Current date: 2026-09-30
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Scoring abstracts
Number of records retrieved: 1061
Keyword score statistics
score 9 -- 1 abstracts
score 7 -- 2 abstracts
score 6 -- 2 abstracts
score 5 -- 2 abstracts
score 4 -- 6 abstracts
score 3 -- 17 abstracts
score 2 -- 21 abstracts
in total -- 51 abstracts
Articles that appeared on 2026-09-30
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[abstract 1 / 51] Wow! (score: 9)
- Title: Very High-Energy GRB Afterglow Fits with Neural-Network Emulation and Bayesian inferenceAuthors: Edilberto Aguilar-Ruiz, Jessica Saldívar Talavera, Ramandeep Gill, Sundar Srinivasan,Comments: Submitted to MNRASSubjects: astro-ph.HECreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
The very high-energy ($E > 100$ GeV) afterglow emission in GAMMA-RAY BURSTs (GRBs) can be explained by SYNCHROTRON self-Compton (SSC). Modeling this emission accurately requires fully numerical codes that solve the time-dependent coupled particle--photon kinetic equations while accounting for Klein--Nishina suppression. However, their substantial computational cost makes them impractical for traditional parameter inference techniques such as Markov Chain Monte Carlo (MCMC) sampling. In this work, we present a highly efficient surrogate model based on artificial neural networks (ANNs) that emulates a one-zone kinetic SSC radiation code. To train our ANN, we use a multi-dimensional model parameter grid that constitutes a sample of 100,800 spectra produced by an infinitely thin spherical blast wave propagating inside a constant density interstellar medium (ISM). The ANN reproduces the numerical spectra well, with the median relative error generally below 2 per cent across the full frequency domain. Using this surrogate framework, we perform Bayesian parameter posterior estimation via MCMC and fit the broadband GRB afterglow observations of GRB 190114C from X-rays to TeV $γ$-rays at different epochs. We find an energetic JET with isotropic-equivalent kinetic energy of $E_{\rm k,iso}\simeq7.2\times10^{54}$ erg moving with a coasting bulk Lorentz factor of $Γ\gtrsim500$ into an ISM with density $n\simeq0.1\,{\rm cm^{-3}}$. The deviation of our model light curve from observations on long timescales suggests that an ISM environment is inconsistent and a radially stratified external medium, as pointed out by \citet{Aguilar-Ruiz+26}, is preferred instead.
[abstract 2 / 51] Wow! (score: 7) - Title: The Effects of Cosmic Ray Protons on Galactic Nonthermal FilamentsAuthors: Mohan Richter-Addo, Roark Habegger, Ellen Zweibel, Dylan M. Paré, David T. Chuss,Comments: Revision: 17 pages, includes changes made in correspondence with referee and proofreader of ApJ. Comments welcome!Subjects: astro-ph.HE astro-ph.GACreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
The Galactic Center (GC) contains a collection of filaments that are typically tens of parsecs in length, illuminated by SYNCHROTRON radiation from COSMIC RAYs (CR). The origin of these nonthermal filaments (NTFs) is unclear. We aim to distinguish two injection mechanisms: the first mechanism posits that NTFs are fueled either by JETs from pulsar wind nebulae and are lepton-dominated; the second mechanism posits that NTFs are fueled by accelerated particles from interstellar shocks and are proton-dominated. We explore these mechanisms using the MAGNETohydrodynamics (MHD) code Athena++, modified to account for radiative and collisional losses, to simulate CR propagation with lepton and proton CR species. We vary parameters such as MAGNETic field strength, plasma density, and the CR diffusion coefficient to determine how the range of conditions present in the GC can affect CRs' propagation, heating, plasma flow, and the observed SYNCHROTRON emission. We find few observable differences between the proton- and lepton-dominated cases, but comparing the models with observed filament properties motivates consideration of a third formation mechanism: the generation of NTFs arise from intermittent structures in Galactic Center turbulence.
[abstract 3 / 51] Wow! (score: 7) - Title: Re-interpreting the GRS 1915+105 observations within the variable TADAF scenarioAuthors: Chun Xu,Comments: preprint, 11 pages, 1 figureSubjects: astro-ph.HECreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
The Galactic microQUASAR GRS 1915+105 is one of the most interesting X-ray binary systems, exhibiting an exceptionally diverse range of observational phenomena. It displays the most complicated and variable X-ray light curves and carries superluminal radio JETs. Its X-ray and radio fluxes change on very different timescales, from seconds to minutes to days and even longer. In recent years, its JET has also displayed large position angle shifts. We find that most of the observational phenomena can be well explained within our newly developed variable turbulent ADAF (TADAF) model. The accretion disk is composed of an outer thin disk and an unstable inner TADAF torus whose size is variable. The previously suggested 'disappearance' and regain of the inner disk is understood as the transition between the thick TADAF and the thin disk. Some types of QSOs are understood in terms of the radius change of the TADAF torus. The JET position angle shift is understood as the direct sideways frame-dragging on the JET by the Lense-Thirring effect from a tilted, spinning BLACK HOLE. The slower the outshooting JET, the larger the angle shift. We note that such an effect also applies to other sources, such as V404 Cygni and the AGN M87. This mechanism may also be applicable to the famous 'precessing' JET in SS 433.
[abstract 4 / 51] Yes (score: 6) - Title: Hierarchical Bayesian Inference on the intrinsic event rate of Type I GAMMA-RAY BURSTs from the {\it FERMI}/GBM catalogueAuthors: Cao Tian-Yong, Yi Shu-Xu, Du Yun-Fei, Yorgancioglu S. Emre, Xiong Shao-Lin,Comments: 31 pages, 8 tables, 9 figures; Accepted for publication in The Astrophysical JournalSubjects: astro-ph.HECreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
The intrinsic event-rate of Type I GAMMA-RAY BURSTs (GRBs) as a function of redshift, provides a probe for binary neutron star (BNS) mergers population. However, the above-mentioned inference is complicated by instrumental selection effects, the lack of redshift measurements for the majority of GRBs, and uncertainties in JET geometry. In this work, we applied a hierarchical Bayesian inference framework to the {\it FERMI}/GBM Type I GRB catalogue to reconstruct the underlying event-rate population. This framework accounts for the selection effects and marginalizes over the limited-information posteriors of individual GRB redshifts and JET structures. The population model uses parameterized luminosity function, distribution of JET structure parameters, the Madau-Dickinson star-formation rate and a delay-time distribution of BNS mergers. The posterior distribution of the hyperparameters in the model are to be inferred, using a GPU-accelerated MCMC algorithm. The intrinsic event rate density as function of redshift is constrained up to $z=5$, which a local rate density of \(R_0 = 22.6^{+15.0}_{-10.6}\,{\rm Gpc^{-3}\,yr^{-1}},\), which is consistent with the latest gravitational-wave measurements.
[abstract 5 / 51] Yes (score: 6) - Title: An Off-Nuclear Tidal Disruption Event Discovered At Late Times: The Case Of TDE 2023mfmAuthors: Itai Sfaradi, Ryan Chornock, Yuhan Yao, Erica Hammerstein, Jean Somalwar, Raffaella Margutti, Huei Sears, Robert Stein, Natalie LeBaron, Adelle J. Goodwin, Sjoert van Velzen, Matthew J. Graham, Kate D. Alexander, Nayana A. J., Edo Berger, Jonathan Carney, Yvette Cendes, Collin T. Christy, Walter W. Golay, Wenbin Lu, James C. A. Miller-Jones, Charlotte Ward, Eli Wiston, Tracy X. Chen, Mansi M. Kasliwal, Frank J. Masci, Jesper Sollerman,Comments: 20 pages, 10 figures, 5 tablesSubjects: astro-ph.GA astro-ph.HECreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
We present the discovery and analysis of the optically selected tidal disruption event (TDE) 2023mfm, which originates from a wandering massive BLACK HOLE (MBH) in a massive ($\sim 10^{11} \,$M$_{\odot}$) galaxy hosting a central low-luminosity ACTIVE GALACTIC NUCLEus (AGN). Our analysis of the ZTF, Lick, Keck, SWIFT, Chandra, XMM-Newton, HST, and VLA observations reveals that TDE 2023mfm is a TDE-H from a $10^{6.2 \pm 0.5}\,$M$_{\odot}$ BLACK HOLE which is offset by $0.66 \pm 0.02$" from the center of its host galaxy, corresponding to a projected distance of $1.08 \pm 0.04$ kpc. TDE 2023mfm displays all the traits of optically selected TDEs. The emission remains hot, $T_{\rm bb} \sim 22,000 \pm 1,000$ K, for more than a month after peak, and the $g$-band light curve peaks at $\left( 2.24^{+0.10} _{-0.11} \right) \times 10^{43} \, \rm erg \, s^{-1}$ and stays above half-maximum luminosity for $47.8^{+3.7}_{-3.5}$ days. The late-time optical-to-UV emission observed with the HST suggests the presence of an unresolved stellar population with a stellar mass of $10^7-10^8\,$M$_{\odot}$ at the position of the TDE, possibly being a low-mass dwarf galaxy or a stripped galaxy from a previous minor merger. The radio emission from TDE 2023mfm emerges at least a year after optical discovery, and we find it likely that it originates from a delayed outflow, however, further observations are needed to determine its true origin.
[abstract 6 / 51] Yes (score: 5) - Title: Fast Radio Bursts from Induced Upscattering. I. Magnetar Polar FireballsAuthors: Rei Nishiura, Kunihito Ioka, Bing Zhang,Comments: 24 pages, 4 figures. Comments welcomeSubjects: astro-ph.HE physics.plasm-phCreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
The extreme brightness temperatures of fast radio bursts (FRBs) demand a coherent process that converts MAGNETar burst energy into millisecond radio emission. We propose that FRBs can be produced within MAGNETar MAGNETospheres by induced (stimulated) upscattering in a RELATIVISTIC fireball outflow. In this paper, we focus on induced Compton upscattering in an electron--positron fireball launched from the polar region of a MAGNETar. Radiation from the X-ray burst accelerates the polar fireball outflow to Lorentz factors of $Γ\sim10$--$10^3$. Low-frequency seed waves, such as fast MAGNETosonic or Alfvén waves, entering the outflow from the side or against its motion undergo induced scattering and are Lorentz-boosted by the RELATIVISTIC bulk motion from $ν_0\sim10\mathrm{kHz}$ to $ν_{\rm obs}\simΓ^2ν_0\sim\mathrm{GHz}$. Combining the polar fireball dynamics with the linear growth and nonlinear saturation of the induced scattering instability, we derive the FRB luminosity $L_{\rm FRB}^{\rm iso}$ and fractional spectral bandwidth $Δν/ν_{\rm c}$. By considering the possible range of pair densities and temperatures, we find that this polar channel can account for the luminosity of Galactic FRB~20200428 and reach luminosities comparable to those of the brightest extragalactic FRBs. If the pair-loaded region is narrower than the RELATIVISTIC beaming angle $1/Γ$, the model also produces a narrow spectrum and predicts $L_{\rm FRB}^{\rm iso}\propto(Δν/ν_{\rm c})^2$, a trend consistent with observations of repeating FRBs. The induced upscattering model thus connects MAGNETar X-ray bursts to FRBs through a coherent emission process grounded in plasma physics and makes observationally testable predictions.
