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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 25 March

Astrophysics of Galaxies

Imprints of tidal interactions on the stellar distribution of satellite galaxies: implications for dark matter deficient galaxies

Zhihao Yin, Go Ogiya and Frank C. van den Bosch

Interactions with the host galaxy strip stars and dark matter from the outer regions of satellite galaxies. Meanwhile, some stars from the central regions can migrate outward due to dynamical heating, producing an excess in the outer surface brightness relative to the extrapolation of the inner Sérsic profile. Recently discovered dark matter deficient galaxies (DMDGs) appear to be representative examples of such tidally disturbed systems. In this work, we investigate how the break radius, defined as the radius beyond which this surface brightness excess emerges, forms and evolves, by performing $N$-body simulations of a satellite galaxy interacting with a host, where the satellite serves as a plausible progenitor of a DMDG. Our simulations naturally reproduce a break radius consistent with that observed in DMDGs. We find that the break radius grows over time and exhibits a characteristic evolutionary behaviour: during each pericentric passage it briefly contracts due to tidal compression, and then rapidly and strongly expands as the satellite undergoes dynamical relaxation. After the satellite reaches a quasi-equilibrium configuration, the break radius shows only mild variations until the next pericentre. Across our suite of simulations, the ratio of the break radius to the effective radius remains approximately constant, even when we change the orbital parameters and internal structure of the satellite. Based on these findings, we develop a prescription for predicting the time evolution of the break radius, which can be used to constrain the tidal interaction history of satellite galaxies, including DMDGs and splashback galaxies.
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High Energy Astrophysical Phenomena

RRAT J1541+4703: A Rotating Radio Transient Exhibiting Normal Pulsar States

Xin Xu, Qijun Zhi, Jie Tian et al. (+6 more)

Rotating Radio Transients (RRATs) are a class of pulsar-like objects characterized by intermittent radio emissions. Among them, RRATs that exhibit both RRAT and normal pulsar (NP) states may represent a key evolutionary stage from nulling pulsars to RRATs. We performed a detailed analysis of RRAT J1574+4703 using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) at a frequency of 1250 MHz. Our findings indicate that this RRAT spends approximately 98% of its time in the RRAT state, with the remainder spent in an NP state exhibiting nulling behavior. Additionally, we observed distinct integral pulse profiles and polarization properties between the two states, suggesting that they originate from different emission heights and magnetospheric structures. Furthermore, it was observed that the NP states of this RRAT exhibit mode switching, with ~44% of the time spent in the normal mode and ~39% in the abnormal mode. Notably, abnormal modes are predominantly detected at the onset and termination of the NP states. This discrepancy between the modes indicates potential instability in the magnetospheric processes that govern the NP states.
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All authors Xin Xu, Qijun Zhi, Jie Tian, Jiguang Lu, Peng Jiang, Shijun Dang, Renxin Xu, Juntao Bai, Ke Yang

Astrophysics of Galaxies

GalSyn I: A Forward-Modeling Code for Synthetic Galaxy Observations from Hydrodynamical Simulations and First Data Release from IllustrisTNG

Abdurro'uf, Henry C. Ferguson, Samir Salim et al. (+9 more)

We present GalSyn (Galaxy Synthesizer), a modular and flexible Python package for generating synthetic observations from hydrodynamical galaxy simulations. GalSyn generates synthetic spectrophotometric data cubes for individual galaxies from simulation cutouts, employing a particle-by-particle spectral modeling approach that enables the rapid production of large synthetic datasets required for statistical population studies, offering a computationally efficient alternative to full radiative transfer codes. Users have full control over the spectral modeling choices, including the stellar population synthesis engine, stellar isochrones, spectral libraries, and initial mass functions. Dust attenuation is modeled at spatially resolved scales using a line-of-sight column-density method, with a comprehensive suite of fixed and adaptive attenuation laws. A decoupled kinematics model independently Doppler-shifts the stellar and nebular components, enabling realistic synthetic integral field unit data cubes. It also provides features to add observational realism, including PSF convolution and noise simulation. Beyond generating imaging and spectroscopic data cubes, GalSyn reconstructs spatially resolved physical property maps and star formation histories (SFHs) of a galaxy. Alongside this paper, we present the first data release of synthetic imaging observations and resolved SFHs generated from the IllustrisTNG simulations. This release includes four mock extragalactic survey fields together with data cubes of the individual galaxies within them, data cubes of 290 local massive galaxies and their progenitors tracked across $0<z<5$, and 259 major-merger systems. Each galaxy data cube contains imaging across 47 filters spanning HST, JWST, Euclid, Rubin/LSST, and the Roman Space Telescope. GalSyn is publicly available at https://github.com/aabdurrouf/GalSyn.
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All authors Abdurro'uf, Henry C. Ferguson, Samir Salim, Kartheik G. Iyer, Larry D. Bradley, Dan Coe, Novan Saputra Haryana, Sultan Hassan, Intae Jung, Gourav Khullar, Takahiro Morishita, Lamiya Mowla

Astrophysics of Galaxies

A Long Stellar Stream in M83: Possible Connection Between XUV Disks and Minor Mergers?

Itsuki Ogami, Sakurako Okamoto, Annette M. N. Ferguson et al. (+5 more)

We present the confirmation and characterization of a long stream (S-stream) in the southern part of M83. This feature is revealed using deep wide-field photometric data obtained by the Hyper Suprime-Cam (HSC) mounted on the Subaru Telescope. Using individual red giant branch (RGB) stars, we successfully trace the stream over a large length of $\sim 81$~kpc and a considerable width of $\sim 9$ kpc. With a mean surface brightness of ${\langle \mu_{\it V} \rangle} \sim 31.8_{-1.9}^{+1.3}$ mag arcsec$^{-2}$, it is one of the most diffuse extragalactic streams currently known. The mean photometric metallicity of the stream is $\langle[{\rm M/H}]\rangle = -1.23\pm0.02$ dex with a standard deviation of $0.28\pm0.01$ dex, and we estimate the stellar mass to be $(8.5_{-2.8}^{+4.2}) \times 10^6~{\rm M_\odot}$ from the luminosity of RGB stars. Compared to its well-known northern counterpart, the S-stream is slightly more metal-poor, but our large-area RGB map shows compelling evidence that these two features are related, originating from a single low-mass merger event. We identify density variations along the S-stream, which more likely reflect intrinsic density structure within the progenitor rather than the interaction with dark matter subhalos. Similarities between the morphology of the S-stream and some features in the \HI distribution suggest that a minor merger event may have disturbed and redistributed M83's outer \HI gas, leading to triggered star formation and the formation of the XUV disk.
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All authors Itsuki Ogami, Sakurako Okamoto, Annette M. N. Ferguson, Yutaka Komiyama, Masashi Chiba, Jin Koda, Kohei Hayashi, Yoshihisa Suzuki

Solar and Stellar Astrophysics

A generalized method for estimating solar wind speeds and densities using spectral broadening for a Kolmogorov turbulence spectrum

Keshav Aggarwal, R. K. Choudhary, Abhirup Datta et al. (+3 more)

