Current date: 2026-10-08
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Scoring abstracts
Number of records retrieved: 773
Keyword score statistics
score 7 -- 1 abstracts
score 6 -- 3 abstracts
score 5 -- 1 abstracts
score 4 -- 3 abstracts
score 3 -- 9 abstracts
score 2 -- 26 abstracts
in total -- 43 abstracts
Articles that appeared on 2026-10-08
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[abstract 1 / 43] Wow! (score: 7)
- Title: Widespread steep X-ray spectra of luminous $z\simeq5.85-7.5$ QUASARs and their implications for future X-ray surveysAuthors: A. Tortosa, L. Zappacosta, E. Piconcelli, I. Saccheo, G. Lanzuisi, E. Bertola, F. Vito, M. Bischetti, M. Brazzini, M. Castellano, S. Carniani, A. Comastri, S. Gallerani, R. Gilli, F. La Franca, P. Madau, R. Maiolino, G. Miniutti, B. Musiimenta, C. Piscitelli, F. Salvestrini, F. Tombesi, R. Tripodi, C. Vignali, M. Volonteri, A. Bongiorno, L. Borrelli, M. Brus, I. V. Chilingaria, F. Civan, S. Cristian, V. D'Odorico, D. De Cicco, C. Done, M. Elvis, X. Fan, C. Feruglio, F. Fiore, A. Grazian, M. Guainazzi, F. Haardt, A. Luminari, N. Menci, R. Middei, F. Nicastro, M. Paolillo, M. Perna, S. Puccetti, R. Schneider, V. Testa, R. Valiante, L. Vallini, E. Vanzella, G. Vietri,Comments: Revised version submitted to A&ASubjects: astro-ph.HE astro-ph.GACreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Luminous QUASARs (QSOs) at the Epoch of Reionization (EoR, $z\gtrsim6$) host billion-solar-mass BLACK HOLEs assembled within the first Gyr of cosmic time. Their X-ray emission probes the innermost accreting regions and constrains the physical state of the corona during early supermassive BLACK HOLE (SMBH) growth. Previous results from the HYPerluminous QUASARs at the Epoch of ReionizatION (HYPERION) sample of $z \gtrsim 6$ QSOs, powered by the most rapidly accreted SMBHs, suggested a link between X-ray spectral slope and long-term growth efficiency. We test whether the steep X-ray spectra of luminous z>6 QSOs are a general property of early SMBH growth or a peculiarity of the most efficiently grown SMBHs, using a sample extended mainly to the lowest growth efficiencies. We analysed the largest and most X-ray sensitive sample of 28 luminous QSOs at $z \simeq 5.85-7.56$ (26 used in the correlation analysis), combining HYPERION targets, luminous non-HYPERION sources, and QSOs powered by moderately accreting SMBHs newly observed in our XMM-Newton Large Programme. We re-derived BLACK HOLE masses and growth indicators for the entire sample homogeneously, incorporating the latest JWST-based spectroscopic measurements to ensure the most consistent and high-quality characterization across all targets. We found no statistically significant correlation between coronal spectral parameters and BH growth indicators: luminous $z \gtrsim 6$ QSOs systematically show steep X-ray continua, with high photon indices and/or low high-energy cutoffs, consistent with cold coronae, possibly linked to rapid accretion. Finally, if steep X-ray slopes are common among early AGN, they may significantly reduce count rates, at fixed intrinsic luminosity, in future surveys of the EoR, affecting the detectability of steep-spectrum X-ray sources and thus the census of the early AGN population.
[abstract 2 / 43] Yes (score: 6) - Title: PEARLS: NUSTAR and XMM-Newton Extragalactic Survey of the JWST North Ecliptic Pole Time-Domain Field V: Unraveling X-ray Spectral VariabilityAuthors: Samantha Creech, Francesca Civano, Daniel Wik, Núria Torres-Alba, Ross Silver, Xiurui Zhao, Tonima Ananna, Gibson Bowling, Norman A. Grogin, Anton M. Koekemoer, Peter Maksym, Sylvia Mesicek, Rafael Ortiz, Payaswini Saikia, Steven Willner, Rogier Windhorst,Comments: 36 pages, 13 figuresSubjects: astro-ph.HECreated: 2026-10-06; Updated: 2026-10-08; Datestamp: 2026-10-08
As one of the first deep time-domain surveys in the hard X-ray band, the NUSTAR campaign in the JWST North Ecliptic Pole Time Domain Field (NEP-TDF) offers a prime opportunity to measure variability in a faint population of Active Galactic Nuclei (AGN) in the medium-to-high redshift universe. In the X-ray band, AGN variability is generally caused by changes in the brightness of the corona ($F_{int}$ variability) or changes in the column density of obscuring material near the SMBH ($N_H$ variability). Broad-band spectroscopy ($\sim$0.5-24 keV) is required to reliably disentangle these two phenomena. With simultaneous NUSTAR and XMM-Newton coverage---as well as 1.8 Ms of Chandra monitoring---the X-ray surveys in the NEP-TDF are ideally situated for this purpose. This work presents the first spectral modeling of the 52 NUSTAR-identified sources discovered in the latter half of the campaign, as well as a spectroscopic variability study of the entire 112-source NUSTAR NEP-TDF catalog. Seven variable candidates are identified. We find that $\gtrsim 1000$ total counts split across many ($\gtrsim 10$) epochs are needed in order to detect variability. Additionally, variable sources are compared to the survey sensitivity in order to inform population synthesis models of how variations can affect the detectability of faint AGN, which dominate the SMBH accretion history. Lastly, the timescale of $N_H$ variability is investigated as a probe for the obscurer location. Significant variability is slightly more common on $> 100$ day timescales, suggesting that the torus may have only slight dominance in driving $N_H$ variability in faint AGN.
[abstract 3 / 43] Yes (score: 6) - Title: Registering Gaia positions on VLBI images: constraining opacity-driven core shift in B 1038+528 / B 1038+529Authors: M. H. Xu, Y. Y. Kovalev,Comments: 7 pages, 4 figures, submitted to A&ASubjects: astro-ph.GA astro-ph.IMCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Because of the complex and time-variable radio structure of ACTIVE GALACTIC NUCLEi (AGNs), absolute astrometric positions cannot generally be registered unambiguously with specific features in VLBI images. We aim to register Gaia optical centroids on VLBI images with about 0.1 mas accuracy and to locate the optical emission relative to the radio core in the QUASAR pair B 1038+528 and B 1038+529, in which the opacity-driven core shift was first discovered. We combine the relative position of the pair from phase-referenced VLBI at four epochs between 1981 and 1995, their Gaia optical positions, and the nearly orthogonal radio-JET directions. Assuming that each Gaia--core displacement lies along the local JET axis, we register the Gaia centroids relative to the radio cores with about 0.1 mas accuracy without using absolute VLBI positions. The Gaia centroids lie upstream of the 8.4-GHz radio cores, by 293 {\pm} 93 μas in B 1038+529 and 169 {\pm} 96 μas in B 1038+528. The latter agrees with the 260 μas 8.4-GHz core shift implied by the 2.3--8.4 GHz shift measured for this QUASAR four decades ago. The absolute astrometric position of B 1038+528 with VLBI lies about 0.6 mas downstream of the core, and its geodetic position time series drifts along the JET by more than 1 mas, showing that the 0.8--1.6 mas Gaia--VLBI offsets of the pair are dominated by source structure rather than by core shift. Gaia positions can be registered on VLBI images with an accuracy set by the astrometry uncertainties. If the Gaia centroids mark the JET base, the measured separations are absolute 8.4-GHz core shifts, corresponding to projected distances of about 1.2 pc and about 2.5 pc from the JET base; a contribution from an optical JET emission would make them lower limits. The method is applicable to AGNs with Gaia detection and phase-referenced VLBI astrometry.
[abstract 4 / 43] Yes (score: 6) - Title: Gamma-rays from BLACK HOLE coronae: disentangling the leptonic and hadronic contributionsAuthors: Sébastien Le Bihan, Daniel Grošelj, Martin Lemoine,Comments: 10 pages, 4 figures, submitted to ApJLSubjects: astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
IceCube detections of TeV neutrinos from nearby Seyfert galaxies imply, if confirmed, that the accompanying gamma rays are substantially reprocessed down to the MeV range by electroMAGNETic cascades, which places multi-messenger constraints on neutrino emission models. However, gamma rays can also be produced by the primary nonthermal electrons of the X-ray corona, as recent radiative kinetic simulations of MAGNETized turbulence have shown. To disentangle the leptonic and hadronic contributions, we self-consistently combine results from these simulations with predictions for hadronically induced electroMAGNETic cascades. Focusing on NGC 4151, we find that the leptonic channel dominates the MeV band, and remains comparable to the hadronic cascade up to $\lesssim$0.1 GeV, when the nonthermal electron tail carries $\gtrsim5\%$ of the electron energy. The leptonic contribution may be detectable in soft gamma rays by the upcoming Compton Spectrometer and Imager (COSI) mission, whereas our predicted hadronic component falls below its sensitivity. We also find that the same nonthermal electron population can account for both the $0.1-1$ MeV excess of the cosmic X-ray background, generally attributed to AGNs, and the MeV tail of Cygnus~X-1 in the hard state, lending observational support to our model. Our results offer a refined view of multi-messenger signals from black-hole coronae, grounded in their nonthermal kinetic physics.
[abstract 5 / 43] Yes (score: 5) - Title: A RELATIVISTIC inflow candidate in a QUASAR at cosmic noonAuthors: Yerong Xu, Xiurui Zhao, Elena Bertola, Valentina Braito, Francesca Civano, Luca Comisso, Luigi Gallo, Vittoria E. Gianolli, Elias Kammoun, Giorgio Lanzuisi, Stefano Marchesi, Mar Mezcua, Ciro Pinto, James N. Reeves, Daniele Rogantini, Núria Torres-Albà, Lizhong Zhang,Comments: 6 pages, 7 figures, 1 table, submittedSubjects: astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Cosmic noon ($z\sim2$) marks the peak epoch of cosmic STAR FORMATION and BLACK HOLE accretion activity, where strong accretion and outflows are expected. We report two candidate absorption features in the \textit{XMM-Newton} spectrum of the QUASAR WISEA~J094835.95+432302.6 at $z=1.893$. Two redshifted features occur at rest-frame energies of $\sim4.65$ and $\sim5.75$keV with confidence levels of 99.3% and 94.1%, respectively, estimated from Monte Carlo (MC) simulations considering the look-elsewhere effect. These features can be explained by the Fe XXV/XXVI K-shell transitions from one ultra-fast inflow (UFI) with an apparent velocity of $0.37^{+0.02}_{-0.01}c$. If confirmed by follow-up \textit{XMM-Newton} observations, these detections would extend reported UFI candidates from the local Universe to cosmic noon, offering a rare laboratory for BLACK HOLE accretion at the peak of their growth.