[abstract 7 / 51] Yes (score: 5) - Title: JWST/MIRI Spectroscopy of the Quiescent Black Hole X-ray Binary XTE J1118+480: Constraints on Jet and Circumbinary Dust Contributions to the Mid-infrared EmissionAuthors: Zihao Zuo, Elena Gallo, Nuria Calvet, Richard M. Plotkin, David M. Russell, Gabriele Cugno, Rob Fender, Fraser Lewis, Joseph Michail, Jon M. Miller, James C. A. Miller-Jones, Fan Zou,Comments: Submitted to ApJ; 14 pages, 5 figuresSubjects: astro-ph.HECreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
We report on JWST/MIRI low-resolution spectroscopy ($5$-$12 μ$m) and imaging ($15$-$25 μ$m) of the BLACK HOLE X-ray binary XTE~J1118+480 in quiescence, at an X-ray luminosity nine orders of magnitude sub-Eddington, together with contemporaneous optical monitoring and a radio upper limit of $4.5~μ$Jy at 6 GHz. With the donor subtracted, the $5$-$12 μ$m continuum is curved, turning over near $6~μ$m; a single power law is rejected in favor of a $764\pm 9$ K blackbody. Longward of the turnover the spectral index is $α= +1.21\pm0.36$, steeper at the $2σ$ level than the flat to slightly inverted spectrum of a compact JET. Interpreted as SYNCHROTRON, the turnover implies equipartition fields of $\sim$$10^{4}$ G on scales of tens of gravitational radii, but the MIRI photometry at $15$-$21~μ$m-taken $2.6$ hr before the spectrum-lies $30$-$90$ per cent above its extrapolation, suggesting a second self-absorbed zone. A single partially self-absorbed JET spectrum can reach the photometry only at the expense of the spectral curvature and the $25.5~μ$m upper limit, so a steady compact JET is disfavored, although not excluded. Representative self-consistent irradiated-disk models instead reproduce the principal features of the $5$-$25~μ$m spectral energy distribution, with a directly illuminated dust wall at $\simeq 5$ binary separations, outside the tidal-truncation radius, and a minimum dust mass of order $10^{22}$ g. This is the first spectroscopic evidence, though not yet conclusive, favoring circumbinary dust over a JET in a quiescent BLACK HOLE X-ray binary.
[abstract 8 / 51] Yes (score: 4) - Title: Temporal Invariance Is an Illusion: Time-Dependent Influences of the Galactic Magnetic Field on UHECR ObservationsAuthors: Veronika Vašíčková, Leonel Morejón, Karl-Heinz Kampert,Comments: 13 pages, 8 figures excl. appendix, or 18 pages, 12 figures incl. appendixSubjects: astro-ph.HECreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Understanding the origin of the Ultra-High-Energy Cosmic Rays (UHECRs) requires explaining the features of their energy spectrum, mass composition, and arrival directions. Current modeling approaches neglect the time evolution of UHECR observables, a factor that is particularly important in the case of bursting UHECR sources. This study focuses on the influence of time delays caused by the galactic MAGNETic field (GMF) on the spectrum and arrival directions of UHECRs observed on Earth. Using CRPropa 3.2, we investigate the rigidity-dependence of the residence time of extragalactic COSMIC RAYs entering our Galaxy. We find that UHECRs entering the Milky Way can experience delays of hundreds of kiloyears relative to light, and we demonstrate that these delays significantly alter the UHECR observables. Notably, a cutoff emerges in the transient scenario within the rigidity range of $10^{18}-10^{19}$ V, which coincides with the spectral break observed in data. We find a progressive shift in composition favoring heavier nuclei, as well as a delay distribution that is correlated with GMF strength. This causes the particles to be less correlated with their initial direction the larger their delays. A dipole-like anisotropy develops over timescales of about $\sim$100 kyr in certain bursts scenarios. Our results provide an alternative explanation for the UHECR spectral cutoff that does not invoke limits on source acceleration. This could potentially revise existing constraints.
[abstract 9 / 51] Yes (score: 4) - Title: SN 1006: A Cosmic Laboratory for Investigating Shock Acceleration PhysicsAuthors: Emma McGinness, Rebecca Diesing, Damiano Caprioli, Fabio Acero,Comments:Subjects: astro-ph.HECreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
SN 1006 is a historical Type Ia SUPERNOVA remnant that exhibits non-thermal emission ranging from radio to multi-TeV $γ$-rays. Most of this emission (particularly X-rays and $γ$-rays) is concentrated in polar caps aligned with the ambient MAGNETic field, which makes it an ideal laboratory for studying COSMIC RAY (CR) acceleration at different shock obliquities and the hadronic/leptonic nature of the $γ$-ray emission. We model SN 1006's morphology, multi-wavelength spectrum, and radial profile using a self-consistent multi-zone kinetic model of particle acceleration that accounts for: CR-driven shock modification, MAGNETic field amplification, drift in MAGNETic fluctuations, and temporal dynamics including adiabatic and SYNCHROTRON losses. Our model can reproduce both the observed spectral and spatial properties, with the exception of the radio profile that we argue requires 3D hydrodynamic effects to replicate. We find that quasi-parallel regions (where the shock normal aligns with the ambient MAGNETic field) exhibit very prominent CR acceleration ($\sim$20% efficiency), while quasi-perpendicular regions exhibit efficiencies below 1%, consistent with the results of kinetic simulations. We also find that electrons are responsible for the majority of the $γ$-ray emission from SN 1006 (i.e., it is a leptonic source), with the exception of the northwest region due to an encounter with a dense cloud.
[abstract 10 / 51] Yes (score: 4) - Title: The interplay between ACTIVE GALACTIC NUCLEus photoionization, radio JET, and STAR FORMATION in the z $\sim$ 3.5 RADIO GALAXy 4C +03.24Authors: Bruno Dall'Agnol de Oliveira, Dominika Wylezalek, Pranav Kukreti, Wuji Wang, Rogério Riffel, Rogemar A. Riffel, Andrey Vayner, Caroline Bertemes, Julian T. Groth, David S. N. Rupke, Carlos De Breuck, Joël Vernet,Comments:Subjects: astro-ph.GACreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
High-redshift RADIO GALAXies (HzRGs) are among the most powerful radio sources, and are associated with the most massive galaxies and dense environments at redshifts z $\gtrsim$ 1. They are ideal laboratories for studying how ACTIVE GALACTIC NUCLEus (AGN) events can shape the evolution of galaxies, as intense radiation, JETs, and STAR FORMATION can be observed simultaneously in these galaxies. We present JWST/NIRSpec integral field spectroscopy ($\sim$ 1.6 kpc spatial resolution) of the 4C +03.24 system, a powerful HzRG at z $\sim$ 3.5 with a bolometric luminosity of $\sim 10^{47.6}$ erg s$^{-1}$. We identified kinematically disturbed regions in the warm ($\sim 10^4$ K) ionized gas by decomposing the emission-line spectra into multiple Gaussian components, which is crucial to avoid overestimating the outflow properties. The outflow power peaks at $\sim$ 2 kpc away from the nucleus, with a corresponding low kinetic coupling efficiency of $\sim 8_{-5}^{+7} \times 10^{-3}$ %. A combined analysis of the rest-frame optical and ultraviolet (from VLT/MUSE and HST imaging) continua revealed an extended emission (spanning $\sim$ 14 kpc), which we interpret as partially tracing star-forming regions. With a clearly delineated bipolar morphology, we show that the AGN photoionization dominates the ionization of the interstellar medium along the radio JET axis. The [C II]$λ$158$μ$m emission gap in this region might be direct evidence of negative AGN feedback. We also discuss a possible scenario where 4C +03.24 could be situated in an overdense environment experiencing multiple galaxy interactions and the possibility of JET-induced star-formation.
[abstract 11 / 51] Yes (score: 4) - Title: Fast radio burst - persistent radio source systems III. The relation between PRS luminosity and FRB rotation measureAuthors: D. Pelliciari, G. Bernardi, L. Bruno, M. Pilia, P. Esposito, L. Beduzzi, A. Geminardi, O. Smirnov,Comments: 14 pages, 5 figures, submitted to A&ASubjects: astro-ph.HECreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Fast radio bursts (FRBs) are millisecond-duration radio transients of extragalactic origin whose physical origin remains uncertain. A small fraction of FRBs are known to repeat, and some of them are associated with persistent radio sources (PRSs), interpreted as SYNCHROTRON-emitting nebulae surrounding the FRB source. In the context of MAGNETar-based models, the rotation measure (RM) of an FRB is expected to correlate with the spectral luminosity of its associated PRS, providing a probe of the physical properties and evolution of the nebula. We investigate the relation between FRB RM and PRS spectral luminosity, constrain the characteristic size of the PRS nebulae, and use the intrinsic scatter of the relation to investigate evolutionary scenarios for FRB--PRS systems. We analyse a sample of 50 FRB sources with known RM, including both PRS detections and spectral luminosity upper limits, using a Bayesian MCMC framework that jointly accounts for detections and non-detections. We model the luminosity--RM relation as $L_ν\propto ζ_e γ_c^2 R^2 {\rm RM}^β$, constraining the characteristic nebular size $R$ and the RM scaling index $β$. For the full sample, we obtain $R = 0.016^{+0.115}_{-0.014}$ pc at $1σ$ confidence for a free $β$, while fixing the RM dependence to the canonical linear scaling, $β= 1$, gives $R = 0.008^{+0.058}_{-0.007}$ pc. The data mildly favour super linear RM scalings, although the inferred values of $β$ remain consistent with $β= 1$ within $2σ$. We find a substantial intrinsic scatter in the luminosity--RM relation, significantly larger than previous estimates based on confirmed PRSs alone. Interpreting this scatter within evolutionary models, our results favour scenarios involving efficient particle acceleration and/or rapid nebular expansion.
[abstract 12 / 51] Yes (score: 4) - Title: Broadband reverberation mapping of QUASARs at cosmic noonAuthors: Juan V. Hernández Santisteban,Comments: 11 pages, 10 figures, to be submitted to MNRAS, comments are welcomedSubjects: astro-ph.GACreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Broadband reverberation mapping provides a powerful tool to investigate the structure of the accretion flow around supermassive BLACK HOLEs. The ultraviolet region of the QUASAR spectrum is of particular interest, as it enables the disentanglement of the relative contributions from the accretion disc and the broad-line region to the observed variability of QUASARs in the local Universe. Observations of QUASARs at cosmic noon ($z\sim 1-2$) offer the opportunity to probe the UV emission across a diverse population, spanning a broad range of BLACK HOLE masses and luminosities. Here we re-analysed the 36 multi-year QUASAR lightcurves from the Dark Energy Survey (DES) between $z\sim0.7-2$ to retrieve interband delays and analyse their spectral energy distribution. Using PyROA, we were able to fit all multiple years of observations and the four optical bands simultaneously, significantly improving the lag detection as this method is able to interpolate over the seasonal gaps. We find robust detections of interband delays in 31/36 QUASARs, suggesting high-Eddington ratios for a large fraction of objects. Their spectral energy distribution is consistent with a geometrically thin disk $f_ν\proptoλ^{-1/3}$, with an ensemble slope of $-0.28\pm0.02$. The full sample of QUASARs do not show excess around the Balmer jump region, suggesting the impact of the broad-line region to the reverberation signals in high-Eddington sources could be small as documented in some AGN in the local Universe. The prospect of LSST to observe thousands of QUASARs in this redshift range should motivate the detailed study of the UV-rest frame of high-Eddington QUASARs to account for the BLR contribution and properly infer disc sizes.