We present a unified method to derive both solar wind velocities and coronal electron densities in the near-Sun corona using Doppler spectral broadening of spacecraft radio signals. The method is generalized to be frequency independent under the assumption that electron density fluctuations follow a Kolmogorov spectrum. We validate the approach using S-band data from India's Mars Orbiter Mission during the October 2021 superior conjunction at 5-8 R$_\odot$, and X-band data from Japan's Akatsuki during June 2016 and October 2022 conjunctions spanning 1.4-10 R$_\odot$. From S-band we obtained wind speeds of 100-150 km s$^{-1}$ and electron densities of order $10^{10}$ m$^{-3}$. X-band results show speeds ranging from $\sim$150 km s$^{-1}$ near the equator to $\sim$400 km s$^{-1}$ in coronal-hole regions, with consistent radial trends in density. We provide a compact, frequency-scaled relation that maps Doppler spectral width to both $v$ and $N_e$. The formulation enables consistent application across telecommunication bands and complements in-situ probes for coronal plasma studies.
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All authors Keshav Aggarwal, R. K. Choudhary, Abhirup Datta, Roopa M.V., Takeshi Imamura, Hiroki Ando

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

Impact of muons on the bulk viscosity of neutron star matter metamodels

José Luis Hernández, Cristina Manuel and Laura Tolos

Recent studies invoke a unified description of different neutron star observables using metamodels, which parametrize the equation of state of neutron star matter close to nuclear saturation density in terms of few nuclear parameters. In this light, the bulk viscosity in the neutrino-transparent regime of dense nuclear matter composed of neutrons, protons and electrons has been recently shown to be mostly sensitive to the value of the nuclear symmetry energy. As muons are also present at densities around nuclear saturation, we further analyze in this manuscript their impact on this transport coefficient as a function of the slope $L$ of the symmetry energy. We find that muons introduce both relevant qualitative and quantitative effects in the bulk viscous dissipation. Increasing $L$ by a factor two has an effect of several orders of magnitude on the (frequency-independent) bulk viscosity. We also find that for all values of $L$ the frequency-dependent bulk viscosity presents a double peak structure for some values of the density, absent without muons. This also represents changes in orders of magnitude of the viscosity in narrow windows of densities that could be attainable in a neutron star for enough high values of $L$. The double-peak structure is due to the fact that direct Urca processes open up at different densities for electrons and muons, the critical values depending on $L$. We present a systematic numerical analysis of both second-order transport coefficients, frequency-dependent bulk viscosity, and damping times of density oscillations as a function of the density and the slope, and find when these could be relevant for the dynamics of the merger of neutrons stars.
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Instrumentation and Methods for Astrophysics

SM-Net: Learning a Continuous Spectral Manifold from Multiple Stellar Libraries

Omar Anwar, Aaron S. G. Robotham, Luca Cortese et al. (+1 more)

We present SM-Net, a machine-learning model that learns a continuous spectral manifold from multiple high-resolution stellar libraries. SM-Net generates stellar spectra directly from the fundamental stellar parameters effective temperature (Teff), surface gravity (log g), and metallicity (log Z). It is trained on a combined grid derived from the PHOENIX-Husser, C3K-Conroy, OB-PoWR, and TMAP-Werner libraries. By combining their parameter spaces, we construct a composite dataset that spans a broader and more continuous region of stellar parameter space than any individual library. The unified grid covers Teff = 2,000-190,000 K, log g = -1 to 9, and log Z = -4 to 1, with spectra spanning 3,000-100,000 Angstrom. Within this domain, SM-Net provides smooth interpolation across heterogeneous library boundaries. Outside the sampled region, it can produce numerically smooth exploratory predictions, although these extrapolations are not directly validated against reference models. Zero or masked flux values are treated as unknowns rather than physical zeros, allowing the network to infer missing regions using correlations learned from neighbouring grid points. Across 3,538 training and 11,530 test spectra, SM-Net achieves mean squared errors of 1.47 x 10^-5 on the training set and 2.34 x 10^-5 on the test set in the transformed log1p-scaled flux representation. Inference throughput exceeds 14,000 spectra per second on a single GPU. We also release the model together with an interactive web dashboard for real-time spectral generation and visualisation. SM-Net provides a fast, robust, and flexible data-driven complement to traditional stellar population synthesis libraries.
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All authors Omar Anwar, Aaron S. G. Robotham, Luca Cortese, Kevin Vinsen

High Energy Astrophysical Phenomena

Near-Infrared and Optical Observations of SN 2024rbc: The First Early Detection of CO and Dust in a Type Ib Supernova

Ryan Hwangbo, Jeonghee Rho, Aravind P. Ravi et al. (+16 more)

We present optical and near-infrared (NIR) observations of the Type Ib supernova (SN) 2024rbc. Emission from the first CO overtone, resting on a dust continuum at $2.3-2.4$ $\mu$m, was observed at 62 days post-explosion. The CO band heads are not resolved, and the emission appears broad, lacking sharp spectral features. This is the first observation of CO in the ejecta of a Type Ib SN reported in literature. The spectra of SN 2024rbc exhibit strong He I lines and numerous neutral and ionized metal lines. Comparing the spectral evolution of SN 2024rbc to other Type Ib, Ic, and IIb SNe indicates it is a Type Ib SN. We compare the velocities of key optical lines to examine the evolution of the ejecta. Additionally, fitting SN light curve models of helium star progenitors computed with the STELLA code to photometric observations indicates a $^{56}$Ni mass of $0.07$ $M_\odot$ and an ejecta mass of $1.7$ $M_\odot$. Fitting a LTE model to the CO overtone implies a CO mass of 5.2 $\times$ 10$^{-4}$ $M_{\odot}$, a CO temperature of $4040$ K, and a CO velocity width of $5905$ km s$^{-1}$. We also fitted a modified blackbody model to the dust continuum, deriving a dust temperature of $910$ K and a dust mass of $1.3$ $\times$ $10^{-3}$ $M_{\odot}$. The CO provides direct evidence for the onset of dust formation, and the observed dust continuum likely originates from newly formed dust in the ejecta. However, robust dust mass estimates require MIR observations.
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All authors Ryan Hwangbo, Jeonghee Rho, Aravind P. Ravi, Seong Hyun Park, Harim Jin, Sung-Chul Yoon, T. R. Geballe, Ryan Foley, Kirsty Taggart, Kyle W. Davis, Kishore C. Patra, S. Tinyanont, Jesper Sollerman, Steve Schulze, Natalie LeBaron, Chang Liu, Charles D. Kilpatrick, David O. Jones, C. Tanner Murphey

Astrophysics of Galaxies

Rigorous Formulation of Finite-Sample and Finite-Window Effects in Galaxy Clustering

