formation rate (SFR)-selected galaxies, the primary process shifts from star formation to gas cooling as the number density increases. These results reveal a correlational dependence of GAB on baryonic processes within the explored Galacticus SAM parameter space.
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All authors Zilan Xiao, Junyu Hua, Zhongxu Zhai, Andrew Benson, Yun Wang

Earth and Planetary Astrophysics · Cross-listed from q-bio.BM

Elemental Stoichiometry as an Ecological Biosignature with Applications to Life Detection

Pilar C. Vergeli, Cole Mathis, John F. Malloy et al. (+5 more)

The vast chemical space of possible small molecules, estimated at 10^60 compounds for molecules composed of just C, N, O, and S, is only sparsely occupied by biology. We propose that where life selects molecules within this space constitutes a detectable ecological signature: a fingerprint not of specific compounds, but of the statistical structure of elemental composition across molecules sam-pled from ecological systems. Here we introduce a framework combining Van Krevelen diagrams and element scaling laws to characterize the elemental composition of regions of chemical space occupied by biological systems and contrast them with other chemical systems. Applying this framework to 11,834 microbial metagenomic samples, we show that microbial metabolisms occupy a region of chemical space, which is enriched in heteroatoms such as P, S, N, and O relative to C, shifted toward higher O:C and H:C ratios. We observe sublinear element scaling with system size, yielding insights into how elemental constraints dictate how biological systems occupy chemical space. These patterns are distinct from a sample of 18,000 compounds from the comprehensive Reaxys synthetic chemical database. Critically, datasets from molecules detected in planetary science mission data occupy statistically distinct regions from both terrestrial biological and Reaxys distributions, demonstrating that with standardized methods for data collection, the approach could be developed to discriminate biotic from abiotic chemical signatures in small molecule data from planetary science missions. Our work shows how a combination of Van Krevelen fingerprinting and elemental scaling laws can provide a new class of ecological biosignatures for life detection leveraging mass spectrometric data from planetary missions, which could generalize beyond Earth's specific biochemistry.
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All authors Pilar C. Vergeli, Cole Mathis, John F. Malloy, L. Felipe Benites, Christopher P. Kempes, Elizabeth Trembath-Reichert, Hilairy E. Hartnett, Sara I. Walker

Earth and Planetary Astrophysics

Active Galactic Nucleus Tori: Potential Birthplace to Millions of Planets

Bhupendra Mishra, Wladimir Lyra, Barry McKernan et al. (+3 more)

The outer regions of AGN disks have temperatures similar to those of circumstellar disks, permitting dust condensation. Therefore, planet formation and growth could be active in these dust tori through similar mechanisms. We aim at quantifying the parameter space for the occurrence of streaming instability, and its outcomes in terms of the masses of the objects formed, their total number, and their continued growth via pebble accretion. We use a a recently proposed disk model with strong magnetization to keep the disk gravitationally stable. We find that the dust grain sizes required for streaming instability are easily attained through coagulation; the dust filaments it produces can contain solar masses, collapsing into tens of millions of planetesimals ranging from Earth to super-Jupiter masses. These planets are usually born in the 3D Bondi regime of pebble accretion, and have mass-doubling times from 10^3 to 10^7 yrs, though 3D Hill and geometric accretion are also realized. Gas accretion occurs concurrently, and crossover mass can be attained while still in the planetary mass range. As a result, vigorous accretion can occur, leading to objects with stellar masses - defining a core accretion channel for star formation. The pebble isolation mass is beyond the hydrogen burning limit, so accretion is limited by stellar feedback instead of gap carving. We also predict a population of exotic objects directly formed above the hydrogen burning limit, yet of pure dust. Our model suggests that AGN dust tori host the largest populations of planets in the universe.
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All authors Bhupendra Mishra, Wladimir Lyra, Barry McKernan, Mordecai-Mark Mac Low, K. E. Saavik Ford, Harrison E. Cook

Astrophysics of Galaxies

Peculiar velocities at low Galactic latitude

Jeremy Mould, Helene M. Courtois, Renee C. Kraan-Korteweg et al. (+1 more)

The Laniakea Supercluster is the closest large scale structure of galaxies. Is such a structure expected in the standard cold dark matter model of cosmology? This would be a relatively simple question to answer, were it not for the fact that the Zone of Avoidance (ZOA) runs right through it. Recent improvements to this paucity of data in the innermost ZOA can be made from systematic 21 cm surveys using the MeerKAT telescope (e.g. Kraan-Korteweg et al. 2024), and implementing these HI-redshifts as an extension to the CosmicFlows4 database for reconstruction (Hollinger et al. 2026). In this paper we test the assumption that for the purpose of reconstruction, additional HI detected galaxies without peculiar velocity determinations could be placed at their Hubble distances. We present infrared photometry of 163 of these in HI detected MeerKAT ZOA galaxies, in addition to 2MASS Extended Sources in the ZOA to determine their peculiar velocities. Averaging these peculiar velocities into redshift bins, we find that peculiar velocity corrections in the Laniakea Supercluster ZoA region are not prohibitively large, and that one can proceed with its reconstruction using the copious redshift data now available.
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All authors Jeremy Mould, Helene M. Courtois, Renee C. Kraan-Korteweg, Amber Hollinger

