Peer Revenue Publish or profit

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 8 October

Solar and Stellar Astrophysics

Gaseous SiO and Silicate Clouds in Three Benchmark Early-L Dwarfs

Zhijun Tu, Shu Wang, Xiaodian Chen et al. (+2 more)

Tracing silicon from gaseous SiO into silicate condensates provides a direct view of the condensation process that forms silicate clouds in L-dwarf atmospheres. Here we present evidence for gaseous SiO in three benchmark early-L dwarfs, HD 89744B, GJ 1048B, and LSPM J0632+5053B, using JWST/NIRSpec and MIRI spectroscopy. Atmospheric retrievals with and without SiO under multiple cloud prescriptions identify the strongest SiO signatures at 4.0–4.2 and 7.7–8.2 $\mu$m, with the local likelihood diagnostic reaching $4.6\sigma$. In the physical cloud retrievals, the 8 $\mu$m band probes lower pressures than the 4 $\mu$m overtone, reaching atmospheric layers where equilibrium SiO is more strongly depleted by silicate condensation. All three objects also show compact Fe opacity at pressures of a few bar. Their inferred gas-phase C/O ratios are consistent with expectations from the host-star compositions after accounting for refractory oxygen sequestration. Within the adopted Mie treatment of amorphous silicate grains, the silicate mineralogies favor Mg$_2$SiO$_4$ for HD 89744B and a mixed Mg$_2$SiO$_4$+MgSiO$_3$ cloud for GJ 1048B. Extending this framework to cooler L dwarfs will trace the coupled evolution of gaseous SiO depletion and silicate-cloud formation along the L-dwarf sequence.
Read the full abstract

All authors Zhijun Tu, Shu Wang, Xiaodian Chen, Haomiao Huang, Jifeng Liu

Instrumentation and Methods for Astrophysics

Pseudo Closed-Loop Bootstrapping for Reinforcement Learning Based AO Control

Eemil Halonen, Jalo Nousiainen, Markus Kasper et al. (+1 more)

High contrast imaging with ground-based telescopes requires extremely precise wavefront control. The performance of the controller ultimately depends on the quality and efficiency of the wavefront sensing technique, which has led to the development of ever more sensitive wavefront sensors (WFS). However, the increase in sensitivity comes at the cost of greater nonlinearity, which poses challenges for conventional linear reconstructors and controllers. Reinforcement Learning (RL) is a branch of machine learning in which control policies are learned by interacting with the environment. RL has recently attracted interest in the field of XAO, and previous studies have demonstrated that a model-based RL variant, the Policy Optimization for Adaptive Optics (PO4AO), can effectively compensate for temporal delays, misregistration errors, and moderate WFS nonlinearities. PO4AO learns an initial control strategy by collecting closed-loop data from the integrator controller with a linear reconstructor. However, in cases of highly non-linear WFS and challenging conditions, closing the loop with the integrator is difficult, and high-fidelity data cannot be collected. Consequently, learning robust control with PO4AO is challenging. We propose a robust learning strategy in which PO4AO is pre-calibrated using an internal light source and a DM, enabling direct on-sky closed-loop operation without a stable integrator controller for bootstrapping the initial models.
Read the full abstract

All authors Eemil Halonen, Jalo Nousiainen, Markus Kasper, Nuutti Hyvönen

High Energy Astrophysical Phenomena

Neutron star cooling with $\Delta$ dUrca processes

Yogeesh N, Monika Sinha and Vishal Parmar

The cooling of neutron stars (NSs) provides insight into their composition and equation of state. However, a complete understanding of this phenomenon is still an open question. The early stage of NS cooling is dominated by neutrino emission from the core, which rapidly cools the star. Urca processes are one such mechanism where neutrinos escape from the core, carrying away most of the heat. Nucleonic and hyperonic direct Urca processes are known rapid cooling mechanisms. The possible appearance of $\Delta$ baryons in dense matter introduces additional weak-interaction channels, including $\Delta$ direct Urca processes. Although such processes have been discussed in the context of $\Delta$-admixed NS matter, their neutrino emissivities and impact on NS cooling have not been systematically investigated. In this work, for the first time we incorporate the neutrino emissivities of the relevant $\Delta$ direct Urca processes into NS cooling simulations. We investigate the thermal evolution of $\Delta$-admixed NSs and assess the impact of these additional neutrino emission channels on their cooling behavior. We find that $\Delta$ direct Urca processes can provide an efficient neutrino-cooling mechanism and significantly accelerate the thermal evolution of NSs. Our results demonstrate that $\Delta$ baryons and their associated weak-interaction processes can play an important role in explaining NSs with unusually low surface temperatures and provide a new connection between the composition of dense matter and NS cooling observations.
Read the full abstract

Instrumentation and Methods for Astrophysics

radio-astro-tools: linking radio astronomical data to the astronomical Python ecosystem

Eric W. Koch, Adam Ginsburg, Thomas P. Robitaille et al. (+15 more)

We present the radio-astro-tools code suite, which consists of several Python packages that enable analysis of radio data, especially interferometric spectral cubes, in the context of the Astropy software ecosystem. While these tools were designed with radio data in mind, they are built to be general and have applications on data sets at other wavelengths. The core package, spectral-cube, handles reading, writing and analysis of cube data, and it enables straightforward parallelization via dask and joblib backends. Support packages include casa-formats-io and radio-beam, which handle reading of CASA tables & images and reading and manipulation of point spread functions, respectively. The pvextractor package facilitates creation of position-velocity diagrams. The uvcombine package implements the "feather" algorithm for combining single-dish and interferometric data. The development of radio-astro-tools included several contributions to other repositories, including matplotlib, astropy, and regions to support interaction between CASA and other parts of the astronomy software ecosystem. We also present a detailed set of tutorials written in Jupyter notebooks that can be run interactively in a browser, providing more accessible access to data analysis for radio spectral-line data cubes.
Read the full abstract