Tsutomu T. Takeuchi, Satoshi Kuriki and Keisuke Yano

Galaxy surveys provide finite catalogs of objects observed within bounded volumes, yet clustering statistics are often interpreted using theoretical frameworks developed for infinite point processes. In this work, we formulate key statistical quantities directly for finite point processes and examine the structural consequences of finite-number and finite-window constraints. We show that several well-known features of galaxy survey analysis arise naturally from finiteness alone. In particular, non-vanishing higher-order connected correlations can occur even in statistically independent samples when the total number of points is fixed, and the integral constraint in two-point statistics appears as an exact identity implied by the finite-number condition rather than as an estimator artifact. We further demonstrate that counts-in-cells and point-centered environmental measures correspond to distinct statistical ensembles. Using Palm conditioning, we derive an exact relation between random-cell and point-centered statistics, showing that the latter probe a tilted version of the underlying distribution. These results provide a probabilistic framework for separating structural effects imposed by finite sampling from correlations reflecting genuine astrophysical processes. The formulation presented here remains valid for realistic survey geometries and finite data sets and clarifies the interpretation of commonly used clustering statistics in galaxy surveys.
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Cosmology and Nongalactic Astrophysics · Cross-listed from physics.ins-det

The read-out electronics for the FLASH experiment

Luigi Calligaris, Claudio Puglia and Gianluca Lamanna

We introduce the FLASH haloscope experiment and present its electronic read-out system, currently under development. FLASH searches for Dark Matter (DM) particles and High-Frequency Gravitational Waves (HFGWs) using two cryogenic resonant cavities to scan the radio frequency spectrum between 117 and 360 MHz, looking for signals as weak as 10-22 W. The signal read-out uses Microstrip Superconducting Quantum Interference Amplifiers (MSAs) as low-noise amplifiers and Software-Defined Radio (SDR) techniques to acquire, preprocess and reduce the physics signal to a format suitable for permanent storage and offline analysis.
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Instrumentation and Methods for Astrophysics

A transdimensional sampling framework for pulsar timing noise modelling

Valentina Di Marco, Nir Guttman, Matthew T. Miles et al. (+3 more)

A careful characterisation of the noise processes in pulsar timing data is a prerequisite for pulsar timing array experiments. While single-pulsar noise analyses are crucial for both gravitational-wave searches and astrophysical studies, they are often computationally intensive and rely on running and comparing multiple fixed noise models. We present tPTABilby, a transdimensional Bayesian inference framework for single-pulsar noise analysis built on the Bilby library. The method flexibly models a wide range of noise processes like radiometer noise, pulse-phase jitter, intrinsic red noise, dispersion measure variations, and chromatic interstellar medium effects. By employing transdimensional sampling, tPTABilby simultaneously infers the number and type of active noise sources, providing a unified treatment of model selection and parameter estimation. We validate the methodology through simulations with known injected noise models, demonstrating accurate recovery of model probabilities and calibrated posterior distributions. We then apply this approach to a single pulsar, PSR J1713+0747, from a MeerKAT Pulsar Timing Array (MPTA) dataset, analysing the data with both tPTABilby and Enterprise, and subsequently compare the results with existing MPTA analyses through posterior predictive checks of the inferred noise spectra. Our results highlight the flexibility of transdimensional approaches to single-pulsar noise analysis, demonstrating consistency with standard fixed-model methods while providing a more statistically robust framework, and present tPTABilby as a simple and reproducible approach for PTA inference.
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All authors Valentina Di Marco, Nir Guttman, Matthew T. Miles, Andrew Zic, Ryan M. Shannon, Eric Thrane

High Energy Astrophysical Phenomena

IXPE view of the Crab pulsar following the 17 July and 6 August 2025 glitches

Paolo Soffitta, Niccolò Bucciantini Josephine Wong Denis Gonzalez Caniulef Matteo Bachetti Riccardo Ferrazzoli Fei Xie Enrico Costa Maura Pilia Nicolò Cibrario Jack T. Dinsmore, Niccolò Di Lalla Philip Kaaret et al. (+7 more)

The Crab pulsar experienced two relatively small glitches separated by only 20 days in September and October 2025. IXPE observed the source twice, with delay times since the glitch epoch ranging between 35 and 75 days, depending on the observation. We carried out a multi-method analysis to investigate whether there is evidence for significant changes in the polarization properties of the pulsar, underlying possible variations in the pulsar magnetosphere itself following the glitches. Specifically, we performed: (1) phase-averaged polarimetry of the Crab pulsar before and after the glitches, following an approach similar to that adopted in 2019 by PolarLight, a non-imaging CubeSat-class photoelectric polarimeter which observed a change in the X-ray polarization within 100 days after a stronger glitch in July 2019; (2) a comparison, before and after the glitch, of phase-resolved X-ray polarimetry with IXPE, not possible with PolarLight. Furthermore, we investigated, by means of phase-resolved optical (OPTIMA) polarimetry, whether a significant change in the X-to-optical lag was present in the data before and after the glitch. We find no evidence of a change in the polarization for the pulsar emission before and after the glitch, We use the upper limits obtained to estimate the maximum change in magnetic obliquity allowed by the data, using the standard rotating vector model and assuming that the glitch is due to a neutron-star quake. We constrain this maximum change to be no greater than $\pm4^{o}$ at the 95% confidence level.
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All authors Paolo Soffitta, Niccolò Bucciantini Josephine Wong Denis Gonzalez Caniulef Matteo Bachetti Riccardo Ferrazzoli Fei Xie Enrico Costa Maura Pilia Nicolò Cibrario Jack T. Dinsmore, Niccolò Di Lalla Philip Kaaret, Kuan Liu, Tsunefumi Mizuno, Michela Negro C.-Y. Ng, Nicola Omodei, Simone Pagliarella, Stefano Silvestri Yi-Jung Yang, Martin C. Weisskopf

Tuesday 24 March

High Energy Astrophysical Phenomena

FRB Searches with the Irish LOFAR Station

D. J. McKenna and E. F. Keane

Here we report null results in the search for radio emission below $200$~MHz from six known fast radio burst sources. The observations reported here were taken using the Irish LOFAR station's high-band antennas over the course of 2020, 2021 and 2022; the cumulative observing time was $218$~h.
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Solar and Stellar Astrophysics

Out-of-Domain Stress Test for Temporal Braid Group Privilege Escalation Detection

Christophe Parisel

In a companion paper, we prove that the Burau-Lyapunov exponent LE discriminates focused from dispersed privilege escalation ratchets in cloud IAM graphs, and that no abelian statistic can replicate this discrimination. To strengthen this claim beyond its synthetic validation corpus, we apply the identical pipeline, with zero parameter retuning, to solar coronal magnetic fields: a physical system with no connection to cloud identity and access management, whose binary eruptive/confined outcome is independently established by decades of astrophysical observation.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.soc-ph

Possible Reforms of the Tibetan Lunisolar Calendar

Tsogtgerel Gantumur

The family of Tibetan lunisolar calendars operates on a shared arithmetic axiom (67 lunar months = 65 solar months) that provides a rigid structure but causes observable seasonal drift. This study deconstructs the calendar through a progressive analytical sequence, first presenting it as an explicit computational procedure, then isolating its structural core of incidence rules and mean-motion models. This separation distinguishes structurally forced features from tradition-dependent ones, allowing inaccuracies to be rigorously decomposed into internal arithmetic drift, sidereal misalignment, and anomaly-phase defects. Crucially, computational analysis also reveals remarkable historical robustness: the discrete arithmetic of traditional day rules renders boundary tie-cases operationally absent, while large internal temporal buffers and the multi-hour inaccuracy of the classical lunar model insulated the calendar against geographic variation. On this basis, the paper develops a stratified reform space rather than a single replacement proposal. The resulting standards range from conservative rational repairs preserving traditional arithmetic to explicit astronomical reconstructions culminating in fully dynamical models of true solar and lunar motion. The guiding question is how far astronomical correction can be carried without discarding the Tibetan calendrical identity embodied in the structural rules for month and day labeling. Finally, calendric reform requires more than new formulas and constants; it demands precise numerical semantics. The proposed standards are thus formulated not merely as abstract models, but as executable, reproducible specifications suitable for implementation, validation, and long-term transmission across computational environments.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.CV

