Current date: 2026-08-17

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Datestamp limit: 2026-08-17 (0 days ago)

Created/updated limit: 2026-08-10 (7 days ago)

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OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-08-17&until=2026-08-17&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 562

Keyword score statistics

score 11 -- 1 abstracts

score 10 -- 1 abstracts

score 9 -- 2 abstracts

score 5 -- 3 abstracts

score 4 -- 2 abstracts

score 3 -- 7 abstracts

score 2 -- 15 abstracts

in total -- 31 abstracts

Articles that appeared on 2026-08-17

[abstract 1 / 31] Wow! (score: 11)
arXiv:2608.12380 [pdf, ps, other]

Title: Synchrotron and Inverse-Compton Signatures of Black to White Hole Explosions: Weibel-Mediated External Shocks in the Interstellar Medium

Authors: Hoang Van Quyet,

Comments: 15 pages, 7 figures,2 tables

Subjects: astro-ph.HE gr-qc

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

We study the non-thermal electroMAGNETic counterpart expected when the RELATIVISTIC, near-isotropic ejecta of a black-to-white hole transition sweep up the interstellar medium (ISM). Building on a photospheric model for the prompt $γ$-ray emission~\cite{Villani2026}, we parametrize the kinetic energy available for an external shock, $\eiso=R_k\egprompt$, and model the resulting collisionless forward shock with a Weibel-mediated field~\cite{Weibel1959,MedvedevLoeb1999,SironiSpitkovsky2011}. We estimate the SYNCHROTRON and SYNCHROTRON self-Compton (SSC) emission from shock-accelerated electrons in a one-zone, Thomson-regime approximation, including inverse-Compton cooling, Klein-Nishina suppression, self-absorption, and $γ$-$γ$ opacity, all at order-of-magnitude or first-order accuracy. For illustrative parameters ($\egprompt\sim10^{44}$ erg, $R_k=0.1$, $Γ_0=100$), the electrons are slow-cooling, so for $p=2.5<3$ the SYNCHROTRON spectrum peaks at the cooling frequency $ν_c$, in the MeV-to-GeV range and softening with time; the afterglow evolves in a fraction of a second to tens of seconds -- orders of magnitude faster than a classical long-duration GRB afterglow at comparable energy, density, and Lorentz factor -- with duration, peak energy, and flux depending sensitively on $R_k$, $\nism$, and $\epse,\epsB,\xie$. We identify parameter regions where a 1 keV photon-count estimate, below the intrinsic peak, exceeds a nominal detection threshold, and discuss features -- a fast, faint, roughly isotropic transient after a hard-spectrum prompt flash, without an achromatic JET break -- that may distinguish this scenario from short GRBs, MAGNETar giant flares, and other fast transients, while flagging the assumptions (forward-shock-only dynamics, one-zone Thomson-regime radiation, an illustrative detectability criterion) limiting its quantitative reach.

[abstract 2 / 31] Wow! (score: 10)
arXiv:2608.14258 [pdf, ps, other]

Title: Launching Jets in Tidal Disruption Events: Magnetic Flux Advection and Plasma Loading

Authors: Rin Oikawa, Yuri Sato,

Comments: 9 pages, 2 figure

Subjects: astro-ph.HE

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

A tidal disruption event (TDE) occurs when a star approaches a BLACK HOLE (BH) and is disrupted by its tidal forces. Although several hundred TDEs have been identified to date, only a small fraction are accompanied by RELATIVISTIC JETs. These JETs are thought to be Poynting-flux-dominated outflows powered by the Blandford--Znajek (BZ) mechanism. However, the origin of the MAGNETic flux and plasma needed to power BZ JETs remain unclear. In this Letter, we propose a scenario in which MAGNETic flux is initially stored in a pre-existing low-Eddington accretion disk around BH, and is subsequently advected toward the BH by the super-Eddington accretion flow formed after the stellar disruption. We show that stars with low densities, such as red giants, can supply sufficient MAGNETic flux to power a BZ JET. Once sufficient MAGNETic flux accumulates near the BH, an equatorial current sheet forms where MAGNETic RECONNECTion produces high-energy gamma rays. We find that photon--photon pair production by these gamma rays supplies the BH MAGNETosphere with sufficient plasma to launch and sustain a BZ JET. We further show that this mechanism simultaneously provides enough radiating particles to account for the observed prompt emission.