[abstract 13 / 51] Yes (score: 4) - Title: Fooled by mass? Recovering the $Γ-λ_{Edd}$ relation of QUASARs from their X-ray variabilityAuthors: Matilde Signorini, Andrea Sacchi, Bartolomeo Trefoloni, Matteo Guainazzi, Elisabeta Lusso, Emanuele Nardini, Chiara Niccolai, Federica Ricci, Anastasia Shlentsova, Mateusz Rałowski,Comments: submitted to A&ASubjects: astro-ph.GA astro-ph.HECreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
We measure the relation between the X-ray photon index $Γ$ and the Eddington ratio $λ_{Edd}$ in unobscured type-1 QUASARs, using as parent sample the cross-match of the SDSS DR16Q catalogue with the 4XMM-DR14 serendipitous catalogue. After cleaning the sample of potential observational biases, we obtain 7835 objects, one order of magnitude larger than most previous analyses in the literature. A single regression of $Γ$ against $\logλ_{Edd}$, with single-epoch virial black-hole masses, returns slopes that depend on the mass indicator (H$β$, MgII, CIV) and on the bolometric correction, and that are generally flat. We interpret this as regression dilution: the systematic uncertainty on virial masses is much larger than the intrinsic spread of $λ_{Edd}$ in SDSS QUASARs. We therefore introduce a different approach, which removes the black-hole mass from the problem. For QUASARs observed by XMM-Newton at multiple epochs, the mass of each object is fixed, and changes in its X-ray luminosity trace changes in its accretion state. We fit the $Γ$-$\log(L_{2keV})$ relation of each object (for a sample of N=893) and combine the per-object posteriors. This recovers the mean response of the population $a_X = 0.35\pm0.03$, which steepens to $\approx0.43$ when only epochs with precisely measured photon indices are used. Translated to the Eddington ratio, this corresponds to $a_λ\approx0.20$-0.25, depending on the choice of bolometric correction and on the LX-LUV slope. The $Γ$--$λ_{Edd}$ relation therefore exists, but it can be uncovered only by exploiting the variability of individual sources, which removes the black-hole mass from the problem. Moreover, its shallowness implies that the differences in Eddington ratio, as currently measured, cannot by themselves account for the variety of photon indices observed among unobscured QUASARs.
[abstract 14 / 51] (score: 3) - Title: Post-Newtonian orbital evolution and gravitational wave forms of inspiralling compact binaries with mass transfer and spin correctionsAuthors: Yifan He, Jie Yang,Comments: Withdrawn for further revision. The authors have identified some points in the manuscript that require more rigorous treatment and wish to refine the arguments before resubmissionSubjects: gr-qcCreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
In this article, we focus on the effects of mass transfer between binary stars and stellar spin on the post-Newtonian (PN) orbital evolution and gravitational waveforms of compact binary systems. We employ the 2.5PN approximation and the mass quadrupole formula to compute the orbital evolution and gravitational waveforms. After an exhaustive discussion of the astrophysical processes relevant to the scenarios of interest, we summarize a one-dimensional mass transfer model that uniformly treats common envelope evolution and tidal disruption, and derive an approximate expression for the dependence of the mass transfer rate of the material flow through the first Lagrange point L1 on the orbital angular velocity. Furthermore, based on the perturbed Keplerian approach, we present a two-dimensional model for the orbital evolution of compact binary systems that simultaneously accounts for mass transfer and stellar spin corrections. Through numerical simulations, we investigate binary systems with significant RELATIVISTIC effects, namely NS-NS (neutron star-neutron star), NS-BH (neutron star-BLACK HOLE), and BH-BH (BLACK HOLE-BLACK HOLE) systems, and demonstrate the influence of mass transfer and spin corrections on the orbital evolution and POLARIZATION waveforms of gravitational waves of these compact binaries systems.
[abstract 15 / 51] (score: 3) - Title: MRX: A differentiable 3D MHD equilibrium solver without nested flux surfacesAuthors: Tobias Blickhan, Julianne Stratton, Alan A. Kaptanoglu,Comments:Subjects: physics.comp-ph physics.plasm-phCreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
This article introduces the 3D MAGNETohydrodynamic (MHD) equilibrium solver MRX, based on relaxation of a MAGNETic field to a lower energy equilibrium state via admissible variations. We describe the mathematical theory behind this method and discuss what can be transferred to the fully discrete setting of a relaxation code. Our code is designed to address a number of traditional challenges to 3D MHD equilibrium solvers: enforcing physical constraints such as divergence-free MAGNETic field, fast convergence, handling strongly shaped polar geometries, and controlling topology changes of the MAGNETic field. Building on the JAX framework, we address questions of computational efficiency on modern computing architectures, user accessibility, and differentiability at each step. The solver is verified on manufactured vacuum solutions and against the vacuum field of a VMEC equilibrium of a quasi-axisymmetric stellarator. Automatic differentiation with respect to the boundary shape is demonstrated by optimizing stellarator shape for quasi-axisymmetry in vacuum. Relaxation is demonstrated on a finite-$β$ configuration, where we study $h$ refinement and the targeted formation of MAGNETic island chains at rational surfaces following an energy criterion. An inexact Newton method enables the computation of high-resolution finite-$β$ equilibria with islands and chaos in minutes on a single GPU.
[abstract 16 / 51] (score: 3) - Title: Long-term X-ray variability of the NLS1 Ark 564Authors: Neha P R, Nikita S Arun, Savithri H. Ezhikode, Ranjeev Misra, Bari Maqbool, Jeena K, Joe Jacob,Comments:Subjects: astro-ph.HECreated: 2026-09-25; Updated: 2026-09-30; Datestamp: 2026-09-30
We present a systematic spectral study of the X-ray emission from the Narrow- Line Seyfert 1 (NLS1) galaxy Ark 564 using SWIFT/XRT observations spanning sixteen years. The source exhibits significant variability in both the soft and hard X-ray bands, along with a strong positive correlation between them, indicating a closely coupled emission mechanism within the accretion flow-corona system. A simple absorbed power-law model is statistically insufficient to describe the spectra, confirming the presence of an additional soft component. To investigate the origin of the soft excess, we performed multi-model spectral fitting. Incor- porating a warm Comptonization component yields a statistically improved fit, supporting the scenario in which the soft excess arises from Comptonization in a warm, optically thick corona. We also applied a RELATIVISTIC reflection model to representative observations; however, given the moderate spectral resolution and limited high-energy coverage of SWIFT/XRT, the current data do not allow us to robustly determine whether reflection provides a superior or physically preferred description. Our results indicate that warm Comptonization offers a consistent explanation for the observed soft excess in Ark 564 within the limitations of the available data, while deeper broadband observations are required to defini- tively distinguish between competing models and comprehensively characterise the long-term X-ray spectral variability of the source
[abstract 17 / 51] (score: 3) - Title: Implicit-Explicit time integration scheme with Physics-based preconditioning for two-fluid tokamak boundary simulationsAuthors: Micol Bassanini, Simone Deparis, Paolo Ricci, Brenno De Lucca, Davide Mancini, Louis Stenger, Sergio García Herreros,Comments:Subjects: physics.plasm-ph cs.NA math.NACreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
In this work, a globally stiffly accurate Implicit-Explicit (IMEX) Runge-Kutta scheme is developed and implemented in the GBS code [Ricci et al., Plasma Phys. Control. Fusion, 2012], for two-fluid plasma turbulence simulations. The stiffest phenomena, governed by shear Alfvén waves and parallel diffusion, are treated implicitly, while the remaining non-stiff terms are advanced explicitly. This splitting enables time steps well beyond the Courant-Friedrichs-Lewy limit, without incurring the full computational cost of a globally implicit formulation. To efficiently solve the implicit subsystem at each time step, a three-dimensional physics-based preconditioner, inspired by techniques developed in the MAGNETohydrodynamic (MHD) context, is used. The resulting framework is verified through the method of manufactured solutions and exhibits both algorithmic and parallel scalability. Significant advantages in numerical stability and computational efficiency are demonstrated with respect to an adaptive explicit Runge-Kutta scheme.
[abstract 18 / 51] (score: 3) - Title: Discovery of a 62-min long-period transient with near-orthogonal rotator geometryAuthors: Scott D. Hyman, Natasha Hurley-Walker, Dale A. Frail, Emil Polisensky, W. D. Cotton,Comments: 23 pages, 11 figures. Accepted for publication in The Astrophysical JournalSubjects: astro-ph.HECreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
We report the serendipitous discovery of J155543.7$-$563102 (hereafter LPT J1555$-$5631) with a period of 62.2 min in MeerKAT and ASKAP survey data. The source emitted bright (10-30 mJy), steep-spectrum ($α\sim-1.5$), highly polarized radio pulses during a 15-hr active window in May 2022, with no other quiescent or pulsed emission detected before or after over $\sim5$ years. The mean light curve exhibits two alternating pulses per cycle. A main pulse (MP) and an interpulse (IP) separated by $Δϕ=165.4^\circ$ with similar amplitudes, but different POLARIZATION properties: the wider MP (3.9%) is partially linearly and circularly polarized and shows a constant POLARIZATION position angle, while the narrow IP (1.1%) is $\sim$100% circularly polarized. We classify LPT J1555$-$5631 as a near-orthogonal rotator, for which emission from both MAGNETic poles is visible during one rotation and the MAGNETic and rotation axes are almost perpendicular. The 14.6$^\circ$ deviation from an antipodal separation and the nearly constant POLARIZATION position angle suggest that the emission does not arise from the standard dipolar polar-cap geometry of ordinary pulsars, but instead originates within a broader, more complex MAGNETosphere. The observed properties of LPT J1555$-$5631 can be accommodated by extended emission regions, and favor coherent emission mechanisms such as the electron cyclotron maser instability, although they do not uniquely determine the progenitor or emission physics. If these inferences apply more broadly to the LPT population, they could account for why their beam widths are decoupled from rotation periods, the prevalence of flat POLARIZATION position angles, and may favor an elevated incidence of orthogonal rotators.
[abstract 19 / 51] (score: 3) - Title: Black Hole Quasinormal Mode Resonances and Reconnections in Coupled SystemsAuthors: Leah Jenks, Hayato Motohashi, Kazufumi Takahashi, Takuya Takahashi, Emanuele Berti,Comments: 10 pages, 6 figuresSubjects: gr-qc astro-ph.HE hep-thCreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
Black hole quasinormal modes (QNMs) provide a window into the underlying structure of BLACK HOLEs and the environments in which they arise. QNMs have particularly rich dynamics in coupled systems beyond general relativity, in which they are known to undergo avoided crossings, resonant excitation, and mode RECONNECTions. Recent work has shown that RECONNECTing QNM trajectories can trace out a distinctive double spiral structure in the complex frequency plane. In this work, we study this phenomenology in a concrete model of perturbed dynamical Chern-Simons (dCS) theory, as well as in a minimal toy model. In the former, we characterize the exceptional points, avoided crossings and RECONNECTions for several values of the perturbation parameters, and find that the limiting frequency of the double spiral endpoints is independent of the perturbation strength. We compute the excitation factors and find that they follow the scaling characteristic of a resonance between the scalar and gravitational modes. To determine whether these phenomena depend on the specific features of dCS, we construct a toy model of coupled degrees of freedom with square potential barriers, and find that we can reproduce the avoided crossings and RECONNECTions, indicating that these phenomena can occur more generally in coupled systems and are highly sensitive to the system parameters.