All authors Eric W. Koch, Adam Ginsburg, Thomas P. Robitaille, Erik W. Rosolowsky, Alyssa Bulatek, Savannah Gramze, Jonathan D. Henshaw, Derek Homeier, Preshanth Jagannathan, Amanda A. Kepley, Adam K. Leroy, Sébastien Maret, Stuart Mumford, George Privon, Álvaro Sánchez-Monge, Srikrishna Sekhar, Brigitta Sipőcz, A.J.M. Thomson

Solar and Stellar Astrophysics

Oxygen isotopic ratio in open cluster RGB stars: A new method for accurate mass and age estimations

O. Straniero, C. Abia, I. Domínguez et al. (+1 more)

Determining precise and homogeneous absolute ages of open clusters (OCs) remains a challenge in stellar astrophysics, mainly due to parameter degeneracies in photometric methods and line-of-sight extinctions. We present a novel method for estimating the ages of intermediate-age and old OCs, based on the strong initial-mass dependence of the surface oxygen isotopic ratio, 16O/17O, measured in RGB stars following the first dredge-up. Using updated theoretical stellar models computed with the FuNS code, we demonstrate how post-FDU CNO isotopic abundances reflect initial stellar masses. We analysed high-resolution near-infrared spectra for 11 RGB stars belonging to four Galactic OCs. For the intermediate-age clusters NGC 7789, NGC 7044, and NGC 6819, we derive ages of 1.80, 1.81, and 2.31 Ga, respectively. For the two stars in NGC 6819 the derived initial stellar mass (1.625 Mo) and age are in excellent agreement with independent estimates from asteroseismology and eclipsing binaries. Conversely, ages estimated by means of machine learning algorithms, trained to recognise specific features in the cluster CMDs, are systematically lower. Regarding the old and super-metal-rich cluster NGC 6791, the low signal-to-noise ratio and the possible line blending hinder precise mass and age constraints. With these limitations, we can only fix a lower bound of about 4 Ga for its age. The surface oxygen isotopic ratio in RGB stars provides a powerful, independent stellar clock, making high-resolution near-infrared spectroscopy of oxygen isotopes a key tool for Galactic archaeology.
Read the full abstract

All authors O. Straniero, C. Abia, I. Domínguez, P. de Laverny

Instrumentation and Methods for Astrophysics · Cross-listed from eess.SY

Reference-Filter-Driven Transition Probabilities for IMM-Based Satellite Maneuver Detection

Euiseok Han, Sangheon Choi and Seung-Hyun Kong

Maneuver detection of non-cooperative satellites is an essential task of space situational awareness. The interacting multiple model (IMM) filter has been applied to detect unannounced maneuvers, but the standard IMM assumes a fixed Markov transition probability matrix (TPM) that must be tuned without knowledge of the maneuver rate of the target. To avoid this tuning, adaptive-TPM approaches update the TPM online from statistics computed inside the IMM. However, these statistics already depend on the TPM through the mixing step, and this dependence forms a feedback loop. Under the dynamics mismatch of orbit tracking, the loop can keep the maneuver probability high in the absence of a maneuver or suppress its rise when a maneuver occurs. In this paper, the TPM is driven by the normalized innovation squared (NIS) of a reference coast filter that is not mixed with the IMM, and the NIS is mapped continuously to the coast-to-maneuver transition probability. The reference-driven IMM (RD-IMM) is evaluated with four space-based optical sensors tracking a geosynchronous target. RD-IMM detects small burns that the fixed-TPM IMM fails to detect, with few false declarations in maneuver-free runs, and avoids both failures of the closed-loop adaptation. Moreover, RD-IMM reduces the position error after a small in-track burn by more than 50% compared with the single-filter approaches.
Read the full abstract

Cosmology and Nongalactic Astrophysics

Pinpointing the cosmic web between massive galaxy clusters I. The incidence of HI and OVI as WHIM tracers

Karen Martínez-Acosta, Nicolas Tejos, Ismael Pessa et al. (+6 more)

At redshift z<1, the $\Lambda$CDM paradigm predicts that $\sim$40-50% of baryons reside in the warm-hot intergalactic medium (WHIM) within cosmic web filaments. Characterizing the physical state and distribution of this dominant baryonic component is crucial for a complete picture of baryon evolution in the low-redshift Universe. However, directly observing the WHIM has been challenging due to its low density and high temperature and ionization state. Absorption-line spectroscopy offers a promising approach, particularly through analyses of broad Ly-$\alpha$ absorbers (BLAs; Doppler parameter b>40 km/s) and OVI absorbers. This work focuses on probing WHIM signatures by analyzing the incidence rates of these tracers in and around putative cosmic web filaments connecting massive galaxy clusters. We use far-ultraviolet (FUV) absorption spectroscopy from HST/COS along ten QSO sightlines at z<1, selected for their proximity in projected distance and velocity to cluster pairs. We focus on absorption features of WHIM tracers (BLAs and OVI) and cold-gas tracers (narrow Ly-$\alpha$ absorbers, or NLAs; b<40 km/s), which are used as a control sample for colder gas. We measure excess incidence rates for total HI, NLAs, BLAs, and OVI within a rest-frame $\Delta v=\pm1000$ km/s and an impact parameter $\Delta d<3$ Mpc relative to the field expectation, and find that the excesses of BLAs and OVI are about twice those of NLAs. Additionally, the covering fractions of BLAs and OVI appear larger by factors of $\sim$1.7 and 1.8, respectively, than in a random field control sample, whereas the NLA covering fraction is consistent with the random expectation. The larger relative excess of WHIM tracers compared to cold-gas tracers near independent cluster pairs indicates the prevalence of warm-hot gas in these environments, representing a potential signature of WHIM detection in inter-cluster filaments.
Read the full abstract

All authors Karen Martínez-Acosta, Nicolas Tejos, Ismael Pessa, J Xavier Prochaska, Joseph Burchett, Britton Smith, Jessica Werk, Nelson Padilla, Sebastián López

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Implications of tachyonic phase transition in classically scale invariant general $U(1)_{X}$ models

