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Papers

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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 24 July

Earth and Planetary Astrophysics

First results of a continuous monitoring campaign of the PLATO Southern field

Thomas Granzer, Jorg Weingrill, Klaus G. Strassmeier et al. (+1 more)

The BMK10k project started as an ancillary project to the PLATO ESA mission, dedicated to photometrically monitor the PLATO Southern field, to help with source confusion, and to mitigate the problem of false-positive exoplanet detections. Planned as a long-term project, the BMK10k should see an operational time-scale in the order of a decade, well above the proposed PLATO operational phase. Thus, BMK10k may help resolving single- event transit issues detected with PLATO and may be in the unique situation to transit-detect cold Jupiters in solar-system analogues, which would help in understanding exoplanet orbit alignments.
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All authors Thomas Granzer, Jorg Weingrill, Klaus G. Strassmeier, Arto Jarvinen

High Energy Astrophysical Phenomena

Observation of Wobbling and Precessing Jet Signatures in Gamma-Ray Emission from Blazar PKS 1424-41

Ajay Sharma and Debanjan Bose

We report a clear observational evidence for jet precession and nutation manifested in the gamma-ray emissions of the blazar PKS 1424$-$41. An analysis of $\sim$16 yr of Fermi-LAT observations reveals three distinct and superimposed quasi-periodic oscillations (QPOs), with characteristic timescales of $\sim$5.26 yr, $\sim$0.96 yr and $\sim$1.3 yr. The longer timescale is detected with a local significance of $\sim 4.1\sigma$ ($99.9958\%$ confidence) and a global significance of $\sim 2.45\sigma$ ($98.5714\%$ confidence). The shorter timescales ($\sim 0.96$ yr and $\sim 1.3$ yr) both show local significances exceeding $3\sigma$. To interpret the origin of these modulations, we examine two physically motivated scenarios: Lense-Thirring precession of a misaligned accretion disk and orbital-driven jet precession in a binary supermassive black hole (BSBH) system. We model the gamma-ray variability using a compound framework that incorporates jet precession together with intrinsic jet rotation (nutation), which successfully reproduces the observed year-like QPOs. Our results indicate that the long-term, persistent $\sim$5.26 yr oscillation is most consistent with a BSBH origin, while the shorter year-like QPO modulation can be naturally attributed to rotation or wobbling of the jet axis. If PKS 1424$-$41 hosts a supermassive black hole binary, it represents a promising target for future space-borne gravitational-wave observatories such as the Laser Interferometer Space Antenna (LISA), providing an independent probe of supermassive black hole binaries.
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Earth and Planetary Astrophysics

Dust characterization of the HD 163296 disk with high-resolution multi-wavelength ALMA observations

Kiyoaki Doi, Myriam Benisty, Akimasa Kataoka et al. (+10 more)

Context. Planets form through the growth and accumulation of dust grains in protoplanetary disks. Characterizing dust properties such as size, surface density, and temperature is key to understanding planet formation. Aims. We characterize the dust properties of the protoplanetary disk around HD 163296 by performing spectral energy distribution (SED) fitting of multi-wavelength high-resolution observations. Methods. We present new high-resolution ALMA Band 9 (0.45 mm) observations, which are sensitive to the temperature. We performed SED fitting at a common resolution of 0.066 arcsec using these new Band 9 observations along with archival ALMA Band 3, 4, 6, and 7 observations. We compared the fitted results with VLA observations and explored multiple dust models with different optical constants and porosities. Results. The Band 9 image shows the central disk, two rings at 0.67 and 1.00 arcsec, and outer extended emission previously seen at other wavelengths. At higher frequencies, the rings appear wider, the gaps appear shallower, and the extended emission appears brighter, which can be explained by optical-depth effects and/or size segregation. We characterized the dust properties, including temperature, surface density, and dust size, for each dust model. However, the inferred dust properties are dependent on the dust model, and the ALMA data alone do not allow us to determine which dust model is preferred. We identified the DSHARP Zubko (porous) model as the preferred model based on VLA profiles and physical and observational constraints. The outer ring temperature is lower than predicted by a passively irradiated disk model, suggesting shadowing by the inner ring. Although the surface density and dust size depend on the dust model, the preferred model indicates that the central disk, both rings, and the extended disk each contain more than a few Earth masses of dust.
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All authors Kiyoaki Doi, Myriam Benisty, Akimasa Kataoka, Haochang Jiang, Francesco Zagaria, Hauyu Baobab Liu, Carsten Dominik, Ryo Tazaki, Takahiro Ueda, Tomohiro C. Yoshida, Takashi Tsukagoshi, Yoshihide Yamato, Ryuta Orihara

Instrumentation and Methods for Astrophysics

LEO-to-ground low elevation optical communication: optimization of an adaptive optics design robust to scintillation

Timothée Vene, Aurélie Montmerle-Bonnefois, Laurent Mugnier et al. (+1 more)

To maximize the duration of optical downlinks with Low-Earth Orbit satellites, it is crucial to ensure the coupling into the single mode fiber of the ground terminal even at low elevations. Adaptive optics systems are designed to correct the wavefront deformation induced by atmospheric turbulence. However, at low elevations, amplitude fluctuations (or scintillation) challenge this correction. Here we propose a methodology to design a wavefront sensor that is robust to scintillation, taking the Shack-Hartmann WFS as an example. We present a slope estimator able to handle the large dynamic intensity range between subapertures. We then present an end-to-end simulation of the AO system to show the decrease in wavefront measurement error brought by a finer sampling of the pupil plane. Finally, we discuss the feasibility of such design by means of a detailed AO error budget in the case of a LEO optical downlink.
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All authors Timothée Vene, Aurélie Montmerle-Bonnefois, Laurent Mugnier, Jean-Marc Conan

Solar and Stellar Astrophysics

Population synthesis of delta Scuti stars: the instability strip, period-luminosity relation, and large-separation distribution