[abstract 20 / 51] (score: 3) - Title: Bayesian Evidence for Inspiraling Hotspot Motion in the Galactic CenterAuthors: Pablo Ruales, Maciek Wielgus, Delilah E. A. Gates, Alejandro Cardenas-Avendano,Comments: 15 pages, 5 figuresSubjects: astro-ph.HE astro-ph.GA gr-qcCreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
During flaring episodes, polarimetric observations of the Galactic Center BLACK HOLE Sagittarius A* (Sgr A*) reveal evolving, loop-like trajectories in the Stokes Q-U plane, the so-called Q-$U loops. Keplerian models of transiently energized orbiting features, hotspots, have been employed to reproduce these polarimetric signatures. In this work, we develop a Bayesian framework to infer the time-dependent kinematics of the hotspot from polarized light curves, using a general prescription for its motion. We model the emitting region's trajectory as a continuous, piecewise sequence of K kinematic segments, each described by radial and azimuthal velocity parameters. We perform analyses with K=1,2,3 and compare these models to millimeter-wavelength ALMA observations of Sgr A* from 2017 April 11 that include two subsequent Q-U loops, extending the observational constraints on the kinematics. We examine the effects of the local MAGNETic field geometry, spectral index, and kinematic profile of the hotspot's trajectory on the polarized signal. We find statistically significant evidence that the emitting region follows a non-geodesic inspiraling trajectory, and this preference over a strictly Keplerian orbit strengthens sharply when a longer data segment is modeled. The inspiraling non-Keplerian models are preferred to a purely Keplerian model based on both the Bayesian log-evidence comparison and the reduced chi-square statistic. Our results offer new insight into the nature of flaring events in the Galactic Center and the episodically produced hotspots associated with them.
[abstract 21 / 51] (score: 3) - Title: Stochastic gravitational-wave background from subsolar neutron stars in collapsar disksAuthors: Valerio De Luca, Loris Del Grosso, Emanuele Berti,Comments: 14 pages, 1 figureSubjects: gr-qc astro-ph.CO astro-ph.HECreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
The fragmentation of the neutrino-cooled accretion disks that surround the BLACK HOLEs formed in collapsars has recently been proposed as an astrophysical channel for the production of neutron stars with masses well below the standard core-collapse floor. These disk-born objects merge either with one another or with the central BLACK HOLE, and the superposition of all such mergers across cosmic history sources a stochastic gravitational-wave background. In this work we compute the energy density of this background for both merger channels, adopting a formation history tied to the observed rate of long GAMMA-RAY BURSTs. We find that the merger of a subsolar neutron star with the central BLACK HOLE is the loudest channel, already constrained by current data and within reach of next-generation observatories, while the binary neutron-star channel is at most two orders of magnitude fainter, with its widest binaries remaining accessible to next-generation detectors. Confronting these predictions with the fourth observing run of the LIGO--Virgo--KAGRA Collaboration, we derive two upper bounds on the fraction of collapsars whose disks produce such mergers: a robust one from the non-detection of an isotropic background, and a tighter one that could be achieved by a dedicated search for resolvable subsolar events in current data. Gravitational waves from non-axisymmetric deformations of the collapsar disk itself would provide an additional independent signature for the collapsar scenario, enabling cross-correlation studies with future deci-Hz detectors. Overall, the background computed here provides a population-level probe of disk-born subsolar neutron stars, which next-generation detectors could bring firmly into view.
[abstract 22 / 51] (score: 3) - Title: Temporal Correlation between Ionospheric Storm-Enhanced Density Plume and Plasmaspheric Plume OccurrenceAuthors: Xiangning Chu, Shunrong Zhang, Jacob Bortnik, Naomi Maruyama, Jerry Goldstein, Kausik Chatterjee, David Malaspina, Phil Erickson,Comments:Subjects: physics.space-ph physics.comp-ph physics.geo-phCreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
We present a statistical evidence of a temporal correlation between ionospheric storm-enhanced density (SED) and plasmaspheric plumes during MAGNETic storms. We identified SED plumes in 75 storms between 2010-2024 with sufficient total electron content (TEC) coverage. We also identified plasmaspheric plumes during these storms using a plasmapause asymmetry (PPA) index derived from the machine-learning-based DEN3D model. We found that all SED plumes coincided with plasmaspheric plumes. The start and end times of both phenomena exhibit near-zero lag within a half-hour delay, confirming their synchronized evolution. For the first time, superposed epoch analyses reveal that plume onsets align with solar wind driving and geoMAGNETic activity, including peaks in the electric field, coupling function, auroral electroJET indices, and the asymmetric ring current index, all of which facilitate plume formation. This work provides timely new insights into MAGNETosphere-ionosphere coupling processes and demonstrates the utility of machine-learning-based diagnostics for space physics/weather.
[abstract 23 / 51] (score: 3) - Title: Applications of Poincaré Boundary Condition for 3D Ideal MHD Equilibrium and OptimizationAuthors: Yigit Gunsur Elmacioglu, Dario Panici, Rory Conlin, Daniel Dudt, Egemen Kolemen,Comments:Subjects: physics.plasm-phCreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
Stellarator ideal MAGNETohydrodynamic (MHD) codes that assume nested flux surfaces such as \texttt{VMEC} and \texttt{DESC} solve the equilibrium problem by prescribing the total toroidal MAGNETic flux, plasma profiles and the last closed flux surface (LCFS), which analytically determines the unique field in vacuum, whereas at finite $β$ bifurcations and distinct equilibria sharing the same boundary have been reported in the literature. In this paper, we propose prescribing the Poincaré cross-section of the field at a single toroidal plane, and implement it in \texttt{DESC}, where the new condition enters only through the linear constraints and therefore costs no more than a fixed-LCFS solve. Fixing the geometry on one plane rather than on a full toroidal surface generally leaves more of the spectral coefficients free, and the ones it frees are those carrying the toroidal variation of the boundary flux surface, which a prescribed LCFS holds fixed at every toroidal angle; together these allow better-converged numerical solutions. We solve equilibria with the cross-section held fixed, starting either from the axisymmetric shape obtained by revolving that cross-section toroidally, or from an existing fixed-LCFS solution. In the latter case, the volume-averaged normalized force error falls by an order of magnitude while the configuration stays close to the original one, and re-solving the resulting boundary with the conventional fixed-LCFS solver recovers the same equilibrium. We further show that the Poincaré coefficients can be used directly as design variables by optimizing a quasi-helical configuration that maintains high-fidelity force balance throughout the process.
[abstract 24 / 51] (score: 3) - Title: What Fraction of Extreme Mass Ratio Inspirals That Merge After the LISA Mission Ends Are Detectable?Authors: Daniel J. Oliver, Aaron D. Johnson, Jonathan E. Thompson, Curt J. Cutler,Comments: 14 pages, 6 figures, 2 tablesSubjects: gr-qc astro-ph.HECreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
Stellar-mass compact objects spiraling into massive BLACK HOLEs in galactic nuclei (referred to as "extreme-mass-ratio inspirals", or EMRIs) will be an important class of sources for the Laser Interferometer Space Antenna (LISA). A stellar-mass compact object can radiate in the millihertz band for years to decades before it plunges into its massive BLACK HOLE, so a substantial fraction of the EMRIs that LISA can detect will still be inspiraling when the mission ends. We calculate what fraction of detectable EMRIs will plunge after the mission ends, and for those we calculate how they are distributed as a function of various parameters, such as their post-mission lifetime. To do this, we draw from astrophysically motivated populations, backward-integrate fully RELATIVISTIC Kerr FastEMRIWaveforms trajectories for a given time to plunge, and compute the full LISA response over both the four-year nominal and ten-year extended observing windows. We calculate the detectable fraction as an explicit function of time to plunge at signal-to-noise ratio (SNR) thresholds of $ρ=10$, 20, and 30. We find that post-mission EMRIs are roughly one in four of the LISA-detectable population at $ρ>20$ over the four-year mission, and roughly one in six over the ten-year extended mission. The in-window detectable fraction varies by nearly a factor of six at $ρ>20$ across the massive BLACK HOLE spins and secondary masses we ran, while the share stays between 25% and 33% for the four-year mission and between 13% and 20% for the ten-year one across all of them. The search for EMRIs that plunge more than $\sim 1$ year after the mission ends may require a different algorithm than the one used for EMRIs that plunge during the mission, and the fact that post-mission detections are a substantial fraction of all detections gives some urgency to developing a detection pipeline suitable for them.
[abstract 25 / 51] (score: 3) - Title: An Energy-Conserving Unstaggered ElectroMAGNETic-Potential Particle-in-Cell Method, Part II: Fully Relativistic Formulation with an Adapted Higuera--Cary PusherAuthors: Andrew Christlieb, Luis Chacon, Sining Gong,Comments:Subjects: math.NA astro-ph.HE cs.NACreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
We develop a fully RELATIVISTIC extension of the energy-conserving, unstaggered electroMAGNETic-potential particle-in-cell method introduced in our earlier nonRELATIVISTIC work. As in the nonRELATIVISTIC generalized-momentum formulation, the fields are advanced by a Crank--Nicolson discretization of the Lorenz-gauge potential equations, the current is deposited from particle orbits, and charge is advanced through the discrete continuity equation. The new ingredient is a generalized-momentum adaptation of the Higuera--Cary RELATIVISTIC particle pusher. The vector-potential force is decomposed into an orbit-discrete-gradient part, which enforces the same finite-difference chain rule used in our earlier nonRELATIVISTIC formulation, and a skew part, which generates a Higuera--Cary MAGNETic rotation in mechanical momentum. For prescribed fields and frozen orbit data, this generalized-momentum Higuera--Cary map is a unit-Jacobian conjugacy of the mechanical Higuera--Cary map and preserves particle phase volume in $(\xx,\PP)$. For the fully coupled implicit step, the same orbit data define the current deposit, mesh-to-particle gather, vector-potential chain rule, and RELATIVISTIC kinetic-energy secant velocity. The resulting particle work cancels the Crank--Nicolson field-energy balance, yielding exact RELATIVISTIC total-energy conservation up to nonlinear solver tolerance, orbit-quadrature error, and roundoff. A self-adjoint Fourier projection removes modes on even-grid Nyquist planes while preserving the particle--grid work identity. Numerical tests are organized around cold RELATIVISTIC two-stream and Weibel/filamentation instabilities, with diagnostics for energy drift, Gauss's law, the Lorenz gauge, particle--grid work, and the orbit chain rule.
[abstract 26 / 51] (score: 3) - Title: Multi-wavelength POLARIZATION degree dependence of Mrk 421 for different particle energy distributionsAuthors: Hritwik Bora, Ranjeev Misra, Rupjyoti Gogoi,Comments:Subjects: astro-ph.HECreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
We report on the constraints obtained from the multi-wavelength POLARIZATION degree and energy spectra measurements for the High Synchrotron Peaked Blazar (HBL) source Mrk 421 using different forms of the electron energy distribution. We find that the optical and X-ray data are consistent with the electron energy distribution being a broken power-law (BPL) or other distributions, with all electrons experiencing the same MAGNETic field configuration. This is in contrast to other HBL sources like the Mrk 501, where, for the BPL distribution, the X-ray producing higher energy electrons need to exist in a more ordered MAGNETic field environment than the optical producing lower energy ones. This is because the break energy of the spectrum produced by the BPL distribution for Mrk 421 lies below the IXPE energy band. We discuss the implications of the findings.