BHCast: Unlocking Black Hole Plasma Dynamics from a Single Blurry Image with Long-Term Forecasting

Renbo Tu, Ali SaraerToosi, Nicholas S. Conroy et al. (+2 more)

The Event Horizon Telescope (EHT) delivered the first image of a black hole by capturing the light from its surrounding accretion flow, revealing structure but not dynamics. Simulations of black hole accretion dynamics are essential for interpreting EHT images but costly to generate and impractical for inference. Motivated by this bottleneck, BHCast presents a framework for forecasting black hole plasma dynamics from a single, blurry snapshot, such as those captured by the EHT. At its core, BHCast is a neural model that transforms a static image into forecasted future frames, revealing the underlying dynamics hidden within one snapshot. With a multi-scale pyramid loss, we demonstrate how autoregressive forecasting can simultaneously super-resolve and evolve a blurry frame into a coherent, high-resolution movie that remains stable over long time horizons. From forecasted dynamics, we can then extract interpretable spatio-temporal features, such as pattern speed (rotation rate) and pitch angle. Finally, BHCast uses gradient-boosting trees to recover black hole properties from these plasma features, including the spin and viewing inclination angle. The separation between forecasting and inference provides modular flexibility, interpretability, and robust uncertainty quantification. We demonstrate the effectiveness of BHCast on simulations of two distinct black hole accretion systems, Sagittarius A* and M87*, by testing on simulated frames blurred to EHT resolution and real EHT images of M87*. Ultimately, our methodology establishes a scalable paradigm for solving inverse problems, demonstrating the potential of learned dynamics to unlock insights from resolution-limited scientific data.
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All authors Renbo Tu, Ali SaraerToosi, Nicholas S. Conroy, Gennady Pekhimenko, Aviad Levis

Solar and Stellar Astrophysics

The Role of Reconnection at Magnetic Separators in Complex Solar Flare Ribbons

Graham Barnes and Karin Dissauer

Solar flare ribbons, manifesting as transient brightenings in the chromosphere, are believed to trace out the footpoints of magnetic field lines that are reconnecting higher in the solar atmosphere. These field lines lie in a separatrix or quasi-separatrix layer that separates domains of different magnetic connectivity and hence forms a natural location for reconnection. Solar flares are typically characterized as being circular ribbon flares, two-ribbon flares, or complex ribbon flares based on the number and shape of the ribbons. There are relatively well-developed models to explain the first two types of flares based on the location of the reconnection powering the flare. The case of complex ribbons is less well understood, but is often posited to be a result of reconnection at multiple locations. We demonstrate here that reconnection at a magnetic separator connecting two coronal null points can naturally explain the complex ribbons observed for two events, an M2.9 class flare from NOAA AR 11112 (SOL2010-10-16T19:12), and an X2.2 class flare from NOAA AR 11158 (SOL2011-02-15T01:56).
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Instrumentation and Methods for Astrophysics

The Vera C. Rubin Observatory Data Preview 1

Vera C Rubin Observatory Team, Tatiana Acero Cuellar, Emily Acosta et al. (+325 more)