[abstract 3 / 31] Wow! (score: 9)
arXiv:2607.05246 [pdf, ps, other]

Title: The emergence of X-ray emission lines during RELATIVISTIC radio-JET formation in the changing-look ACTIVE GALACTIC NUCLEus 1ES 1927+654

Authors: Dev R. Sadaula, Sibasish Laha, Eileen T. Meyer, Onic I. Shuvo, Main Pal, Ritesh Ghosh, Matteo Guainazzi, Fabio Pacucci, Stefano Bianchi, Luigi Gallo, Rostom Mbarek, Amelia M. Hankla, Fabio La Franca, Tahir Yaqoob, Megan Masterson, Erin Kara, Missagh Mehdipour, Claudio Ricci, Javier A Garcia, Timothy R. Kallman, Ralf Ballhausen, Mitchell C. Begelman, Alexander Philippov, Suvendu Rakshit, Francesca Panessa, Ehud Behar, S. Bradley Cenko, Federica Ricci, Ilaria Villani, James N. Reeves,

Comments:

Subjects: astro-ph.HE astro-ph.GA hep-ph

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

We present results from a comprehensive multi-wavelength monitoring campaign of the changing-look ACTIVE GALACTIC NUCLEus 1ES 1927+654 during the onset and evolution of a RELATIVISTIC radio JET $\sim$(May 2022 - August 2025), using observations from XMM-Newton, SWIFT, TNG, ZTF, VLA, and VLBA. The soft X-ray emission lines at $\sim 0.56$ keV and $\sim 1$ keV have appeared with variable strength and width during the formation of the nascent JET. We note that the $\sim 1$ keV feature has been persisting since the post-2017 flare phase. We also report the detection of a broad ($\sim 800$ eV) FeK emission feature at $(6-7)$ keV in the $\sim 70$ ks stacked EPIC-pn spectra, marking the first such detection, which historically was lacking in this source. The joint spectral fitting of XMM-Newton EPIC-pn and RGS data reveals the presence of ionized absorbers in 2022 ($\log{ξ\mathrm{/erg\ cm\ s^{-1}}}\sim 1.5\pm 0.3$, $\mathrm{N_H} \sim 2.5\pm 0.9\times 10^{20} \mathrm{cm^{-2}}$), but weaker than that detected during the high accretion state in 2018 (Eddington ratio, $λ_{\rm Edd}>1$). The absorption features further weakened in 2023-2025 and were marginally detectable ($\mathrm{N_H} \le 10^{20}\mathrm{cm^{-2}}$). The entire scenario is suggestive of a real-time transition of the accretion flow (from $λ_{\rm Edd}>1$ to $λ_{\rm Edd}\sim 0.3$) during which the winds become weaker and the JET starts to form and evolve. Furthermore, both the soft X-ray $(0.3-2)$ keV and 5 GHz radio fluxes, which increased by factors of $\sim 10$ and $\sim 60$, respectively, since 2022, have recently plateaued at elevated levels, indicating a stabilized accretion disk, corona, and JET configuration.