[abstract 27 / 51] (score: 3) - Title: Caught in the act: diffuse stellar and Ly$α$ emission around a halo-less QUASAR in the assembling cluster CARLA J0800+4029 at z=2Authors: Sofia G. Gallego, Simona Mei, Emanuele Daddi, Gaël Noirot, Dominika Wylezalek, R. Michael Rich,Comments: 8 figures, 1 table. Submitted to Astronomy & AstrophysicsSubjects: astro-ph.GACreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Extended Ly$α$ emission is commonly detected around luminous QUASARs at $z\sim2$-3 and traces cold gas in the circumgalactic environment of the AGN. Together with the spatial distribution of galaxies, Ly$α$ probes gas and galaxy assembly in high-redshift overdensities. We use deep KCWI wide-field spectroscopy and HST/F140W imaging to investigate the assembling cluster CARLA J0800+4029 at $z=1.986\pm0.014$. No robust extended Ly$α$ emission is detected at the radio-loud QUASAR position. Instead, the dominant Ly$α$ emission is offset from the AGN and coincides with a disturbed structure composed of galaxies, tidal features, and diffuse intra-halo light (IHL). The detected structure has $L_{\rm Lyα}=1.42\times10^{43}$ erg/s and reaches surface-brightness levels of $\sim10^{-17}$ erg/s/cm$^2$/arcsec$^2$. At the QUASAR position, a matched $3σ$ limit gives $L_{\rm Lyα}<4.20\times10^{42}$ erg/s, a factor of $\sim3.4$ below the detected offset emission and among the most stringent constraints at similar redshift. The Ly$α$ emission is dominated by one extended region near systemic velocity, with FWHM $\sim300$-500 km/s. The associated tidal structure has an IHL fraction of 18.8%, and contains a spatially coherent absorption-like decrement at $\sim+1000$ km/s. The offset and alignment between Ly$α$ emission and IHL suggest that gas and stars have been redistributed together during assembly. The lack of a comparable Ly$α$ halo around the QUASAR further suggests that gas in the immediate AGN environment is ionized, depleted, or suppressed, while the offset region remains favorable for Ly$α$ emission. CARLA J0800+4029 reveals baryon redistribution during cluster assembly, with the dominant observable Ly$α$ reservoir decoupled from the central AGN and linked to ongoing tidal assembly.
[abstract 28 / 51] (score: 3) - Title: GA-NIFS: sRMS, a new method for disentangling resolved and unresolved emission in integral field spectroscopy. Application to distant QUASARsAuthors: Michele Perna, Santiago Arribas, Carlota Prieto-Jiménez, Isabella Lamperti, Lorenzo Ulivi, Hannah Übler, Giovanni Cresci, Bruno Rodríguez Del Pino, Torsten Böker, Andrew J. Bunker, Stéphane Charlot, Roberto Maiolino, Chris J. Willott, Ivan Delvecchio, Elena Bertola, Madeline A. Marshall, Eleonora Parlanti, Pablo G. Pérez-González, Giacomo Venturi, Sandra Zamora, Filippo Mannucci, Quirino D'Amato, Alessandra De Rosa, Ismael García-Bernete, Miguel Pereira-Santaella, Fabio Rigamonti, Martina Scialpi, Paola Severgnini, Cristian Vignali, Maria Vittoria Zanchettin,Comments:Subjects: astro-ph.GACreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
The interpretation of AGN emission-line profiles in type1 AGN is often complicated by the dominance of bright, spatially unresolved nuclear continuum and broad-line region (BLR) emission over narrower and blended components from the narrow-line region (NLR) and the host galaxy. This remains challenging even with integral-field spectroscopy (IFS), as the relevant spatial variations can occur on scales smaller than the angular resolution, particularly in the compact host of distant AGN. We introduce the spatial root-mean-square (sRMS) technique, a new approach to analyse single-epoch IFS that uses the spatial variance of spectra extracted from partially overlapping apertures to isolate off-nuclear emission of high-z BL-AGN, and investigate whether the resulting kinematic information can improve the decomposition of their integrated spectra. We construct sRMS spectra from ensembles of overlapping apertures centred on the unresolved nucleus. Emission that is spatially invariant on the scales probed by the apertures is consequently suppressed, whereas spatially varying emission is retained. We apply the procedure to JWST/NIRSpec data of two z~6.5 QSOs. We model the resulting sRMS spectra with multiple Gaussian components to determine the kinematics of the spatially varying emission, and use these kinematic constraints to model the integrated spectra. The sRMS technique identifies spatially varying narrow-line emission on scales up to ~5x smaller than the NIRSpec PSF and provides robust constraints on the kinematics of individual kinematic components. Imposing these kinematic constraints on the integrated-spectrum fit reduces significantly the degeneracy of multi-component decompositions. Simulations further demonstrate the potential of the method to detect spatially offset BLR emission from close dual BL-AGN, down to projected separations of ~200 pc at z~6.5 for a BLR flux ratio of ~10.
[abstract 29 / 51] (score: 3) - Title: Effects of Alfvénicity on the Compressible Energy Cascade in Magnetohydrodynamic Solar Wind Turbulence: Evidence from Parker Solar Probe, Solar Orbiter, and WIND observationsAuthors: Nahuel Andrés, Carlos A. Gonzalez, Norberto Romanelli,Comments:Subjects: physics.plasm-ph astro-ph.SR physics.space-phCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
The compressible MHD energy cascade in the solar wind is shaped by Alfvénicity, plasma fluctuations, and proton temperature, yet how these factors regulate the relative weight of compressible and incompressible energy transfer across heliocentric distances remains poorly understood. We apply compressible and incompressible exact relations to a large sample of 2-hour intervals from WIND (1~au), Parker Solar Probe ($<0.25$~au), and Solar Orbiter (0.3--1~au), classifying intervals as Alfvénic ($|σ_c|>0.75$) or non-Alfvénic ($|σ_c|<0.25$) and by wind speed, and examine the Yaglom-like and purely compressible components of the compressible cascade. Velocity fluctuation amplitude is the strongest predictor of the compressible cascade rate $\langle|\varepsilon_c|\rangle$, followed by density and MAGNETic field fluctuations. $\langle|\varepsilon_c|\rangle$ and $\langle|\varepsilon_i|\rangle$ are tightly correlated in all regimes, with their ratio organized by Alfvénicity and wind speed: non-Alfvénic and Alfvénic fast winds cluster along $\langle|\varepsilon_c|\rangle=\langle|\varepsilon_i|\rangle$, while Alfvénic slow wind shows a systematic excess consistent with internal energy contributions. The largest $\langle|\varepsilon_c|\rangle$ systematically occur in hotter intervals, with a two-decade increase from cool to hot events in Alfvénic slow and non-Alfvénic wind, a trend carried mainly by the purely compressible term, while the dominant Yaglom-like term controls the overall cascade magnitude. Alfvénicity and wind speed thus govern the efficiency of turbulent energy transfer across heliocentric distances, and the tight coupling between compressible and incompressible rates points to the need for compressible, multi-fluid descriptions of the solar wind dissipation budget.
[abstract 30 / 51] (score: 3) - Title: An End-to-End Numerical Framework for Tidal Disruption Events with AthenaKAuthors: Hong-Xuan Jiang, Mengqi Yang, David A. Velasco-Romero, Fangyuan Yu, Jing-Ze Xia, Xinyu Li, Yosuke Mizuno,Comments: 28 pages, 18 figures, to be resubmited. Code available at https://github.com/HongxuanJiang/athenak-transientsSubjects: astro-ph.IM astro-ph.HECreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
In a tidal disruption event (TDE), a star is torn apart by the tidal field of a BLACK HOLE (BH), and its bound debris returns over many orbits to form an accretion disk. We present a framework built on the GPU-accelerated finite-volume code AthenaK that follows these stages in a single simulation with self-gravity throughout. We extend AthenaK with a moving simulation frame, restart remapping between domains, a multigrid Poisson solver on the adaptive mesh, a tabulated hydrogen-helium equation of state including recombination, a dual-energy update for the cold supersonic debris stream, a moving BH potential with excision, and localized adaptive time stepping (LAT), in which each MeshBlock advances on its own timestep, speeding up the production calculation by more than a factor of three. Each component is validated separately and in combination. The gravity solver maintains an isolated Lane-Emden sphere to a radial density error of 2.0e-3 over 16.3 dynamical times, and dual-energy recovery reduces the pressure error of a Mach 7.75e7 entropy wave from 15.7 to 4.0e-12. We demonstrate the framework with a Newtonian beta=1 disruption of a 1 Msun, 1 Rsun star by a 10^3 Msun BH. The debris has the expected energy spread, which is insensitive to the self-gravity update interval, splits evenly into bound and unbound material, and yields a fallback rate that approaches t^(-5/3) at late times. At the pericenter nozzle, the thermal energy gained in the high-resolution run matches the vertical kinetic energy lost to within 5%, whereas the fiducial run (4x lower resolution in x,y and 8x in z) suffers from excessive numerical dissipation that overheats the thinnest early stream. The heating in the two runs agrees to 12% once the returning stream has thickened. Multifrequency LTE post-processing turns the snapshots into synthetic images and luminosities.
[abstract 31 / 51] (score: 2) - Title: Complex dynamical regimes of the Tayler-Spruit dynamoAuthors: Paul Barrüre, Jérôme Guilet, Basile Gallet, Raphaël Raynaud,Comments: 17 pages, 12 figures, accepted for publication in Physical Review FluidsSubjects: astro-ph.HE astro-ph.SR physics.flu-dynCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Astrophysical dynamos feature various spatial structures and dynamical regimes, ranging from hemispherical MAGNETic fields to the random reversals of the geodynamo. The Tayler-Spruit dynamo, recently confirmed in direct numerical simulations, has been invoked to explain angular momentum transport in stellar radiative zones and MAGNETar formation in a proto-neutron star spun up by fallback accretion. Whether this dynamo mechanism can lead to different dynamical regimes remains an open question. Using three-dimensional direct numerical simulations, we model the dynamics of a stably stratified spherical Couette flow, with the outer sphere rotating faster than the inner one. While the generation of strong stationary and hemispherical dynamos has been observed in our previous studies, we report for the first time the existence of reversals and complex temporal dynamics. We observe that the dynamics is strongly correlated with the equatorial symmetry breaking of the flow. Focusing on a fiducial dynamo simulation, we propose an interpretation of its dynamics that consists in the coupling of two large-scale MAGNETic modes with opposite equatorial symmetries by the flow symmetry breaking. While this interpretation captures the simplest observed dynamics, the nonlinear interaction between a higher number of MAGNETic modes is certainly required to describe more complex regimes. The wide diversity of dynamical regimes generated by the Tayler-Spruit dynamo may have interesting implications for the geometry of the neutron star MAGNETic fields, and therefore neutron star emissions.