[abstract 6 / 43] Yes (score: 4) - Title: Multi-wavelength study of EP250416a / GRB 250416C: An Optically Dark Long GRB with a Late Jet BreakAuthors: Guoying Zhao, Duo-Le Cao, Rong-Feng Shen, Hui Sun, Chi-Chuan Jin, Wei-Min Yuan, Chen-Wei Wang, Shao-Lin Xiong, Dmitry Svinkin, Dong Xu, Shuai-Qing Jiang, Peter G. Jonker, Yun Wang, Hao Zhou, Chang Zhou, Xinlei Chen, Kaushik Chatterjee, Xue-Feng Wu, Xiao-Feng Wang, Chun Chen, Yuan Liu, Andrew J. Levan, Jennifer Alexandra Chacon Chavez, Jonathan Quirola-Vásquez, Franz E. Bauer, Antonio Martin-Carrillo, Gregory Corcoran, Daniele B. Malesani, Dmitry Frederiks, Anna Ridnaia, Alexandra L. Lysenko, Mikhail Ulanov,Comments: Accepted for publication in A&ASubjects: astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
We present multi-wavelength study of the $γ$/X-ray transient EP250416a (also designated GRB 250416C), triggered by the Einstein Probe (EP) Wide-field X-ray Telescope and also by SVOM and Konus-Wind (KW). Observations spanning the $γ$-ray, X-ray, and optical bands facilitated detailed analysis of the burst's prompt emission, afterglow evolution, and physical origin. GRB 250416C exhibits a burst duration of 30 s in X-ray and 17.7 s in $γ$-rays, with joint spectral fitting of 0.5-5000 keV data gives $E\rm_{peak}=342_{-232}^{+90}$ keV. Optical spectroscopy of the afterglow, acquired with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South, yielded a redshift of $z=0.963$. Accounting for the measured redshift, the isotropic energies are $E\rm_{X,iso}=2.7_{-0.5}^{+0.9}\times10^{50}$ erg and $E\rm_{γ,iso}=7.34_{-2.1}^{+5.1}\times10^{51}$ erg, aligning with the Amati relation for long GRBs. The fluence ratio $\rm S(25-50~keV)/S(50-100~keV)=0.78_{-0.12}^{+0.10}$ classifies GRB 250416C as an X-ray rich (XRR) GRB. The X-ray afterglow shows an initial shallow decay ($α\approx -0.5$) transitioning to a canonical decay phase ($α\approx -1$), with a very late JET break at $t\sim 1.5\times 10^6$ s, corresponding to a JET half-opening angle of $θ_j=10.6_{-1.8}^{+1.9}$ degrees. GRB 250416C is optically dark, as it shows only a faint $r$-band detection ($r=24.16\pm 0.13$ mag) from Gemini South-GMOS and a low optical-to-X-ray spectral index $β_{\rm OX} = 0.3$. This may be attributed to significant host-galaxy extinction, with a required $A_V^{\text{host}}=2.7\pm 0.3\ \text{mag}$ derived from the extinction curve model.
[abstract 7 / 43] Yes (score: 4) - Title: Polarised X-ray emission from the accreting millisecond pulsar SAX J1808.4-3658 during an X-ray outburst and a type-I X-ray burstAuthors: A. Papitto, A. Di Marco, M. C. Baglio, D. Baldi Tomei, C. Ballocco, G. Illiano, R. La Placa, C. Malacaria, A. Bobrikova, J. Poutanen, T. Salmi, A. Sanna, A. Veledina, F. Ambrosino, L. Burderi, S. Campana, F. Coti Zelati, D. de Martino, T. Di Salvo, G. L. Israel, F. La Monaca, A. Marino, A. Miraval Zanon, M. Pilia, L. Stella,Comments: Submitted as a Letter to A&A, 9 pages, 10 figuresSubjects: astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Modelling the X-ray pulse profiles of accreting millisecond pulsars (AMSPs) is a key technique to constrain the masses and radii of neutron stars. To this end, measuring the properties of polarised X-rays provides crucial information on the system geometry. We present the significant detection by IXPE of linearly polarised 2-8 keV X-rays during the decay of the 2025 outburst of the 2.5 ms AMSP SAX J1808.4-3658, with an average polarisation degree of $2.9\%\pm0.5\%$ and a polarisation angle of $46°\pm5°$, broadly consistent with the direction observed in the optical band. This level of polarisation is similar to that found in the only other source of this class that has been targeted so far. By using a pulse-phase timing solution obtained with IXPE and NUSTAR, which confirms the long-term evolution of the pulsar spin and orbit, we did not find any significant pulse phase-resolved variability in the Stokes parameters. Interpreting the polarised X-rays as originating from hot spots on the NS surface indicates they are almost aligned with the spin axis. We also report an indication for linearly polarised emission with a degree of $16\%\pm6\%$ (2-6 keV) during the peak of a type-I thermonuclear X-ray burst, with an angle almost orthogonal to that of the persistent emission. If confirmed, this level would exceed expectations for X-rays reflected by a thin accretion disc.
[abstract 8 / 43] Yes (score: 4) - Title: Quasi-periodic eruption spectral-timing: EMRIs crossing warped accretion disksAuthors: Joheen Chakraborty, Andrew Mummery, Eliot Quataert, Riccardo Arcodia, Itai Linial, Erin Kara,Comments: Submitted, comments welcome!Subjects: astro-ph.HE astro-ph.GA gr-qcCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Quasi-periodic eruptions (QPEs) are repeating X-ray transients from galactic nuclei potentially caused by a stellar-mass orbiter repeatedly colliding with the accretion disk of a supermassive BLACK HOLE (SMBH) in an extreme mass-ratio inspiral (EMRI). In this picture, the eruption arrival times encode the orbit and its RELATIVISTIC precessions, while the quiescent spectral energy distribution (SED) probes the same disk and SMBH, providing two independent constraints on the same orbit-disk system. We present a joint spectral-timing framework that takes advantage of this by simultaneously fitting an analytic QPE timing model built on Kerr geodesic frequencies and a warped disk geometry, coupled to a self-irradiated disk SED model sharing the same SMBH mass, spin, and disk parameters. We apply it to the QPE sources GSN 069 and eRO-QPE2, showing that the QPE timings and quiescent spectra can be reproduced simultaneously in each, providing circumstantial support for the EMRI model and warped disks in these systems. However, given the sparse timing data in both sources, neither admits a unique solution. In eRO-QPE2, we identify six physical modes which reproduce the timings and SED comparably well, motivating denser observing campaigns to identify one unambiguously. Our results demonstrate both the promise of QPE spectral-timing as a precision probe of SMBHs, their accretion disks, and orbiting companions, and the aliasing subtleties of sparsely sampled QPE timings.
[abstract 9 / 43] (score: 3) - Title: Blazar-Boosted Dark Matter: Novel Signatures via Elastic and Inelastic ScatteringAuthors: Jin-Wei Wang,Comments: Only a typo in Eq. (6) has been corrected. The numerical calculations and all conclusions remain unchangedSubjects: hep-phCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Blazar-Boosted Dark Matter (BBDM) is a novel mechanism whereby DARK MATTER (DM) particles are accelerated to ultraRELATIVISTIC energies through interactions with BLAZAR JETs. Focusing on a vector portal DM model, we systematically investigate both elastic and inelastic scattering processes between DM and protons. By analyzing multi-messenger data from ground- and space-based observatories, we derive stringent constraints on the DM-proton scattering cross section $σ_{χp}$. Our results improve upon previous limits from the constant cross section and pure elastic scattering scenarios by several orders of magnitude. The distinctive high-energy gamma ray and neutrino fluxes produced through deep inelastic scattering provide powerful signatures for BBDM indirect detection, enabling constraints that significantly surpass those from traditional direct detection experiments. Notably, our results suggest that DM could be a new source of high-energy neutrinos from BLAZARs, potentially offering an explanation for IceCube's observation of TXS 0506+056.
[abstract 10 / 43] (score: 3) - Title: Relativistic second gradient theory of continuous mediaAuthors: Mina Chapon, Lionel Darondeau, Rodrigue Desmorat, Clément Ecker, Boris Kolev,Comments:Subjects: gr-qcCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Variational Relativity is a framework developed by Souriau in the sixties to better formulate General Relativity and its classical limit\,: Classical Continuum Mechanics. It has been used, for instance, to formulate elasticity from a Lagrangian (or Action) in General Relativity. In that case, two primary variables are involved, the universe (Lorentzian) metric $g$ and the matter field $Ψ$. A Lagrangian density depending on the 1-JET of these variables is then introduced which must satisfy the principle of General Covariance. Souriau proved in 1958 that under these hypotheses, the Lagrangian density depends only on the punctual value of the matter field $Ψ$ and of a secondary variable $\mathbf{K}$, the conformation, an invariant of the diffeomorphism group, which is the Relativistic analog of the inverse of the right Cauchy--Green tensor. In the present work, an extension of Souriau's results to a second order gradient theory in General Relativity is presented. Accordingly, new higher order diffeomorphisms invariants are found. Their classical limits are calculated, showing that the 3-dimensional Continuum Mechanics second gradient theory can be derived from such a RELATIVISTIC theory. Some of these invariants converge to objective quantities in the Galilean limit (such as the fundamental variables of finite strain second gradient theory, modeling solids), others to non-objective quantities (such as those encountered in the modeling of fluids): objectivity is thus natural for the constitutive variables of solids and unnatural for those of fluids. The present work contributes to clarify the theoretical foundation of higher gradient Continuum Mechanics theory.