Cosmology and Nongalactic Astrophysics

Faraday Complexity and Depolarization in LOFAR Two-metre Sky Survey (LoTSS-DR2) Polarized Radio Sources

Rudra Sinha and Abhik Ghosh

We present a broadband spectro-polarimetric analysis of 1,565 polarized radio sources from the LOFAR Two-Metre Sky Survey Data Release 2 (LoTSS-DR2) RM Grid catalogue. This study uses frequency-dependent Stokes Q and U spectra across the 120-168 MHz LOFAR HBA band to investigate their polarization properties. The polarization behaviour of each source is modelled with multi-component Faraday depolarization models to investigate the magneto-ionic environments responsible for low-frequency depolarization. Significant Faraday complexity is observed throughout the sample, with 43.2% of sources requiring two or three Faraday components. External Faraday dispersion dominates the depolarization behaviour, with 54.1% of sources classified as external-screen dominated and approximately 60% showing statistically significant evidence for turbulent external Faraday-active media, while only 10.3% are consistent with pure internal differential Faraday rotation. The intrinsic polarization angle and RM separations between fitted components are generally small, suggesting that many RM components trace physically related emission regions embedded within common magneto-ionic environments. A weak but statistically significant anti-correlation is detected between the polarization spectral index, $\beta$, and weighted Faraday dispersion, $\sigma_{\rm RM,wtd}$, for two-component systems, whereas one- and three-component populations show no significant trend. The rest-frame Faraday dispersion, $\sigma_{\rm RM,rest}$, exhibits significant positive correlations with redshift for the external-screen dominated and mixed depolarization populations, even after controlling for radio luminosity, indicating increasingly turbulent or strongly magnetized environments surrounding radio AGN at earlier cosmic epochs.
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Cosmology and Nongalactic Astrophysics

Taking Inventory of the Most Promising Lensed Radio Sources for Constraining Fundamental Properties of Dark Matter

Michael N. Martinez

While dark matter (DM) makes up roughly 80% of the total matter in the Universe, its microscopic properties remain one of the biggest questions in Cosmology today. Fortunately, those properties dictate the distribution and form of macro-scale gravitational structures in the universe, allowing for indirect studies which can distinguish between competing particle models. One such avenue for this research is via strong gravitational lensing systems, where dark halos in the lens substructure and along the line of sight perturb image positions and flux. However, the current population of sources suitable for this analysis is limited, especially at radio wavelengths where astrometric perturbations are observable. I will first discuss which properties of lens systems make them especially useful for DM constraints and examine the minimum amount of information necessary for such an experiment. Then, I present the results of two successful searches for new radio lenses in existing radio and optical surveys, utilizing a new method to expand the potential follow-up population for dark matter studies in the future. I conclude with a discussion of the completeness of this population.
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High Energy Astrophysical Phenomena

Temporal evolution of the circumstellar disk orientation in the transient X-ray pulsar GRO J1008-57

Yongfeng Hu, Hua Xiao, Sergey S. Tsygankov et al. (+3 more)

The transient X-ray pulsar GRO J1008-57 was previously found to exhibit Type I outbursts occurring at stable orbital phases before its first observed Type II outburst in 2012. In this work, we extend the study to investigate the phase evolution after several Type II outbursts using long-term Swift/BAT and MAXI/GSC observations. Our results reveal that the orbital phases of Type I outbursts follow a step-like evolution: they remain largely stable over many orbital periods but undergo abrupt, small-amplitude jumps coincident with each Type II outburst. Such a step-like behavior is difficult to explain with the commonly proposed mechanisms involving a highly eccentric or precessing disk around the Be star. The energetics of Type I X-ray outbursts show a systematic increase before Type II outbursts, followed by a rapid decline and a subsequent gradual recovery. This behavior suggests cycles of disk depletion and reconstruction driven by Type II outbursts. Considering the small amplitude of each phase jump, we propose that this step-like phase evolution may be related to the long orbital period of GRO J1008-57, implying infrequent neutron star-disk interactions. After disk depletion by Type II outbursts, the disk around the Be star has enough time to rebuild its density and restore a geometric structure similar to its pre-Type II outburst state. Consequently, the orbital phases of subsequent Type I outbursts not only change very slightly but can also remain stable over many orbital periods until the next Type II-driven disk reconfiguration, yielding the observed step-like evolution.
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All authors Yongfeng Hu, Hua Xiao, Sergey S. Tsygankov, Long Ji, Juri Poutanen, Runting Huang

Monday 18 May

High Energy Astrophysical Phenomena

Reconciling GW170817 and GW190814 with a Nonmonotonic Sound-Speed Equation of State

Marlon M. S. Mendes, Odilon Lourenço da Silva Filho and César H. Lenzi

We show that the GW170817-GW190814 tension can be reconciled within General Relativity by a structured causal EoS basin found with a Constrained Evolutionary TOV Discovery pipeline (CETD). The basin contains ~1.4x10^4 unique EoS with M_max = 2.3-2.8 M_sun, R_1.4 = 11.97-12.29 km, Lambda_1.4 <= 580, and double-peaked sound speeds reaching c_s^2/c^2 = 0.86-0.99.
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Astrophysics of Galaxies

Observing the Peculiar Acceleration of our Solar System with Quasar Proper Motions