[abstract 4 / 31] Wow! (score: 9)
arXiv:2608.14412 [pdf, ps, other]

Title: Optical Spectroscopy of TeV-emitting BL Lac Candidates

Authors: Cassidy Metzger, Ryan C. Hickox, John R. Thorstensen,

Comments:

Subjects: astro-ph.HE

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

TeV-emitting BL Lacertae (BL Lac) BLAZARs have important implications for the study of JET phenomenology, particle acceleration, and ultra high-energy COSMIC RAY production. They also allow for indirect studies of the extragalactic background light, cosmic MAGNETic fields, and axion-like particles. The upcoming Cherenkov Telescope Array (CTA), a ground-based gamma-ray observatory, will expand the observed TeV-emitting BL Lac population and enhance the aforementioned fields of study. However, reliable redshifts are crucial for planning and interpreting observations with CTA and only about 50% of gamma-ray BL Lacs have spectroscopic redshifts. We performed medium resolution optical spectroscopy of 16 TeV-emitting BL Lac candidates with the SALT and MDM telescopes. We measured spectroscopic redshifts for the full sample, ranging from 0.059 to 0.4, including 5 new spectroscopic redshift measurements.

[abstract 5 / 31] Yes (score: 5)
arXiv:2608.13645 [pdf, ps, other]

Title: Observational Constraints on Horizonless Compact Objects from Thermal Emission in AGNs

Authors: Ekin Oran, Avery Broderick, Kiana Salehi,

Comments:

Subjects: astro-ph.HE

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

The SWIFT Burst Alert Telescope Active Galactic Nuclei Spectroscopic Survey (BASS DR2) provides one of the largest and most complete samples of bright, local (z < 0.1) ACTIVE GALACTIC NUCLEi (AGNs) with high-quality spectroscopic measurements. These sources are typically interpreted within the framework of Kerr BLACK HOLEs; however, a wide range of horizonless compact-object scenarios-including naked singularities, BLACK HOLE mimickers, and other exotic compact objects-have been proposed as alternatives. Largely independent of the physics of the particular horizonless model invoked, an accretion powered, thermally radiating photosphere is expected to develop on astronomically short timescales. In this paper, we investigate whether the presence of such a photosphere is consistent with the observed properties of an appropriate subsample of BASS AGNs. We find that in no instances is such a spectral feature present, and can exclude its existence in significant fraction of objects. For the remaining sources, modest improvements in observational sensitivity and spectral coverage could enable robust exclusion. Our results extend previous horizon-scale tests performed for M87* and Sgr A* to a large AGN population, providing strong, population-level evidence against horizonless alternatives. We conclude by outlining future observational strategies that can further tighten these constraints and significantly increase the number of objects for which horizons are required.

[abstract 6 / 31] Yes (score: 5)
arXiv:2608.13697 [pdf, ps, other]

Title: The second Arcminute Microkelvin Imager -- Large Array Gamma-ray burst radio afterglow catalog

Authors: L. Rhodes, D. Ibrahim, N. Sqalli, G. E. Anderson, R. Fender, A. J. van der Horst, J. S. Bright, A. K. Hughes, D. R. A. Williams-Baldwin, D. A. Green, D. Haggard, A. Horesh, Y. Perrott, P. Scott, T. Staley, D. Titterington,

Comments: 25 pages and 20 figures (included appendices). Submitted to ApJ

Subjects: astro-ph.HE

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

Radio observations of GAMMA-RAY BURST afterglows provide insight in to the different emitting regions within the JET, its hydrodynamics and burst environment. In this paper, we present the second iteration of the Arcminute Microkelvin Imager - Large Array (AMI-LA) Gamma-ray burst (GRB) radio afterglow catalog. The catalog consists of 1035 observations of 210 bursts. Our observations range from 0.04 to 900days post-burst. We detect radio emission associated with 19 events with flux densities spanning 0.1-40mJy, and present a detailed analysis of six events whose light curves have not been published elsewhere. In our individual afterglow analyses, we find that our radio counterparts show evidence of reverse shock emission 60% of the time. Two of the detected afterglows show evidence of scintillation which we use to place source size limits at tens of days. Of the whole catalog, 50 events have redshift measurements which we use to find the radio afterglow luminosity distribution for our sample. Our luminosity distribution spans five orders of magnitude, a larger range than seen in optical and X-ray bands, indicative of the strong dependence of the radio counterparts on the GRB's physical parameters.