[abstract 11 / 43] (score: 3) - Title: Tidal disruption of stellar binaries as a pathway to exotic transientsAuthors: Mauricio González-Servín, Emilio Tejeda, Susana Lizano, Luis A. Manzaneda, Raúl Cano-Villegas,Comments: 27 pages, 18 figues. Accepted for publication in MNRAS, 2026Subjects: astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Tidal disruption event (TDE) progenitors are commonly modelled as single stars on parabolic orbits around a supermassive BLACK HOLE (SMBH), yet observations reveal a richer diversity of dynamical pathways. We show that tidal separation of stellar binaries by a $10^6\,M_\odot$ SMBH provides a natural mechanism for producing eccentric TDEs. Using restricted three-body and SPH simulations, we model a solar-like star (SLS)--white dwarf (WD) binary on a parabolic orbit. The binary orbital phase governs the outcome: one component is captured onto a tightly bound orbit while the other is ejected as a hypervelocity object, naturally producing TDEs with eccentricities $e \neq 1$. We classify these into Elliptical TDEs (eTDEs) and Hyperbolic TDEs (hTDEs), occurring with equal probability. For $\sim 88\%$ of orientations the disruption is clean, with no mass accreted by the WD. The remaining $\sim 12\%$, in two narrow phase windows, leaves the WD with a captured debris envelope (WDDE). About a third of that, $\sim 4\%$ of orientations, involves a direct WD--SLS collision near pericenter, with fallback peaking up to five times earlier and twenty times higher than for a single star; for the innermost $\sim 1.5\%$ the total WDDE mass exceeds $1.4\,M_\odot$, though the degenerate core does not, since the captured material forms a non-degenerate envelope, suggesting outcomes ranging from nova-like events to peculiar red giant-like objects. Depending on the phase, the mechanism may also produce repeating partial TDEs (rTDEs) and quasi-periodic eruptions (QPEs). Binary--SMBH encounters provide a robust channel for generating diverse TDEs with distinct observational signatures.
[abstract 12 / 43] (score: 3) - Title: Predictions for Short Gamma-Ray Burst Detections by COSIAuthors: Eliza Neights, Eric Burns, Nicolò Parmiggiani, Yong Sheng, Savitri Gallego, Aldo Aguilar-Nadalini, Aaron C. Trigg, Sylvain Guiriec, Koothodil Abhijith Augustine, Matthew G. Baring, Anna L. Butterworth, Hsiang-Kuang Chang, Che-Yen Chu, Niccolò Di Lalla, Christopher Fryer, Hadar Lazar, Israel Martinez-Castellanos, Marion Sudvarg, Péter Veres, Steven E. Boggs, Dieter H. Hartmann, Carolyn A. Kierans, John A. Tomsick, Andreas Zoglauer,Comments: Submitted to ApJSubjects: astro-ph.HECreated: 2026-10-06; Updated: 2026-10-08; Datestamp: 2026-10-08
The Compton Spectrometer and Imager (COSI) is a soft gamma-ray telescope scheduled to launch in 2027. COSI will trigger onboard the spacecraft in response to short-duration transients, including GAMMA-RAY BURSTs, and it will promptly disseminate alerts which include localizations to the community. This will enable rapid follow-up observations of the afterglow and associations with transients identified by other instruments. By simulating COSI observations of short GAMMA-RAY BURSTs (sGRBs) and processing them with the trigger algorithm which will run onboard the spacecraft, we estimate the sensitivity of COSI to sGRBs. We then convolve this with a simulated set of sGRBs representing the intrinsic population in the universe to predict the rate that will be detected by COSI. We find that COSI is expected to trigger on $\sim$47-89 sGRBs per year with $\sim$7-10 localized to within 2.5°. With the gravitational wave sensitivity anticipated in the O5 run, we predict 0-3 joint detections with gravitational waves.
[abstract 13 / 43] (score: 3) - Title: The Prompt Emission of Gamma-Ray Bursts from Population III StarsAuthors: Nathan Walker, Davide Lazzati, Tyler Parsotan, Rosalba Perna, Matteo Cantiello, Jake Hassan, Brian Morsony,Comments:Subjects: astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Population (Pop) III stars, the first generation of stars in the Universe, have eluded direct detection for decades. The advent of the James Webb Space Telescope, with its unprecedented sensitivity to high-redshift sources, has renewed interest in the prospects for identifying these primordial stars. While previous studies have explored the direct detection of Pop III stars through gravitational lensing, here we investigate an alternative approach: identifying Pop III stars through GAMMA-RAY BURSTs (GRBs) produced by the deaths of massive Pop III progenitors. We generate source-frame mock observables and find that, although Pop III and Pop I GRBs share many common properties, several observables can potentially distinguish between the two populations. In particular, light-curve timescales, isotropic-equivalent energies, peak energies, and the locations of GRBs in empirical prompt-emission correlations depend sensitively on the mass and explosion energy of the progenitor. We find that Pop III GRBs tend to exhibit longer characteristic timescales and higher isotropic-equivalent peak energies than their Pop I counterparts. Finally, we show that Pop III GRBs may provide a promising origin for the population of soft X-ray prompt emission recently detected by the Einstein Probe, offering a complementary avenue for probing the first generations of stars.
[abstract 14 / 43] (score: 3) - Title: Evidence for a Similar Physical Origin Between Prompt Emission and X-Ray Flares of Gamma-Ray BurstsAuthors: Wen-Yuan Yu, Wen-Long Zhang, Hou-Jun Lü,Comments: 14 pages, 2 tables, and 6 figures. Accepted for publication in ApJ, and matched with the published verisonSubjects: astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Statistical properties of X-ray flares are highly similar to those of the prompt emission in GAMMA-RAY BURSTs (GRBs), suggesting that they may share a common physical origin (e.g., central engine activity). However, comparable statistical studies of afterglow X-ray flares and prompt gamma-ray pulses that are not observed simultaneously remain incomplete. In this paper, by systematically searching for gamma-ray emission simultaneous with X-ray flares, we identify 38 GRBs containing 50 pulse--flare pairs, 19 of which have measured redshifts. We perform joint temporal and spectral analyses of the gamma-ray pulses and X-ray flares over their overlapping time intervals, and find that the spectrum of each pair can be well described by an absorbed power-law (PL), PL plus blackbody (PL+BB), cutoff power-law (CPL), and Band function. More importantly, by applying self-organized criticality (SOC) analysis to both the prompt gamma-ray pulses and the simultaneously observed X-ray flares, we find that the temporal parameters (e.g., waiting time, rise time, peak time, decay time, and duration) of the two components follow similar power-law distributions, with the largest absolute difference of $Δα\sim0.36$ for the waiting time and much smaller differences ($Δα\lesssim0.12$) for the other four parameters. For the isotropic energy derived from the subsample with measured redshifts, the difference between the two components is $Δα\sim0.54$. These results suggest that the X-ray flares and the prompt emission are likely to share the same physical origin.
[abstract 15 / 43] (score: 3) - Title: The existence of null points of flow and MAGNETic fields as prerequisites for the presence of astropauses and their co-locationAuthors: Dieter H. Nickeler, Kuljeet S. Saddal, Rodrigo Meneses Pacheco, Michaela Kraus,Comments: 8 pages, 2 figures, 1 table, accepted for publication in A&ASubjects: astro-ph.SR physics.flu-dyn physics.plasm-ph physics.space-phCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Astropauses can be defined via MAGNETic or fluid separatrices. For the boundary layer between the stellar wind and the local interstellar medium, two separatrices can occur, the MAGNETopause and the hydropause. The question is whether they are identical. To address this, we investigate under which conditions the null points of the MAGNETic and velocity field, which define the corresponding separatrices, coincide spatially. We analysed the case of a non-monotonous pressure distribution driving stationary counterstreaming ideal HD flows and demonstrate that the existence of an extremum of the pressure in the 3D case together with a non-degeneracy condition on the velocity field implies that this point is also a stagnation point. Turning to ideal MHD and considering the regularity of all fields, we formulated the momentum equations, revealing their quasi-linearity. This allowed us to prove the occurrence of null points by examining the rank of the Jacobians of the vector fields. We found that for a given null point of either the velocity or the MAGNETic field at the pressure extremum, the pendant vector field has a co-located null if the Jacobian of this field is non-singular. We extended the analysis to resistive MHD and further to MHD with general non-ideal terms and proved that if at least one of the first-order momentum equations is ideal, the stagnation point and the MAGNETic null point are co-located. Even for general fluid theory, the two null points co-locate as long as the curl of the generalised non-ideal terms is zero at one of them or can be represented by a linear operator in the MAGNETic and velocity field. In general, it is not excluded that the velocity and MAGNETic nulls are dislocated. However, this would require specific properties of the curl of the non-ideal term, which would reduce the probability of a relaxed quasi-stationary configuration.
[abstract 16 / 43] (score: 3) - Title: Analytic parity-violating greybody factors of a dynamical Chern-Simons BLACK HOLEAuthors: Abhishek Rout,Comments: 18 pages, 2 figures, 6 tables. Submitted to General Relativity and Gravitation. Reproducibility package: Zenodo doi:10.5281/zenodo.23078252Subjects: gr-qc astro-ph.HE hep-thCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
We study the low-frequency scattering of gravitational and pseudoscalar waves off a non-rotating BLACK HOLE in dynamical Chern-Simons (dCS) gravity, where the axial (odd-parity) gravitational sector is irreducibly coupled to the dynamical pseudoscalar while the polar sector remains general RELATIVISTIC. Working to first order in the dimensionless coupling zeta = (ell_CS/M)^4 and using matched asymptotic expansions, we obtain an exact closed form for the graviton-to-pseudoscalar conversion probability, d_2 = 3(pi^2-9)^2/8, and a high-precision reconstruction, in a proven transcendental basis, of the graviton greybody (absorption) asymmetry, kappa_2 = (21/80) pi^4 + (27/8) pi^2 - 89833/1536, for the quadrupole (ell=2) channel. Both reduce to combinations of pi^4, pi^2, and rational numbers, with no ln2 or odd-zeta terms in the reconstructed basis; the transmission-phase sector, by contrast, contains an analytically derived zeta(3)-9/8 static integral, while its overall matching prefactor is identified numerically. The leading reflection-phase asymmetry vanishes, so that no POLARIZATION rotation is imprinted on the reflected wave at leading low-frequency order, while a subleading O(omegazeta) asymmetry remains in the transmitted phase. The normalized flux asymmetries are numerically consistent with a 1/(Momega)^2 falloff in the geometric-optics limit, where the leading remaining flux effect is conversion loss. The matched-asymptotic results are checked against direct two-channel integration, while the one-dimensional integral determining kappa_2 is evaluated to high precision within an analytically controlled transcendental basis. The results provide analytic targets linking dCS parity violation in absorption and mode conversion to the axial/polar quasinormal-mode splitting.