Arindam Das, Katsuya Hashino, Yuta Orikasa et al. (+1 more)

We investigate the complementarity between collider searches and gravitational-wave (GW) observations in the classically scale-invariant general $U(1)_X$ extension of the Standard Model. The $U(1)_X$ scale is generated radiatively through the Coleman-Weinberg mechanism, while the electroweak scale is induced through the Higgs portal, without explicit mass terms in the scalar potential. Three right-handed neutrinos are introduced to ensure anomaly cancellation and acquire Majorana masses upon $U(1)_X$ symmetry breaking, which also generates the mass of the neutral gauge boson $Z'$. In the strongly supercooled regime, a tachyonic $U(1)_X$ phase transition can produce a stochastic GW background. Assuming three heavy Majorana neutrinos, we study their effects on the phase-transition dynamics and reheating, and estimate the resulting GW signals. We identify the regions of the $U(1)_X$ gauge coupling and $Z'$ mass accessible to future GW observatories, including LISA and DECIGO, and compare them with existing LEP and LHC constraints. We find that GWs from tachyonic phase transitions can probe regions with small gauge couplings and heavy $Z'$ bosons that are difficult to access through collider searches, demonstrating the complementarity of these probes.
Read the full abstract

All authors Arindam Das, Katsuya Hashino, Yuta Orikasa, Masanori Tanaka

Solar and Stellar Astrophysics

Direct Numerical Comparison of Data Driving Strategies for Solar Flux Emergence in Magnetohydrodynamics: B-driving vs E-driving

Kyriakos Christos Tapinou, Axel Raboonik, David I. Pontin et al. (+3 more)

Data driving is an important technique for modelling realistic magnetic field and plasma evolution in regions of the solar atmosphere where direct observations are either absent or insufficient. This technique uses observational data to drive the evolution of the simulation, while the modelled solar atmosphere evolves self-consistently. A common approach for data-driven simulations is B-driving, which uses the observed magnetic field at the surface of the Sun as a boundary condition. However, only prescribing B at the boundary does not generally determine its numerical evolution when the update depends on the reconstructed interface states or fluxes. To address this, E-driving provides an alternative approach by instead driving the simulation using the electric field on the boundary, which directly controls the magnetic field update. We systematically quantify the performance of B- and E-driving in a controlled set of numerical experiments. We test both methods in the Athena++ solver using (a) an analytical flux-emergence model (Y. Fan & S. Gibson 2003) and (b) a "ground-truth" reference simulation (S. Toriumi & S. Takasao 2017; S. Toriumi et al. 2020) of active region emergence. For E-driving, the electric field is incorporated into Athena++'s constrained-transport (CT) update, preserving the discrete solenoidal constraint. We assess the reproduction of (i) boundary magnetic flux, (ii) relative magnetic helicity, (iii) total and free magnetic energy, and (iv) magnetic morphology. Across these diagnostics, E-driving gives better overall reproduction of the reference evolution than B-driving. For the configurations considered in an Eulerian CT scheme, E-driving is more accurate than the commonly used ghost-cell B-driving strategies and simpler than constructing an update-consistent B-driving boundary condition.
Read the full abstract

All authors Kyriakos Christos Tapinou, Axel Raboonik, David I. Pontin, Michael S. Wheatland, Mark C.M. Cheung, Hannah Schunker

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

Analysis of p-Wave Sommerfeld Resonance Behavior in Finite-Size Dark Matter

Wu-Long Xu, Jin Min Yang and Rui Zhu

Different stages of cosmic evolution impose different requirements on the dark matter annihilation cross section. Sommerfeld enhancement provides a possible way to accommodate them. However, in the point-like dark matter scenario, satisfying these requirements with either $s$-wave or $p$-wave Sommerfeld enhancement can strongly constrain the dark matter and mediator masses and their coupling. A finite dark matter size introduces an additional parameter and may relax these constraints. Motivated by this possibility, in this work we study the $p$-wave Sommerfeld resonances of finite-size dark matter (like proton or neutron) without specifying its internal structure. We find that the $p$-wave contribution can exceed the $s$-wave contribution. Nevertheless, the finite-size $p$-wave resonances are weaker than those in the point-like case. Despite this suppression, their velocity dependence remains similar to that of point-like dark matter. We then extend our analysis to nugget dark matter composed of a small number of constituents. In this case, the $p$-wave Sommerfeld enhancement exhibits behavior similar to that of point-like dark matter.
Read the full abstract

High Energy Astrophysical Phenomena

Improved analysis of time delays between radio wavelengths and X-ray of Sgr A* flares in the shock oscillation model

Ramiz Aktar, Toru Okuda and Chandra B. Singh

We present an improved analysis of the time delays between radio and X-ray flares from the supermassive black hole Sagittarius A* (Sgr A*), extending our previous shock oscillation model by incorporating Compton scattering. Our simulations predict delay times of 1-4 h between X-ray and radio flares, 20-40 min and 0.5-1 h between 334 GHz and 4.5 $\mu$m and 2-8 keV flares, and 7-20 min and 0.5-1 h between 22-43 GHz and 350 GHz radio flares, respectively, in good agreement with recent observations. The delay time between the radio emissions (synchrotron) and X-ray emissions (bremsstrahlung) is interpreted as the transit time for sound waves traveling from the central core near the event horizon to the location of the oscillating shock. Additionally, the delay time observed between different radio wavelengths corresponds to the transit time of sound waves moving between the frequency-dependent effective radii $R_{\rm eff}(\nu)$, where the optical thickness $\tau_{\nu}(R)$ at frequency $\nu$ equals one on the surface of the accretion disc. The X-ray emission and the radio emission at lower frequencies peak later than the radio emission at higher frequencies. This delay occurs because the acoustic perturbations created by synchrotron emission peak near the event horizon and then expand outward. Conversely, an inverse delay happens when the acoustic waves generated by the upstream shock wave travel toward the event horizon. The predicted delay times from this interpretation qualitatively match the numerical results obtained in simulations.
Read the full abstract