Simon J. Murphy and Anuj Gautam

Interpreting the observed properties of intermediate-mass stars requires accounting for rotation, binarity, intrinsic population diversity, and measurement uncertainty. We combine these effects in population-synthesis models of 1.4-2.5 M$_{\odot}$ stars that include pulsation properties of $\delta$ Sct variables. The synthetic populations successfully reproduce the distributions of stars observed in young associations, validating the mapping between intrinsic and observed stellar properties. Using these models, we infer a semi-empirical $\delta$ Sct instability strip by matching synthetic and observed populations. The resulting instability strip is systematically hotter than widely used theoretical prescriptions, implying that $\delta$ Sct stars are on average 0.1 M$_{\odot}$ more massive than previously assumed, with 95% of the population spanning approximately 1.50-2.30 M$_{\odot}$. We then investigate the $\delta$ Sct period-luminosity relation and reproduce its recently identified second ridge with mixture models in which roughly one-third of stars have the fifth or sixth radial overtone as their dominant mode; the fraction increases in younger populations. In contrast, unresolved binarity does not account for the second ridge. Finally, we predict the population-wide distribution of asteroseismic large separations, $\Delta\nu$, finding a peak between 6 and 7 d$^{-1}$, in agreement with recent observations. We also demonstrate that $\Delta\nu$ is most reliably measured with the échelle technique, while autocorrelation methods can produce spurious detections when used in isolation. These results show that population synthesis provides a powerful framework for interpreting populations of $\delta$ Sct stars and for linking stellar evolution, pulsation, and observation.
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Cosmology and Nongalactic Astrophysics

ZTF SN Ia DR2 follow-up: early excess in Type Ia supernova light curves

Tomás E. Müller-Bravo, Kate Maguire, Alaa Alburai et al. (+15 more)

There is broad consensus that Type Ia supernovae (SNe Ia) are the thermonuclear explosions of C/O white dwarfs (WDs) in binary systems, but their progenitors and explosion mechanisms remain uncertain. Their earliest light curves probe the outermost ejecta and provide important constraints on the explosion. We analyse the ZTF DR2 sample of SNe Ia to search for objects exhibiting early flux excess (EEx SNe Ia). We employ two complementary approaches: (i) identifying deviations from models without early excess using power-law and SALT2 fits, and (ii) comparing observations with double-detonation (DD) and companion-interaction (CI) models. The latter identify 145 and 199 candidates, respectively, although the methods disagree substantially on both the objects selected and the total number of candidates. Combining all methods, we identify 17 robust EEx SN Ia candidates, including six over-luminous events (five 91T-like and one 03fg-like). The strongest excesses reach ${\sim}10$–17% of the peak flux. The best candidates have, on average, higher stretch and preferentially occur in lower-mass, bluer host galaxies, suggesting younger stellar populations. We estimate that EEx SNe Ia comprise $\lesssim25\%$ of all SNe Ia, consistent with previous work, with over-luminous subtypes showing a higher relative incidence than normal SNe Ia. Among the DD models, the preferred solutions favour intermediate WD core masses ($1 M_{\odot}$), low shell-burning fractions ($20\%$), and heavier He-burning products ($^{56}$Ni), whereas the CI models show no clear parameter trends. Overall, we find no compelling evidence that either scenario is preferred as the origin of the observed early flux excesses.
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All authors Tomás E. Müller-Bravo, Kate Maguire, Alaa Alburai, Umut Burgaz, Georgios Dimitriadis, Lluís Galbany, Joel Johansson, Young-Lo Kim, Chang Liu, Adam A. Miller, Mathew Smith, Jesper Sollerman, Eric C. Bellm, Joahan Castaneda Jaimes, Mansi M. Kasliwal, Russ R. Laher, Roger Smith, Niharika Sravan

High Energy Astrophysical Phenomena

Revealing Four Subpopulations of Binary Black-Hole Mergers with the Fifth Gravitational-Wave Transient Catalog

Nir Guttman, Paul D. Lasky and Eric Thrane

Gravitational-wave data are beginning to reveal a structured landscape of black-hole masses and spins, suggesting multiple formation processes are now being resolved observationally. We analyze data from LIGO–Virgo–KAGRA's (LVK's) fifth Gravitational-Wave Transient Catalog and find that the population is naturally described by four distinct subpopulations. The dominant component, contributing $\simeq70\%$ of the astrophysical merger rate, is characterised by a low-mass population centred near $10M_\odot$ and is separated from heavier systems by a depletion near $14M_\odot$. This component may be associated with black holes formed from failed supernovae. Above this depletion, we find two intermediate-mass components: an unequal-mass branch pairing the lower-mass, $\simeq10M_\odot$ black hole with a heavier black hole, perhaps associated with isolated-binary/stable-mass-transfer formation, and a nearly equal-mass branch peaking near $30$–$35M_\odot$ whose low spins and mass distribution favour first-generation systems possibly born in dense stellar environments. A fourth, percent-level component extends to higher masses and is characterized by a broad mass-ratio distribution and large spin magnitudes, consistent with a hierarchical-merger population. Our four-component model is overwhelmingly preferred over a standard LVK population model by a natural-log Bayes factor of $\ln(\mathrm{BF}) = 19.2$. Our work observationally unveils a new subpopulation of black-hole mergers utilising a new hybrid data-driven and parametric-model discovery method, bringing us one step closer to understanding stellar-mass black-hole archaeology.
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Astrophysics of Galaxies

Kinematic scaling of thin and thick discs from SAMI to NewHorizon

Sree Oh, J. K. Jang, Giulia Santucci et al. (+8 more)