We present Rubin Data Preview 1 DP1, the first data from the NSF DOE Vera C Rubin Observatory, comprising raw and calibrated single epoch images, coadds, difference images, detection catalogs, and ancillary data products. DP1 is based on 1792 optical near infrared exposures acquired over 48 distinct nights by the Rubin Commissioning Camera LSSTComCam on the Simonyi Survey Telescope at the Summit Facility on Cerro Pachón Chile in late 2024. DP1 covers $\sim$15 deg$^2$ distributed across seven roughly equal-sized non-contiguous fields, each independently observed in six broad photometric bands $ugrizy$. The median FWHM of the point spread function across all bands is approximately 1.14 arcseconds, with the sharpest images reaching about 0.58 arcseconds. The 5$\sigma$ point source depths for coadded images in the deepest field the Extended Chandra Deep Field South are $u$ = 24.55, $g$ = 26.18, $r$ = 25.96, $i$ = 25.71, $z$ = 25.07, $y$ = 23.1. Other fields are no more than 2.2 magnitudes shallower in any band where they have nonzero coverage. DP1 contains approximately 2.3 million distinct astrophysical objects, of which 1.6 million are extended in at least one band in coadds and 431 solar system objects of which 93 are new discoveries. DP1 is approximately 3.5 TB in size and is available to Rubin data rights holders via the Rubin Science Platform a cloud based environment for the analysis of petascale astronomical data. While small compared to future LSST releases its high quality and diversity of data support a broad range of early science investigations ahead of full operations in 2026.
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All authors Vera C Rubin Observatory Team, Tatiana Acero Cuellar, Emily Acosta, Christina L Adair, Prakruth Adari, Jennifer K Adelman McCarthy, Anastasia Alexov, Russ Allbery, Robyn Allsman, Yusra AlSayyad, Jhonatan Amado, Nathan Amouroux, Pierre Antilogus, Alexis Aracena Alcayaga, Gonzalo Aravena Rojas, Claudio H Araya Cortes, Eric Aubourg, Tim S Axelrod, John Banovetz, Carlos Barria, Amanda E Bauer, Brian J Bauman, Ellen Bechtol, Keith Bechtol, Andrew C Becker, Valerie R Becker, Mark G Beckett, Eric C Bellm, Pedro H Bernardinelli, Federica Bettina Bianco, Robert D Blum, Joanne Bogart, Adam Bolton, Michael T Booth, James F Bosch, Alexandre Boucaud, Dominique Boutigny, Robert A Bovill, Andrew Bradshaw, Johan Bregeon, Massimo Brescia, Brian J Brondel, Alexander Broughton, Audrey Budlong, Dimitri Buffat, Rodolfo Canestrari, Neven Caplar, Jeffrey L Carlin, Ross Ceballo, Colin Orion Chandler, Chihway Chang, Glenaver Charles Emerson, Hsin Fang Chiang, James Chiang, Yumi Choi, Eric J Christensen, Charles F Claver, Andy W Clements, Joseph J Cockrum, Johann Cohen Tanugi, Franco Colleoni, Celine Combet, Andrew J Connolly, Julio Eduardo Constanzo Cordova, Hans E Contreras, John Franklin Crenshaw, Sylvie Dagoret Campagne, Scott F Daniel, Felipe Daruich, Guillaume Daubard, Greg Daues, Erik Dennihy, Stephanie J H Deppe, Seth W Digel, Peter E Doherty, Cyrille Doux, Alex Drlica Wagner, Gregory P Dubois Felsmann, Frossie Economou, Orion Eiger, Lukas Eisert, Alan M Eisner, Anthony Englert, Baden Erb, Juan A Fabrega, Parker Fagrelius, Kevin Fanning, Angelo Fausti Neto, Peter S Ferguson, Agnes Ferte, Krzysztof Findeisen, Merlin Fisher Levine, Gloria Fonseca Alvarez, Michael D Foss, Dominique Fouchez, Dan C Fuchs, Shenming Fu, Emmanuel Gangler, Igor Gaponenko, Julen Garcia, John H Gates, Ranpal K Gill, Enrico Giro, Thomas Glanzman, Robinson Godoy, Iain Goodenow, Miranda R Gorsuch, Michelle Gower, Melissa L Graham, Mikael Granvik, Sarah Greenstreet, Wen Guan, Thibault Guillemin, Leanne P Guy, Diane Hascall, Patrick A Hascall, Aren Nathaniel Heinze, Fabio Hernandez, Kenneth Herner, Ardis Herrold, Clare R Higgs, Joshua Hoblitt, Erin Leigh Howard, Minhee Hyun, Amanda Ibsen, Patrick Ingraham, David H Irving, Zeljko Ivezic, Suzanne H Jacoby, Buell T Jannuzi, Sreevani Jarugula, M James Jee, Tim Jenness, Toby C Jennings, Andrea Jeremie, Garrett Jernigan, David Jimenez Mejias, Anthony S Johnson, R Lynne Jones, Roger William Lewis Jones, Claire Juramy Gilles, Mario Juric, Steven M Kahn, J Bryce Kalmbach, Yijung Kang, Arun Kannawadi, Jeffrey P Kantor, Edward Karavakis, Kshitija Kelkar, Lee S Kelvin, Scot J Kleinman, Ivan V Kotov, Gabor Kovacs, Mikolaj Kowalik, Victor L Krabbendam, K Simon Krughoff, Petr Kubanek, Jacob A Kurlander, Mile Kusulja, Craig S Lage, Paulo J A Lago, Katherine Laliotis, Travis Lange, Didier Laporte, Ryan M Lau, Juan Carlos Lazarte, Quentin Le Boulch, Pierre Francois Leget, Laurent Le Guillou, Benjamin Levine, Ming Liang, Shuang Liang, Kian Tat Lim, Anja von der Linden, Huan Lin, Margaux Lopez, Juan J Lopez Toro, Peter Love, Robert H Lupton, Nate B Lust, Lauren A MacArthur, Sean Patrick MacBride, Greg M Madejski, Gabriele Mainetti, Steven J Margheim, Thomas W Markiewicz, Phil Marshall, Stuart Marshall, Guido Maulen, Sidney Mau, Morgan May, Jeremy McCormick, David McKay, Robert McKercher, Guillem Megias Homar, Aaron M Meisner, Felipe Menanteau, Heather R Mentzer, Kristen Metzger, Joshua E Meyers, Michelle Miller, David J Mills, Joachim Moeyens, Marc Moniez, Fred E Moolekamp, C A L Morales Marin, Fritz Mueller, James R Mullaney, Freddy Munoz Arancibia, Kate Napier, Homer Neal, Eric H Neilsen Jr, Jeremy Neveu, Timothy Noble, Erfan Nourbakhsh, Knut Olsen, William OMullane, Dmitry Onoprienko, Marco Oriunno, Shawn Osier, Russell E Owen, Aashay Pai, John K Parejko, Hye Yun Park, James B Parsons, Maria T Patterson, Marina S Pavlovic, Karla Pena Ramirez, John R Peterson, Stephen R Pietrowicz, Andres A Plazas Malagon, Rebekah Polen, Hannah Mary Margaret Pollek, Paul A Price, Bruno C Quint, Jose Miguel Quintero Marin, Markus Rabus, Benjamin Racine, Veljko Radeka, Manon Ramel, Arianna Ranabhat, Andrew P Rasmussen, David A Rathfelder, Meredith L Rawls, Sophie L Reed, Kevin A Reil, David J Reiss, Michael A Reuter, Tiago Ribeiro, Mickael Rigault, Vincent J Riot, Steven M Ritz, Mario F Rivera Rivera, Brant E Robertson, William Roby, Gabriele Rodeghiero, Aaron Roodman, Luca Rosignoli, Cecile Roucelle, Matthew R Rumore, Stefano Russo, Eli S Rykoff, Andrei Salnikov, Bruno O Sanchez, David Sanmartim, Clare Saunders, Rafe H Schindler, Samuel J Schmidt, Jacques Sebag, Nima Sedaghat, Brian Selvy, Edgard Esteban Sepulveda Valenzuela, Gonzalo Seriche, Jacqueline C Seron Navarrete, Ignacio Sevilla Noarbe, Alysha B Shugart, Jonathan Sick, Cristian Silva, Mathew C Sims, Jaladh Singhal, Kevin Benjamin Siruno, Colin T Slater, Brianna M Smart, Adam Snyder, Christine Soldahl, Ioana Sotuela Elorriaga, Brian Stalder, Hernan Stockebrand, Alan L Strauss, Michael A Strauss, Krzysztof Suberlak, Ian S Sullivan, John D Swinbank, Diego Tapia, Alessio Taranto, Dan S Taranu, John Gregg Thayer, Sandrine Thomas, Adam J Thornton, Roberto Tighe, Laura Toribio San Cipriano, Te Wei Tsai, Douglas L Tucker, Max Turri, J Anthony Tyson, Elana K Urbach, Yousuke Utsumi, Brian Van Klaveren, Wouter van Reeven, Peter Anthony Vaucher, Paulina Venegas, Aprajita Verma, Antonia Sierra Villarreal, Stelios Voutsinas, Christopher W Walter, Yuankun David Wang, Christopher Z Waters, Christina C Williams, Beth Willman, Matthias Wittgen, W M Wood Vasey, Wei Yang, Zhaoyu Yang, Brian P Yanny, Peter Yoachim, Tianqing Zhang, Conghao Zhou, Danica Zilkova

Solar and Stellar Astrophysics

Thermally inflated accretors in post-mass transfer binaries: Abell 35 and its class revisited

Soumyadeep Bhattacharjee, Kareem El-Badry, Jim Fuller et al. (+2 more)