Phu Huy Nguyen and Calum Murray

We measured the proper motion dipole of quasars observed by Gaia to determine the acceleration of the Solar System with respect to the quasar rest frame. We characterised the full angular power spectrum of the proper motion field using the pseudo-$C_\ell$ formalism and employed simulation-based inference to jointly constrain the dipole and higher multipole power. Cross-correlation with the Gaia scanning strategy, stellar density and stellar proper motion maps was used to diagnose the origin of systematic power beyond the dipole. We applied this framework to both the Gaia EDR3 quasar catalogue and the Quaia catalogue. The inferred acceleration is consistent with the previous determination, but the credible intervals widen by factors of 1.5 to 5 when higher-multipole degeneracies are properly marginalised, indicating that previous uncertainty estimates were optimistic. Our best estimate, based on the Quaia catalogue, is ($g_x,\,g_y,\,g_z$) = $\left(1.01^{+0.72}_{-0.72}, \,-4.94^{+0.54}_{-0.55},\,-2.13^{+0.58}_{-0.58}\right) \;\rm \mu as \,yr^{-1}$. This corresponds to an amplitude of $5.55_{-0.53}^{+0.54}\,\rm \;\mu as\,yr^{-1}$, where $\mathbf{g} = \mathbf{a}/c$ is the Solar System acceleration expressed as a proper motion drift in equatorial coordinates. The inferred acceleration is directed towards $(l,\, b) = \left(11.71^{+7.0}_{-6.8},\, -9.01^{+7.0}_{-6.9}\right)^\circ$, equivalently $(\alpha,\, \delta) = \left(281.39^{+7.8}_{-8.0},\, -22.93^{+6.5}_{-6.2}\right)^\circ$. This is in good agreement with a Galactic centre–dominated acceleration. The acceleration components show no significant dependence on source redshift, providing further evidence of the acceleration's kinematic origin.
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Cosmology and Nongalactic Astrophysics

Lossless Compression of Cosmological Information from Type Ia Supernova Distance Measurements

Zhenyuan Wang and Yun Wang

We perform model-independent distance measurements on four Type Ia supernovae (SNe Ia) compilations (Pantheon, Pantheon+, DES-Dovekie, Union3) and compress each dataset into the values of $\log r_p(z)$ at eleven redshift knots, where $r_p(z)$ is a rescaled comoving distance. These Gaussian distributed compressed values, together with their full covariance, completely capture the distance-redshift relation information from each dataset. We demonstrate this by using these to perform an Markov Chain Monte Carlo (MCMC) likelihood analysis to infer cosmological parameters in flat $\Lambda$CDM, flat $w_0 w_a$CDM, and a non-parametric reconstruction of the dark-energy density $X(z) \equiv \rho_{\rm DE}(z)/\rho_{\rm DE}(0)$. Across all datasets and flux-averaging configurations and all three cosmological models, the resulting parameter contours and figures of merit reproduce the corresponding full distance-modulus analyses using the original SNe Ia data sets within the statistical sampling noise of the chains, demonstrating that the eleven $\log r_p$ data points are an operationally lossless compression of the cosmological information in the dataset. Our SN Ia data compression enables an analytic analysis that completes in $O(10^{-2})$ s per dataset and reduces the downstream cosmological MCMC to the fast evaluation of an $11$-dimensional Gaussian likelihood, with a per-step cost set by the number of knots and independent of the SNe Ia sample size. Our methodology will benefit the data analysis of future surveys from Euclid, Roman, and LSST, which will deliver SNe Ia samples one to three orders of magnitude larger than current ones.
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Earth and Planetary Astrophysics

A Cloud-Based Tool for Meteorite Recovery Using Drones and Machine Learning

Seamus L. Anderson, Hadrien A. R. Devillepoix, Lewis Lakerink et al. (+30 more)

We present a cloud-based tool that uses drones and machine learning to help recover instrumentally observed meteorite falls. We showcase a collection of improvements made upon previous iterations of our system, as well as detail the successes and limitations of this technique when applied to observed meteorite falls in South and Western Australia. This tool is available to the meteoritics research community upon request at https://find.gfo.rocks.
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All authors Seamus L. Anderson, Hadrien A. R. Devillepoix, Lewis Lakerink, Sawitchaya Tippaya, Dale P. Giancono, Martin C. Towner, Iona Clemente, Martin Cupák, Ashley F. Rogers, John H. Fairweather, Mia Walker, Daniel Burgin, Michael A. Frazer, Sophie E. Deam, Veronika Pazderová, Eleanor K. Sansom, Benjamin A. D. Hartig, Hely C. Branco, Thomas Stevenson, Isabella Hatty, Anna Zappatini, Anthony Lagain, Tom Lovelock, Auriane Egal, Lucy Forman, David Belton, Simon Windsor, Shibli Saleheen, Asher Leslie, Gregory B. Poole, Andrew Langendam, Rachel S. Kirby, Andrew G. Tomkins

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

GstLAL O4 Online Results Paper

Shomik Adhicary, Pratyusava Baral, Amanda Baylor et al. (+39 more)