We revisit the relation between disc stellar mass and disc velocity dispersion (M_*-\sigma_e) and extend it to thin and thick subcomponents using orbit-based dynamical models of 161 SAMI galaxies and counterpart measurements for 31 disc galaxies in the NewHorizon simulation. On the observational side, we apply Schwarzschild orbit superposition to recover orbital circularity distributions and component kinematics. On the simulation side, we sample thin and thick discs by circularity and, separately, by stellar age to test classification dependence. Our analysis reveals three main results. (1) Discs follow a tight M_*-\sigma_e relation, nearly parallel to the bulge relation. (2) For both circularity- and age-based definitions, the thick-disc component is systematically hotter than the thin-disc component, and the thin-thick dispersion ratio varies only weakly with mass. However, age cuts yield a smaller kinematic contrast, indicating that stellar age and orbital circularity do not map one-to-one and that no single global age threshold reproduces the circularity-based split. (3) Method and data systematics are present, with Schwarzschild modelling returning slightly higher disc \sigma_e than spectroscopic bulge-disc decompositions, and simulated discs showing lower \sigma_e at fixed mass than observed. All these results are consistent with a baseline set by vertical-equilibrium scalings, with secular heating accumulating over time and modulating the dispersion at fixed mass. Occasional minor interactions may add localised heating but do not appear to be essential for explaining the qualitative, global trends reported here. Future tests with chemo-dynamical modelling and higher-resolution, chemistry-tracking simulations will provide stronger constraints on disc substructures in external galaxies.
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All authors Sree Oh, J. K. Jang, Giulia Santucci, Sukyoung K. Yi, Matthew Colless, Scott M. Croom, Yohan Dubois, Stefania Barsanti, Christophe Pichon, Sébastien Peirani, Madusha L. P. Gunawardhana

High Energy Astrophysical Phenomena

A post-hypercritical accretion small-scale dynamo in newborn neutron stars

David F. Bambague, Cristian G. Bernal and J. A. Rueda

Hypercritical fallback accretion can advect the surface magnetic field of a newborn neutron star into the newly accreted outer layers. Before this material joins the solid crust and enters the Hall-Ohmic regime, part of it may remain hot, dense, and liquid, allowing turbulent magnetic amplification. We investigate whether a small-scale dynamo (SSD) can operate under these conditions using six local 3D resistive MHD simulations performed with FLASH 4.7 in a periodic domain with externally forced subsonic turbulence. We explore magnetic Reynolds numbers from about 700 to 3700 and examine the effects of the equation of state, neutrino cooling, and numerical resolution. The magnetic field grows exponentially from an initial strength of 1e12 G and saturates at about (3-7)e13 G within milliseconds. The saturated magnetic energy remains below equipartition, with magnetic-to-kinetic energy ratios of about 0.2-0.3, consistent with SSD behavior for magnetic Prandtl number near unity. The reference simulations at 128^3 and 256^3 resolution agree within a few percent. Neutrino cooling has little effect over the simulated times, while the equation of state only weakly modifies the dynamo properties. These results indicate that a local SSD can efficiently amplify magnetic fields in the liquid post-hypercritical accretion layer and support scenarios for magnetic field reemergence in newborn neutron stars.
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High Energy Astrophysical Phenomena

Radio Core Size of Low-luminosity Active Galactic Nuclei under the MAD-jet model

Yue Xu and Fu-Guo Xie

After decades of efforts, there are now fruitful high-resolution radio observations of low-luminosity active galactic nuclei (LLAGNs), and the observed frequency has extended from $\sim$10 GHz up to $\sim$200 GHz. In this work, based on a model that combines a magnetically arrested disk (MAD) and a Blandford-Znajek-like jet, we carried out detailed analysis on size and location of the radio core of LLAGNs. The radio core size of nearby LLAGN M104 is re-visited based on this new model. We successfully reproduce a $size\propto\nu^{-1}$ scaling between 1 GHz and tens of GHz, if more than $50\%$ of electrons in jet follow a power-law (PL) distribution. We further confirm that, at high radio frequencies emission from MAD exceeds that from jet, and a flatter size-frequency slope is observed. The impact of PL electrons in MAD is also investigated. For those $L_{\rm bol}/L_{\rm Edd} \gtrsim (3-8)\times 10^{-6}$ LLAGNs and black hole binaries in their hard state, PL electrons are expected to be highly suppressed due to strong radiative cooling (so-called `synchrotron boiler' effect).
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High Energy Astrophysical Phenomena

The Distinctive Evolution and Spectral Energy Distribution of Binary Massive Black Hole Accretion

Yue Xu, Fu-Guo Xie, Ya-Ping Li et al. (+2 more)

Binary (super-)massive black holes (BHs) are expected to reside in the center of some galaxies. In this work, we re-visit accretion onto binary massive BHs, incorporating recent advances in both accretion theory and the mass transfer rate between the two massive BHs. We focus on relatively bright systems with an Eddington ratio of 0.1 for a binary with total BH mass $10^8\,M_\odot$, but consider a wide range of mass ratios $10^{-4} \le q \le 0.5$. The binary system consists of two mini-disks surrounding two individual BHs and a circumbinary disk surrounding the mass center of binary BHs. Depending on the mass ratio, the two mini-disks can be hot accretion flows, standard thin (cold) disks, or Slim disks. The radiative contributions from all three disks, each potentially in different accretion modes, are taken into account self-consistently. The spectral energy distributions of the binary BH system show universal “notch” features from the near-infrared to ultraviolet bands, caused by the gap or cavity in the accretion disk, consistent with previous studies. Binary with different mass ratios exhibit distinct spectral energy distribution properties, offering opportunities for testing (identifying candidates) with future broad band (infrared up to X-rays) observations. We also investigate the evolution of these binary systems, and find that, for systems with initial mass ratios $q \lesssim \text{a few} \times 10^{-3}$, the mass ratio evolves toward an equilibrium value $q \sim 10^{-3}$. For binary BH systems with a larger initial mass ratio, their mass ratio instead evolves toward unity.
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All authors Yue Xu, Fu-Guo Xie, Ya-Ping Li, Yinhao Wu, Luis C. Ho

Earth and Planetary Astrophysics

A Stable Mineral Fingerprint in the Fading Warm Debris Disk around HD 15407A

Shu Wang, Zhuochao Huang, Xiaodian Chen et al. (+2 more)