Astrophysics of Galaxies

The Binary Fraction of Milky Way Field Stars in DESI: Dependence on Chemical Abundance

Tian Qiu, Wenting Wang, Sergey E. Koposov et al. (+39 more)

Binary populations encode information about the physical conditions of star formation and the subsequent evolution of stellar populations. Adopting a statistical method based on multi-epoch line-of-sight velocity variations, we constrain the binary fraction, $f_b$, of field main-sequence turn-off stars in the Milky Way using data from the second data release of the DESI Milky Way Survey. $f_b$ is found to primarily increase with lower [Fe/H]. At $[\mathrm{Fe}/\mathrm{H}]\gtrsim -1.3$, $f_b$ shows a modest increase with increasing [Mg/Fe], whereas no clear trend is detected at lower [Fe/H]. The apparent variations of $f_b$ with angular momentum and Galactic height are largely explained by their underlying [Fe/H] distributions, while the remaining variations broadly follow differences in [Mg/Fe]. Within overlapping regions of the [Fe/H]–[Mg/Fe] plane, the thin disk, thick disk, stellar halo and GSE populations exhibit no significant differences in their binary fractions. Thus, our measurements indicate that the variation in $f_b$ is dominated by chemical abundance, which could be explained by the metallicity-dependent gas cooling efficiency and fragmentation. The weaker [Mg/Fe] dependence at fixed [Fe/H] might be associated with the formation conditions of stars, with higher [Mg/Fe] stars generally forming earlier under a more gas-rich and turbulent environment.
Read the full abstract

All authors Tian Qiu, Wenting Wang, Sergey E. Koposov, Songting Li, Nathan Sandford, Ting S. Li, Joan Najita, Jessica Nicole Aguilar, Steven Ahlen, Davide Bianchi, David Brooks, Aurelio Carnero Rosell, Todd Claybaugh, Andrei Cuceu, Axel de la Macorra, Arjun Dey, Peter Doel, Jaime E. Forero-Romero, Enrique Gaztañaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Stephanie Juneau, Robert Kehoe, Martin Landriau, Laurent Le Guillou, Aaron Meisner, Ramon Miquel, Enrique Paillas, Will Percival, Francisco Prada, Ignasi Pérez-Ràfols, Corentin Ravoux, Graziano Rossi, Eusebio Sanchez, Christoph Saulder, Edward Schlafly, David Schlegel, Michael Schubnell, Joseph Harry Silber, Małgorzata Siudek, Gregory Tarlé, Benjamin Alan Weaver

High Energy Astrophysical Phenomena · Cross-listed from nucl-th

Production Memory of the $^{225}\mathrm{Ra}$-$^{225}\mathrm{Ac}$ Clock in Neutron-Star Merger Ejecta

Hisham Anwer

Radioactive nuclei in neutron-star merger ejecta carry information about both their abundance and their production history. Using the $^{225}\mathrm{Ra}$-$^{225}\mathrm{Ac}$ sequence, we establish exact conditions linking a surviving isotope partition to the time available for parent decay. An Ac fraction of 0.1 produced solely through Ra decay requires at least 2.456 days, providing a direct consistency test for proposed source states. We show that subsequent activity retains additional production memory: two histories with the same mean birth time can produce different response crossings. This distinction is captured analytically and separates mean chronology from the influence of the production-time distribution. A controlled radiation calculation then shows how deposition and photon escape transform the nuclear contrast into a common light-curve pivot for fixed ejecta properties. The results connect nuclear production chronology to late-time merger emission and provide benchmarks for nucleosynthesis and radiation-transport calculations.
Read the full abstract

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

Systematic Uncertainties in Ultralight Boson Constraints from Superradiance

P.S. Aswathi and Ling Sun

Ultralight bosons are well-motivated candidates for physics beyond the Standard Model and may constitute part or all of the dark matter. Black-hole superradiance provides a powerful means of probing these particles through their gravitational interaction with rotating black holes. This mechanism has motivated a growing body of constraints from electromagnetic measurements of black-hole spins and, more recently, gravitational-wave observations. Gravitational-wave probes draw on several distinct signatures: the spins of merging binary black holes, gravitational radiation emitted by boson clouds, and potential imprints of cloud-induced changes to binary dynamics. The interpretation of these probes depends on method-specific astrophysical and theoretical assumptions, including black hole formation, natal spin, age, accretion history, population priors, and boson self-interactions. In this paper, we review the principal electromagnetic and gravitational-wave constraints derived from black-hole superradiance, with particular emphasis on their underlying assumptions and systematic uncertainties. The distinct observational signatures and systematic uncertainties of these approaches offer complementary perspectives on the viability of ultralight-boson models. In particular, their overlapping coverage around boson masses of $10^{-13}$-$10^{-12}$ eV makes this region particularly informative for comparing constraints, with attention to the assumptions underlying each result.
Read the full abstract

Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc

Accounting for detector calibration uncertainty in black-hole ringdown analysis

Rowina S. Nathan, Shingo Hido, Neil Lu et al. (+3 more)

Detector calibration systematics can bias measurements of a remnant black hole's mass and spin, producing spurious evidence against general relativity if unaccounted for. The ringdown phase in the gravitational-wave signal produced by a binary black-hole merger encodes the remnant properties: at sufficiently late times, the signal is well described by a superposition of quasinormal modes, each with a frequency and damping time set only by the remnant mass and spin. Here we present two complementary approaches for analyzing the ringdown portion of the data to estimate the remnant mass and spin in the presence of a nonnegligible detector calibration error, using the quasinormal-mode rational filter (QNMRF). With a well-measured error, we apply the best-estimated calibration correction to the strain before conducting the standard analysis; with an unknown error, we instead jointly sample the remnant mass, spin and the frequency-dependent calibration error, marginalizing over an uncertainty prior. By injecting the numerical-relativity waveform SXS:BBH:0305 into colored detector noise, at a full-signal matched-filter signal-to-noise ratio of $\sim60$ and with simulated calibration errors of $\pm25\%$ in magnitude and $\pm25^\circ$ in phase, marginalizing over the calibration uncertainty recovers the true mass and spin within the 90% credible interval, whereas the estimated values are biased if the calibration errors are ignored. We apply the method to GW250207, an event recorded while the Hanford detector response was not well characterized, and recover a remnant consistent with the inspiral-merger-ringdown prediction using the ringdown portion alone, both by correcting for a best-estimated calibration error and by marginalizing over a broad uncertainty prior.
Read the full abstract