[abstract 7 / 31] Yes (score: 5)
arXiv:2608.14547 [pdf, ps, other]

Title: Cosmic Ray Diffusion and the Origin of Very High Energy Gamma-Ray Emission in Young Massive Stellar Clusters

Authors: Lucas Barreto-Mota, Elisabete M. de Gouveia Dal Pino, Gaetano Di Marco, Rafael Alves Batista, Stela Adduci Faria,

Comments:

Subjects: astro-ph.HE

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

The search for Galactic sources capable of accelerating COSMIC RAYs (CRs) to PeV energies has advanced significantly in recent years. High-energy observatories such as LHAASO have detected extended gamma-ray halos around several sources, suggesting that CRs escape their acceleration sites through anomalously slow diffusion. Theoretical studies propose that MAGNETic mirror diffusion combined with pitch-angle scattering in turbulent flow can naturally suppress CR transport. Here, we first show how mirror diffusion combined with scattering suppresses cosmic-ray transport, leading to an energy-dependent diffusion coefficient $D(E)\propto E^{1/3}$. We then combine a 3D MAGNETohydrodynamic (MHD) simulation of a young massive stellar cluster (YMSC) with Monte Carlo CR propagation calculations (CRPropa). The model includes the background gas density, MAGNETic field, stellar blackbody and dust emission, the cosmic microwave background, and the Galactic interstellar radiation field. Using the YMSC W43 as a benchmark, we compare two CR injection geometries: a central source and a spherical shell representing the cluster's collective wind shock. We show that mirror+scattering diffusion $D(E)\propto E^{1/3}$, combined with a CR injection spectrum $E^{-2}$, reproduces the gamma-ray spectrum observed by FERMI and LHAASO. In contrast, stronger energy-dependent diffusion requires a harder CR injection spectrum, $\sim E^{-1.6}$, to match the data. The relative contributions of leptonic inverse-Compton and hadronic emission depend sensitively on the diffusion regime. Finally, the resulting spectra show little dependence on the CR injection location, aside from a lower injection luminosity in the central-source case. Overall, our results indicate that the observed gamma-ray emission is shaped primarily by the diffusive propagation regime rather than by the precise location of the CR source.

[abstract 8 / 31] Yes (score: 4)
arXiv:2608.13680 [pdf, ps, other]

Title: High-Energy Neutrinos from Supernova Shock Breakouts in Circumstellar Media: Light Curves, Spectra, and Contribution to the Extragalactic Neutrino Background

Authors: Tal Wasserman, Eli Waxman, Kohta Murase,

Comments: Submitted to ApJ, comments welcome

Subjects: astro-ph.HE

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

Enhanced mass loss from core-collapse SUPERNOVA (SN) progenitors shortly before explosion appears to be common, creating a compact, optically thick circumstellar medium (CSM) at $\sim10^{14}-10^{15}$ cm. We derive an analytic description of the light curves and spectra of high-energy neutrinos emitted by nonRELATIVISTIC SN shock breakouts through such CSM, as a function of shock velocity and CSM parameters, accounting for the evolution of the hydrodynamic structure and the electroMAGNETic (EM) spectrum as the shock transitions from being radiation-mediated to collisionless. This evolution determines the time-dependent neutrino production efficiency, the maximum proton/neutrino energy, and the pair-production optical depth. A significant fraction of the neutrino energy is typically emitted within a few days of explosion, during breakout and before the EM light curve peak, with $1-100$ TeV neutrinos carrying $\approx10\%$ of the energy of shock-accelerated protons. The escape of high-energy photons ($>1$~GeV) is suppressed by pair-production for compact CSM configurations. If enhanced mass losses are common, and assuming that shock-accelerated protons carry $\approx10\%$ of the collisionless shock energy, CSM SN breakouts may significantly contribute to the observed high-energy neutrino background, without overproducing a corresponding high-energy gamma-ray background. SNe producing $>1$ neutrino events in a $1\left(10\right){\rm km^2}$ detector are expected at a rate of $\sim0.05\left(1\right){\rm yr^{-1}}$.