Gravitational-wave observations of merging binary neutron stars and black holes are now routinely made by detectors in the Advanced LIGO-Virgo-KAGRA network. Neutron star binary systems may also produce detectable electromagnetic and particle emission over times scales ranging from seconds to years. Real-time gravitational-wave searches play a central role in enabling time-critical electromagnetic and/or neutrino follow-up observations. During the fourth observing run (O4) of the Advanced LIGO-Virgo-KAGRA network, multiple real-time searches operated continuously to identify candidate gravitational-wave events and publicly disseminate information about these discoveries. Here, the performance and results of the GstLAL real-time analysis are reported. The analysis is designed to identify candidates with low latency, high detection efficiency, and sustained operational uptime over long observing periods. Across O4, it produced initial candidate uploads with a median latency of 15.8 s while maintaining an effective uptime of 98% during the first two parts of the observing run. During the run, the analysis contributed to 250 candidates classified as astrophysically plausible, provided the first upload for 222 of these, and was the sole contributor for 75. Among Gravitational-Wave Transient Catalog events with a false-alarm rate below one per year, 88% were identified as significant in low latency and promoted for expert vetting and public dissemination. The low-latency astrophysical classifications agreed with the final catalog classifications for 93% of the events considered.
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All authors Shomik Adhicary, Pratyusava Baral, Amanda Baylor, Becca Ewing, Yun-Jing Huang, Rachael Huxford, Prathamesh Joshi, James Kennington, Ryan Magee, Cody Messick, Wanting Niu, Cort Posnansky, Surabhi Sachdev, Shio Sakon, Urja Shah, Divya Singh, Leo Tsukada, Zach Yarbrough, Noah Zhang, Kipp Cannon, Sarah Caudill, Bryce Cousins, Jolien D. E. Creighton, Heather Fong, Richard N. George, Olivia Godwin, Reiko Harada, Soichiro Kuwahara, Alvin K. Y. Li, Duncan Meacher, Soichiro Morisaki, Debnandini Mukherjee, Alexander Pace, Anarya Ray, Stefano Schmidt, Ron Tapia, Koh Ueno, Aaron Viets, Leslie Wade, Madeline Wade, Graham Woan, Chad Hanna

High Energy Astrophysical Phenomena

Radiative PIC simulations of relativistic pair plasma: multiple interacting current sheets and turbulent evolution

Fulvia Pucci, Elena Amato, Dario Borgogno et al. (+5 more)

Two-dimensional relativistic particle-in-cell (PIC) simulations of radiative magnetic reconnection in pair plasmas with multiple interacting current sheets are carried out to mimic the dynamics in high-energy astrophysical environments, such as particle acceleration regions in pulsar wind nebulae and relativistic outflows, where the magnetic field is expected to reverse polarity multiple times. Initially, due to reconnection within each isolated sheet, particles are accelerated and synchrotron emission beyond the burn-off limit is confirmed, even if the particle distribution function shows steep slopes. After this phase, plasmoids lead to cross-sheet interactions and merging, with new current sheets formed. In this regime a Kolmogorov-like spectrum for the magnetic energy develops over a couple of decades, followed by a dissipation range starting around 5~$d_e$ (electron inertial lengths), showing that multi-sheet reconnection evolves nonlinearly into well-developed turbulence. This phase provides secondary acceleration and further cooling by synchrotron emission, with intermittent radiative bursts. We show that high energy accelerated particles by the primary current sheets are further energized during the turbulent phase, while the distribution of the most energetic particles remains steep.
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All authors Fulvia Pucci, Elena Amato, Dario Borgogno, Niccolo' Bucciantini, Maria Elena Innocenti, Kevin M Shoeffler, Marco Tavani, Valerio Vittorini

Earth and Planetary Astrophysics

Dependence on the Equation of State in SPH Simulations of Proto-Uranian Disk Formation from a Giant Impact

Keiya Murashima and Takanori Sasaki

The $98^\circ$ obliquity of Uranus is widely attributed to a giant impact that ejected material and formed a debris disk, which subsequently coalesced into its regular satellites. Previous Smoothed Particle Hydrodynamics (SPH) studies have yielded inconsistent disk compositions, a discrepancy often linked to the variety of numerical and physical modeling assumptions. We address this by presenting SPH simulations that systematically test three distinct EOS models alongside two SPH schemes (standard SPH, and the enhanced density-independent SPH). We utilized a $3M_{\oplus}$ impactor and explored a range of impact parameters which are capable of reproducing Uranus's current spin state. Our primary finding is that for impacts capable of reproducing Uranus's current rotation, the choice of EOS or SPH scheme barely affects macroscopic features such as the post-impact rotation period, disk mass, or disk size; these properties are primarily controlled by the impact's angular momentum. In contrast, the disk's rock fraction is highly EOS-dependent. Our results clarify that while disk mass and size are robust outcomes, the final disk composition is highly model-dependent. Therefore, accurate EOS modeling, integrated with detailed disk evolution studies, is essential to definitively validate the giant impact scenario for Uranus.
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Astrophysics of Galaxies

JWST Observations of Starbursts: Molecular Hydrogen Excitation and Disequilibrium in M82

Sara E. Duval, J.D.T. Smith, Alberto D. Bolatto et al. (+24 more)