All authors Rowina S. Nathan, Shingo Hido, Neil Lu, Mallika R. Sinha, Sizheng Ma, Ling Sun

Cosmology and Nongalactic Astrophysics

Galaxy Clustering Can Reveal Host-Galaxy Properties of Binary Black Hole Mergers

Daiki Watarai, Hayato Imafuku and Fumihiro Chuman

Galaxy clustering encodes information about the host galaxies of binary black hole (BBH) mergers even when individual hosts remain unidentified, because the distribution of neighboring galaxies depends statistically on the host-galaxy population. We construct event-level host-type likelihoods from host-conditioned galaxy-count distributions within gravitational-wave localization regions and combine them to infer the fractions of BBH mergers hosted by different galaxy populations. The framework applies to common and rare galaxy populations without prescribing formation efficiencies or merger delay-time distributions. Using measured star-forming and quenched galaxy clustering, idealized one-year forecasts assuming all mergers occur in quenched galaxies yield median one-sided 90% lower credible limits of 0.19, 0.48, and 0.92 on the quenched-host fraction for O5, post-O5, and third-generation networks. These forecasts illustrate the potential for host-galaxy population inference before the third-generation detector era.
Read the full abstract

Wednesday 7 October

Astrophysics of Galaxies

NGC 6426: Colour-Magnitude diagram and variable star population as indicators of metallicity, distance, and age

A. Arellano Ferro, R. Michel, D. Deras et al. (+3 more)

We present new VI CCD photometry of the globular cluster NGC 6426. The membership status of all point sources and, in particular, of all the variables in the field of view is discussed, including four recently detected variables. The double mode nature of variables V3 and V9 is confirmed and their periods are calculated. The presence of a cluster member anomalous Cepheid (V17) is reported. Employing only likely members we produce a decontaminated colour-magnitude diagram (CMD) differentially dereddened, which enables us to compare it with theoretical predictions and to study the variable stars distribution. The mean cluster metallicity and distance were calculated via the RR Lyrae V-band light curve Fourier decomposition and an I-band calibration of the Period-Magnitude-Metallicity relation. Further, a comparison using a Bayesian approach between theoretical isochrones of Dartmouth Stellar Evolution Database (DSED), with a deep HST CMD, gave us independent estimates of distance modulus, metallicity, colour excess, and cluster age.
Read the full abstract

All authors A. Arellano Ferro, R. Michel, D. Deras, M. Vaca Montejano, S. Muneer, I. Bustos Fierro

Instrumentation and Methods for Astrophysics

DeepDISC on LSST Data Preview 1: Scene-Level Detection, Deblending, and Star/Galaxy Classification in the ECDFS and EDFS Fields

Prince Yadav, Yaswant Sai Ejjagiri, Xin Liu et al. (+2 more)

We present the first application of DeepDISC, a scene-level deep-learning framework, to real LSST data, using the Data Preview 1 (DP1) coadded images of the Extended Chandra Deep Field-South and the Euclid Deep Field-South fields. In a single pass, DeepDISC jointly detects, segments, and classifies sources as stars or galaxies, rather than treating these tasks as separate steps as in traditional pipelines. We warm-start from a model pretrained on LSST simulations and fine-tune it on DP1 six-band images, using the DP1 catalog's extendedness flag (point-like versus extended) as provisional class labels. The classification part of the network is then fine-tuned alone on a curated sample of stars and galaxies with spectroscopic, Gaia, and photometric identifications, so the final output is a star/galaxy classification. Fine-tuning on real DP1 observations substantially improves source recovery relative to the un-fine-tuned model, raising galaxy and star completeness from 40.2% and 13% to 84.2% and 49.1% under strict class-aware matching; under class-agnostic matching the fine-tuned model reaches 84.9% and 74.3%. On a common sample of sources that neither classifier saw in training, DeepDISC classifies to within about one percentage point of a published photometry-based Random Forest for the same field (97.4% vs. 98.5%); at fainter magnitudes DeepDISC labels more sources as stars than the Random Forest, and independent labels favor the Random Forest in most of these disagreements. Cross-matching to deeper HST/CANDELS imaging on a held-out footprint gives an unrecognized-blend fraction for DeepDISC of 14.9% (95% CI 12.5-17.8%), consistent with or modestly below the 18.0% we measure for the production DP1 catalog. This work establishes a baseline for DeepDISC on real LSST data and a foundation for self-supervised pretraining and for LSST Data Preview 2.
Read the full abstract

All authors Prince Yadav, Yaswant Sai Ejjagiri, Xin Liu, Grant Merz, the LSST Dark Energy Science Collaboration

High Energy Astrophysical Phenomena

Flux Dependence of the 1\,keV Soft X-ray Feature in SAX J1808.4-3658 with NICER

Katherine Bruce, Anne M. Lohfink, Jaiverdhan Chauhan et al. (+3 more)

We present a systematic X-ray spectral analysis of the 2019 and 2022 outbursts of the accreting millisecond pulsar SAX J1808.4-3658 with extit{NICER} with a particular emphasis on the nature of the longstanding $\sim$1\,keV spectral feature. We report here the first clear evidence that the 0.9-1.0 keV feature varies systematically with source brightness, exhibiting strong correlations with both continuum and blackbody flux. This establishes that the feature is directly coupled to the accretion process. The scaling and energy distribution of the feature differ between outbursts, corresponding to a $\sim$2\,dex change in reprocessor density (log\,$n_e \approx 19.1$ in 2019 vs. $\sim$17.3 in 2022), which naturally explains the stronger, broader feature in 2019 and the weaker, more localized $\sim$1\,keV feature in 2022, in agreement with high-density reflection models. These results provide the strongest constraints to date on the origin of the $\sim$1\,keV feature in SAX J1808.4-3658.
Read the full abstract