[abstract 17 / 43] (score: 3) - Title: Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. VII. Testing Disk-Corona Diagnostics with eROSITAAuthors: Wei-Jian Guo, Shuo Zhai, Zhu-Heng Yao, Huaqing Cheng, Jingwei Hu, Jun-Jie Jin,Comments: 17 pages, 9 figures. Accepted for publication in MNRASSubjects: astro-ph.GA astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Changing-look ACTIVE GALACTIC NUCLEi (CL-AGN) have been proposed to follow an X-ray-binary-like, V-shaped relation between the optical/ultraviolet-to-X-ray spectral slope, $α_{\rm OX}$, and the Eddington ratio, $λ_{\rm Edd}\equiv L_{\rm bol}/L_{\rm Edd}$. We test this interpretation using CL-AGN selected from the Dark Energy Spectroscopic Instrument (DESI) and control samples matched to the eROSITA all-sky survey (eRASS). We find that the apparent positive correlation between $α_{\rm OX}$ and the optical-continuum-based Eddington ratio, $λ_{\rm Edd,opt}$, is not unique to CL-AGN, but also appears in matched non-changing-look samples. In broad-H$α$ AGN, our main statistical sample, this structure is largely driven by the known dependence of $α_{\rm OX}$ on ultraviolet luminosity and by the covariance between the rest-frame 2500 Angstrom luminosity, $L_{2500}$, the black-hole mass, $M_{\rm BH}$, and $λ_{\rm Edd,opt}$. When an X-ray-based Eddington ratio is used instead, the relation reverses sign because the X-ray luminosity, $L_X$, enters the two axes with opposite signs. An apparent $α_{\rm OX}$-Eddington-ratio V-shape can therefore be induced by the luminosity estimator and is not a standalone accretion-state diagnostic. As a complementary test, we examine the eRASS effective photon index, $Γ_{\rm eff}$, inferred from catalogue band fluxes. In broad-line AGN, it shows a weak positive association with the X-ray-independent optical Eddington ratio. However, the weaker hard-band trend depends on the null model and does not isolate coronal softening. These results motivate further X-ray spectroscopy, combined with independently estimated Eddington ratios, to test for intrinsic changes in the disk-corona system.
[abstract 18 / 43] (score: 2) - Title: Solar Vortices as Conduits for Magnetoacoustic Waves: Multi-Layer Coupling and Their Role in Atmospheric HeatingAuthors: Suzana S. A. Silva, Ioannis Dakanalis, Luiz A. C. A. Schiavo, Kostas Tziotziou, Istvan Ballai, Shahin Jafarzadeh, Tiago M. D. Pereira, Georgia Tsiropoula, Gary Verth, Iñaki Esnaola, James A. McLaughlin, Gert J. J. Botha, Viktor Fedun,Comments: Accepted for publication in ApJSubjects: astro-ph.SR physics.plasm-phCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Vortices are widespread throughout the solar atmosphere and commonly interpreted as channels for Alfvén wave energy transport. However, this interpretation has mostly been inferred from the apparent alignment of rotating plasma structures with the MAGNETic field, rather than direct evidence of the nature of the waves involved. We present observational and numerical evidence that solar vortices act as coherent waveguides dominated by MAGNEToacoustic waves in the lower atmosphere, combining high-resolution SST observations and Bifrost simulation data. Using Normalised Mutual Information and Jensen-Shannon Divergence as coupling diagnostics, we provide the first observational identification of a solar vortex footpoint through information-theoretic metrics, locating it in the photospheric region of highest shared information with the chromospheric swirl. Spectral Proper Orthogonal Decomposition separates dominant dynamical patterns, allowing us to identify sausage, kink, and helical wave modes propagating along vortex structures. In the Bifrost simulation, we find no evidence for torsional Alfvén waves supported by vortices below 1 Mm. Instead, the waves supported by vortices are MAGNEToacoustic, and their energy transport is predominantly compressive in the lower atmosphere, with the MAGNETic component becoming dominant only at greater heights. Even the compressive wave component alone reaches nanoflare-level magnitudes ($\sim10^{25}$~erg), indicating that vortex-associated compressive perturbations may provide an energetically relevant contribution in regimes where MAGNETic-energy transport dominates. The recovery of sausage and helical modes in temperature perturbations shows that these modes carry a thermal signature, further supporting their relevance for chromospheric energy transport and localised heating.
[abstract 19 / 43] (score: 2) - Title: A Unified Charge-Dependent Modulation Model for AMS-02 Proton and Antiproton Fluxes during Solar MinimumAuthors: Hui-Ming Zhang, Su-Jie Lin, Jie Feng, Jie-Teng Jiang, Yu-Dong Cui, Yi-Han Liu, Li-Li Yang,Comments: 24 pages, 10 figuresSubjects: astro-ph.HE astro-ph.SR physics.space-phCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
We develop a unified charge-dependent solar modulation model by solving the three-dimensional Parker transport equation, incorporating a realistic wavy heliospheric current sheet to treat drift effects self-consistently. Using a local interstellar spectrum from GALPROP constrained by Voyager data, we fit the model to time-resolved proton and antiproton fluxes measured by the Alpha Magnetic Spectrometer-02 (AMS-02) from May 2011 to June 2022, excluding the heliospheric MAGNETic field (HMF) polarity-reversal epoch (mid-2012 to early 2015). To enable rapid parameter scans, we employ neural-network-based surrogate models to compute propagation and modulation matrices efficiently. The results demonstrate that the model simultaneously describes the observed proton and antiproton fluxes with physically reasonable parameters, providing a unified account of charge-dependent modulation.
[abstract 20 / 43] (score: 2) - Title: Forward Modeling of Spectral-Line Polarization for Weak Magnetic-Field ImagingAuthors: Chuanpeng Hou, Huirong Yan, Siqi Zhao,Comments: 7 Figures, 3 Tables. Accepted for publication in ApJSubjects: physics.space-ph physics.geo-phCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Measurements of interplanetary MAGNETic fields rely mainly on spacecraft observations that provide in-situ sampling and cannot directly reveal global MAGNETic structures. In addition, the Zeeman effect is generally too weak to image weak interplanetary MAGNETic fields. Here, we investigate the suitability of spectral-line POLARIZATION for spatially resolved imaging of weak MAGNETic fields, focusing on the Na I D lines in Mercury's MAGNETosphere. We calculate the spectral-line POLARIZATION produced by anisotropic solar radiation and modified by the MAGNETic-field orientation. Using a three-dimensional forward-imaging model of Mercury's MAGNETosphere, we generate synthetic maps of Na I D-line intensity and linear POLARIZATION. The resulting POLARIZATION maps trace the large-scale MAGNETospheric MAGNETic-field geometry, demonstrating the potential of Na I D-line polarimetric imaging to constrain the spatial structure of Mercury's MAGNETosphere. We further show that, with a 1.8-m telescope, Na I D-line linear-POLARIZATION imaging of Mercury's MAGNETosphere at a spatial resolution of 2" is feasible with an exposure time of approximately ten minutes.
[abstract 21 / 43] (score: 2) - Title: Transitions in the Mass-ratio and Spin Properties of Binary Black Holes in GWTC-5Authors: Elizabeth Flanagan, Fabio Antonini, Thomas Callister, Debatri Chattopadhyay, Fani Dosopoulou, Isobel Romero-Shaw, Jakob Stegmann,Comments: Accepted to ApJLSubjects: astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
We analyze the mass-ratio and effective-spin ($χ_{\rm eff}$) distributions of binary BLACK HOLE mergers in the latest gravitational-wave catalog, GWTC-5, as a function of primary mass. Using hierarchical Bayesian inference with flexible Gaussian-process population models, we identify four distinct mass regions separated by sharp transitions in both mass-ratio and spin properties. Below $\sim15~M_{\odot}$, the population strongly favors equal-mass binaries and exhibits a narrow $χ_{\rm eff}$ distribution peaked at positive values. In the range $18$-$30\,M_{\odot}$, the mass-ratio distribution becomes substantially flatter, while the $χ_{\rm eff}$ distribution broadens, shifts to a peak consistent with zero, and shows tentative--but not statistically required--evidence for positive skewness. The region associated with the feature near $\simeq35~M_{\odot}$ returns to a narrow $χ_{\rm eff}$ distribution consistent with symmetry at zero and strongly favors equal-mass binaries. Above $\simeq 45~M_{\odot}$, both the mass-ratio and $χ_{\rm eff}$ distributions broaden significantly. The inferred support of the spin distribution converges toward the range expected for binaries containing remnants of previous BLACK HOLE mergers, making the highest-mass region fully consistent with a star cluster population of hierarchical mergers. The close correspondence between transitions in mass ratio and effective spin suggests that different primary-mass ranges trace distinct formation channels, with isolated binary or triple evolution likely dominating the lower-mass population and dynamical assembly becoming increasingly important at higher masses.