Extreme debris disks provide time-domain probes of rocky planet assembly after giant impacts. We compare Spitzer and JWST spectra of the warm debris disk around HD 15407A, obtained 14.95 yr apart. Across 6-25$\mu$m, the stellar-subtracted mid-infrared excess declined by $14.0\pm1.2$%, while the mineral fingerprint is nearly unchanged. Within the adopted common reduced mineral basis, Mg-rich pyroxene dominates the normalized fitted mineral weights at about 65%, while silica and forsterite contribute about 22-23% and 12-13%, respectively. In both epochs, about 93-94% of the fitted mineral weight is carried by 5.0$\mu$m grains. The fitted optically thin surface-component amplitude drops by 32%, consistent with reduced mineral-emitting flux from the disk surface rather than the appearance of a new dust composition. A simple collisional-cascade guide fitted to the IRAS-to-JWST multi-epoch ratios gives $t_c=87^{+17}_{-12}$ yr, for which the Spitzer-normalized dust-excess ratio reaches 0.5 after one $t_c$. HD 15407A is consistent with an evolved post-impact reservoir with limited recent supply of very small grains: its rocky mineral fingerprint has remained stable since at least 2008, while its warm mineral-emitting flux is gradually fading over several hundred years.
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All authors Shu Wang, Zhuochao Huang, Xiaodian Chen, Junming He, Haomiao Huang

Astrophysics of Galaxies

The disrupted chemical enrichment history of the Milky Way driven by gas accretion

Jianhui Lian, Qinhao Shao, Min Du et al. (+4 more)

As the only galaxy enabling temporally-resolved observations from an internal vantage point, the Milky Way as a galaxy offers unique insights into galactic chemical enrichment history, establishment of fundamental scaling relations, and the underlying astrophysical processes. However, this insider perspective also introduces strong selection effects, hindering direct measurement of the Milky Way's global properties and comparison with the broader galaxy population, for the vast majority of which only integrated properties can be measured. {Here we report our measurements of the Milky Way's temporally-resolved galaxy-scale average metallicity using data from the APOGEE survey after correction for the selection function. Our findings unveil a present-day metallicity of the Milky Way close to the Sun, an interrupted integrated age-metallicity relation, and a disturbed evolutionary trajectory in the mass-metallicity diagram, likely caused by dilution and inside-out growth associated with external gas accretion around 7~Gyr ago. Our results highlight the critical role of gas accretion in disrupting the galactic enrichment histories and introducing scatter in mass-metallicity relations.
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All authors Jianhui Lian, Qinhao Shao, Min Du, Hanyuan Zhang, Xinxin Duan, Xin Wang, Zheng Zheng

Astrophysics of Galaxies

Long Tidal Tails of NGC 5024 Hidden in LMS-1 and NGC 5053 Tidal Streams

Xianhao Ye, Yong Yang, Jingkun Zhao et al. (+3 more)

We report the discovery of long tidal tails associated with the globular cluster (GC) NGC 5024. A modified matched filter applied to Gaia DR3 data reveals a broad stellar stream spanning $\alpha \approx 230^{\circ}-175^{\circ}$. The stellar stream overlaps on the sky with the LMS-1 and with the simulated stream of the GC NGC 5053, and all three share similar proper motions and metallicity. Our member candidates may therefore be a mixture of stars from NGC 5024, NGC 5053, and LMS-1. Nevertheless, the trailing tail extends roughly $20^{\circ}$ beyond the known LMS-1 stream. Furthermore, the radial velocity (RV) as a function of $\alpha$ is used to distinguish the genuine stream candidates of NGC 5024 from the streams of NGC 5053 and LMS-1. Among the sources in common with DESI (Dark Energy Spectroscopic Instrument) DR1, we found two distinct sequences in RV-$\alpha$ plane, corresponding to the stellar streams of NGC 5024 and NGC 5053 (or LMS-1), respectively. This constitutes the first strong evidence for the existence of extensive tidal tails around NGC 5024.
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All authors Xianhao Ye, Yong Yang, Jingkun Zhao, Hao Tian, Yuqin Chen, Gang Zhao

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

From the Early Slope to Curvature: Future Prospects and challenges for Astrophysical Parameter Estimation Using the Core-Collapse Supernova High-Frequency Feature

Alejandro Casallas-Lagos, Marek Szczepańczyk, Michele Zanolin et al. (+1 more)

Gravitational-wave (GW) signals from core-collapse supernovae (CCSNe) contain both stochastic and deterministic components. Among these, the High-Frequency Feature (HFF), associated with PNS oscillations, has emerged as a robust observable for probing dense-matter physics. Previous studies of the HFF have primarily focused on the early-time slope as a diagnostic of PNS contraction and its dependence on the equation of state (EOS). In this work, we extend the analysis beyond the early-time linear regime. In particular, we discuss how higher-order features of the HFF evolution, such as its curvature, may encode additional information about the time-dependent structure of the PNS and the transition between oscillation modes. Using real interferometric noise and reconstruction techniques on detected candidates by the coherent WaveBurst (cWB) algorithm in its cWB-XP implementation, we illustrate how such features can be accessed. By comparing reconstructed signals at different source distances, we assess the relative impact of detector noise.
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All authors Alejandro Casallas-Lagos, Marek Szczepańczyk, Michele Zanolin, Anthony Mezzacappa

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

Classifying the nuclear equation of state in LVK interferometric noise through core-collapse supernova gravitational-wave signatures using convolutional neural networks

Alejandro Casallas-Lagos, Marek J. Szczepańczyk, Michele Zanolin et al. (+4 more)

This paper presents a convolutional neural network (CNN) approach to classifying the nuclear equation of state (EOS). As illustrative examples, we use five two-dimensional core-collapse supernova (CCSN) simulations that differ only in their EOS. We analyze estimates of the initial slope of the high-frequency feature (HFF) reconstructed in real interferometric data from the O3b LIGO-Virgo-KAGRA (LVK) observing run at Galactic source distances of 1, 5, and 10 kpc. The CNN classifier achieves an overall accuracy of 98.58% at 1 kpc and 52.43% at 5 kpc. At 10 kpc, its ability to distinguish among the EOS classes is effectively lost. The successful EOS classification at 1 kpc suggests that this approach may be scalable to next-generation observatories. The expected order-of-magnitude sensitivity improvements of Cosmic Explorer and the Einstein Telescope could enable comparable classification performance at approximately ten times the current distance. More detailed performance metrics, including the macro-averaged one-vs-rest (OvR) area under the curve (AUC), yield values of 0.97 and 0.98 at 1 kpc. These results indicate strong classification performance both across the complete set of EOS classes and for the individual classes.
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All authors Alejandro Casallas-Lagos, Marek J. Szczepańczyk, Michele Zanolin, Anthony Mezzacappa, Javier M. Antelis, Daniel Murphy, Claudia Moreno