All authors Katherine Bruce, Anne M. Lohfink, Jaiverdhan Chauhan, Suchismito Chattopadhyay, Sachiko Tsuruta, Andrew C. Liebmann

Astrophysics of Galaxies

Central stellar depletion in the Draco dwarf from Subaru photometry

Eduardo Vitral, Kyosuke S. Sato, Jorge Peñarrubia et al. (+2 more)

Dark matter subhaloes are a fundamental prediction of the standard cosmological model, but their low-mass population remains difficult to constrain observationally. Recent work has shown that interactions between subhaloes and dwarf spheroidal galaxies can induce large-scale, out-of-equilibrium fluctuations in their stellar surface density fields, identifiable through Fourier-based statistics. We apply this formalism to deep Subaru photometry of the Draco dwarf, extending previous tests to $\gtrsim\mathcal{O}(10^{4})$ resolved stars. We use artificial-star tests to assign completeness weights to individual stars and incorporate them into a discrete likelihood-based framework. Relative to a cored axisymmetric Plummer model, Draco shows radial corrugations that appear in the filtered normalised residuals as a central stellar depletion surrounded by a ring-like excess. The same feature appears in Fourier space as a low-frequency peak with a signal-to-noise ratio ${\rm S/N}=6.0$. Independently, fitting the surface density $\Sigma$ with an $\alpha\beta\gamma$ model yields ${\rm d}\Sigma/{\rm d}R>0$ at $>99.9\%$ confidence – i.e., a profile that decreases towards the centre. Although these signatures cannot yet be regarded as robust evidence for dark subhaloes, they suggest that central stellar depletion in dwarf galaxies may reflect genuine physical structure rather than crowding alone.
Read the full abstract

All authors Eduardo Vitral, Kyosuke S. Sato, Jorge Peñarrubia, Sakurako Okamoto, Veronika Dornan

Astrophysics of Galaxies

The conditional colour-magnitude distribution: III. A study of galaxy colour- and luminosity-dependent counts-in-cells statistics

Raymon Isaac and Zheng Zheng

The conditional colour-magnitude distribution (CCMD) model connects the galaxy colour-luminosity distribution with dark matter halo mass, which has been constrained in Xu et al. by jointly modelling the two-point correlation functions of a large galaxy sample of the Sloan Digital Sky Survey (SDSS) in fine bins of galaxy colour and luminosity. We test the CCMD model of the galaxy-halo connection using counts-in-cells (CIC) statistics by comparing CCMD model predictions with SDSS measurements for 16 subsamples of galaxies in various luminosity and colour bins. In addition, we compare SDSS measurements with three analytic models of CIC distribution. The CCMD model provides a good description of the SDSS CIC measurements for most subsamples. The exceptions are the void probability functions and CIC distributions with cell radius 5 Mpc/h for a few subsamples in the luminous bins, which are not well described by the analytic models, either. For these subsamples, in general, removing the Sloan Great Wall from SDSS or introducing velocity bias to the CCMD model does not resolve the disagreement. Finally, with the help of the CCMD mocks, we investigate the cause of the variations of the galaxy counts in cells. For small cells or cells with a low mean galaxy count, the variation reflects effects from fluctuations in both the matter environment and the halo occupation distribution, while for large cells or cells with a high mean galaxy count, the environment effect dominates. We discuss the implications of our work for investigating galaxy assembly bias.
Read the full abstract

Earth and Planetary Astrophysics

Stochastic Snowball States in Planetary Climate

Duc Thach Son Vu and John S. Wettlaufer

Motivated by the recent finding of Ji and Abbot (2025) that at moderate eccentricity (0.2–0.3) the planetary Snowball bistability vanishes, we have introduced stochasticity of the orbital eccentricity into a simplified version of the energy balance model of Eisenman and Wettlaufer (2009) to study a general Earth-like planet. The stochastic eccentricity is approximated by two dominant time scales, annual and daily, and is introduced through an analysis of the Kepler equation. We find that, apart from mean eccentricities less than 0.1, the stochastic dynamics are quantitatively and qualitatively different than the deterministic dynamics. For a fixed mean eccentricity, fluctuations in eccentricity amplify the asymmetry and intermittency in radiative flux forcing, thereby increasing the time it takes to reach a stable seasonal cycle. As the mean eccentricity increases above 0.1, the stochastic transition from the Snowball to non-Snowball state occurs over a range of mean stellar flux $\Delta S^*$ rather that at a particular stellar flux $S^*$ for the deterministic case. Moreover, as the mean eccentricity increases from 0.1 and the variance of the annual eccentricity fluctuations increases, $\Delta S^*$ increases and the probability of the system reaching a steady state and experiencing a Snowball to non-Snowball bifurcation decreases. This implies that there may be many high eccentricity planetary systems in a perpetually transient state.
Read the full abstract

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Massive de Sitter Correlators as Finite Mellin-Barnes Integrals

Amara McCune

Using the Mellin-Barnes representation of de Sitter propagators, we reduce tree-level heavy-particle exchange to finite integrals that converge at physical kinematics on mass-independent contours, and one-loop diagrams to the same integrand times a flat-space momentum factor. We evaluate the triple-exchange bispectrum without analytic continuation and compute the complete one-loop triangle at general mass. These give cosmological collider predictions, the oscillatory signatures of heavy particles during inflation, for multiple exchanges and loops at arbitrary masses.
Read the full abstract

Solar and Stellar Astrophysics

Understanding how Coronal Heating and Magnetic Field Scaling Affect Global Properties of the Low and Middle Corona