[abstract 22 / 43] (score: 2) - Title: FERMI-eROSITA cross-correlations suggest annihilation lines of $\sim70$ GeV WIMPsAuthors: Uri Keshet,Comments: Added mock tests and line-recovery corrections; corrected nonad scan; expanded discussionSubjects: astro-ph.HE astro-ph.CO hep-phCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
The deep potential wells of galaxy clusters provide some of the strongest constraints on the velocity-dependent ($p$-wave) annihilation of weakly interacting massive particle (WIMP) DARK MATTER. Cross-correlating high-latitude FERMI-LAT 16.3-year data with the western Galactic hemisphere eROSITA map facilitates high-sensitivity tests. A blind composite matched-filter scan of the cross-correlated spectrum for the $χχ\toγγ$, $γZ$, and $γh$ annihilation-line triad of a single WIMP $χ$ finds $m_χc^2\simeq71.9$ and $67.5$ GeV triads, each with a local $Z$-score $\sim3$ and a (henceforth global) $1.6σ$ (trial-corrected by pixel shuffles; $1.8$-$2.1σ$ in Monte Carlo and analytic estimates), insensitive to details of detrending, sky masks, and filters. Scanning for the line nonad of two cross-annihilating WIMPs finds $66.4$ and $71.9$ GeV masses (with a weak $69.2$ GeV cross-annihilation triad) at $2.3σ$. The leading $\sim72$ GeV triad coincides with the mass implied by interpreting the recently reported $\sim43.2$ GeV $γ$-ray line in three nearby clusters as its $γZ$ channel. At this externally fixed mass, the triad reaches $3.0σ$ alone, and $5.1σ$ when combined with the reported line ($3.9σ$ under alternative assumptions). The triad, absent from the ambient (X-ray-uncorrelated) spectrum, presents in different Galactic sectors, strengthens under cosmological (positive) but not negative redshift broadening $Δz$, and peaks at $Δz\simeq 0.05$, consistent with expectations; its two non-$43$ GeV channels reach $2.3σ$ by themselves. Measured (not loss-corrected) intrinsic cross sections are a few $10^{-19}$ cm$^3$ s$^{-1}$ for WIMPs tracing the X-ray gas.
[abstract 23 / 43] (score: 2) - Title: Massive scalar fields in eccentric regime: Detectability and constraints from LISA observations of extreme mass-ratio inspiralsAuthors: Tieguang Zi, Shailesh Kumar, Genliang Li, Jun-Kun Zhao, Bao-Min Gu, Fu-Wen Shu,Comments: V2: 31 pages, 13 figures, 7 tables, Fisher-information-matrix diagnostics with Markov-chain Monte Carlo analysis added, Resonant massive-scalar fluxes included, Version accepted to appear in Physical Review DSubjects: gr-qc astro-ph.HE hep-thCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Extreme mass-ratio inspirals (EMRIs) are among the most promising sources for future space-based gravitational wave (GW) observatories and provide sensitive probes of additional fundamental fields in the strong-gravity regime. In the present work, we investigate eccentric equatorial EMRIs around Kerr BLACK HOLEs in the presence of a massive scalar field. We assume that the inspiralling object carries a scalar charge, therefore, emits scalar radiation in addition to GWs. By solving the massive scalar perturbation equation in the frequency domain, we compute the RELATIVISTIC scalar energy fluxes at the event horizon and at infinity and incorporate them into an adiabatic inspiral model. We investigate the impact of the scalar charge and scalar field mass on the orbital evolution and gravitational waveforms by analysing the accumulated phase differences and waveform mismatches relative to both general relativity (GR) and the massless scalar limit. Our results show that the massive scalar radiation can produce significant GW dephasing, with the effect becoming increasingly pronounced for more eccentric orbits. In addition, the scalar flux is suppressed for larger scalar field masses as fewer scalar harmonics satisfy the propagation condition at infinity. Finally, using both Fisher-information-matrix forecasts and Bayesian parameter estimation, we assess the capability of the Laser Interferometer Space Antenna to constrain the scalar charge and scalar field mass. The two inference approaches gives consistent constraints, demonstrating that eccentric EMRIs provide a promising avenue for probing massive scalar fields and scalar-tensor extensions of gravity in the strong-field regime.
[abstract 24 / 43] (score: 2) - Title: A Common $\sim$55 GeV Inelastic Dark Matter Origin of the LZ, FERMI-LAT, and AMS-02 Excesses and Paleo-Detector ProspectsAuthors: Meiwen Yang, Quan-feng Wu, Kai-Kai Duan, Zi-Qing Xia, Yue-Lin Sming Tsai, Yi-Zhong Fan,Comments: 9 pages, 4 figuresSubjects: hep-ph astro-ph.CO astro-ph.HECreated: 2026-10-05; Updated: 2026-10-08; Datestamp: 2026-10-08
We investigate the 248~keV nuclear recoil excess reported by LUX-ZEPLIN (LZ) in a leptophobic inelastic DARK MATTER framework, in which the mass splitting naturally suppresses low-energy recoils. We find two viable branches, including the endothermic solution with a high DARK MATTER mass $m_χ\gtrsim400$~GeV and the exothermic one with a mass of tens GeV. Remarkably, the exothermic DARK MATTER scenario with $m_χ\sim55$~GeV can simultaneously account for the LZ excess, the Galactic Center GeV gamma-ray excess, and the AMS-02 antiproton excess. The favored annihilation cross-section is slightly below the one required for the observed relic abundance, resulting in an overabundant relic in the minimal setup. An additional neutrino-portal mediator can provide the required depletion while leaving the gamma-ray and antiproton signals essentially unchanged. We further show that paleo-detectors provide a powerful probe of the inelastic interpretation, requiring exposures of $\sim10$ and $\sim100$~mg Gyr for the endothermic and exothermic scenarios, respectively.
[abstract 25 / 43] (score: 2) - Title: Lifetime reversals of neutral and charged scalar clouds around nonminimal Einstein-Yang-Mills BLACK HOLEsAuthors: S. V. Bolokhov,Comments: 21 pages, 7 figuresSubjects: gr-qcCreated: 2026-10-04; Updated: 2026-10-08; Datestamp: 2026-10-08
We calculate quasi-bound states of neutral gauge-singlet scalars and charged scalar doublets and triplets around the asymptotically flat, nonminimal Einstein--Yang--Mills BLACK HOLE. For neutral monopoles, the principal result is a reversal in the lifetime response to the nonminimal coupling: weakly bound clouds decay more slowly than on the corresponding Reissner--Nordström geometry, whereas increasing the field mass changes suppression into enhancement of absorption. The weak-binding behavior approaches a horizon-area law, but that law alone does not determine the finite-mass ordering. At representative couplings, dipole and quadrupole widths instead decrease substantially while their level energies change very little. Two-sided integration and an independent arbitrary-precision continued fraction check both the real frequencies and the much smaller imaginary parts. We recover the Schwarzschild and Reissner--Nordström limits, test hydrogenic binding and the low-frequency absorption scaling, and distinguish the loss of a potential well from the disappearance of a quasi-bound pole. An exact horizon-domain analysis fixes the black-hole parameter range, and a positive-potential argument excludes exponentially growing modes of the canonical test scalars. The MAGNETic Wu--Yang connection separates the charged multiplets into quantized monopole sectors, without an electric frequency shift. Their lowest channels exhibit twelve located lifetime crossings within the sampled trapping region and noninteger weak-binding decay powers. At fixed total angular momentum within the triplet, charged states can instead decay hundreds of times faster than neutral states. These comparisons show that neither gauge charge nor nonminimal coupling universally prolongs cloud survival.
[abstract 26 / 43] (score: 2) - Title: Modeling the nanohertz gravitational wave background with the t-process: Improved frequentist analysis of gravitational-wave powerAuthors: B. E. Moreschi, K. A. Gersbach, G. Shaifullah, S. R. Taylor, A. Sesana,Comments:Subjects: astro-ph.GA astro-ph.HE astro-ph.IMCreated: 2026-10-06; Updated: 2026-10-08; Datestamp: 2026-10-08
Pulsar timing array (PTA) collaborations have recently reported evidence for a gravitational wave background (GWB) signal in the nanohertz band, which most likely originates from the incoherent superposition of GWs emitted by a population of supermassive BLACK HOLE binaries (SMBHBs). Since the number of binaries emitting in each frequency bin is finite, and since individual loud sources can dominate the GWB, the power spectral density (PSD) of the background is expected to deviate significantly from the smooth power law that describes an idealized population. PTA searches usually describe the PSD either with a power law or with a free spectrum model, which fits the PSD in each frequency bin as a free parameter. In this paper, we explore the t-process as a third model; it assumes a power law as the underlying spectrum but leaves each frequency bin free to deviate from it. We compare the performance of these three models on simulated datasets, injecting $100$ realizations of a realistic SMBHB population, to evaluate how well each model recovers a complex PSD. Using Bayesian and frequentist tools, we find that the t-process model gives the most precise PSD results, with uncertainties $43\%$ and $26\%$ narrower than those obtained with the power law and the free spectrum, respectively, while the improvement in accuracy is smaller. Moreover, using the t-process model, we compute isotropic and anisotropic signal-to-noise ratios with median gains of about $46\%$ over the power law and $65\%$ over the free spectrum in the first nine frequency bins. The t-process also returns lower anisotropy p-values and among the frequency bins with $p<0.01$, it allows to localize the loudest binary within the angular resolution of the sky maps in $14.3\%$ of the cases, compared to the $10\%$ for the power law and the $6.2\%$ for the free spectrum.
[abstract 27 / 43] (score: 2) - Title: The price of regularity: core gradient instability in nonsingular dyonic BLACK HOLEsAuthors: Lodovico Capuano, Alessandro Longo,Comments: 24 pagesSubjects: gr-qc hep-thCreated: 2026-10-06; Updated: 2026-10-08; Datestamp: 2026-10-08
Spacetime singularities displayed by classical BLACK HOLE solutions are expected to be cured by high-energy effects, beyond the regime of validity of General Relativity. On the other hand, there are well-known examples of classical theories allowing for nonsingular BLACK HOLE solutions. The most prominent is obtained by complementing the gravitational sector of General Relativity with a minimally coupled nonlinear-electrodynamics sector. It has recently been shown that purely electric/purely MAGNETic nonsingular BLACK HOLEs in an Einstein-nonlinear-electrodynamics setup are always plagued by a gradient instability. In this work, we derive the quadratic action for linear perturbations of static, spherically symmetric dyonic solutions of Einstein-nonlinear-electrodynamics theories with a general dependence on both invariants. We show that regularity of the center, absence of ghosts and angular gradient stability cannot hold simultaneously: arbitrarily close to a regular center, at least one photon POLARIZATION has a negative squared angular propagation speed. We further show that regularity drives one electroMAGNETic kinetic eigenvalue to zero at the center, which may limit perturbative control near the core. Evading the obstruction requires extending the theory, for example by introducing additional degrees of freedom.