Emission from the pure rotational transitions of H$_2$ traces warm molecular gas, providing insight into its temperature distribution and local heating conditions. We have extended previous power-law H$_2$ temperature models to account for differential extinction by dust as well as non-equilibrium ortho-to-para-H$_2$ ratios (OPR). The turbulent environment of the M82 starburst offers a unique opportunity to study H$_2$ out of equilibrium conditions, using ~15 pc spatially resolved measurements from MIRI/MRS on JWST. With extensive detections of H$_2$ S(1)-S(7), we use our model to assess spatial variations in local heating conditions of molecular gas across a ~500 pc region of the M82 central starburst. The average slope of the recovered H$_2$ power law temperature distribution is consistent with prior studies, and the slope strongly anti-correlates with relative [Fe II]/H$_2$ S(1)-S(2) strength, pointing to the importance of shock-heating. Our models indicate that the OPR is, on average, about half of its equilibrium value. This suppression is attributed to cloud mixing timescales which are short compared to timescales for spin conversion, with molecular gas remembering its ”cooler past”. By accounting for OPR disequilibrium, we can identify instances of recent and rapid heating to better understand the flow of energy through the interstellar medium and track its thermal history.
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All authors Sara E. Duval, J.D.T. Smith, Alberto D. Bolatto, B.T. Draine, Thomas S.-Y. Lai, Karin M. Sandstrom, Simon C. O. Glover, Ralf S. Klessen, Elisabeth A.C. Mills, Rebecca C. Levy, Sylvain Veilleux, Daniel A. Dale, Aditya Togi, Paul P. van der Werf, Vicente Villanueva, Utsav Siwakoti, Serena A. Cronin, Evan D. Skillman, Deanne B. Fisher, Yu-Hsuan Teng, David S. Meier, Leindert A. Boogaard, Elizabeth Tarantino, Laura Lenkić, Rodrigo Herrera-Camus, Fabian Walter, Patricia A. Arens

Solar and Stellar Astrophysics

VarWISE: Infrared Variability via NEOWISE Single Exposure Photometry

Matthew Paz, J. Davy Kirkpatrick, Rajiv Uttamchandani et al. (+2 more)

The Near-Earth Object Wide-field Infrared Explorer (NEOWISE) mission provides a decade of all-sky time-series data at 3.4 and 4.6um and an unprecedented opportunity for the discovery and characterization of variable objects. This paper presents VarWISE, a catalog of infrared-variable objects discovered within the NEOWISE single-exposure data. We employ unique methodologies, including the spatial clustering of apparitions and the adoption of novel machine learning-based variable detection (VARnet) and classification (XGBoost) to identify and characterize significant variability. The catalog includes a prediction of variable object type and best-fit period values for each object, if its variations are cyclical, along with other calculated parameters to characterize the nature of the variability. The VarWISE Pure Catalog, containing only variables of highest confidence, has 457,080 objects, 49.81% of which are new discoveries; the VarWISE Extended Catalog, containing all sources, has 1,918,082 objects, 82.02% of which are new. We discuss caveats for each variable type and highlight a few new objects found during a quick perusal of the catalogs' contents.
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All authors Matthew Paz, J. Davy Kirkpatrick, Rajiv Uttamchandani, Troy Raen, Roc M. Cutri

High Energy Astrophysical Phenomena

Magnetohydrodynamics Simulations

E. A. Huerta

Magnetohydrodynamics (MHD) couples the Navier–Stokes and Maxwell equations into a nonlinear system of partial differential equations governing stellar interiors, astrophysical jets, fusion plasmas, and space weather. Numerical advances, including finite-volume Godunov schemes, constrained-transport algorithms, high-order spectral-element and discontinuous-Galerkin discretisations, and adaptive mesh refinement, have made MHD a predictive tool for solar eruptions, tokamak confinement, and magnetised turbulence. A fundamental barrier nevertheless remains. In three-dimensional MHD turbulence, the degrees of freedom required to resolve all active scales grow as $\mathcal{O}(\mathrm{Re}^{9/4})$ or faster, where $\mathrm{Re}$ is the Reynolds number. Direct numerical simulation is therefore intractable at astrophysical and fusion-relevant parameters, particularly when the Lundquist number $S$ exceeds $10^{10}$ and both viscous and resistive dissipation ranges must be resolved. Kinetic closures, radiation transport, and uncertainty quantification further increase the cost. This chapter examines how AI may help bridge this gap. We review physics-informed neural networks, Fourier neural operators and physics-informed neural operators, which learn solution operators across families of MHD problems; and hybrid operator-diffusion frameworks that combine deterministic surrogates with score-based generative models to recover broadband turbulent spectra. These developments are set within the wider landscape of exascale high-order solvers, GPU acceleration, task-based parallelism, data-driven sub-grid closures, and prospective quantum algorithms for implicit linear systems in resistive MHD. The central claim is that physics-informed AI, integrated with conventional solvers and trained on leadership-scale simulations, offers a credible route to regimes beyond the reach of classical discretisation alone.
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High Energy Astrophysical Phenomena

IceCube Second Track Data Release IceTracks-DR2: Data from 2008-2022 for Neutrino Source Searches