[abstract 9 / 31] Yes (score: 4)
arXiv:2608.14010 [pdf, ps, other]

Title: Detection of possible burst oscillation in the neutron star low-mass X-ray binary 4U 1323-62

Authors: Manoj Mandal, Sachindra Naik,

Comments: Accepted for publication in ApJ

Subjects: astro-ph.HE

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

Burst oscillations observed during thermonuclear X-ray bursts arise from asymmetric brightness patterns on the neutron star surface and provide a direct probe of the neutron star spin frequency. We present a detailed timing analysis of the neutron star low-mass X-ray binary 4U 1323-62 using 2024 observations with XMM-Newton and NUSTAR observatories. We identify nine thermonuclear X-ray bursts in the XMM-Newton/EPIC-pn data, along with eclipsing dips in the light curve. One of the XMM-Newton bursts exhibits a rare doublet structure. In addition, NUSTAR detects six bursts, four of which occur simultaneously with those observed with XMM-Newton. We identify a possible burst oscillation signal at $\sim$611.5 Hz in the XMM-Newton data. The strongest oscillation, detected during the primary burst of the doublet burst, reaches a maximum $Z_1^{2}$ power of $\sim35$. An analytical estimate accounting for the searched frequency and time intervals gives a significance of $\sim3.0σ$, whereas independent Monte Carlo simulations yield a more robust global significance of only $\sim2.4σ$. We therefore interpret the signal as a tentative detection of burst oscillation. The folded pulse profile in the 0.5-10 keV band is well described by a sinusoid, with a fractional rms amplitude of $\sim30\pm6$%. The oscillation frequency corresponds to a neutron-star spin period of $\sim$1.635 ms, suggesting that 4U 1323-62 may harbor a rapidly rotating millisecond neutron star.

[abstract 10 / 31] (score: 3)
arXiv:2601.02812 [pdf, ps, other]

Title: Beyond Sgr A* and M87*: Sub-Microarcsecond Black Hole Shadow Detection via Lunar-based Extremely Long Baseline Interferometry

Authors: Shan-Shan Zhao, Ru-Sen Lu, Lei Liu, Zhiqiang Shen, Yosuke Mizuno,

Comments:

Subjects: astro-ph.GA astro-ph.IM

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

The 1.3 mm ground-based very long baseline interferometry (VLBI) array Event Horizon Telescope (EHT), is limited by Earth's diameter, restricting horizon-scale imaging to only M87* and Sgr A*. Extending baselines to the Moon would achieve ~0.7 microarcsecond angular resolution at 230 GHz, enabling shadow detection for many more supermassive BLACK HOLEs (SMBHs). The concept is motivated by space VLBI missions and lunar exploration, including the ongoing Lunar Orbit VLBI EXperiment (LOVEX) aboard QueQiao-2 (Chang'E-7) and the planned International Lunar Research Station (ILRS). We assess shadow detectability for 31 SMBHs with predicted large angular sizes, assuming optically thin emission at 230 GHz, exploring different telescope locations and antenna sizes. Assuming a telescope at the lunar antipode, we simulate the Moon-Earth (u,v) coverage and show that sources near the Moon's orbital plane yield projected baselines spanning a wide range, enabling sampling of the first visibility null - a key shadow signature. Using a geometric ring model, we identify six shadow-detectable candidates: M104, NGC 5077, and NGC 1052 are detectable with a 5 m lunar-based telescope; PGC 049940 with 10 m; NGC 524 with 20 m; and NGC 5252 with 40 m. If additional space telescopes fill the baseline coverage gaps between Moon and Earth, 14 candidates are detectable for the n=1 photon-ring region with a lunar-based telescope up to 40 m. These results provide a clear scientific and technical motivation for lunar-based telescopes in future BLACK HOLE shadow studies.