Caroline L. Evans, Cooper Downs and Donald Schmit

The magnetic field of the Sun is a key driver of coronal heating and solar wind acceleration. In tandem, these influence the observable morphology of the corona, along with defining the magnetic connectivity and magnitude of open magnetic flux. Here,we investigate how coronal heating affects the magnetothermal state of the 3D global corona by analyzing a series of data-constrained, thermodynamic magnetohydrodynamic (MHD) simulations for solar minimum conditions. We vary the overall heat deposited in the corona via modifying the input Poynting flux of a wave-turbulence-driven (WTD) model for coronal heating and by scaling the inner boundary magnetic field. We quantify the magnetic, thermodynamic, and combined magnetothermal effects on our simulations. We find that increasing the overall amount of heat leads to a higher magnitude of open flux and a more visibly open white-light morphology in the K-Corona between 1.5 and 6 Rsun. We quantify how plasma beta evolves and drives morphological differences between simulations. We also compare these runs to an extremely high-resolution reference solution that includes small-scale magnetic information in the surface boundary condition. This latter comparison provides insight into the further development of 'subgrid' corrections for low(er) resolution models to best represent the structure and observables of the corona and inner heliosphere.
Read the full abstract

Astrophysics of Galaxies

Mass Proxy Quality of Halo Properties in IllustrisTNG and FLAMINGO Simulations: II. Galaxies, Stars, and Black Holes

Eddie Aljamal, August E. Evrard, Arya Farahi et al. (+1 more)

We study the stellar, black hole, and satellite galaxy populations of group- and cluster-scale halos in the IllustrisTNG, TNG-Cluster, and FLAMINGO cosmological hydrodynamical simulations. We characterize the mass-conditioned scaling relations, covariance, conditional likelihoods, and mass proxy quality (MPQ) of integral properties within $R_{\rm 500c}$: total stellar mass ($M_{\star,\,\rm tot}$), brightest central galaxy stellar mass ($M_{\star,\,\rm BCG}$), intracluster light mass ($M_{\star,\,\rm ICL}$), total black hole mass ($M_{\rm BH}$), satellite occupation ($N_{\rm sat}$), and satellite velocity dispersion ($\sigma_{\rm sat,\,1D}$), at $z\in \{0,0.5,1,2\}$. While normalization differences of up to a factor of two emerge among simulations, many properties exhibit remarkably similar mass-localized slopes, intrinsic scatters, and MPQs across halo samples and redshifts. Correlations among stellar, satellite, and gas properties are generally consistent in sign and their dependence on halo mass and redshift, whereas those involving $M_{\rm BH}$ and $N_{\rm sat}$ show greater variation, particularly in TNG-Cluster. Conditional likelihoods are nearly lognormal for many properties, including $M_{\star,\,\rm tot}$, $N_{\rm sat}$, and $\sigma_{\rm sat,\,1D}$, while $M_{\star,\,\rm BCG}$ and $M_{\star,\,\rm ICL}$ are negatively skewed. Among the properties considered here, total stellar mass is the best mass proxy, with a halo mass scatter of $7$-$14\%$, followed by $N_{\rm sat}$ with a mass scatter of $9$-$18\%$. The consistent correlation behavior of $M_{\star,\,\rm ICL}$ highlights its potential for next-generation observational studies. Finally, $\sigma_{\rm sat,\,1D}$ exhibits highly consistent scaling, with mass-independent slope and scatter and a largely neutral correlation structure, suggesting that it is relatively insensitive to astrophysical complexity.
Read the full abstract

All authors Eddie Aljamal, August E. Evrard, Arya Farahi, Dylan Nelson

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

Observational Signatures of Dyonic Black Holes in Non-Linear Electrodynamics

Sobhan Kazempour, Sichun Sun, Zhiqing He et al. (+1 more)

We study the observational features of thin-disk accretion and emission spectra for static, spherically symmetric dyonic black holes in non-linear electrodynamics (NLED). In contrast to classical Maxwell theory, where electromagnetic duality assumes equal charges, the coupling parameters in NLED introduce a new gravitational potential and modify the geometry in the strong-field regime. We also study the kinematic characteristics of particles on circular orbits, such as their angular velocity, specific energy, and specific angular momentum. It is found that modifications of NLED lead to a shrinkage of the ISCO radius, resulting in a shift of the radiation spectrum thermal maximum towards smaller radii and, consequently, an increase in the local effective temperature in comparison with the standard Schwarzschild and Reissner-Nordström solutions. Additionally, we compute null-geodesic orbits to determine the optical edge of both the photon sphere and the black hole shadow. In order to assess the observational validity of the aforementioned alternatives, we carry out a $\chi^2$ goodness-of-fit test through the angular diameter constraints at the horizon scale collected by the Event Horizon Telescope (EHT) concerning Sagittarius A* ($\text{Sgr A}^*$). We prove that both these dyonic NLED and purely magnetic models have good statistical agreement with experimental data.
Read the full abstract

All authors Sobhan Kazempour, Sichun Sun, Zhiqing He, Chengye Yu

Earth and Planetary Astrophysics

Systematic non-compliance of satellite megaconstellations with IAU brightness limits

Jack Rayworth, Denis Vida, Pauline Barmby et al. (+7 more)

Satellite megaconstellations in low Earth orbit interfere with ground-based optical astronomy, but the scale of that interference has been hard to measure. Here we report an uncued photometric survey from a mid-northern latitude site in late 2024 which recorded some 25,000 tracks of 5,118 individual satellites to a limiting visual magnitude of +9.0. The observed population is systematically brighter than the altitude-adjusted limit of order seventh magnitude recommended by the International Astronomical Union Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS). Starlink satellites exceeded that limit on roughly a quarter of all geometrically possible passes, rocket bodies on about a fifth, and the emerging Guowang/Hulianwang constellation on more than half. OneWeb was the most compliant major operator (exceeding the IAU CPS limit on only about one in twenty possible passes), which shows that effective brightness mitigation is achievable with current technology. Satellite visibility is concentrated into the two hours after sunset and before sunrise and into limited regions of the sky. From the measured plane-of-sky satellite flux we predict that of order one in three 30 s twilight exposures at the Vera C. Rubin Observatory will carry a satellite trail.
Read the full abstract