Solar and Stellar Astrophysics

Spectral evolution of mildly relativistic electrons in solar flares

Gregory D. Fleishman, Tatyana Kaltman, Sijie Yu et al. (+1 more)

Solar flares are a powerful engine capable of accelerating ambient plasma particles to high nonthermal energies. A key characteristic of these particles is their energy spectrum. Numerous studies of nonthermal hard X-ray emission established that a typical spectral evolution of the nonthermal electrons with energies of dozens keV follows a soft-hard-soft pattern in impulsive events and soft-hard-harder pattern in some long-duration events. Here we extend the study of the spectral evolution to the case of flare-accelerated mildly relativistic electrons primarily responsible for the flare microwave emission. We examine the spatially resolved microwave emission observed with the Expanded Owens Valley Solar Array in twelve solar flares and find that they also typically follow a soft-hard-soft spectral evolution. However, the revealed spectral evolution of the mildly relativistic electrons covers the spectral index range from 2-4 to 15 or more and, thus, is much more prominent than for the X-ray-producing electrons. The evolution of the spectral index is closely correlated with the emission flux and does not show any noticeable time delay. The spectral index displays a prominent correlation with the brightness temperature with a pattern similar to all events considered. We conclude that the revealed relationships and the evolutionary pattern is an inherent property of particle acceleration in the solar flares.
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All authors Gregory D. Fleishman, Tatyana Kaltman, Sijie Yu, Gelu Nita

Thursday 23 July

Earth and Planetary Astrophysics · Cross-listed from physics.geo-ph

High solubility of water in post-perovskite and bridgmanite in the Earth's deep lower mantle

Megumi Semba, Naoya Sakamoto, Shuhei Mita et al. (+5 more)

Water in the Earth's mantle induces melting, giving rise to strong chemical heterogeneity, and alters its rheological and transport properties, which are keys to understanding seismic-wave speeds anomalies, convective motions and electrical conductivity. However, the abundance of water and its role in the deep mantle remain uncertain and controversial, particularly at conditions of the core-mantle boundary (CMB) region. Here we carry out melting experiments on a hydrous, natural mantle composition including both $H_2O$ and $D_2O$ over the entire pressure range of the Earth's lower mantle, in which melt coexists with bridgmanite (Bdg) and/or post-perovskite (PPv), the primary constituents of the respective lower and lowermost mantle. High-resolution secondary-ion mass spectroscopy (Cryo-SIMS) measurements reveal high water concentrations in Bdg (up to 5,500 ppm by weight) and PPv (up to 1.22 wt%) with strong enrichment in deuterium/hydrogen (D/H) relative to coexisting melt. The high solubilities of water in Bdg and PPv at CMB conditions suggest that subducting slabs do not release water when they reach the bottom of the mantle, and such a process cannot account for strong chemical heterogeneities inferred in the lowermost mantle and the topmost outer core, nor for ultralow-velocity zone (ULVZ)-like structures in seismically fast regions. Water-rich Bdg and PPv may be present in the large low shear velocity provinces and ULVZs, which may be the residue of a basal magma ocean and are predicted to host a deep low D/H water reservoir inherited from the early Earth that is occasionally sampled by plumes of a lowermost-mantle origin.
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All authors Megumi Semba, Naoya Sakamoto, Shuhei Mita, Kei Hirose, Yutaro Tsutsumi, Keisuke Ozawa, John W. Hernlund, Shiro Miwa

Instrumentation and Methods for Astrophysics

Jointly Modeling Roman Coronagraph Astrometry and Photometry Improves Orbital Parameter Estimates

Farrah Molina, Sarah Blunt and Jason Wang

Launching in 2027, the Nancy Roman Grace Space Telescope (Roman) has the potential to directly image exoplanets in reflected light for the first time. Roman imaging will introduce new constraints on exoplanet orbital parameters, since reflected-light intensity depends on orbital phase. In this Note, we discuss an addition to the open-source Python package orbitize!, which allows users to model exoplanet orbits using joint constraints from astrometry and photometric variations due to orbital phase. To investigate the impact of adding photometric data into the orbital model, we simulated realistic measurements of partial orbits, both including and excluding photometry in our model, and computed orbital posteriors. We found that fitting both astrometry and photometry improves posterior precision relative to fitting astrometry alone. This effect was more pronounced for higher-SNR images; for example, photometric data with SNR=10 yielded 33% improvement in inclination precision when including photometry, while SNR=3 data yielded only 12% improvement.
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Astrophysics of Galaxies

Stacked Reverberation Mapping of High Redshift Quasars in DESI. I. Feasibility Analysis

Rahma Alfarsy, R.E.A. Canning, Eva-Maria Mueller et al. (+49 more)