A small but growing class of binaries containing hot ($T_{\rm eff}\sim10^5\ {\rm K}$) white dwarfs (WDs) and rapidly rotating, apparently subgiant companions – including the prototype, Abell 35 – show companions that are too large and luminous to be ordinary main-sequence stars yet too numerous to be explained as finely tuned near-twin binaries. We argue that these stars are instead main-sequence accretors temporarily inflated out of thermal equilibrium by recent mass transfer. For the subgiant of Abell 35, a new Gaia DR3 astrometric orbit ($P_{\rm orb}=790\ {\rm d}$), combined with updated photometric and spectroscopic constraints, yields $T_{\rm eff}\approx4925\pm75\ {\rm K}$, $R\approx3\pm0.05\ R_{\odot}$, near-solar metallicity, and rapid rotation aligned with the orbit ($v_{\rm rot}\approx195\pm3\ {\rm km\ s^{-1}}$), indicating substantial recent accretion and spin-up. Dynamical mass limits disfavor a coeval twin-binary origin, supporting the inflated-accretor interpretation. We test this scenario using self-consistent MESA binary evolution calculations with a new accretion prescription in which accreted material retains a fraction of its infall energy, rather than adopting the default assumption that its entropy equals that of the accretor's surface. The accretor expands to giant-like radii when $\dot{M}$ is high yet remains within its Roche lobe, allowing stable mass transfer even for mass ratios traditionally considered unstable. After mass transfer ceases, the star contracts on Myr timescales through a bloated, rapidly rotating phase whose temperatures, radii, and spins match those observed in Abell 35-type systems. This framework naturally explains the population and unifies Abell 35-type binaries with post-AGB binaries, blue lurkers, and wide WD+main-sequence systems as successive stages of the same post-mass-transfer evolutionary pathway.
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All authors Soumyadeep Bhattacharjee, Kareem El-Badry, Jim Fuller, Cheyanne Shariat, Natsuko Yamaguchi

Astrophysics of Galaxies

The shortest detected intra-day variability of active galactic nuclei in TESS survey

Heechan Yuk, Xinyu Dai and Natalie Kovacevic

AGNs are known to be variable in almost all wavelengths and timescales. The shortest variability timescale of AGNs can be used to probe the smallest scale structures within AGNs. We aim to measure the shortest detected variability timescale, $t_{min,ul}$, of type 1 radio-quiet Seyfert galaxies and analyse their characteristics. We extracted TESS light curves of 47 Seyfert 1 galaxies. We measured the PSDs of the sample, modelled by a power law model plus a constant noise, and constrained the shortest detected AGN variability timescale as the power law component exceeds the constant noise and systematic uncertainties indicated by the upper limits of non-variable quiescent galaxies' PSDs. We measured the upper limits of the shortest variability timescale to be $\log(t_{min,ul}/hrs)=0.85\pm0.55$. We compared these upper limits to a range of theoretical AGN variability timescales, and the natural interpretation of our measured $t_{min,ul}$ is the light crossing scale from a coherently varying region, where the measured $t_{min,ul}$ corresponds to the range from a few to thousands of gravitational radii. A significant fraction of these light crossing scales is smaller than the accretion disk emission sizes measured by quasar microlensing, reverberation mapping, or theoretical accretion disk models. Since we only measure the upper limits, the true physical shortest variability timescales are even shorter. We measure the power law index to be $2.0\pm0.2$, and find weak anticorrelations with the black hole mass and luminosity. Our analysis suggests that the shortest optical variability is driven by a compact region smaller than the accretion disk size, potentially by X-ray reprocessing. Alternatively, this shortest timescale variability suggests that the accretion disk can be inhomogeneous potentially caused by turbulence from magnetorotational instability or magnetic reconnections. (abridged)
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Astrophysics of Galaxies

Estimation of the magnetic field strength from ALMA dust polarization in the protocluster G327.29

A. Koley, P. Sanhueza, A. M. Stutz et al. (+5 more)

Magnetic fields and turbulence may play a crucial role in the evolution of molecular clouds and ultimately in the formation of dense cores and stars. Despite being studied in many molecular clouds, the exact role of magnetic fields and turbulence in star formation is still poorly understood. Here, we report the high resolution plane of sky magnetic field (B_pos) morphology toward the high mass star forming region G327.29, obtained with the 12-meter of the Atacama Large Millimeter/sub-millimeter Array (ALMA) telescope. From our analysis, we obtain a complex B_pos morphology where the magnetic field orientation is uniformly distributed across the entire range from -90 to +90 deg. The observed area is composed of one filament and one dense central clump, which harbor multiple dense cores. The total magnetic field strengths (B_tot) in these regions are 1.4 \pm 0.7 mG and 2.0 \pm 0.8 mG at a number density (n) of 6.8 \pm 1.5 x 10^5 and 1.1 \pm 0.3 x 10^6 cm^-3 , derived from the angular dispersion function (ADF) method. The virial parameters ({\alpha} vir )in these regions are 7.7 \pm 7.1 and 0.7 \pm 0.6, suggesting that the regions may be gravitationally bound or unbound after accounting for the errors. Moreover, the ratio of turbulent to magnetic energy (~ 0.25) indicates that the magnetic field is dynamically more important than turbulence. The relative influence of turbulence and magnetic fields on core dynamics appears to depend on how the B_tot scales with gas density (h̊o}) in the densest regions. In summary, this work presents a comprehensive analysis of the relative roles of magnetic fields, turbulence, and gravity in regulating high-mass star formation in G327.29, enabled by high-resolution ALMA observations.
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All authors A. Koley, P. Sanhueza, A. M. Stutz, P. Saha, F. A. Olguin, A. Ginsburg, N. Sandoval-Garrido, N. Castro-Toledo

Astrophysics of Galaxies

Benchmarking Astrochemistry Paradigms: Relative Absence of C6H5CN+ in the Diffuse ISM

Daniel Majaess, Cercis Morera-Boado, Tina A. Harriott et al. (+4 more)

The detectability of C6H5CN+ (benzonitrile cation) in the diffuse ISM is re-evaluated. A holistic evidentiary framework suggests C6H5CN+ is relatively absent in the diffuse ISM owing to the following concurrently: a marginal intramolecular vibrational energy redistribution (IVR) favoring fragmentation, recurrent fluorescence being an improbable mechanism in this case to prevent dissociation, unceasing photon strikes, mismatches between observed DIBs and experimental results, and the hitherto absence of DIBs matching any similarly sized cations. The putative gap in bottom-up synthesis is reaffirmed (diffuse ISM), and although DIB sources are largely unknown, within a broader approach the lines can help benchmark astrochemistry paradigms. The results relied on new advantageous Daly et al. experimental spectra, an expanded observational DIB analysis (APO catalog), and complementary $\omega$B97X-D/cc-pVTZ computations.
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All authors Daniel Majaess, Cercis Morera-Boado, Tina A. Harriott, Quazi Rahi, Halis Seuret, Lou Massa, Cherif F. Matta

Earth and Planetary Astrophysics

The KPF-SLOPE Survey - Small, Compact Multi-Planet Systems Appear Spin-Orbit Aligned

Luke B. Handley, Andrew W. Howard, Fei Dai et al. (+16 more)

The angle between stellar spin axes and planetary orbits – stellar obliquity – probes the dynamics of planetary migration and evolution. The obliquities of giant planets have been extensively studied because they are the most easily measured. Smaller planets, while more difficult to measure, have the advantage of better reflecting the dynamics of planetary systems because they trigger negligible back-reactions onto the host star. This paper introduces a new observational campaign called the Small, Low-mass Oblique Planets Experiment (SLOPE) survey with the Keck Planet Finder (KPF) spectrograph, and presents four new obliquity measurements. The SLOPE survey focuses on planets smaller than Saturn across a variety of system architectures. The sky-projected obliquities of the four planets measured – TOI-1386b, TOI-480b, TOI-4596b, and TOI-1823b – are all consistent with spin-orbit alignment. We validate the planetary nature of TOI-4596b with a significant obliquity detection. Including these measurements, we conducted a statistical analysis of the obliquities of sub-Saturn size planets in different planetary system architectures. Compared to other architectures, those in compact multi-planet systems reside in orbits that appear preferentially aligned with the stellar equator with 6 sigma confidence.
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All authors Luke B. Handley, Andrew W. Howard, Fei Dai, Ryan A. Rubenzahl, Steven Giacalone, Howard Isaacson, J. M. Joel Ong, Theron W. Carmichael, Yaguang Li, Jack Lubin, Pranav H. Premnath, Claire J. Rogers, Pranav Nagarajan, Gregory J. Gilbert, Benjamin Fulton, Steven R. Gibson, Arpita Roy, Jerry Edelstein, Christopher Smith