[abstract 11 / 31] (score: 3)
arXiv:2606.26231 [pdf, ps, other]

Title: 3D Kinematic Reconstruction of the Crab Nebula That Includes the Northern Ejecta `Jet'

Authors: Ziwei Ding, Dan Milisavljevic, Thomas Martin, Tea Temim, John C. Raymond, Soham Mandal, Laurent Drissen,

Comments: 23 pages, 15 figures, now published in ApJ. Animations available at https://doi.org/10.5281/zenodo.20822317 and https://www.youtube.com/watch?v=Pi7XSaW6ZPo

Subjects: astro-ph.HE

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

We present new detailed three-dimensional kinematic reconstructions of the Crab Nebula created from hyperspectral cubes obtained with the SITELLE instrument mounted on the Canada--France--Hawaii Telescope. Our data cubes span a wavelength range from 3600Å to 7000Å, covering major emission lines including [O II] $λλ$3726, 3729, H$β$, [O III] $λλ$4959, 5007, [N II] $λ$5755, He I $λ$5876, [N II] $λλ$6548, 6584, [S II] $λλ$6717, 6731, and H$α$. The field of view encompasses the ``chimney" or ``JET," a 45-arcsec-wide funnel-shaped structure that extends 100 arcsec beyond the northern limb of the nebula. Our 3D reconstructions confirm and geometrically resolve a cavity at the JET's base that was suggested by earlier kinematic studies, establishing a direct physical connection between the filamentary network and the JET funnel. The morphology and kinematics indicate that the early pulsar wind nebula (PWN) played a central role in forming the JET. Several formation scenarios, which are not necessarily mutually exclusive, remain viable, including a bipolar outflow shaped by a circumstellar disk, a breach or underdensity in the ejecta shell, and a pre-existing progenitor mass-loss trail acting as a low-density channel. Collectively, these scenarios exhibit differing abilities to account for the JET's pronounced collimation, the absence of a southern counterpart, and its near-ballistic motion. Discriminating among them will require fully three-dimensional hydrodynamic simulations that trace the remnant's evolution from the progenitor phase through late-time PWN expansion.

[abstract 12 / 31] (score: 3)
arXiv:2607.07795 [pdf, ps, other]

Title: The incidence of eROSITA X-ray AGN in the local Universe: from dwarf to massive galaxies

Authors: Z. Igo, A. Merloni, A. Georgakakis, J. Buchner, R. Arcodia, M. Salvato, J. Aird, K. Nandra, B. Trakhtenbrot, P. G. Boorman, J. Comparat, G. Lamer, B. Laloux, M. Kluge, W. Roster, E. Bulbul, F. Balzer, T. Dwelly, W. N. Brandt, R. Seppi, S. Morrison, E. Kyritsis, J. Gelfand, S. F. Anderson, D. P. Schneider,

Comments: 27 pages, 20 figures; accepted for publication in A&A

Subjects: astro-ph.GA astro-ph.HE

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

Combining deep, wide-area X-ray surveys with multi-wavelength catalogues provides insights into rare, highly-accreting AGN and low-mass galaxies at low redshift, the latter potentially representing local analogues of the first galaxies in the early Universe. We use the four-pass eROSITA All Sky Survey to select the largest catalogue of X-ray AGN in a highly complete sample of low-redshift galaxies, including low-mass (logM*/Msol<10) ones. We probe their distribution of specific accretion rates, $λ$_SAR, and the cumulative AGN fraction above varying $λ$_SAR thresholds. Our parent sample consists of ~5.35 million galaxies selected from the Legacy Survey DR10 with z-band fluxes brighter than 20 mag and redshifts 0.03AGN in low-mass galaxies, most of them newly discovered as X-ray emitters. Thanks to a Bayesian framework that makes use of the X-ray information from all parent sample galaxies, we constrain the specific accretion rate distribution, p(log$λ$_SAR | M*, z), across a wide range of $λ$_SAR and uncover second-order mass-dependent effects. We detect a break at high $λ$_SAR, possibly indicating Eddington-limited, self-regulated BLACK HOLE growth. Integrating p(log$λ$_SAR | M*, z) above $λ$_SAR>10^-3, we find a cumulative AGN fraction of ~1% for low-mass galaxies, placing a firm lower limit on the BLACK HOLE occupation fraction in this regime. Overall, our specific accretion rate distributions, sampling down to the as-of-yet unexplored low-mass regime, highlight a more nuanced, mass-dependent view of AGN growth and accretion history that must be taken into account in future modelling.