R. Abbasi, M. Ackermann, J. Adams et al. (+412 more)

We present IceCube's latest release of muon track data for neutrino point-source searches, extending the previously published 10-year dataset to cover 14 years of observations (April 6, 2008 - May 23, 2022). This release features an updated event selection and improved detector calibration for data recorded after June 1, 2010. The release also includes binned instrument response functions and effective areas, enabling the community to perform sensitive searches for steady and transient neutrino sources. We report on key science results obtained with this dataset using internal IceCube analysis tools and compare them to those derived from analyses based on the binned response functions included in this public release. To facilitate reproducible research, we provide benchmark results obtained using this data release and publicly available software. This release represents IceCube's most sensitive and comprehensive publicly available all-sky muon track dataset to date and should be preferred over previous releases.
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All authors R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, J.M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, Y. Ashida, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, A. Balagopal V., S. W. Barwick, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, R. T. Burley, D. Butterfield, K. Carloni, J. Carpio, N. Chau, Y. C. Chen, Z. Chen, D. Chirkin, S. Choi, A. Chubarov, B. A. Clark, G. H. Collin, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häußler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, A. Hollnagel, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, T. Kim, H. Kimku, F. Kirchner, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, S. Koch, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, T. Krishnan, K. Kruiswijk, E. Krupczak, A. Kumar, E. Kun, N. Kurahashi, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, D. Mousadi, E. Moyaux, T. Mukherjee, M. Nakos, U. Naumann, L. Neste, M. Neumann, H. Niederhausen, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, B. Owens, V. Palusova, H. Pandya, A. Parenti, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, S. Pick, M. Plum, A. Pontén, V. Poojyam, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, S. Rodan, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, M. Scarnera, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, A. Scholz, F. G. Schröder, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, S. Shefali, N. Shimizu, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, D. Song, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, S. Tilav, K. Tollefson, J. A. Torres, S. Toscano, D. Tosi, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, D. Veske, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, R. Young, F. Yu, S. Yu, T. Yuan, S. Yun-Cárcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman, C. Zilleruelo Cañas

Instrumentation and Methods for Astrophysics

Optimal mitigation of random telegraph noise for improved photometry at high frame rates

Christopher Layden, Daniel-Rolf Harbeck, Tejus Deo-Dixit et al. (+3 more)

Random telegraph noise (RTN) is a major contributor to read noise in many CMOS image sensors considered for astronomical use. While scientific CMOS image sensors deliver lower read noise than traditional charge-coupled devices, mitigating RTN would widen this gap and enable more precise photometry when using the fast readout rates achievable by CMOS image sensors. We report the levels of RTN in three CMOS image sensors used in astronomical instruments: the Sony IMX455, Gpixel GSENSE400, and Fairchild Imaging HWK4123. For the IMX455 in a high gain mode, RTN is the dominant source of pixels with high read noise and increases the overall read noise floor by >20%. RTN is present in the GSENSE400 and HWK4123 but to smaller effects. We compare two strategies for RTN mitigation: masking pixels exhibiting RTN or using a new algorithm for correcting RTN jumps. For faint (< 3 e-/pix/frame) observations of a stellar field with the IMX455, both masking and our algorithm improved the signal-to-noise ratio (SNR) of light curves by >5% on average. Larger improvements were achieved for sources falling on multiple RTN pixels. Our algorithm outperforms masking, especially when the point spread function is undersampled, masked pixels are near the source center, or read noise and shot noise are comparable. In such cases, masking may even deteriorate photometric precision. In other cases, masking remains an effective RTN mitigation technique. We have made available our software for identifying RTN pixels, parametrizing their bias level distributions, and applying our correction algorithm.
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All authors Christopher Layden, Daniel-Rolf Harbeck, Tejus Deo-Dixit, Nathan Lourie, Gabor Furesz, Kevin Burdge

Earth and Planetary Astrophysics

Detection of propadiene (CH$_2$CCH$_2$), propene (C$_3$H$_6$) and non-detection of propane (C$_3$H$_8$) in Jupiter's northern polar stratosphere

James A. Sinclair, Thomas K. Greathouse, Rohini S. Giles et al. (+8 more)

We report the first detection of stratospheric propadiene (CH$_2$CCH$_2$) and propene (C$_3$H$_6$) at Jupiter's mid-to-high northern latitudes using IRTF-TEXES measurements recorded on March 5-6, 2025. Using radiative transfer software to quantitatively test for the presence of propadiene and propene, we report a $>$12-$\sigma$ detection of propadiene and a $>$17-$\sigma$ detection of propene inside Jupiter's northern auroral region (henceforth 'NAR'), where the species are most concentrated. For example, at 62$^\circ$N inside Jupiter's NAR, we derive a 1-mbar propadiene abundance of 2.0 $\pm$ 0.2 ppbv, which is 40 $\pm$ 3 higher than abundances predicted by the Moses & Poppe (2017) photochemical model (henceforth 'MP17'), and significantly higher than the 1.2-ppbv upper limit abundance derived at 42$^\circ$N (the lowest latitude sampled by the observations). Similarly, we derive a 1-mbar propene abundance of 8.1 $\pm$ 0.5 ppbv at 62$^\circ$N inside Jupiter's NAR, which is 28 $\pm$ 2 higher than the MP17 predicted abundance and higher than the 6-ppbv 1-mbar upper limit abundance derived at 42$^\circ$N. The fact that propadiene and propene are most enriched inside Jupiter's NAR strongly suggests that perturbations to the chemistry by auroral-related heating and exogenous ions/electrons are responsible for their significant enrichment. Spectral features of propane (C$_3$H$_8$) were not detected at any of the locations sampled by the data: 3-$\sigma$ upper limits of 10 ppbv were derived at the 10-mbar level at 62$^\circ$N inside Jupiter's NAR. The non-detection of propane could, in part, be explained by the vertical sensitivity of its spectral features to deeper pressures, where there is negligible auroral-related heating. The results of this work advocate for development of ion-neutral chemistry models of Jupiter's polar stratosphere.
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All authors James A. Sinclair, Thomas K. Greathouse, Rohini S. Giles, Keeyoon Sung, Conor A. Nixon, Nicholas A. Lombardo, Vincent Hue, Julianne I. Moses, Leigh N. Fletcher, Patrick G. J. Irwin, Glenn S. Orton