All authors Jack Rayworth, Denis Vida, Pauline Barmby, Peter G. Brown, Sarah Gallagher, Michael J. Mazur, David L. Clark, Maximilian Vovk, Stanimir Metchev, Lauchie Scott

High Energy Astrophysical Phenomena

Shortening the Baseline: Characterising Type Ia Supernovae Using $\Delta m_{10}(X)$

Joel M. Velasco, Paolo A. Mazzali, Christopher Ashall et al. (+8 more)

An explorative study of Type Ia Supernovae (SNe Ia) light curves is presented. $\Delta m_{t}(X)$ decline-rate metrics are used to evaluate alternative characterisations of light curve diversity and the Luminosity-Width Relation (LWR). Using a sample of 362 SNe Ia from the Carnegie Supernova Project (CSP-I and CSP-II), Gaussian Process regression is used to fit $B$- and $g$-band light curves and measure decline-rates across multiple post-maximum timescales. The LWR is calibrated using a clean subsample of SNe Ia with host-independent distance moduli and Fitzpatrick (1999) reddening corrections. Decline-rates $\Delta m_{10}(B)$ and $\Delta m_{10}(g)$ are found to capture the LWR effectively, while mitigating the severe degeneracy that affects longer timescales for fast-declining ($\Delta m_{15}(B) \geq 1.6$ mag) events. Continuous, piecewise linear models are presented that seamlessly anchor the transition between normal and fast-declining regimes. The decline-rate $\Delta m_{10}(X)$ closely approximates the results of the more complex colour-stretch parameters, requiring less post-maximum temporal coverage than $\Delta m_{15}(B)$ or $s_{BV}$, and offers an even greater sensitivity for slow decliners. $\Delta m_{10}(B)$ provides a precise and practical tool for large-scale photometric surveys and real-time observer classification.photometric surveys and real-time observer classification.
Read the full abstract

All authors Joel M. Velasco, Paolo A. Mazzali, Christopher Ashall, Christopher R. Burns, Mark M. Phillips, Lluis Galbany, Nidia Morrell, Maximilian D. Stritzinger, Peter Hoeflich, Eric Y. Hsiao, Syed A. Uddin

Astrophysics of Galaxies

The progenitor galaxies of the intracluster light

Rebecca J. Mayes, Facundo A. Gómez and Antonela Monachesi

Intracluster Light (ICL) is a diffuse stellar component of galaxy groups and clusters, bound to the structure's potential rather than to individual galaxies and primarily formed through the stripping and mergers of intermediate-mass galaxies. Its formation and evolution is strongly linked to the central galaxies of groups and clusters, typically the Brightest Cluster Galaxies (BCGs) in clusters. To determine the properties of the progenitor galaxies of the ICL of clusters and groups at redshift z = 0 and compare them with the progenitors of their BCGs. We select 127 clusters and groups in the hydrodynamic Illustris-TNG100 simulation above a mass of 10^{13}~$M_{\odot}$. We divide the ICL from the BCG by applying a surface brightness cut at the Holmberg radius of 26.5 mag/arcsec^{-2}, where star particles within this radius are defined as attached to the BCG, and outside, the ICL. We then determine the masses and contributions of progenitor galaxies of the ICL and BCG. We find that the number of ICL progenitors increases with structure mass, and that the ICL has more progenitors than the BCG. The ICL has a larger percentage of material from low-mass galaxies. Quenched galaxies contributed a large fraction of the ICL, and this fraction increases with galaxy mass. The mean mass radial gradient of ex-situ material in structures for the ICL and the BCG+ICL is generally negative and increases with structure mass, indicating that material from more massive progenitors is found towards the centres of clusters. The mean mass radial gradient is significantly impacted by structure formation history. ICL progenitor properties are impacted by structure history and are therefore highly individual to each system. At a given structure mass, there is diversity in the properties of the progenitors that formed the ICL. Although the BCG and the ICL co-evolve, the BCG has fewer, more massive progenitors.
Read the full abstract

Cosmology and Nongalactic Astrophysics

Debiasing Local Cluster Infall Reveals $\boldsymbol{H_0}$: Application to the Virgo Cluster

Bastien Carreres, David Benisty, Jenny Wagner et al. (+3 more)

Galaxy recession velocities are commonly used to measure the Hubble constant, $H_0$, with peculiar velocities treated as random noise. Around massive clusters, however, these motions can be predicted by the gravitational potential of the central halo, allowing them to be modeled rather than averaged over. Past analyses relied on analytic approximations for the distance-infall-velocity relation, whose accuracy has not been tested using realistic cosmological simulations. We use halos from the IllustrisTNG simulation to quantify the bias and precision of several commonly used Hubble-flow models. We find that widely used fitting functions systematically underestimate $H_0$, whereas the full analytical solution reduces but does not eliminate these biases. We develop a simulation-based method to infer $H_0$ and apply it to TRGB distance samples around the Virgo Cluster. We find $H_0=74.4\pm 2.9$ and $73.4\pm 3.9$ km s$^{-1}$ Mpc$^{-1}$ (stat) for the minor and the major infall models, respectively. Correcting for the bias calibrated on TNG halos, these measurements raise the value of $H_0$ to $81.6 \pm 7.8$ and $87.3 \pm 8.8$ km s$^{-1}$ Mpc$^{-1}$ (stat+sys), where the minor infall model has the smallest bias from the Virgo mocks. We show that statistical errors are dominated by the residual velocity scatter around the infall model, while systematic errors are dominated by the transformation to the structure's comoving frame and halo population variance. These results establish a framework for interpreting cluster infall measurements and explain trends in previous $H_0$ inferences.
Read the full abstract

All authors Bastien Carreres, David Benisty, Jenny Wagner, Avery Erlenbach, Dan Scolnic, Adam Riess