[abstract 32 / 51] (score: 2) - Title: Higher-order statistics of the stochastic gravitational wave background from supermassive BLACK HOLE binariesAuthors: Hinano Hisamatsu, Koutarou Kyutoku,Comments: 15 pages, 10 figuresSubjects: astro-ph.HE astro-ph.GA gr-qcCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Recent progress in gravitational wave observations has positioned pulsar timing arrays as a key tool for detecting the stochastic gravitational wave background in the nanohertz band. It is widely believed that this background is primarily attributed to the cosmic ensemble of inspiraling supermassive BLACK HOLE binaries. While traditional analyses have predominantly focused on the spectral amplitude and frequency dependence of the gravitational wave background, higher-order statistics such as variance, skewness, and excess kurtosis could potentially be useful for extracting further physical information. However, these statistical moments are known to diverge when the redshift integration is extended down to z=0. In this study, we propose a strategy to resolve this issue by introducing a physically motivated lower integration limit, z_min, defined by the sensitivity for detecting individual sources. Since higher-order statistics are primarily determined by local sources, we may adopt the lowest-order approximation with respect to redshift in their computations. Under this approximation, we demonstrate that all higher-order statistics beyond the expectation value depend on the mass function only through a weighted average of the chirp mass, <\mathcal{M}^{10/3}>, irrespective of the redshift evolution model. We show that the ratio of the variance to the expectation value provides information on <\mathcal{M}^{10/3}>/<\mathcal{M}^{5/3}> independently of the total number of mergers. We also find a consistency relation between the excess kurtosis and the squared skewness, paving the way for testing the binary-origin hypothesis of the gravitational wave background. Our findings demonstrate that higher-order statistics provide a new window for interpreting the gravitational wave background, offering a methodology to break existing degeneracies and refine our understanding of the mass function.
[abstract 33 / 51] (score: 2) - Title: The Chirp-Mass Ladder: A New Rung EmergesAuthors: Vaibhav Tiwari,Comments:Subjects: astro-ph.HECreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
We study the binary BLACK HOLE (BBH) population observed through gravitational waves (GWs) using 256 events from the latest release of GWTC-5.0. The inferred chirp-mass distribution shows prominent peaks at approximately $7.5M_{\odot}$, $14M_{\odot}$, and $27M_{\odot}$, with subsequent peaks spaced by approximately a factor of two. A parsimonious explanation for this structured distribution is a hierarchical merger scenario, in which the first peak arises from mergers of BLACK HOLEs of stellar origin, and higher-mass peaks arise from repeated mergers. Notably, with the addition of new observations, an intermediate peak near $19M_{\odot}$ emerges. This feature was anticipated in earlier work as a consequence of intergenerational mergers involving second- and third-generation (G) BLACK HOLEs, highlighting the predictive expectations of the hierarchical-merger interpretation. Furthermore, two groups of $1G+2G$ mergers recently reported in separate studies can be understood as distinct rungs---$1G+2G$ and $3G+4G$---within this hierarchical chirp-mass ladder, a unification that describes both spin transitions with a single mechanism. Although we observe expected correlations between mass ratios and spins in multiple events across the mass range, the lack of clear signatures across all rungs invites investigation into the role of hierarchical mergers in shaping the BBH population.
[abstract 34 / 51] (score: 2) - Title: Horizon-Evanescent Scalar Clouds from Coupled Rotation and Magnetic Fields around Black HolesAuthors: Hengyu Xu, Haowei Chen, Shao-Jun Zhang,Comments: 32 pages, 7 figures. v4: matches the published version in JHEP; clarified the weak-field separability, generalized the positive-gap criterion with a Melvin-Kerr example, and expanded the astrophysical discussionSubjects: gr-qcCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
We show that black-hole rotation and an external MAGNETic field can jointly generate a distinct class of scalar clouds. Using the Kerr-Bertotti-Robinson geometry as a separable laboratory for MAGNETized rotating BLACK HOLEs, we study a charged massive scalar field and map the radial Klein-Gordon equation into a one-dimensional Schrödinger-like form. The MAGNETic coupling shifts the near-horizon dispersion relation and realizes a positive horizon gap: a sufficient near-horizon criterion under which the horizon wavenumber becomes purely imaginary in a finite frequency band below the usual kinematic synchronization frequency. In this band the physical horizon boundary condition is no longer a propagating ingoing wave, but a regular exponentially decaying state. This rotation-MAGNETic-field mechanism quenches the superradiant flux and supports horizon-decaying scalar clouds (Type-II), distinct from the usual synchronized propagating clouds (Type-I). Matched asymptotic expansions and numerical shooting solutions are used to exhibit both branches and their spatial profiles. Thus the Kerr-Bertotti-Robinson solution is not an isolated curiosity, but an explicit realization of a broader positive-gap criterion for horizon-evanescent stationary configurations that are absent in isolated Kerr systems.
[abstract 35 / 51] (score: 2) - Title: Photon sphere JET equivalence and the non-uniqueness of black-hole thermodynamicsAuthors: Nikko John Leo S. Lobos, Emmanuel T. Rodulfo,Comments: 2 figures, 21 pagesSubjects: gr-qcCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
We examine whether scalar eikonal quasinormal-mode data determine black-hole thermodynamics. For static, spherically symmetric, asymptotically flat, nonextremal geometries, we prove that the formal fixed-overtone expansion of a neutral, minimally coupled, massless scalar through order $L^{-N}$ depends only on the $(2N+2)$ JET of the lapse at the unstable photon sphere. For every finite $N$, real-analytic deformations can preserve this JET and the asymptotic Reissner--Nordström coefficients while changing the surface gravity and Hawking temperature. We also construct a nonanalytic $C^\infty$ deformation that is flat at the photon sphere. This deformation preserves the complete formal eikonal series to every algebraic order but changes the horizon position, temperature, and Einstein area entropy. A nonempty charged subfamily satisfies the weak energy condition as an effective Einstein source. Together, these four results establish the new finite-JET and all-orders thermodynamic obstruction. To separate geometric information from action-dependent information, we incorporate a previously established Reissner--Nordström--MOG comparison. The mapped backgrounds have identical normalized metrics, neutral-scalar boundary-value problems, exact scalar spectra, and Hawking temperatures, yet their Wald entropies differ because their curvature couplings differ. The resulting hierarchy shows that local photon-sphere data do not determine horizon thermodynamics and that even exact action-blind scalar data do not determine gravitational entropy. Agreement of the formal eikonal expansions for the deformed metrics does not imply exact finite-$\ell$ isospectrality. Global differences may appear beyond every algebraic order. Thermodynamic reconstruction from eikonal ringdown is therefore conditional on assumptions about the global metric and the gravitational action.
[abstract 36 / 51] (score: 2) - Title: New Formalism for Modelling Flowing Plasmas in a Magnetic FieldAuthors: Subhasish Bag, Ashish Ganguli, Vikrant Saxena, Ramesh Narayanan, Debaprasad Sahu,Comments: 23 pages, 31 figuresSubjects: physics.plasm-phCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
A new formalism for modelling a flowing plasma in a MAGNETic field, having potential for application in plasma thrusters, materials processing, space plasmas, etc., is developed. In this framework, the plasma expands downstream from the source region into an expansion chamber along an axisymmetric MAGNETic field. For plasma flowing along a MAGNETic field, the ion velocity parallel to the MAGNETic field lines is much greater than the perpendicular velocity. This characteristic permits a unique ordering of the relevant flow variables when the flow equations are transformed into a MAGNETic coordinate system (MCS), in which the coordinate axes are parallel and perpendicular to the field lines. The ordering of the flow variables in the MCS further simplifies the flow equations by allowing them to be split into sets of reduced equations. As a specific implementation, the proposed formalism was validated by using data (for boundary conditions) from a small volume plasma system experiment (Ganguli et al 2016 Plasma Sources Sci. Technol. 25 025026). The model shows favourable agreement with the experiments and is used to predict various physical quantities relevant for applications. The corresponding physical implications are discussed in detail.
[abstract 37 / 51] (score: 2) - Title: CHAMPS: Data Reduction and Detection of ~3300 Dusty Galaxies at 1.2 mmAuthors: Felix Martinez, Jeyhan S. Karaltepe, Andreas L. Faisst, Arianna S. Long, Jorge A. Zavala, Caitlin M. Casey, Jed McKinney, Ezequiel Treister, Maximilien Franco, Sune Toft, Manuel Aravena, John D. Silverman, Hollis B. Akins, Hiddo S. B. Algera, Jacqueline Antwi-Danso, Andrew J. Battisti, Yingjie Cheng, Olivia R. Cooper, Nicole E. Drakos, Carter Flayhart, Fabrizio Gentile, Steven Gillman, Ghassem Gozaliasl, Santosh Harish, Simon Hempel-Costello, Michaela Hirschmann, Olivier Ilbert, Bingcheng Jin, Shuowen Jin, Koki Kakiichi, Thresa Kelly, Zihao Li, Daizhong Liu, Lun-Jun Liu, Sinclaire M. Manning, Henry Joy McCracken, Romain A. Meyer, Louise Paquereau, Maria Pudoka, Jason Rhodes, Brant E. Robertson, Giulia Rodighiero, Rasha M. Samir, David B. Sanders, Marko Shuntov, Margherita Talia, Mattia Vaccari, Francesco Valentino, Aswin P. Vijayan, Feige Wang, Wuji Wang, Can Xu, Jinyi Yang, Yongda Zhu, Siwei Zou,Comments:Subjects: astro-ph.GACreated: 2026-09-28; Updated: 2026-09-30; Datestamp: 2026-09-30
We present the reduction and source catalogs for the \textit{COSMOS High-$z$ ALMA-MIRI Population Survey} (CHAMPS), the largest Atacama Large (Sub)Millimeter Array (ALMA) blank field survey to date at 0.2\,deg$^2$. With observing frequency centered at $250\, $GHz ($1.2\,$mm) and bandwidth of 7.5 GHz, CHAMPS covers the JWST/NIRCam+MIRI footprint in the COSMOS field, taking advantage of the rich, multiwavelength ancillary datasets in COSMOS ranging from X-ray to radio. The majority of the CHAMPS survey (90$\%$) has depths at or below 200 $μ$Jy beam$^{-1}$ and with an average RMS of 146 $μ$Jy beam$^{-1}$. The reduced CHAMPS mosaic has a beam size of $θ_{\rm res} = 1.1'' \times 1.1''$. CHAMPS identifies sources via two detection methods, a blind search for high-SNR sources, and a prior-based search involving MIRI detections to identify faint sources. The blind search yields a total of 595 sources down to an SNR $\ge4.5σ$ while the prior catalog yields a total of 3162 source down to an SNR $\ge3σ$, leading to a full sample of 3355 unique objects detected across both catalogs. We identify a unique population of 385 SNR $\ge5σ$ sources across the two catalogs; after excluding 9 likely spurious edge detections we define a robust science sample of 376 sources above $\ge5σ$. These sources have a median redshift of $\langle z_{1.2 \text{ mm}}\rangle = 2.54^{+0.89}_{-1.69}$ based on optical/near-IR/mid-IR photometric redshifts and high-quality spectroscopic redshifts, and hold a median stellar mass of $\langle\log (\rm M_\star/M_\odot)\rangle = 10.79^{+0.42}_{-3.08}$. We have further identified 68/376 ($\sim18\%$) sources as candidate AGN through X-ray, UV-optical, infrared and radio selection techniques.