[abstract 28 / 43] (score: 2) - Title: A Newly Identified Transient Ultraluminous X-ray Source in M31Authors: Ferdinand, Murray Brightman, Jean-Marie Hameury, Elias Kammoun, Dominic J. Walton, Matthew J. Middleton, Hannah Earnshaw, Felix Fürst, Wynn V. Jacobson-Galán, Jacob E. Jencson, Margaret Lazzarini, Mark T. Reynolds,Comments: 20 pages, 9 figures, 2 tables, submitted to ApJSubjects: astro-ph.HECreated: 2026-10-06; Updated: 2026-10-08; Datestamp: 2026-10-08
Ultraluminous X-ray sources (ULXs) are off-nuclear X-ray sources with luminosities exceeding the Eddington limit of typical stellar-mass compact objects. While most known ULXs are relatively persistent sources, transient ULXs have emerged as a distinct population that offer unique insight into extreme, super-Eddington accretion. We report the discovery and X-ray characterization of a newly identified transient ULX in M31. First detected serendipitously on 2021 June 9, the source reached a peak unabsorbed $0.3 - 10$ keV luminosity of $\sim10^{39}\ \rm erg\ s^{-1}$. Its spectral evolution suggests increasing advection at later epochs, opposite to the expected transition from a super-Eddington slim disk toward a standard thin disk during the decay of the outburst. The observed X-ray light curve can be reproduced using the disk-instability model of Hameury & Lasota, with characteristic timescales of $\sim41-61$ days. The inferred mass-accretion rate is super-Eddington for a $1.4\,M_{\odot}$ neutron star but approximately Eddington for a $10\,M_{\odot}$ stellar-mass BLACK HOLE. Nearby optical sources from the Hubble Source Catalog suggest a possible giant donor with an age of $\log_{10}({\rm age/yr})\sim8.5$ and a mass of $\sim3.2\,M_{\odot}$, when compared with stellar isochrones with an assumed $A_V=1.58$. We estimate a transient ULX occurrence rate in M31 of $0.18\pm0.10\ {\rm yr^{-1}}$. This rate is lower than those reported for other galaxies in previous studies. M31 ULX-3 expands the small population of known transient ULXs in M31 and highlights the importance of continued, regular X-ray monitoring of nearby galaxies.
[abstract 29 / 43] (score: 2) - Title: Can LISA See Inside the Little Red Dots?Authors: Samuel Gómez Gómez, Xisco Jimenez Forteza, Carlos Palenzuela, Rosalba Perna,Comments: 8 pages, 4 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-10-06; Updated: 2026-10-08; Datestamp: 2026-10-08
The Little Red Dots (LRDs) are compact, broad-line sources that appear to contain accreting BLACK HOLEs (BHs) embedded in dense gas. Proposed models for their central environments (including quasi-stars, radiative BH envelopes and super-Eddington accretion discs) predict gas densities at the radii probed by an extreme-mass-ratio inspiral that differ by many orders of magnitude. We compute the inspiral of a $10$--$30\Msun$ BH for a range of LRD interior models, including environmental effects from the gas, and test with a mismatch criterion whether the resulting waveforms can be distinguished from vacuum and from one another. Dense interiors (Bondi-like free-fall cavities and radiative envelopes) produce measurable deviations from vacuum in essentially every detectable event. Convective quasi-star interiors are measurable for $\MBH\lesssim10^5\Msun$ and $z\lesssim0.6$, while a co-rotating disc leaves no measurable imprint. In favorable cases the models are also mutually distinguishable. None of the 14 JWST LRDs at $z>3.9$ would be detectable with a $10\Msun$ companion, but 30 of 31 LRDs at $z<0.9$ would be if their BLACK HOLEs are $\sim100$ times less massive than their virial estimates, and in many of them the interior's imprint would be measurable. Across the LRD population to $z=6$, a 4-yr LISA mission would yield $0.08$--$0.8$ detectable events for $10^5\Msun$ hosts and $10\Msun$ companions ($1.5$--$15$ for $30\Msun$) if LRD nuclei host inspirals at the rate of ordinary galactic nuclei. In dense clusters, where captures are plunges, this falls to $\lesssim10^{-4}$.
[abstract 30 / 43] (score: 2) - Title: Coupled Thermochemical Ablation and Rarefied Particle Erosion during Mars EntryAuthors: Hyeon Woo Nam, Sung Min Jo,Comments:Subjects: physics.flu-dynCreated: 2026-10-06; Updated: 2026-10-08; Datestamp: 2026-10-08
Martian dust particles are a few micrometers in diameter, comparable to the mean free path of the gas in the hypersonic shock layer. Their Knudsen number ranges from approximately 0.2 to 100, placing them in the transitional and free-molecular regimes, whereas the flow around the vehicle is a continuum. The two-way flow-particle coupling previously developed by the authors for a two-temperature thermochemical nonequilibrium flow is extended to a receding and pyrolyzing heat shield surface. The gas-surface interaction and the in-depth material response are solved on separate time scales. The surface balances are exchanged at every flow step, while the in-depth response is coupled implicitly over physical time windows. The flow-material coupling is assessed against graphite arc-JET measurements. The framework is applied to the Schiaparelli trajectory from 50 to 30 km. Three surface chemistry models (equilibrium, Park-5, and Zhluktov-Abe) are compared for fixed geometry, char-induced recession, and combined char ablation and particle erosion. At the final trajectory point, the stagnation point heat flux differs by 30-75% among the chemistry models. For the equilibrium model, surface recession changes this heat flux by less than 1% but lowers wall temperature and increases pyrolysis gas injection. Particle erosion contributes 1.73 mm of stagnation point recession, exceeding the char-induced recession, and more than doubles the total recession for all three models. To the authors' knowledge, this study provides the first quantitative comparison of particle erosion between rarefied and continuum drag correlations, and the continuum correlation underestimates the stagnation point erosion rate by 31-35%.
[abstract 31 / 43] (score: 2) - Title: The Impact of Galaxy Catalogue Completeness with GLADE+ on Dark Siren Cosmology: A Line-of-Sight Prior Analysis of GWTC-3 EventsAuthors: Juan Esteban Rivera, Antonio Enea Romano, Rachel Gray, Sergio Vallejo-Peña, Riccardo Sturani,Comments:Subjects: astro-ph.COCreated: 2026-10-06; Updated: 2026-10-08; Datestamp: 2026-10-08
Cosmological parameters can be estimated from dark sirens, gravitational waves events without electroMAGNETic counterpart, by using inference methods which estimate statistically the source redshift from galaxy catalogs. We study the effects of applying different apparent magnitude cuts to the GLADE+ catalog, analyzing events from the third LIGO-Virgo-KAGRA gravitational wave transient catalog (GWTC-3), consisting of 42 binary BLACK HOLEs, 3 neutron star BLACK HOLE systems and the event GW190425 associated to a binary neutron star coalescence. We find that the inclusion of fainter galaxies has no significant effects on the joint analysis of almost all the events, while for some single well localized event, the effects can be more important, in particular for the event GW190814. To understand why inclusion of fainter galaxies in general has negligible impact on the estimation of cosmological parameters, we compare the redshift of the events with the redshift distribution of dimmer galaxies, and find that most of them are not located in redshift proximity of the events, explaining the limited impact of their inclusion. The event, GW190814 is an exception, as its distance localization, converted into redshift, overlaps with fainter galaxies, unlike what happens for other events, which are farther away. These results show the importance of event localization and catalog depth in determining the impact of catalog completeness on cosmological parameters estimation. To check quantitatively what is the information gained by adding fainter galaxies we have analyzed its impact on the line of sight prior calculation. Based on the results for GW190814 we expect that fainter galaxies will play a more significant role in the estimation of cosmological parameters also for the joint analysis of multiple events, when deeper catalogs will be available.
[abstract 32 / 43] (score: 2) - Title: Effects of Magnetic Fields on Solar Inertial Modes in Global Nonlinear SimulationsAuthors: Conrado S. Finotti, Gustavo Guerrero, Santiago A. Triana, Mausumi Dikpati, Piotr K. Smolarkiewicz,Comments: Submitted to The Astrophysical Journal. Accompanying animations available at https://doi.org/10.5281/zenodo.23044227Subjects: astro-ph.SRCreated: 2026-10-06; Updated: 2026-10-08; Datestamp: 2026-10-08
Solar inertial modes are increasingly viewed as probes of the solar interior, with recent helioseismic evidence indicating that these modes may be sensitive to the internal MAGNETic field. We investigate the role of MAGNETic fields on inertial mode excitation and dynamics using global nonlinear MHD simulations with differential rotation forced toward a helioseismically derived profile. Initial poloidal fields of varying strengths and topologies self-consistently generate different toroidal field configurations through the $Ω$-effect. In all cases, baroclinic instability excites high-latitude inertial modes, with weak fields enhancing its growth rate above the hydrodynamic value. For stronger fields, the response depends on topology and depth. As a consequence, the polar vortex emerges earlier and modifies its relative amplitude, handedness, and hemispheric asymmetry. Only MAGNETic topologies exhibiting toroidal bands at the upper convection zone develop a second, MAGNETo-shear ("edge") instability at the equatorward edges of these bands. Powered mainly by the toroidal field, this instability sets in earlier and grows faster for stronger initial fields. It excites equatorial modes absent in the hydrodynamic simulation, with fast MAGNETo-Rossby signatures approaching the classical Rossby dispersion relation at tachocline depths. Alfvénic signatures and tentative slow MAGNETo-Rossby branches also appear. Inertial-mode excitation and frequencies thus depend on MAGNETic topology and spatial distribution, not merely field strength.