Cosmology and Nongalactic Astrophysics

Brightest Cluster Galaxy ellipticity as proxy for halo shape: Orientation bias, assembly bias, and potential selection effects in SZ-selected clusters

Radhakrishnan Srinivasan, Tae-hyeon Shin, Anja von der Linden et al. (+93 more)

The orientation of triaxial galaxy clusters with respect to the line-of-sight is expected to be one of the prime sources of scatter and potential bias in optical observables (e.g., richness and weak-lensing signal) of galaxy clusters. In this work, we use the observed shape of the central Brightest Cluster Galaxy (BCG) as proxy for the orientation along the line-of-sight for clusters selected via the Sunyaev-Zel'dovich (SZ) effect from the South Pole Telescope (SPT) and Atacama Cosmology Telescope (ACT) surveys, matched to optically selected clusters from the Dark Energy Survey Year 3 (DES). We construct two samples of clusters that are designed to be identical in SZ mass estimate and redshift but with the roundest vs. the most elliptical BCGs, which we expect to correspond to BCGs (and clusters) with major axes aligned along the line-of-sight vs. in the plane of the sky, respectively. We find that the optical richness of round-BCG clusters is $\sim 10$% larger than that of elliptical-BCG clusters, in agreement with the expectation from projection effects and presenting the first such detection in data. The density profiles, however, are not in agreement with the expectation from projection effects: the 1-halo term (below $6~h^{-1}\rm{Mpc}$) of both the weak-lensing and galaxy density profiles are the same for the subsamples, contrary to previous studies based on X-ray selected clusters. In the 2-halo regime (above $6~h^{-1}\rm{Mpc}$), we find a significant excess of the elliptical-BCG cluster profiles compared to the round-BCG cluster profiles, which is the opposite of the expectation from numerical simulations. We hypothesize that the intrinsic shape of the BCG reflects not just the orientation angle, but also intrinsic properties of the cluster which can affect both the SZ signal and the amplitude of the 2-halo term.
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All authors Radhakrishnan Srinivasan, Tae-hyeon Shin, Anja von der Linden, Ricardo Herbonnet, Matthias Klein, Tamas N. Varga, Antonio Frigo, Lindsey E. Bleem, Hao-Yi Wu, Zhuowen Zhang, Benjamin Levine, Alex Alarcon, Alexandra Amon, Matthew B. Bayliss, Keith Bechtol, Matthew Becker, Gary Bernstein, Sebastian Bocquet, Andresa Campos, Aurelio Carnero Rosell, Matias Carrasco Kind, Chihway Chang, Rebecca Chen, Ami Choi, Juan De Vicente, Joseph DeRose, Scott Dodelson, Cyrille Doux, Alex Drlica-Wagner, Jack Elvin-Poole, Spencer Everett, Agnès Ferté, Marco Gatti, Raven Gassis, Michael D. Gladders, Sebastian Grandis, Daniel Gruen, Robert Gruendl, Ian Harrison, Mike Jarvis, Niall MacCrann, Jamie McCullough, Michael A. McDonald, Justin Myles, Andres Navarro Alsina, Shivam Pandey, Judit Prat, Marco Raveri, Christian L. Reichardt, Richard Rollins, Eli Rykoff, Carles Sanchez, Arnab Sarkar, Lucas F. Secco, Ignacio Sevilla, Erin Sheldon, Taweewat Somboonpanyakul, Brian Stalder, Anthony A. Stark, Michael A. Troxel, Isaac Tutusaus, Brian Yanny, Boyan Yin, Michel Aguena, Sahar Allam, Felipe Andrade-Oliveira, David Bacon, Jonathan Blazek, David Brooks, David Burke, Ryan Camilleri, Jorge Carretero, Matteo Costanzi, Luiz da Costa, Maria Elidaiana da Silva Pereira, Shantanu Desai, H. Thomas Diehl, Juan Garcia-Bellido, Gaston Gutierrez, Samuel Hinton, Devon L. Hollowood, Sujeong Lee, Jennifer Marshall, Juan Mena-Fernández, Felipe Menanteau, Ramon Miquel, Andrés Plazas Malagón, Ricardo Ogando, Kathy Romer, Aaron Roodman, Eusebio Sanchez, David Sanchez Cid, Eric Suchyta, Molly Swanson, Noah Weaverdyck, Jochen Weller

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

A rotating GUP black hole: metric, shadow, and bounds on quantum parameters

Federica Fragomeno, Samantha Hergott, Saeed Rastgoo et al. (+1 more)

Recently, for the first time, a metric of a static spherically symmetric generalized uncertainty inspired quantum black hole was derived. We apply the modified Newman-Janis algorithm to this metric and derive its rotating counterpart. We show that this metric has all the correct limits, while due to Newman-Janis side effects, the singularity which was resolved in the static case, is introduced back into the model. However, the slowly-rotating limit of this black hole is singularity-free. Furthermore, we show that the presence of quantum parameters modifies the location of the horizons, temperature, and entropy of the black hole, and allows the existence of naked singularities even if the ratio of the spin parameter to mass of the black hole is less than unity. Finally, by computing the shadow parameters of this black hole and comparing them with data from the Event Horizon Telescope for both M87* and Sgr A*, we set bounds on one of the quantum parameters of the model, and show that there is a limit on the angular momentum of M87* if this model is valid.
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All authors Federica Fragomeno, Samantha Hergott, Saeed Rastgoo, Evan Vienneau

Astrophysics of Galaxies

MICONIC: JWST/MIRI-MRS reveals heavily reprocessed PAH emission in the circum-nuclear disc of Centaurus A