[abstract 38 / 51] (score: 2) - Title: Diffusion prior for KSTAR equilibrium reconstruction under sensor dropoutAuthors: Hyungkeun Nam, Jaemin Seo,Comments:Subjects: physics.plasm-phCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
We study equilibrium reconstruction for the Korea Superconducting Tokamak Advanced Research (KSTAR) device under MAGNETic sensor dropout, with a diffusion model as the prior. Magnetic measurements leave most components of the toroidal current density $J_ϕ$ undetermined, and sensor loss leaves more of them to the prior. The diffusion model learns only $J_ϕ$, conditioned on the coil currents, the plasma current and the product of major radius and toroidal field, which do not depend on the dropout. The physics enters through a linear forward operator built from sensor response matrices of the LIUQE code. Because the observations are linear, a variant of decoupled annealing posterior sampling fits them with a closed-form linear correction. On measured signals of 37 KSTAR shots, we switch off a random fraction (0.0 to 0.9, ten settings) of the 124 MAGNETic channels in use and compare with LIUQE under the same masks, taking the full-sensor LIUQE reconstruction as the label. Both methods fit the remaining channels to a similar level. The median relative distance of $J_ϕ$ from the label stays at 3.22--4.07\% for the diffusion reconstruction in all settings, whereas that of LIUQE reaches 11.89\% at dropout 0.9. At dropout 0.5--0.9, the diffusion reconstruction is closer to the label on 27--37 of the 37 shots. At low dropout, LIUQE is closer on most shots. For the derived flux, the diffusion reconstruction is closer on 21--36 shots at dropout 0.5--0.9, and its error at high dropout comes from the vessel current estimate, not from the prior.
[abstract 39 / 51] (score: 2) - Title: Correspondence between multileaf topology of closed geodesics and spatiotemporal autocorrelations of hotspot images in Schwarzschild spacetimeAuthors: Fengting Xie, Qing-Hua Zhu, Xin Li,Comments: 20 pages, 10 figuresSubjects: gr-qcCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
The classification of RELATIVISTIC closed orbits by their multileaf structures provides a framework for studying strong-field dynamics. Identifying these structures in astronomical images remains challenging. Using ray tracing, we construct the spatiotemporal autocorrelations of the primary image of a pointlike hotspot moving along bound closed geodesics around a Schwarzschild BLACK HOLE. These orbits are classified by three integers $(z,w,v)$, where $z$ counts the leaves, $w$ counts the additional whirls during each radial period, and $v$ specifies the order in which the orbital leaves are traced. For the orbit families examined, our numerical results establish a correspondence between the topological integers $(z,w,v)$ and the numbers of correlation bands $N_{\rm band}$ and recurrence points $N_{\rm rec}$. The integers are recovered as $z=N_{\rm rec}-1$, $w=\left\lfloor (N_{\rm band}+1)/(N_{\rm rec}-1)\right\rfloor-1$, and $v=(N_{\rm band}+1)\bmod(N_{\rm rec}-1)$. Here, $\lfloor x\rfloor$ denotes the greatest integer not exceeding $x$, and $\bmod$ denotes the remainder operation. These relations provide a quantitative method for recovering closed-orbit topology from hotspot image autocorrelations.
[abstract 40 / 51] (score: 2) - Title: Weak Lensing Measurements from the Lyman-$α$ ForestAuthors: Anže Slosar,Comments: 13 pages, 13 figures, to be submitted to PRDSubjects: astro-ph.COCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
We attempt to measure the weak lensing of the Lyman-$α$ forest by projecting a quadratic estimator of the forest-forest and QUASAR-forest pair correlations, built from the DESI DR1 data, onto deflection templates constructed from low-redshift galaxies and QUASARs from DESI and BOSS. After validating deflection templates against the ACT DR6 and Planck PR4 CMB lensing maps and testing the estimator with injected displacements we measure the lensing amplitude $A_L$ on the data. Consistent with predictions in the literature, the current generation of public data does not have sufficient signal-to-noise to measure this effect unequivocally: we find the lensing amplitude $A_L=0.42\pm0.43$ from the forest auto-correlation and $0.87\pm0.48$ from the QUASAR--forest cross-correlation. These two nearly independent measurements combine to $A_L=0.62\pm0.33$, consistent with both the fiducial value $A_L=1$ and with no lensing.
[abstract 41 / 51] (score: 2) - Title: Beyond circular and equatorial orbits: Bayesian constraint on vector charge with the adiabatic inspirals of generic Kerr geodesicsAuthors: Tieguang Zi, Genliang Li,Comments: 25 pages, 7 figuresSubjects: gr-qcCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Extreme-mass-ratio inspirals (EMRIs) offer a powerful probe of additional fundamental fields through their cumulative influence on gravitational-wave phases. However, modeling vector radiation from generic Kerr orbits requires the evolution of the Carter constant, which cannot be determined from energy and angular-momentum balance alone. Here we derive the orbit-averaged electroMAGNETic Carter-constant flux for eccentric and inclined, nonresonant Kerr geodesics, including sections at infinity and event horizon. Combining the gravitational and electroMAGNETic energy and angular-momentum fluxes, we construct generic adiabatic inspirals using a four-dimensional Chebyshev interpolation mathod. We incorporate the RELATIVISTIC trajectories into the state of the art of FastEMRIWaveform package and perform Bayesian inference of vector charge carried by secondaries. Our analysis reveals substantial correlations between the charge and intrinsic source parameters, with vector charge constraints exhibiting a nonmonotonic dependence on orbital inclination. These results establish a framework for investigating additional vector-radiation channels in generic EMRIs and their implications for tests of gravity with future space-based gravitational wave observations.
[abstract 42 / 51] (score: 2) - Title: Search for compressed electroweak SUSY production in final states with two $τ$-leptons in $\sqrt{s} = 13$ and $13.6$ TeV $pp$ collisions with the ATLAS detectorAuthors: ATLAS Collaboration,Comments: 77 pages, author list starting at page 60, 12 figures, 26 tables, submitted to JHEP. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HMBS-2024-07/Subjects: hep-exCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Searches for the production of $τ$-sleptons ($\tildeτ$), charginos ($\tildeχ^{\pm}_1$), and neutralinos ($\tildeχ^0_2$) in events with at least one hadronically decaying $τ$-lepton are presented, targeting compressed mass spectra scenarios. For charginos and neutralinos, the cascade decays producing either a $τ$-slepton or a $τ$-sneutrino are considered. Two final selections are studied, requiring either one hadronically decaying $τ$-lepton and one other charged lepton, or two or more hadronically decaying $τ$-leptons. To enhance sensitivity to the compressed mass spectra, production modes with initial-state radiation (ISR) JETs are considered. The searches use 140 $\mathrm{fb}^{-1}$ and 53 $\mathrm{fb}^{-1}$ of proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider during 2015-2018 at a centre-of-mass energy of $\sqrt{s} = 13$ TeV and 2022-2023 at a centre-of-mass energy of $\sqrt{s} = 13.6$ TeV, respectively. The searches provide sensitivity to the compressed mass spectra scenarios with light $τ$-sleptons. The results are generally consistent with the Standard Model, although several deviations with local significances of $2.1-2.4 σ$ are observed. These deviations weaken the observed exclusion limits. For direct $τ$-slepton production, in the ISR channel alone the limits are set for $Δm(\tildeτ, \tildeχ^0_1) = 30$ GeV for $τ$-slepton masses up to $115$ GeV at 95% confidence level. Given the observed data, no exclusion limits are set for direct $τ$-sleptons production when statistically combining all considered channels. For electroweakino production, limits are set for $Δm(\tildeχ^0_2, \tildeχ^0_1) = 30$ GeV for $\tildeχ^0_2$ masses up to $200$ GeV. For pure chargino pair-production, limits are set for chargino masses up to $175$ GeV for the same mass splitting.
[abstract 43 / 51] (score: 2) - Title: Global Phase Locking in Superradiant Chorus EmissionsAuthors: Xin Tao, Fulvio Zonca, Liu Chen,Comments:Subjects: physics.plasm-phCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Coherent wave amplification in inhomogeneous systems is usually described in terms of resonance and nonlinear phase locking, but these local phase conditions do not determine how the wave amplitude evolves when the resonance condition changes during wave propagation. Here we identify a global phase-locking principle, in which the stable resonant phase remains nearly unchanged as the resonance detuning evolves. This condition requires the wave amplitude to track the evolving detuning and leads to linear amplitude growth with distance, producing the quadratic intensity scaling characteristic of superradiant emission. We demonstrate this mechanism using self-consistent kinetic simulations of whistler-mode chorus waves, one of the most important coherent electroMAGNETic emissions in Earth's MAGNETosphere. The simulated chorus amplitude and effective growth rate follow the predicted superradiant scalings, rather than exponential growth. Direct phase-space analysis further shows that the resonant electron trapping island remains centred at an approximately fixed phase during amplification. These results identify global phase locking as the dynamical origin of superradiant chorus growth and reveal a general phase-organization principle for coherent radiation in evolving resonant systems.
[abstract 44 / 51] (score: 2) - Title: The NewMag crystal-field code for f-element systems: Implementation for extended active spaces, second-order correlated energies, and generalisation to fn configurationsAuthors: Gwenhaël Duplaix-Rata, Dumitru-Claudiu Sergentu, Boris Le Guennic, Rémi Maurice,Comments:Subjects: physics.chem-phCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
We report a massive update of the NewMag program, which enables to extract Stevens crystal-field parameters (CFPs) after RELATIVISTIC and multiconfigurational calculations are performed. The code can now post-treat ORCA and OpenMolcas outputs that contain state-average complete active space self-consistend field (SA-CASSCF) calculations with minimal or extended active spaces, second-order NEVPT2 or CASPT2 calculations, and spin-orbit configuration interaction (SOCI) calculations. Stevens parameters are extracted following the original Stevens convention with the so-called "extended" parameters. Rotation invariant indicators are also computed, after applying a correction of the parameter values to ensure normalization, following Rudowicz. At the SOCI level, the spin-orbit coupling (SOC) constant is also extracted within a spherical approximation of the SOC operator. For all the reference calculation levels, the model spectrum is reconstructed, allowing a direct assessment of its quality. The reported implementation is successfully applicable to f-element systems with a non-void, non-half-filled/empty or non-full f shell, that is for f^n configurations with n != 0, != 7 and != 14. Similarities and differences with the SINGLE_ANISO and AILFT codes are discussed. With selected examples, we showcase the interest of determining CFPs in f-element systems to understand their MAGNETic and optical properties in general, and more specifically the added value of NewMag. Finally, application of this approach to d-element systems is discussed, to reveal when it readily and successfully applies and when it may fail in reproducing satisfactorily the ab initio energies.