[abstract 33 / 43] (score: 2) - Title: Numerical error analysis of EMC3-EIRENE simulations in the HSX stellaratorAuthors: F. A. Chavarria, D. Boeyaert, H. Frerichs, K. A. Garcia, B. Geiger,Comments: 21 pages, 7 figures, submitted to Nuclear FusionSubjects: physics.plasm-phCreated: 2026-10-06; Updated: 2026-10-08; Datestamp: 2026-10-08
Plasma edge simulations with codes like EMC3-EIRENE are widely used to study fusion MAGNETic confinement devices. However, numerical errors can significantly impact the simulation solution and are often insufficiently characterized. These errors consist of the statistical error, bias, and time integration error, resulting from the finite sampling and tracking of Monte Carlo particles, and the discretization error, resulting from a finite grid resolution. This work presents the first comprehensive numerical error analysis of EMC3-EIRENE simulations in stellarator geometries, focusing on edge plasmas in the Helically Symmetric eXperiment (HSX). Fundamental plasma and neutral quantities are analyzed, and error reduction rates are compared against theoretical expectations. The statistical error, bias, and time integration error are fully characterized; however, quantification of the discretization error remains challenging because of the complex grid geometries used in EMC3-EIRENE. The commonly used volume averaged relative change metric is shown to systematically underestimate the statistical error, highlighting a critical flaw in EMC3-EIRENE analysis, where convergence is claimed despite significant noise remaining in the simulation solution. Dominant contributions of the time integration error are shown to differ in stellarator simulations compared to tokamak simulations, related to the relative importance of cross-field transport between the two devices. Based on these results and existing literature, we establish best practices towards improved accuracy and efficiency in general stellarator modeling with EMC3-EIRENE.
[abstract 34 / 43] (score: 2) - Title: Collisions of Multiple Black Holes: A Numerical Relativity StudyAuthors: Chen-Kai Qiao, Shu-Yuan Liu,Comments: 18 pages, 5 fguresSubjects: gr-qcCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Numerical relativity has a profound impact on gravitational theory and gravitational wave astronomy. In this work, we present a systematic study of the head-on collisions of multipule BLACK HOLE systems within the framework of numerical relativity using the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation. The numerical simulations of the dynamical evolution of gravitational fields are computed using the AMSS-NCKU code. We report numerical results for BLACK HOLE collisions in several symmetric and non-symmetric configurations, in which the BLACK HOLEs are initially at rest and are described by Bowen-York type initial data. Our results suggest that BLACK HOLE systems with perfectly symmetric configurations (e.g., BLACK HOLEs located at the vertices of a regular polygon or a regular polyhedron) impose strong constraints on the emitted gravitational waves, and no gravitational kick arises in these symmetric systems. For regular polygonal configurations, the radiation is dominated by the plus POLARIZATION of the $l=2$, $m=0$ mode. For regular polyhedral configurations, all the quadrupole modes with $l=2$ nearly vanish, and gravitational wave amplitudes are strongly suppressed to the order of $10^{-4}$ or below, which is in accordance with an analysis based on the quadrupole approximation. Gravitational radiations from $m \ne 0$ modes become non-negligible only when non-symmetric configurations are encountered. Keywords: Numerical Relativity, Black Holes, Gravitational Waves, N-Body Systems
[abstract 35 / 43] (score: 2) - Title: The contribution of Soviet scientists to the emergence of high-energy neutrino astrophysics: from the Cherenkov effect to underwater and in-ice telescopesAuthors: Bakhromzod Rizoi,Comments: 2 tablesSubjects: physics.hist-ph astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
The 2026 Nobel Prize in Physics was awarded to Francis Halzen @for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.@ This article examines the Soviet contribution to the broader historical development of high-energy neutrino astrophysics. Four interconnected strands are distinguished: the physics of Cherenkov radiation and its application to COSMIC RAYs; early proposals for large-scale neutrino detection underground and in natural water; the theory of atmospheric, cosmogenic, and astrophysical neutrinos; and the development of underground, underwater, radio, and in-ice detection techniques. The article shows that M. A. Markov s 1960 proposal was concerned primarily with atmospheric neutrinos and with detecting charged secondary particles through Cherenkov radiation in water, whereas the use of Antarctic ice was initially developed in the Soviet Union in the radio domain. The optical concept of a detector in deep polar ice was formulated by F. Halzen and J. G. Learned in 1988. The Pamir cosmic-ray school, the theoretical work of G. T. Zatsepin, V. A. Kuzmin, and V. S. Berezinsky, the Baksan Neutrino Observatory, Soviet participation in DUMAND, and the formation of the Lake Baikal neutrino program are considered separately. The Pamir material is included as historical and methodological context; it does not imply a direct experimental lineage from Pamir installations to IceCube. The historical links of these strands to IceCube are therefore different in character: conceptual and citation-based in some cases, methodological or institutional in others. This distinction helps separate documented continuity of ideas from the broader scientific context in which modern high-energy neutrino astronomy emerged.
[abstract 36 / 43] (score: 2) - Title: $r$-Process as Production of Lanthanides from Compact Object MergersAuthors: Li-ming Zhuo, Hou-Jun Lü, Xiao-Xuan Liu, Meng-Hua Chen, En-Wei Liang,Comments: 16 pages, 1 table, 8 Figures. Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
The relative contributions of binary neutron star (BNS) and BLACK HOLE-neutron star (BH-NS) mergers to the Galactic enrichment from the rapid neutron-capture process ($r$-process) remain an open question in nuclear astrophysics. In this paper, we present end-to-end numerical simulations of binary population synthesis, nucleosynthesis, and Galactic chemical evolution (GCE) via Compact Object Mergers Population Astrophysics and Statistics (COMPAS), SkyNet network, and a stochastic multi-zone model, respectively. By considering five equations of state (EOS) of NS and different spins of BH for BNS and BH-NS mergers, it is found that the averaged abundance seems not to be significantly dependent on the EOS of NS and spin of BH for BNS and BH-NS mergers. For given EOSs of NS, the abundance of BNS is higher than that of BH-NS mergers before the second peak (for mass number $A\sim$130), but it is lower when the mass number is greater than 130. Moreover, the lighter $r$-process elements ($A<$130) are predominantly produced by the disk wind, while the heavier elements ($A>$130) originate mainly from the dynamical ejecta. The purely BNS mergers, on the other hand, are the dominant contributors to the production of lanthanides like europium (Eu) at the later stage of GCE, but BH-NS mergers make only a small contribution of heavy $r$-process elements for the $\rm Eu/Fe$ evolutionary tracks in the Milky Way.
[abstract 37 / 43] (score: 2) - Title: Dynamical pairing in gravitational wave populationsAuthors: Fabio Antonini, Aleksandra Olejak, Isobel Romero-Shaw, Matthew Mould,Comments: 20 pages, 11 figures. Comments are welcomedSubjects: astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Binary BLACK HOLEs formed dynamically in star clusters are often associated with nearly equal-mass pairing. We show that this expectation is incomplete. The more general prediction of dynamical assembly is an ordered-pairing relation in which the two BLACK HOLEs are drawn independently from a common one--body mass spectrum and then ordered by mass. Once the primary-mass distribution is known, this relation fixes the conditional companion distribution $p(m_2\mid m_1)$. We validate this picture with cluster simulations. In these models, the ordered-draw relation reproduces the morphology of the mass-pairing distribution, including fixed-$m_2$ ridges that are inherited from the one--body mass spectrum: features at nearly constant secondary mass that extend over a range of primary masses and therefore correspond to decreasing $q=m_2/m_1$ as $m_1$ increases. Thus, the geometry of the mass distribution itself becomes a formation-channel diagnostic. Dynamical pairing maps peaks of the primary-mass spectrum into fixed-$m_2$ ridges with predictable amplitude, whereas isolated binary evolution more naturally produces structures at fixed $q$. Applying this test to a non-parametric reconstruction of the gravitational-wave population, we find a tentative enhancement at $m_2\simeq 30~ M_\odot$ for $m_1\gtrsim 40~ M_\odot$ that is broadly compatible with ordered pairing. Finally, we show that dynamical formation naturally explains the rapid decline of the secondary-mass distribution above $\sim30~M_\odot$ recently reported by the LIGO--Virgo--KAGRA Collaboration.
[abstract 38 / 43] (score: 2) - Title: On the particle and electroMAGNETic boundary conditions in a mesothermal plasma flowAuthors: J. Gonzalez,Comments:Subjects: physics.plasm-phCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
The fully kinetic modeling of mesothermal plasma flows presents significant challenges in the description of boundary conditions for the electrons and the electroMAGNETic field. Due to their higher mobility compared to ions, electrons extend downstream of the ions, which hinders the implementation of the outflow boundary conditions during transient states. Although the electron drift velocity, $u_e$, is usually neglected as $u_e \simeq u_i < v_{th,e}$, where $u_i$ is the bulk velocity of the ions and $v_{th,e}$ is the thermal velocity of the electrons, we will show how accounting for it, both at the injection of particles and at the outflow boundary condition, is of great importance to achieve quasi-neutrality of charge and current densities. A new partial reflection model for electrons is presented to represent quasi-steady and transitory states. Additionally, we will show how we can employ Ampere-Maxwell's law to better represent the transitory electric field at the outflow boundary compared to the classical `zero-field' Neumann boundary without requiring any numerical parameters. With these new boundary conditions, we improve the quasi-steady and transitory descriptions of expanding mesothermal plasmas.
[abstract 39 / 43] (score: 2) - Title: Acceleration radiation, quasinormal modes and quasi-bound states in generic rotating regular BLACK HOLEsAuthors: Uktamjon Uktamov, Ali Övgün, Reggie C. Pantig, Bobomurat Ahmedov,Comments:Subjects: gr-qcCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
We study horizon-brightened acceleration radiation for a neutral scalar field in separable Kerr-like rotating metrics with nonlinear-electrodynamic mass profiles. The principal branch has $M=0$ and $μ=3$, with finite but direction-dependent central curvature limits. An analytic extremal charge--spin parametrization fixes the BLACK HOLE domain. At a simple outer horizon, the scalar equation reduces to local conformal quantum mechanics with corotating energy $\epsh=ω-m\OmH$. For an isolated outgoing channel we derive the first finite-gap correction in proper time, including the radial Frobenius coefficient, angular variation, geodesic terms, and switching slope. This replaces a coordinate-dependent trajectory-phase multiplier by a protocol-defined detailed-balance affinity. Direct integration of the outgoing scalar equation and an equatorial infalling trajectory validates the expansion for an explicitly specified finite gate; a solvable logarithmic-mode limit separates switching from geometric contributions. We also analyze forced equatorial circular atoms and show that co-rotating and counter-rotating ultra-RELATIVISTIC motion yields a mode-dependent orbital response rather than the infalling Hawking affinity. We identify the shrinking near-extremal radial scale and quantify the effect of an unselected second radial branch, without asserting a uniform extremal limit. Random atomic injection gives a selected-mode master equation and a nonnegative population entropy-production identity. A direct first-law integrability test shows why horizon-area bookkeeping remains conditional for this off-shell metric. Independently converged Chebyshev scalar quasinormal frequencies validate the WKB results and probe the exterior geometry beyond the leading horizon data. The calculation distinguishes branch-resolved horizon thermality, finite detector protocol, and exterior scalar dynamics.