L. Pantoni, M. Baes, L. Decin et al. (+23 more)

Polycyclic aromatic hydrocarbons (PAHs) are key dust components in galaxies and play a fundamental role in the physics of the interstellar medium (ISM), yet their response to AGN feedback remains debated. We present a spatially resolved analysis of PAHs in the central $7^{\prime\prime}\times12^{\prime\prime}$ ($\sim100\times200$ pc$^2$) of Centaurus A. We use JWST/MIRI-MRS observations at 5-28 $\mu$m from the MIRI European consortium GTO program MICONIC, with angular resolution of $0.35^{\prime\prime}-1^{\prime\prime}$ (about 6-17 pc). We derive PAH moment-0 maps via local continuum subtraction and extract one-dimensional spectra from five regions of interest, including the nucleus, the circumnuclear disc, and a PAH-deficient region. The spectra are decomposed into continuum, emission lines, and PAHs to measure feature intensities and equivalent widths (EWs). PAH emission is primarily distributed in a ring-like structure with localized enhancements at $\sim40$ pc from the nucleus. A distinct PAH-deficient region is observed to the north-west, roughly perpendicular to the jet axis, and coincident with enhanced ionized-gas velocity dispersion and inflowing molecular streamers. The 11.3/7.7 $\mu$m and 6.2/7.7 $\mu$m ratios exceed model predictions for pericondensed PAHs, indicating processed populations with more open structures. The 11.3/12.7 $\mu$m ratio suggests a dominance of solo hydrogen sites and partial dehydrogenation, particularly in the PAH-deficient region, where shocks likely drive erosion. The largest EWs are found in the ring, while reduced values in the deficient region point to partial destruction; in the nucleus, low EWs are mainly due to continuum dilution.
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All authors L. Pantoni, M. Baes, L. Decin, P. Guillard, A. Alonso Herrero, L. Evangelista, L. Hermosa Muñoz, I. García-Bernete, F. Donnan, V. Buiten, S. Garcia-Burillo, G. Wright, L. Colina, T. Böker, G. Östlin, D. Dicken, A. Labiano, D. Rouan, P. van der Werf, A. Eckart, M. García-Marín, M. Güdel, Th. Henning, P.-O. Lagage, F. Walter, M. J. Ward

Astrophysics of Galaxies

Large Variations Seen in First Ultraviolet Spectroscopic M33 Dust Extinction Curves

Karl D. Gordon, Petia Yanchulova Merica-Jones, Geoffrey C. Clayton et al. (+4 more)

Dust extinction curves provide one of the main avenues to understanding the detailed nature of dust grains and accounting for the effects of dust on observations of many astrophysical objects. For the first time, spectroscopic ultraviolet (UV) extinction curves are measured in M33 expanding the sample of Local Group galaxies with such measurements to five. These curves are based on Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra and literature photometry from the UV to the near-infrared. The four measured curves show large variations in their UV shapes including their 2175 A bump and UV slope strengths. The average extinction of these four sightlines is lower than the averages for other Local Group Galaxies and does not follow the Milky Way R(V) dependent relationship. The variations between UV extinction shape parameters and gas-to-dust ratios for the M33 sightlines fall within the variations seen in the combined sample of UV extinction curves in the Milky Way, Large and Small Magellanic Clouds, and M31. The correlation with gas-to-dust ratio is much stronger than the correlation with global metallicity. This strengthens the picture that local conditions like radiation field density and shocks dominate over global galaxy properties like metallicity in determining the wavelength dependence of dust extinction.
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All authors Karl D. Gordon, Petia Yanchulova Merica-Jones, Geoffrey C. Clayton, Ralph Bohlin, Marjorie Decleir, Claire E. Murray, Luciana Bianchi

Earth and Planetary Astrophysics

No strong associations between eccentricity and orbital architecture in Kepler compact multis

Gregory J. Gilbert, Erik A. Petigura and Paige M. Entrican

The dynamical history of a planetary system is recorded in the present day architecture of its constituent planets' sizes, orbital periods, and eccentricities. Studying the relationships between these quantities for large populations provides a window into the processes by which planetary systems form and evolve. Recently, Gilbert, Petigura, and Entrican (2025) performed a hierarchical Bayesian analysis of 1626 planets from the Kepler census, demonstrating a strong relationship between planet radius $R_p$ and orbital eccentricity $e$. Here, we build upon that work to search for correlations between eccentricity and system architecture, focusing on compact systems of small planets. We find that small planets on short orbits ($P < 4$ days) show evidence of tidal circularization. This trend is well established for Jovian planets but a novel finding for super-Earths and sub-Neptunes. We reproduce the known wherein trend single-transiting systems possess elevated eccentricities relative to their multi-transiting counterparts. We further show that systems with two transiting planets have higher eccentricities than those with three or more transiting planets. When compared to population synthesis models, these multiplicity-eccentricity relationships imply that Kepler singles have intrinsic multiplicity ${\sim}3$ and Kepler multis have intrinsic multiplicity ${\sim}4{-}6$. We detect no statistically significant associations between eccentricity and planetary period ratios, gap complexity, size inequality, or size ordering. We interpret these findings as evidence either in favor of a quiescent formation history or against dynamical processes which excite eccentricity but not inclination. Sub-significant relationships between eccentricity and architecture imply that subtle, multi-factor trends may be detectable in the future using more sophisticated statistical techniques.
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High Energy Astrophysical Phenomena

Radiation-ionization hydrodynamic simulations of AGN line-driven winds lead to transient shielding and BAL/UFO signatures

Nicolas Scepi, Christian Knigge, Amin Mosallanezhad et al. (+4 more)

Disc winds from active galactic nuclei (AGN) can be launched by radiation pressure acting on spectral lines. However, launching a line-driven wind in the X-ray rich environment of AGN is challenging, as the wind easily gets over-ionized. Previous simulations suggested that X-ray self-shielding could enable line driving, though it remained unclear whether this relied on simplified treatments of radiation and ionization. Here, we revisit the X-ray shielding scenario using the first multi-frequency, multi-directional Monte-Carlo radiative photo-ionization hydrodynamical simulations of AGN line-driven winds. We find that sustaining a steady wind with mass-loss rates of $\approx20\%$ of the accretion rate requires an unrealistically weak X-ray flux ($\alpha_{\rm OX}<-3$). For stronger X-ray emission ($-3<\alpha_{\rm OX}<-1$), self-shielding is only transient, leading to episodic ejections with mass-loss rates approaching the accretion rate. Our steady winds naturally produce FeLoBAL, HiBAL, and broad emission line signatures, depending on the disc spectral energy distribution and the observer's inclination. At moderate X-ray luminosities ($\alpha_{\rm OX}\sim-3$), transient winds can generate short-lived BAL and ultra-fast outflow (UFO) features. At the highest X-ray luminosities ($\alpha_{\rm OX}\sim-1$), the winds are too ionized to form BALs, but still produce UFOs. These results imply that additional physics is required to explain BAL outflows at realistic X-ray levels and to drive winds strong enough for AGN feedback. Nonetheless, our simulations provide a new framework for interpreting the observed diversity of AGN outflow signatures with fully coupled radiation and dynamics.
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All authors Nicolas Scepi, Christian Knigge, Amin Mosallanezhad, Knox S. Long, James H. Matthews, Stuart A. Sim, Austen Wallis

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

Testing Dark Energy with Black Hole Ringdown

Laurens Smulders, Johannes Noller and Sergi Sirera

We show that dynamical dark energy theories can imprint $O(1)$ modifications on the quasi-normal mode (QNM) spectrum characterising black hole ringdown. The time dependence of dynamical dark energy naturally gives rise to cosmological 'hair' around a black hole. Taking the cubic Galileon as a concrete example, which admits the only known stable solution of this kind, we parametrically connect the cosmological and black hole regimes, derive the induced QNM shifts and forecast the resulting dark energy constraints. We find that the dark energy field profile can be constrained with an accuracy of up to $10^{-2}$ for LVK and $10^{-4}$ for LISA.
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