Earth and Planetary Astrophysics

Exoplanets in ancient stellar populations: occurrence constraints and hot-Jupiter candidates in the Galactic halo

Dolev Bashi, Michelle Kunimoto, Kevin K. Hardegree-Ullman et al. (+3 more)

The Galactic halo preserves a record of the Milky Way's earliest assembly and contains both in-situ stars and stars accreted from dwarf galaxies. Possible planets around these stars, therefore, probe formation in ancient, metal-poor environments, including systems of extragalactic origin. We present a search for short-period transiting planets around kinematically selected halo dwarfs using Gaia DR3 and TESS, focusing on planets with periods of $1 < P < 10$ days. We identify two hot-Jupiter (HJ) candidates, one in the in-situ and one in the accreted halo, although the latter is highly grazing and excluded from the occurrence analysis. The accreted candidate, if confirmed, would orbit the most metal-poor HJ host known ([Fe/H] $\approx -1$). Using injection–recovery tests and automated vetting, we constrain occurrence in the full halo, in-situ, and accreted samples. In the HJ regime ($8\,R_\oplus < R_{\rm p} < 22\,R_\oplus$, $1\,\text{day}\ < P < 10$ days), the non-grazing candidate implies an overall halo occurrence rate of $0.13^{+0.12}_{-0.07}\%$ if planetary, while the absence of confirmed detections gives a corresponding $1\sigma$ upper limit of $<0.14\%$. For the in-situ halo, we infer $0.17^{+0.17}_{-0.10}\%$ (or $<0.19\%$ assuming no detections), while for the accreted halo we derive an upper limit of $<0.56\%$. These rates lie well below the corresponding short-period giant-planet occurrence measured in the Galactic disc. A forward model assuming Kepler-like occurrence also predicts $10 \pm 3$ detections compared with at most one observed. We find no significant occurrence difference between the in-situ and accreted halo populations, strengthening the evidence that close-in giant planets are rare across the old, metal-poor halo.
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All authors Dolev Bashi, Michelle Kunimoto, Kevin K. Hardegree-Ullman, Tianjun Gan, Sharon X. Wang, Zhen Yuan

Solar and Stellar Astrophysics

Blue Straggler Stars in Old Open Clusters and the Kraft Break

Evan Linck and Robert D. Mathieu

We measure the projected rotational velocities ($v \sin i$) of the solar-like blue straggler stars (BSSs) in the old ($\geq4$ Gyr) open clusters M67, NGC 188, and NGC 6791. We find that the BSS rotation distribution shows a Kraft break similar to that found in the field. The main-sequence progenitors of these BSSs were cooler than the Kraft break and have spun down by their age. The binary interactions that create BSSs are expected to spin up these progenitors, so current BSS rotation rates are due to transformation and any subsequent spin-down. We observe that BSSs hotter than the Kraft break are rapidly rotating, showing that binary evolution spins up these, and likely all, BSSs to initial rotational periods below two days, still below critical velocity. BSSs below the Kraft break currently have slow rotation rates, and those within the Kraft break have a mixture of rotation rates suggesting rotational transition. This dependence of rotation on effective temperature indicates that BSS envelopes behave like those of single stars, becoming convective and generating magnetic fields at the same temperatures. For globular cluster BSSs with [Fe/H]$\sim-1.5$, we find evidence of a BSS rotation transition region that is 100-250 K hotter than at solar metallicity. We find the $v \sin i$ distributions of BSSs in open clusters have similar characteristics to both high- and low-density globular clusters, indicating the density of environment is not the only factor that can determine rotational distributions. We suggest that velocity dispersion plays an important role.
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Astrophysics of Galaxies

Summary of Discussion Sessions from "The Dusty Universe 2025: The Fifth Pandust Conference"

Marjorie Decleir, Karl D. Gordon, Annalisa De Cia et al. (+16 more)