[abstract 40 / 43] (score: 2) - Title: MUSE-ALMA Haloes XIV: The ALMA Large Programme Data ReleaseAuthors: Céline Péroux, Jianhang Chen, Victoria Bollo, Tamsyn O'Beirne, Capucine Barfety, Simon Weng, Ramona Augustin, Benedetta Casavecchia, Martin Zwaan, Linda Tacconi, Natascha Föster Schreiber, Laurent Chemin, Varsha Kulkarni,Comments: Accepted for publication in A&A in February 2026. We acknowledge that works relevant to these results have been published since then. Part of the MUSE-ALMA survey series, see simultaneously posted papers by Barfety et al. and O'Beirne et al. The reduced data are available here: https://almascience.eso.org/alma-data/lp/alma-muse/Subjects: astro-ph.GACreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
The interactions between gas and galaxies are of paramount importance to our understanding of structure formation. A fundamental element of such baryon cycle studies is a complete census of the condensed matter (stars and cold gas) in both galaxies and their immediate surroundings, the so-called circumgalactic medium. Of particular importance are the processes of converting molecular gas into stars and deciphering whether this <100K gas is tracing gas flows. The MUSE-ALMA Haloes survey has assembled probes of the neutral atomic gas HI, ionised gas and stellar component for a sample of 79 $z\sim0.5$ galaxies. This is achieved by combining absorption line spectroscopy of background QUASARs with projected impact parameter as low as 5 kpc and up to 250 kpc to probe the low density circumgalactic gas with emission line tracers of both ionised gas and stars. This paper presents the Large Programme observational set-up and releases the data characterising the molecular phase of some of the MUSE-ALMA Haloes targets so as to reach a complete census of their condensed baryons. ALMA's unique millimetre coverage and high sensitivity is ideal to characterise the CO emission of these $z\sim0.5$ HI-selected galaxies. By measuring the molecular mass, kinematics, gas flows and gas fractions, this project then: i) quantifies the role of molecular gas in HI-rich galaxies, ii) characterises the molecular phase of gas flows from morpho-kinematics analyses, and iii) establishes a census of the condensed baryons in the interstellar and circumgalactic media. Ultimately, these results will provide unique insights into the baryon cycle - a crucial component of galaxy formation.
[abstract 41 / 43] (score: 2) - Title: A Gravitationally Lensed Low-Luminosity AGN From The Cosmic NoonAuthors: Marko Mićić, Olivia Holmes, Xinyu Dai, Kevin Hainline, Haikun Xue, Zijun Gao,Comments: 6 pages, 3 figures, submittedSubjects: astro-ph.GA astro-ph.HECreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Strong gravitational lensing provides a unique tool of studying intrinsically faint high-redshift ACTIVE GALACTIC NUCLEi (AGN). In particular, low-luminosity AGN (LLAGN) can probe black-hole growth in low-mass galaxies that current X-ray surveys cannot otherwise access. We investigate the nature and physical properties of a faint X-ray source triply imaged by the galaxy cluster SDSS J2243$-$0935, and determine whether the source hosts an AGN. We combine archival Hubble Space Telescope imaging and Chandra X-ray observations with the published strong-lensing models of SDSS J2243$-$0935. We constrain the source redshift geometrically, derive magnification maps, and infer the physical properties of the host galaxy. The geometric lensing analysis gives a source redshift of $z=2.14^{+0.12}_{-0.17}$, consistent with the photometric redshift estimate, and a total magnification of $μ=78\pm7$. The source is triply lensed and detected only in the HST F160W band, with an intrinsic magnitude of $m_{\rm AB}=28.2\pm0.2$. The rest-frame optical emission implies a stellar mass of $8.6\lesssim\log(M_\star/M_\odot)\lesssim9.4$. The unobscured STAR FORMATION rate is constrained to $\mathrm{SFR}_{\rm UV}<0.009\,M_\odot\,\mathrm{yr}^{-1}$, although substantial dust obscuration remains possible. Chandra detects X-ray point-source counterparts to all three HST-detected lensed images. The combined X-ray spectrum contains $100\pm11$ net counts and is consistent with a moderately absorbed power law, with $Γ\simeq 1.48$ and $N_{\rm H}=(5.5\pm4.4)\times10^{22}\,\mathrm{cm}^{-2}$. After correcting for gravitational magnification, we obtain an intrinsic rest-frame $2$--$10$ keV luminosity of $L_{\rm X}=1.2\pm0.3\times10^{42}\,\mathrm{erg\,s^{-1}}$. The X-ray emission is likely dominated by an AGN hosted by a low-mass galaxy at $z\simeq2.14$, making this system a strongly lensed LLAGN at cosmic noon (abridged).
[abstract 42 / 43] (score: 2) - Title: A Decade-Scale Ionization Echo of Black-Hole Accretion in Galactic NucleiAuthors: Wei-Jian Guo, Shuo Zhai, Chen Hu, David M. Alexander, Bin Luo, Pu Du, Matthew J. Temple, Leah K. Morabito, Feige Wang, Jinyi Yang, Victoria A. Fawcett, Swayamtrupta Panda, Claire L. Greenwell, Yan-Rong Li, Cheng Cheng, Shengxiu Sun, Zhi-Qiang Chen, Alessandro Marconi, Jian-Min Wang,Comments: 29 pages, 16 figuresSubjects: astro-ph.GACreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
Circumnuclear structures in ACTIVE GALACTIC NUCLEi respond to accretion variability over different spatial and temporal scales, but whether compact narrow-line gas responds on decade timescales has not been systematically established. We use repeat Sloan Digital Sky Survey and Dark Energy Spectroscopic Instrument spectroscopy of 473 variability-selected galactic nuclei with evidence for recent nuclear brightening. We identify 19 sources whose narrow [O III] $\lambda5007$ flux increased by more than a factor of two over rest-frame baselines of 12.0-20.4 yr, which we term narrow-line ionization echoes (NIEs). In equal-weight stacked spectra, [O III] increased by $229\pm22\%$, while lower-ionization lines remained nearly unchanged or declined, indicating an ionization-dependent response rather than uniform spectral rescaling. The NIE hosts also moved coherently toward higher excitation in optical diagnostic diagrams, with mean increases of $0.46\pm0.18$ dex in $\log([\mathrm{O III}]/\mathrm{H}β)$ and $0.58\pm0.13$ dex in $\log([\mathrm{O III}]/[\mathrm{O II}])$. Photoionization models reproduce this evolution with a higher ionization parameter and a harder AGN-like ionizing spectrum at fixed gas abundance. For 13 sources with well-defined mid-infrared outbursts, the integrated W1+W2 excess energy correlates strongly with the absolute [O III] luminosity change ($r=0.87$), linking the dust and narrow-line responses to the same nuclear event. The mid-infrared timescale and spectroscopic baseline constrain the variable [O III]-emitting gas to characteristic scales of 1.5-5.2 pc. Compact narrow-line gas therefore appears to form an intermediate, decade-scale response layer between the infrared dust echo and the long-lived extended narrow-line region.
[abstract 43 / 43] (score: 2) - Title: Constraints on Primordial Oscillatory Features from the Power Spectrum and Bispectrum of Redshift-Space Galaxy Clustering in DESI DR1Authors: Shi-Fan Chen, Anton Chudaykin, Mikhail M. Ivanov, Oliver H. E. Philcox, Mario Ballardini,Comments: 18 pages, 7 figures, to be submitted to PRDSubjects: astro-ph.COCreated: 2026-10-07; Updated: 2026-10-08; Datestamp: 2026-10-08
We constrain oscillatory features in the primordial power spectrum using the public DESI DR1 galaxy and QUASAR clustering data. Our analysis is based on a custom pipeline for the redshift-space power spectrum and bispectrum of the six main DESI DR1 tracers, modeled with the Lagrangian effective field theory,which provides a principled resummation of the non-linear damping of the features. We consider oscillations that are linear and logarithmic in wavenumber, and, for the first time, consistently include the galaxy bispectrum in the search. We also study the dependence of the results on the background cosmology, which is important given the tension between the DESI BAO and \textit{Planck} data within the baseline cosmological model. Marginalizing over $Λ$CDM parameters, we bound the amplitude of linear and logarithmic oscillations to $A_{\rm lin}<0.033$ and $A_{\rm log}<0.035$ respectively (at 95$\%~$CL) across the frequency ranges $ω_{\rm lin}^{\rm phys}\in(20,800)~{\rm Mpc}$ and $ω_{\rm log}\in(2.5,80)$. The constraints reach percent-level precision away from the frequencies degenerate with the baryon acoustic oscillations (BAO). Fixing to the \textit{Planck} 2018 cosmology, the bounds tighten to $A_{\rm lin}<0.024$ and $A_{\rm log}<0.031$, but in this case we also find a $\simeq 3σ$ global preference for a logarithmic feature with $ω_{\rm log}\simeq 15$, dominated by the LRG2 sample, whose local wavelength matches the apparent BAO scale at wavenumbers best constrained by DESI. Since the preference for this feature disappears once the cosmological parameters are varied, we expect that it is a manifestation of the known distance-scale tension between the DESI and \textit{Planck} data rather than a primordial signal. Our analysis thus emphasizes the importance of cosmology marginalization in searches for primordial features.
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