[abstract 13 / 31] (score: 3)
arXiv:2608.13641 [pdf, ps, other]

Title: Orbital Migration of Interacting Stellar Mass Black Holes in Disks around Supermassive Black Holes. III. Mass Distribution of Hierarchical Mergers

Authors: Katherine L. Gonglewski, Amy Secunda, Mordecai-Mark Mac Low, K. E. Saavik Ford, Barry McKernan, Fabian R. N. Schneider,

Comments: 18 pages, 10 figures, submitted to ApJ

Subjects: astro-ph.GA astro-ph.HE

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

Active galactic nucleus (AGN) disks are a promising location for the formation of binary BLACK HOLEs (BBHs) that will merge on relatively short timescales and be detected by LIGO-Virgo-KAGRA (LVK). To compare the mass function (MF) of BLACK HOLEs (BHs) undergoing hierarchical mergers in AGN disks to the inferred MFs from LVK observations, we perform 360 simulations with an N-body code augmented to include an analytic model for migration torques and other gas forces. We focus on the region surrounding migration traps in AGN disks where migration torques cancel out and BHs converge. We find that regardless of changes in the initial MF and BBH merger criteria, frequent mergers deplete the number of BHs with masses $\lesssim 10$~$M_\odot$ and fill the upper mass gap with a roughly uniform distribution from 40--100~$M_\odot$, with a slight overabundance around ${\approx}70~M_\odot$ from resonant orbiters. We also find an average merger rate of $\sim 6$~Gpc$^{-3}$~yr$^{-1}$ for migration-trap-aided BBH mergers in our AGN disk model. $\sim 40\%$ of these mergers have uneven mass ratios and 16\% have a primary mass $\in[50-100]~M_\odot$. Therefore, AGN disks could easily be the source of BBH mergers observed by LVK that are difficult to produce through traditional stellar evolution channels. Our simulations also form a separate higher-mass intermediate mass BLACK HOLE (IMBH) population $>200~M_\odot$ after $\sim 2$~Myr. Future gravitational wave detectors can use observations of this IMBH population to constrain models of AGN accretion disks.

[abstract 14 / 31] (score: 3)
arXiv:2608.13642 [pdf, ps, other]

Title: Explosions from Rotating Very Massive Star Collapses to Black Holes: Effects of Nuclear Burning

Authors: Sho Fujibayashi, Alan Tsz-Lok Lam, Yuichiro Sekiguchi, Masaru Shibata,

Comments: 23 pages, 13 figures. Submitted to ApJ

Subjects: astro-ph.HE gr-qc

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

We investigate the collapse of rotating very massive and supermassive stellar cores using numerical relativity simulations including an alpha-chain nuclear reaction network and neutrino cooling. Our main survey focuses on newly constructed models with initial core masses of $2 \times {10}^{3}-5\times 10^4M_\odot$. The collapse is triggered either by pair instability in lower-mass cores or by general-RELATIVISTIC instability in higher-mass cores. We find that higher-mass cores undergo a nearly homologous collapse, whereas lower-mass cores show a more runaway-like collapse because neutrino cooling becomes more efficient at their higher densities and temperatures. Consequently, the BLACK HOLE formed in lower-mass models initially contains a smaller fraction of the core mass, and disk formation occurs while a larger amount of matter remains outside the BLACK HOLE. The lower compactness of pair-unstable cores also allows larger dimensionless angular momentum, favoring the formation of rapidly rotating BLACK HOLEs and massive disks. The disk bounce drives mass ejection with ejecta masses of order $10-10^3M_\odot$ and kinetic energies of order $10^{53}-10^{55}\,\mathrm{erg}$. Significant $^{56}$Ni production in the disk-bounce ejecta occurs only in the lowest-mass models. For selected models, we further follow the viscous evolution of the disk and find that viscosity enhances the ejecta mass and kinetic energy. In models with $\lesssim10^4M_\odot$, the viscosity-driven ejecta can originate from disk matter that has reached nuclear statistical equilibrium and can therefore become rich in $^{56}$Ni. These results suggest that rotating very massive star collapses can produce massive, energetic ejecta and, for sufficiently low core masses, substantial iron-group elements.