"The Dusty Universe: The Fifth Pandust Conference" took place in Tucson (AZ, USA) from November 10 until 14, 2025. The goal of this meeting was to get the dust community together to review where we are, hear exciting new results, and make plans for the future. The meeting encompassed all aspects of dust investigations including observations, theory, modeling, and laboratory studies. The conference consisted of invited review talks, contributed talks and posters. Science topics included interstellar dust (Milky Way & nearby galaxies), circumstellar dust (including Solar System & exoplanets), dust in Galaxies (including high-z), lifecycle of dust, and future needs (laboratory, theory, & observations), with a particular focus on results from JWST and ALMA, and on nanodust (including PAHs). On November 12th, we organized breakout discussion sessions covering a wide range of interesting dust-related topics. The purpose of this document is to capture the main topics/questions that were discussed, the key conclusions of these discussions, the challenges and possible solutions that were brought up, and the open questions that still remain to be answered. We hope that this document records our findings and challenges for the future generation.
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All authors Marjorie Decleir, Karl D. Gordon, Annalisa De Cia, Brandon S. Hensley, Maarten Baes, Chian-Chou Chen, Meriem Elyajouri, Frédéric Galliano, Thomas Henning, Jacob Jencson, Thomas S.-Y. Lai, Mikako Matsuura, Jed McKinney, Samir Salim, Andrew K. Saydjari, Irene Shivaei, J.D.T. Smith, Aki Takigawa, Elizabeth Tarantino

Astrophysics of Galaxies

High-resolution X-ray spectroscopy with XRISM/Resolve reveals super-Solar abundance ratios in Virgo/M87

J. Martin, A. Simionescu, F. Mernier et al. (+26 more)

The chemical composition of the intracluster medium (ICM) provides key insights into the enrichment history of galaxy clusters. However, high-resolution abundance measurements with X-ray microcalorimeters remain available for only a few systems. While most cool-core clusters exhibit near-Solar elemental abundance ratios relative to Fe, previous studies of the Virgo cluster suggested super-Solar ratios in its core. We investigate the chemical properties of the Virgo cluster core using XRISM/Resolve observations, focusing on precise measurements of Si, S, Ar, Ca, Cr, Fe, and Ni abundances. We aim to determine whether Virgo displays abundance patterns distinct from other nearby cool-core clusters and to explore the origin of any differences. We analysed XRISM/Resolve spectra in four regions of the Virgo core (center, east, northwest, and southwest) in the 1.7-11 keV band. Single-temperature, multi-temperature, and multi-abundance models were applied to characterize the thermal structure and derive elemental abundances. The resulting abundance ratios were compared between pointings, with previous studies of Virgo/M87, and with recent XRISM measurements of other clusters. All four pointings exhibit systematically super-Solar X/Fe ratios, although the northwest region shows values closer to Solar. Multi-abundance modeling of the eastern and southwestern regions reveals that cool, metal-rich gas uplifted by the AGN coexists with a hotter, more chemically homogeneous ambient ICM. The super-Solar ratios are robust against variations in bandpass and temperature structure. We interpret these enhanced ratios as reflecting the enrichment history of the old stellar population in M87 combined with a limited cold gas reservoir. The Virgo core exhibits spatially resolved chemical enrichment that differs from the abundance patterns observed in other cool-core clusters.
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All authors J. Martin, A. Simionescu, F. Mernier, C. Kilbourne, A. Tümer, H. R. Russell, M. Charbonneau, N. Dizdar, D. Eckert, Y. Ezoe, R. Fujimoto, M. Fujita, K. Fukushima, L. Gu, E. Hodges-Kluck, Y. Ichinohe, D. Ito, S. Kitamoto, M. A. Leutenegger, M. Loewenstein, H. McCall, B. R. McNamara, E. D. Miller, I. Mitsuishi, K. Nakazawa, A. Ogorzalek, K. Sato, A. Szymkowiak, I. Zhuravleva

Astrophysics of Galaxies

How High-Specific-Energy Winds Regulate the Circumgalactic Medium of Dwarf Galaxies

Michael Messere and Greg L. Bryan

We investigate the role of ejective and preventive feedback in $\mathrm{\sim10^{10}-10^{11}\,M_\odot}$ dwarf halos using cosmological zoom-in simulations. These simulations use adaptive mesh refinement to capture high-specific-energy outflows, together with an implementation of discrete supernovae (SNe). We show that episodic, SNe-driven shock heating sustains the circumgalactic medium (CGM) at $\mathrm{\sim T_{vir}}$. This process also increases the ratio $\mathrm{t_{cool}/t_{ff} > 10}$ in the outer CGM and intergalactic medium (IGM), placing the gas in a radiatively stable regime. Hot outflows ($\mathrm{\gtrsim10^5\, K}$) dominate the energy budget, and their high specific energy allows them to traverse the CGM, escape the halo, and heat the IGM. In contrast, warm outflows ($\mathrm{\lesssim10^5\, K}$) dominate the mass budget and are largely recycled back into the interstellar medium (ISM), where they fuel future star formation. We identify a gradual transition at $\mathrm{\sim 5\, Gyr}$ that marks a shift in the balance between ejective and preventive feedback. At early times ($\mathrm{< 5\, Gyr}$), although the CGM cooling rate dominates for a larger fraction of time, the infrequent yet powerful SNe energy injection into the CGM is able to quickly dominate the cumulative energy balance. These outflows and their high specific energy are able to 'sweep' up mass in the CGM and IGM. At late times ($\mathrm{> 5\, Gyr}$), the CGM baryon fraction is only $\mathrm{\sim0.1}$, leading to a transition toward a preventive feedback mode in which SNe maintain $\mathrm{t_{cool}/t_{ff} > 10}$ and prevent $\mathrm{\sim75\%}$ of the expected baryon accretion rate.
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