[abstract 45 / 51] (score: 2) - Title: PHASE: Multi-Regime Modeling of Incompressible MagnetohydrodynamicsAuthors: Radhika Achikanath Chirakkara, Rajdeep Haldar, Zezheng Song, Jiequn Han,Comments: 22 pages, 13 figuresSubjects: cs.LG physics.comp-ph physics.plasm-phCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Magnetohydrodynamics (MHD) is central to plasma modeling in astrophysics, space science, fusion, and engineering, but resolving multiscale MHD dynamics is computationally expensive. Machine-learning surrogates enable fast inference by learning reusable solution operators, yet existing models require separate training for each physical regime, limiting generalization across varying parameter settings. We introduce PHASE, a PHysics-Adaptive Scalable operator with residual Error correction, designed to model incompressible MHD across varying physical parameters with a single model. PHASE combines transfer learning, regime-aware adaptation, physics-centered learning, and residual refinement to improve both physical fidelity and generalization across MHD regimes. Together, these improvements achieve state-of-the-art prediction accuracy on two-dimensional MHD turbulence by reducing relative $L_2$ errors on physical fields by more than an order of magnitude compared to prior MHD neural-operator baselines. Moreover, PHASE generalizes successfully to unseen parameter values without retraining, demonstrating the cross-regime adaptability expected from operator learning. We evaluate PHASE beyond point-wise prediction errors using derived physical fields, spectral analysis, and distribution statistics, consistently observing improved physical fidelity. We further show that our framework can accurately simulate MHD instabilities by testing it on the Kelvin--Helmholtz instability, demonstrating the robustness of our method.
[abstract 46 / 51] (score: 2) - Title: Common Envelope Evolution: Too stochastic to be deterministicAuthors: Noam Soker,Comments: It will be submitted in two days to allow for comments (including missing references)Subjects: astro-ph.SRCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
I argue for significant stochastic behavior in the common envelope evolution (CEE) of cool giants and main-sequence companions to the degree that it is almost impossible to know the exact CEE outcome of an individual binary system from the average properties of the stars and their initial orbit. I start with two observational properties of post-CEE planetary nebulae: many have JET-shaped morphologies, and they show a wide variety of morphologies. The first suggests that the standard CEE model should include JETs, and the second shows that the CEE has a wide variety of evolutionary routes; for example, JETs can be launched before, during, and/or after the main CEE phase. I show that the properties of the disk with which the main-sequence companion enters the CEE depend sensitively and stochastically on the pulsations and convection of the giant star. Pulsations and giant-envelope convection stochastically determine the evolution of the accretion disk inside the envelope. The stochastic nature of the accretion disk properties implies that JET power is also stochastic. Adopting the view that JETs play a major role in CEE outcomes, I conclude that the CEE outcome is stochastic. I conclude that the CEE efficiency parameter alpha(CE) has little merit for individual systems, although it still has meaning in population synthesis and other studies of large populations.
[abstract 47 / 51] (score: 2) - Title: Assessment of subgrid scale mixing models used in LES at high pressuresAuthors: Neelakantan Padmanabhan, Richard S. Miller,Comments:Subjects: physics.flu-dyn cs.NA math.NACreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Molecular mixing models for the conditional scalar diffusion (CSD) term in the filtered mass density function (FMDF) transport equation used in Large Eddy Simulation (LES-FMDF) approach are evaluated against direct numerical simulation (DNS) of spatially evolving JETs. A database of DNS of turbulent mixing slot JETs of $C_{7}H_{16} / O_2$ and $C_{7}H_{16} / Air$ is developed. The formulation includes the compressible form of the governing equations, a generalized multicomponent diffusion model, a cubic real gas equation of state and realistic property models. Simulations are conducted over a wide range of initial pressures ($1 atm < P_0 < 100 atm$) and JET width based Reynolds numbers of 850 and 1300. FMDF of mixture fraction at various filter widths are obtained from the simulation at several spatial locations within the flow. The CSD term in the exact transport equation of FMDF is calculated from the DNS. An \textit{a priori} analysis of Interaction by Exchange of Mean (IEM), Modified Curl (MC) and Mapping Closure (MAPPING) mixing models for CSD is conducted. At high pressures, significant deviations are observed between the CSD measured from the DNS and those predicted by the models. The source of the deviations is determined to be the mixing frequency used in the models. The significance of the mixing frequency and its variation with change in pressure and diffusion models is studied. The primary objective of this work is to assess the applicability of aforementioned mixing models to flows at large pressures and determine the causes for deviation in prediction.
[abstract 48 / 51] (score: 2) - Title: Detection of fine-structured radio bursts during a superflare on EQ PegAuthors: Zhanhao Zhao, Xin Cheng, Yuankun Kou, Guoyin Chen, Hao Ning, Yao Chen, Baolin Tan, Keping Qiu, Mingde Ding,Comments:Subjects: astro-ph.SR astro-ph.EP astro-ph.HECreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
Superflares are frequently observed on MAGNETically active stars, particularly on active M-dwarfs, thereby influencing the habitability of nearby exoplanets. However, the causes of superflares remain unclear. Here, combining FAST and TESS, we detected a finely structured decimetric radio burst appearing as groups of spikes during a white-light superflare (total bolometric energy $\sim 10^{33} \ \mathrm{erg}$) on the M-dwarf binary EQ Peg on September 8th, 2022. The most significant ones appeared near the peak time of the optical flare and lasted for about $100 \ \mathrm{s}$. The radio spikes present extremely high brightness temperatures ($\gtrsim 10^{13} \ \mathrm{K}$) and high degrees of circular POLARIZATION ($\sim 0.84 \pm 0.16$), indicating the origin of a coherent emission process, most likely the electron cyclotron maser. Based on Zeeman-Doppler Imaging measurements of EQ Peg, we further locate the sources of the radio spikes, including their heights and latitudes, under the assumption of a large-scale dipolar MAGNETic field configuration. The results provide strong evidence for finely structured decimetric radio bursts generated by stellar flares and shed light on the origin of superflares.
[abstract 49 / 51] (score: 2) - Title: Joint Mass-Radius and Magnetic-Geometry Inference of PSR J0740+6620Authors: Chun Huang, Tuomo Salmi, Alexander Y. Chen,Comments: 30 pages, 18 figures. Comments are welcomeSubjects: astro-ph.HE astro-ph.SR gr-qc nucl-thCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
X-ray pulse-profile modeling can measure neutron-star radii, but its physical interpretation remains limited by the largely phenomenological description of the surface hotspots. Here we connect the X-ray hotspots directly to the pulsar MAGNETospheric structure and jointly infer the mass, radius, and MAGNETic geometry of the massive millisecond pulsar PSR J0740+6620 from \emph{NICER} and \emph{XMM-Newton} observations. Using a GPU-accelerated implementation, we compare two low-dimensional MAGNETic configurations that can produce non-antipodal emission: a centered axisymmetric dipole--quadrupole and a shifted dipole. The shifted-dipole model is decisively favored under the adopted priors, with $Δ\ln Z=5.65$ (Bayes factor $\sim285$), and yields $M=2.059^{+0.068}_{-0.069}\,M_{\odot}$ and $R=13.28^{+1.47}_{-1.07}\,\mathrm{km}$, broadly consistent with previous phenomenological analyses, while requiring nearly symmetric heating of the two polar caps. Both the marginalized shifted-dipole posterior and the timing-compatible representative require an effective X-ray-emitting footprint much smaller than the nominal force-free polar cap calibrated for a centered dipole. This compact footprint is not reproduced by our exploratory photon-conversion estimates and instead points to missing physics in the mapping from MAGNETospheric currents to observable X-ray emission. Our results show that physically motivated hotspots can preserve the mass--radius inference while turning hotspot morphology into a probe of pulsar MAGNETospheric structure and emission physics.
[abstract 50 / 51] (score: 2) - Title: A shape-similarity latent space for fluid interfaces: invertible reduced-order modelling of droplet morphologyAuthors: Ali R. Hashemi, Mohammad R. Hashemi, Pavel B. Ryzhakov,Comments: 40 pages, 19 figuresSubjects: physics.flu-dyn physics.comp-ph physics.data-an stat.MLCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
A droplet breaks up in tens of microseconds, and a recording captures perhaps a dozen frames. The states in between cannot be recovered without repeating the experiment, and simulating them is too costly to sweep an operating envelope. Yet they are present in the corpus as a whole: a campaign spanning a device's actuation range produces morphologies resembling those any single recording missed. Exploiting that requires a representation that is low-dimensional, invertible, and faithful to shape rather than to sampling. Proper orthogonal decomposition supplies the first two but measures distance in sampled coordinates; manifold learning supplies the third but no map back to a shape; elastic shape analysis supplies a shape metric but no reduced coordinates. SHROM composes all three. Interfaces are represented by their square-root velocity functions, a neighbour graph is built over that shape space, and an autoencoder is trained to reconstruct while penalising latents in which graph neighbours are not latent neighbours. The demonstration uses 301,539 inkJET droplet contours and four filmed break-up sequences. The graph term does not improve reconstruction. It determines whether position in the latent carries meaning: clustering the latent of an otherwise identical model recovers the shape-space partition at chance level (ARI = 0.063 +/- 0.059), and at 0.781 +/- 0.049 with the term active. Waveform parameters predict the full contour at R^2 = 0.878 +/- 0.026. Negative results are reported in the same terms. The graph metric proved immaterial across five choices, and interpolation error saturates at the reconstruction limit, so a plain autoencoder leads that task. The main limitation is interpolation across a topology change: no component of the regularised latent holds both a single-component and a post-break-up shape, whereas an unregularised autoencoder mixes them freely.
[abstract 51 / 51] (score: 2) - Title: Orbital stability, RELATIVISTIC precession, and QPO constraints for constant-curvature BLACK HOLEs in $f(R)$ gravityAuthors: Kourosh Nozari, Sara Saghafi, Khadijeh Salahshour, Moisés Bravo-Gaete,Comments: 33 pages, 11 figures, 6 tablesSubjects: gr-qcCreated: 2026-09-29; Updated: 2026-09-30; Datestamp: 2026-09-30
We analyze circular-orbit stability, epicyclic resonances, RELATIVISTIC precession, and quasi-periodic-oscillation (QPO) constraints in the constant-curvature vacuum sector of metric $f(R)$ gravity. The Schwarzschild--(anti-)de~Sitter and Kerr--(anti-)de~Sitter backgrounds are characterized by curvature $R_0$ satisfying the algebraic trace equation. We derive stationary-coordinate-time orbital and epicyclic frequencies and determine stable timelike circular-orbit domains. Positive curvature confines stable motion between innermost and outermost stable circular orbits, which merge at a critical curvature, and permits two resonance radii for suitable frequency ratios. Negative curvature allows stable motion to arbitrarily large radii, with $Ω_θ/Ω_r\rightarrow1/2$, compared with unity in the asymptotically flat limit. We determine the $3{:}2$, $2{:}1$, and $3{:}1$ resonance branches and signed nodal precession, recovering the Lense--Thirring limit. We also evaluate angular-momentum-weighted rigid-flow precession and viscous alignment, with the outermost stable orbit bounding positive-curvature flows. A Bayesian Markov chain Monte Carlo analysis combining the simultaneous GRO J1655--40 QPO triplet with an independent dynamical-mass measurement yields $R_0M^2=-5.57^{+12.94}_{-16.15}\times10^{-4}$ at $68\%$ credibility, conditional on the geodesic RELATIVISTIC-precession prescription and adopted time normalization. Kerr remains allowed, with negligible fit improvement from nonzero curvature. Doubling the mass uncertainty broadens the curvature interval by approximately $2.1$; removing the mass likelihood reveals an extended, prior-dependent degeneracy. This is therefore a joint QPO and dynamical-mass constraint, with no significant evidence for departure from Kerr.
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