The broad line region of quasars has long been probed by reverberation mapping techniques that measure time lags between continuum and broad emission line variations. Stacked reverberation mapping has been proposed as a less observationally expensive alternative to traditional methods. This ensemble approach also reduces biases from small-number statistics. The Dark Energy Spectroscopic Instrument (DESI) is conducting the most extensive spectroscopic survey of quasars to date. We create mock light curves emulating expected DESI quasar observations at redshifts $1.48<z<5.2$ and luminosities $ 44.68 \leq \log L_{1350} \lambda / \mathrm{erg\,s^{-1}} \leq 45.99 $ to test stacked reverberation mapping feasibility using sparse spectroscopic data paired with well-sampled photometric data. The pipeline, using the lag estimation code JAVELIN, successfully recovers the simulated C IV lags within one sigma of the true values using spectroscopic light curves composed of only a few spectral epochs (2-10) with irregular cadences. We investigate how observational factors, including C IV flux error magnitude, number of stacked quasars, and spectral epoch count, affect performance. This work motivates a pathway for future stacked reverberation mapping projects with large scale spectroscopic surveys of quasars having $\geq 2$ spectroscopic observations. Our results suggest an economical alternative for constraining and extending the radius-luminosity relation to higher redshifts and luminosities. Subsequently, this relation can be employed more reliably in single-epoch black hole mass measurements and quasar cosmology in these distant regimes.
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All authors Rahma Alfarsy, R.E.A. Canning, Eva-Maria Mueller, Jessica Aguilar, Steven Ahlen, David Alexander, Davide Bianchi, David Brooks, Peter Clark, Todd Claybaugh, Andrei Cuceu, Tamara Davis, Axel de la Macorra, Saisrinivas Dhavala, Victoria A. Fawcett, Benjamin Floyd, Andreu Font-Ribera, Jaime Forero-Romero, Enrique Gaztañaga, Wei-Jian Guo, Gaston Gutierrez, Klaus Honscheid, Richard Joyce, Stephanie Juneau, David Kirkby, Theodore Kisner, Anthony Kremin, Claire Lamman, Martin Landriau, Laurent Le Guillou, Paul Martini, Hugh McDougall, Aaron Meisner, Ramon Miquel, John Moustakas, Seshadri Nadathur, Nathalie Palanque-Delabrouille, Zhiwei Pan, Swayamtrupta Panda, Ignasi Pérez-Ràfols, Francisco Prada, Ragadeepika Pucha, Graziano Rossi, Eusebio Sanchez, David Schlegel, Michael Schubnell, Tom Shanks, Małgorzata Siudek, David Sprayberry, Gregory Tarlé, Benjamin Alan Weaver, Hu Zou

High Energy Astrophysical Phenomena

A GRMHD-Calibrated Semi-Analytical Model for Hot Sub-Keplerian Accretion Flows in Kerr Spacetime

Nabin Bhushal, Manil Khatiwada, Yogesh Maharjan et al. (+2 more)

We develop a simple, semi-analytical, kinematic model for hot, thick accretion flows, constructed by interpolating between Keplerian and free-fall geodesic solutions in the Kerr metric. Unlike self-consistent general relativistic magnetohydrodynamics (GRMHD) frameworks, our model contains no explicit magnetic fields or stress terms; instead, it uses a smooth, radially varying transition function T(r) to connect the velocity components from near-Keplerian rotation at large distances to a free-fall state near the event horizon. While the coefficients $\alpha$ and $\beta$ remain constant, the transition function is a true function of radius, allowing the flow properties to vary smoothly with radius. We calibrate and validate this model against time- and azimuthally averaged profiles from long-duration magnetically arrested disk (MAD) simulations spanning a wide range of black hole spins ($a=-0.9$ to $+0.9$). The model successfully captures the properties of accretion flow parameters across both prograde and retrograde configurations. Quantitatively, the predicted radial velocity, angular velocity, and density profiles match the simulation data to within an average factor of approximately 1.8, 1.6, and 1.6, respectively, while the specific angular momentum exhibits the closest agreement, remaining within a factor of approximately 1.2. This fast semi-analytical prescription gives significantly lower errors than previous constant-coefficient models and it is a computationally affordable tool for various applications such as ray tracing, accretion parameter exploration, and spectral modelling.
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All authors Nabin Bhushal, Manil Khatiwada, Yogesh Maharjan, David Garofalo, Chandra B. Singh

Solar and Stellar Astrophysics

Magnetically guided accretion and extremely slow rotation in a metal-enriched white dwarf

S. Bagnulo, M.A. Stroet, C.P. Folsom et al. (+3 more)

White dwarfs that show atmospheric metal enrichment offer a direct window into the bulk composition of exoplanetary material and provide some of the most direct constraints on the building blocks of rocky exoplanetary systems. Recent work has suggested that magnetic fields may influence how this material is accreted, potentially channelling debris along field lines and retaining it near magnetic poles rather than allowing it to be redistributed uniformly across the stellar surface. Here we report the discovery of photometric, spectroscopic, and spectropolarimetric variability in the magnetic DZ white dwarf WD1532+129, revealing a rotation period of about 289 days, by far the longest yet directly measured for any degenerate star. The observed period may result from the combined effect of angular-momentum loss during the evolution leading to the white dwarf stage and an unusually slowly rotating progenitor, perhaps a magnetic Ap star. The white dwarf exhibits surface abundance inhomogeneities, with metals concentrated near both magnetic poles, and the observed modulation is consistent with localised metal-rich regions aligned with the magnetic geometry. WD1532+129 is the third of the four known magnetic DZ white dwarfs within 20 pc to show evidence for polar metal enhancement, indicating that magnetically guided inhomogeneities are a common property of magnetic metal-enriched white dwarfs.
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All authors S. Bagnulo, M.A. Stroet, C.P. Folsom, M.A. Hollands, J.D. Landstreet, G. Ramsay

Solar and Stellar Astrophysics

Rate of caustic crossing microlensing events in stellar binary lenses with significant orbital motion

Arjun Murlidhar, B. Scott Gaudi and Todd. A. Thompson

Binary lens microlensing events in which the source crosses a caustic produce sharp, distinctive magnification peaks and can therefore be readily identified. In this paper, we explore the importance of binary orbital motion for the binary lens caustic crossing cross section. If the orbital timescale of the binary system is smaller than the Einstein ring crossing timescale, the caustics sweep out a larger area in the source plane, generally enhancing the cross section. We find that face-on binaries in circular orbits exhibit a substantial increase (up to 4$\times$) in the cross section for caustic crossings. However, highly inclined orbits produce a net decrease relative to a static face-on binary with the same semi-major axis. Using a sample of ~$2800$ synthetic binary microlensing events drawn from a realistic Milky Way population-synthesis model, we calculate the average change in the caustic crossing cross section for individual systems with and without orbital motion. Although orbital motion can significantly alter the cross section for specific geometries, we find that, when averaged over the full population, it produces only a small, negligible increase of ~$0.1\%$ in the average cross section. We also compute the overall rate of caustic crossing binary events in the simulated sample and find that, with sufficiently dense photometric sampling, $6.3 \pm 0.2\%$ of microlensing events with impact parameter $u_0 < 1$ should exhibit caustic crossings. This rate depends on the distributions of binary separation, mass ratio, and multiplicity of stars and compact objects, and can therefore be used to test our understanding of these underlying properties.
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Astrophysics of Galaxies

A Multiwavelength Inventory for the Local Group L-band Survey I: Atlas and Radial Profiles of Local Group Galaxies

Cosima Eibensteiner, Adam K. Leroy, Jiayi Sun et al. (+21 more)

Resolving atomic gas at $\lesssim100$ pc physical resolution is currently feasible only for the very nearest galaxies. We combine 120 pc resolution HI data using the Karl G. Jansky Very Large Array (VLA) from the first data release of the Local Group L-Band Survey (LGLBS) with uniformly processed infrared, ultraviolet, H$\alpha$, and CO maps. We analyze the radial profiles of gas, stars, and recent star formation for six local galaxies: M31, M33, IC 10, IC 1613, NGC 6822, and WLM. Across the sample, atomic-gas disks are the most extended component, reaching $r_{\rm HI}=2.8$-$5.8$ kpc in the dwarfs and $13$-$26$ kpc in M33 and M31. Azimuthally averaged $\Sigma_{\rm HI}$ profiles are often flat or only slowly declining compared to the steeper decline of $\Sigma_{\star}$ and $\Sigma_\mathrm{SFR}$, with outer HI scale lengths of $l_{\rm HI}^{\rm outer}\approx1.0$-$8.5$ kpc. The mass-weighted HI surface densities on 120 pc scale generally exceed the azimuthally averaged values by 10-70%, showing that localized high-column-density atomic structures persist even where azimuthally averaged profiles appear smooth. Atomic-gas depletion times rise from $\tau_{\rm dep}^{\rm atom}\approx0.8$-17 Gyr within the stellar half-mass radius to 10s-100 Gyr in the outer disks. Molecular depletion times are shorter. We provide a public release of these multi-wavelength data, which provide a valuable reference for the LGLBS targets and also form the basis for a companion paper that relates star formation, gas phases, and midplane pressure on 120 pc scales.
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All authors Cosima Eibensteiner, Adam K. Leroy, Jiayi Sun, Erik Roslowsky, Eric W. Koch, Nickolas Pingel, Chang-Goo Kim, Laura B. Chomiuk, Ryan Chown, Alberto D. Bolatto, Michael P. Busch, Julianne J. Dalcanton, Amanda A. Kepley, Christina W. Lindberg, Eve C. Ostriker, Jürgen Ott, Sumit K. Sarbadhicary, Adam Smercina, Snežana Stanimirović, Elizabeth Tarantino, Vicente Villanueva, Tobin M. Wainer, Fabian Walter, Thomas G. Williams

Cosmology and Nongalactic Astrophysics

The diffraction-lensing interpretation of GW231123 with astrophysical priors

Mark Ho-Yeuk Cheung, Digvijay Wadekar, Matias Zaldarriaga et al. (+3 more)

GW231123, if unlensed, is a rare binary black hole merger with high masses and high spins for both progenitors. We show that the signal is better fitted by a lower-mass, lower-spin merger that is diffraction-lensed by an isolated object of redshifted mass $\sim 1000\,\rm M_\odot$, modeled either as a point mass or as a spherically symmetric compact halo. Because diffraction-lensed events are also rare, hypothesis testing should quote the posterior odds ratio rather than the Bayes factor, which requires quantifying our prior belief in the two hypotheses. We adopt the GWTC-5 population distribution as our source parameter prior, and quantify the prior on the lens hypothesis through the lensing optical depth. For a point-mass lens, observational constraints on the abundance of black holes in the Universe yield an upper bound on the optical depth, and hence on the posterior odds, which do not rule out lensing. However, using a predicted mass function of intermediate-mass black holes formed in star clusters gives a low optical depth that strongly disfavors lensing. For a dark matter halo lens, standard collisionless cold dark matter does not form halos compact enough to give the required optical depth, but self-interacting dark matter with a large cross section at low velocities can trigger gravothermal collapse and form them, in which case the posterior odds are inconclusive. In either case, from a frequentist perspective, we show that detecting a lensed event with properties like GW231123 is unlikely. These conclusions apply to isolated lenses, while a lens embedded in an external gravitational potential could change the picture.
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All authors Mark Ho-Yeuk Cheung, Digvijay Wadekar, Matias Zaldarriaga, Tejaswi Venumadhav, Javier Roulet, Ajit Kumar Mehta

Astrophysics of Galaxies

From relics to stripped systems: the environmental origin of compact galaxies

Guangwen Chen, J. Alfonso L. Aguerri, Carlos del Burgo et al. (+1 more)

Compact galaxies represent a key population for understanding galaxy evolution, but the relative role of internal structure and environment in shaping their origin remains unclear. We aim to investigate how the abundance and quenching of compact galaxies depend on environment, and to determine whether their formation is governed by a single evolutionary pathway or multiple channels. We analyse a large sample of galaxies in the nearby Universe ($z<0.05$) with stellar masses in the range $8.2<\log(M_\star/M_\odot)<10.5$, comparing compact and control populations as a function of local overdensity. We find that the environmental dependence of compact galaxies is non-monotonic, with two characteristic overdensities, the transition overdensity ($\delta_t$) and the critical overdensity ($\delta_c$), defining three distinct regimes. Below $\delta_t$, compact galaxies are relatively more abundant than the control population, while between $\delta_t$ and $\delta_c$ their relative abundance decreases significantly. Above $\delta_c$, compact galaxies become increasingly overabundant again. The environmental trends show a strong stellar-mass dependence, with low-mass galaxies exhibiting the strongest deficit at intermediate overdensities and high-mass galaxies dominating the excess population above $\delta_c$. In addition, the red galaxy fraction increases with local overdensity and is systematically higher in compact galaxies. Our results support a unified evolutionary framework in which compact galaxies do not arise from a single evolutionary channel, but instead reflect multiple pathways whose relative importance depends strongly on stellar mass and environment. Low-mass compact galaxies are closely linked to environmentally driven transformation, whereas high-mass compact galaxies occur across all environments and become increasingly overabundant in the densest regions.
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All authors Guangwen Chen, J. Alfonso L. Aguerri, Carlos del Burgo, Stefano Zarattini

Astrophysics of Galaxies

Emissivity line ratios for [Mn III] and spectral diagnostics of H II regions

Zher Samak, Sultana N. Nahar and Anil K. Pradhan

We present the first theoretical emission-line study of Mn III as potential determinant of physical conditions and manganese abundance. We compute atomic data for a set of Mn III lines and line emissivity ratios as temperature-density diagnostics. Accurate relativistic Breit-Pauli R-matrix calculations have been carried out for electron impact excitation of Mn III transitions that have not been previously studied. Selected forbidden lines are shown to be sensitive to temperature and density under nebular conditions in H II regions such as SNRs. The coupled channel R-matrix calculations include a wavefunction expansion that includes 38 levels of Mn III dominated by the ground and first excited electronic configurations $3d^5$ and $3d^44s$. Collision strengths for all 703 forbidden transitions among those levels, and Maxwellian averaged rate coefficients are obtained. A collisional-radiative model yields emissivity line ratios using calculated collision strengths and radiative decay A-values. Based on the present analysis, certain [Mn III] lines are predicted to be sensitive to density and/or in the typical nebular range. The detection of those lines could also yield cosmic Mn abundance relative to other elements.
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Instrumentation and Methods for Astrophysics

Determination of Earth's Orbital Parameters Using Doppler Measurements

Gary Atkins, Marcus Leech, Daniel Marlow et al. (+1 more)

Precision determinations of the parameters of Earth's orbit around the Sun using methods based on the Doppler shift of 21-cm emissions from the galaxy and the repetition rate of pulsar J0332+5434 are reported. The observed values and statistical errors for the orbital parameters for the 21-cm observations are semi-major axis $a = 1.00020 \pm 0.00015~{\rm au}$ and eccentricity $e= 0.017077 \pm 0.000077$. For the pulsar observations, the observed values are $a = 1.000034 \pm 0.000034~{\rm au}$ and $e=0.016667 \pm 0.000017$. The observations are based on a year-long campaign of daily drift-scan observations using a 12.8-m parabolic antenna and a receiver chain tuned to the 21-cm frequency band. The data used in the analysis are available for use in educational exercises in the supplementary material
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All authors Gary Atkins, Marcus Leech, Daniel Marlow, Doug Yuill

Instrumentation and Methods for Astrophysics

The FastrSHWFS Development & Test Results

Natasha Popenoe, Benjamin Gerard and Dominic Sanchez

The recent 2020 Decadal Survey of Astronomy and Astrophysics listed habitable exoplanet imaging with future extreme adaptive optics (AO) on 30m-class telescopes as a key priority in the coming decade. However, there is a current 100x contrast gap between the best systems today and what is needed to enable this goal. Astronomical AO is a required approach to enable ground-based diffraction-limited imaging of exoplanets on future extremely large telescopes. Time lag between the end of an exposure and the application of deformable mirror commands is a major contributor to the error budget in many AO systems, and detector read time is often a large component of this lag. We present two designs for a modified Shack Hartmann wavefront sensor (SHWFS), named Focal plane Actualized Shifted Technique Realized for a SHWFS (fastrSHWFS), to reduce the time lag component. This design steers the spot pattern at the focal plane into a rectangular or linear array with a custom aspect ratio, reducing readout time. These masks were made by a recently available gray-scale two photon polymerization 3D printing technology that in principle provides sufficient depth resolution and dynamic range for such masks. The mask with focus yields aberrated results while the mask with tip/tilt only yields some defined spots. This manuscript outlines the current SHWFS concept, our fastrSHWFS theoretical solution to addressing time lag, reflection and quality analysis of printed mask designs, and results from testing both masks on the High Contrast Testbed at Lawrence Livermore National Lab. This work follows the test of a previous fabricated fastrSHWFS masks that had insufficient optical quality.
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Astrophysics of Galaxies

Where Do Quasars Live? DESI DR1 Constraints from PAC Measurements

Shanquan Gui, Kun Xu and Donghai Zhao

Quasar environments connect the growth of supermassive black holes, active galactic nucleus feedback, and galaxy evolution. Small-scale quasar clustering probes the one-halo regime and can test whether quasar activity depends on central–satellite status. We seek to obtain precise small-scale measurements of quasar environments at $0.8<z<1.0$ and use them to constrain the quasar–halo connection, particularly the relative probability for satellite subhalos and central halos of the same halo accretion mass to host a quasar. We apply the Photometric Objects Around Cosmic Webs (PAC) method to DESI Data Release~1 quasars and photometric galaxies from the DESI Legacy Imaging Surveys DR9, measuring the excess projected surface density of neighbouring galaxies around quasars, $\bar{n}_{2}w_{\rm p}$, down to a stellar mass of $M_{\ast}=10^{10.80}M_{\odot}$ over $0.1<r_{\rm p}/(h^{-1}\,\mathrm{Mpc})<15$. we jointly model the excess surface-density measurements, the quasar and luminous red galaxy (LRG) autocorrelation functions, and the quasar–LRG cross-correlation. We interpret these measurements using an N-body simulation together with a stellar-to-halo mass relation, an explicit stellar-mass-incompleteness model, and a Gaussian quasar occupation as a function of halo accretion mass. The Gaussian quasar occupation peaks at $\log_{10}(M_{\rm acc}/h^{-1}M_{\odot})=12.88^{+0.02}_{-0.02}$ with width $\sigma_{\rm q}=0.51^{+0.02}_{-0.01}$, and the relative satellite-hosting parameter, $B$, defined as the quasar-hosting probability of a satellite subhalo relative to that of a central halo at fixed halo accretion mass, is $B=1.01^{+0.03}_{-0.03}$. Within the adopted model framework, quasars are consistent with being equally likely to reside in central halos and satellite subhalos at fixed halo accretion mass. PAC has strong potential to deliver precise small-scale measurements of quasar environments.
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