[abstract 15 / 31] (score: 3)
arXiv:2608.13653 [pdf, ps, other]

Title: Radio Properties of RS Canum Venaticorum Variables in VLASS and RACS

Authors: Suhasini S. Rao, Gregory R. Sivakoff, Craig O. Heinke, Swetha Arumugam, Dougal Dobie, Laura Driessen, David L. Kaplan, Emil Lenc, Joshua Pritchard,

Comments: 26 pages, 12 figures, 2 MRT tables (Tables 2 & 3), Accepted for publication in ApJ

Subjects: astro-ph.SR astro-ph.HE

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

We performed a systematic search for radio emission from RS Canum Venaticorum (RS CVn) binaries, selected from the International Variable Star Index (VSX) catalog, in the Very Large Array Sky Survey (VLASS; three epochs) and Rapid ASKAP Continuum Survey (RACS; two epochs) data. We detected 108 candidate radio-emitting RS CVn in at least one epoch. Several of these systems rank among the most radio-luminous RS CVn binaries reported to date. The radio and X-ray luminosities, obtained from cross-matching with the eROSITA and ROSAT X-ray catalogs, are consistent with the Guedel-Benz relation for MAGNETically active stars, but are also comparable to radio-luminous quiescent BLACK HOLE X-ray binaries, indicating a potential for misidentification between these two classes. Analysis of optical, radio, and stellar properties indicates that optically bright RS CVn (i.e., those with at least one giant component) are radio-quieter and have periods that are consistent with lower coronal activity. However, two of these optically bright RS CVn systems show persistent and unusually high radio specific luminosities (>2e17 erg/s/Hz) across all observed epochs, showing that stellar activity can produce relatively persistent radio signals as bright as quiescent BLACK HOLE binaries.

[abstract 16 / 31] (score: 3)
arXiv:2608.14151 [pdf, ps, other]

Title: Physics of Circular Polarized Ion-Scale Waves in Hybrid Simulations of Alfvénic Fluctuations

Authors: Hai Yang Harry Qian, Trevor A. Bowen, Carlos A. Gonzalez, Nikos Sioulas, Alfred Mallet, Kristopher G. Klein, Daniel Verscharen, Stuart D. Bale,

Comments: 16 pages, 8 figures, accepted in The Astrophysical Journal

Subjects: physics.plasm-ph astro-ph.SR

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

Ion cyclotron waves (ICW) and fast MAGNETosonic/whistler waves (FMW) are fundamental electroMAGNETic modes at ion kinetic scales, yet their generation mechanisms and roles in plasma evolution remain poorly understood. We analyze a 2.5D hybrid simulation of broadband Alfvénic fluctuations, where the proton velocity distribution is modeled as a sum of two bi-Maxwellian components: a thermal core and a drifting beam. Using wavelet-based wave identification, bi-Maxwellian VDF fitting, and the PLUME linear dispersion solver, we find that ICW behave as linear modes. Growth is intermittent, occurring when core temperature anisotropy builds up, and is driven mainly by the core (the beam contributes negligibly). Poynting flux analysis shows that ICW are predominantly forward-propagating, with a net energy flux ratio of $+1$ across all frequencies, consistent with the initial condition. FMW present a stark contrast: PLUME solutions often yield very small (near-zero) linear growth/damping rates. The species decomposition breaks down when $|γ/ω_r| \gtrsim 0.368$, indicating that linear theory predicts these waves to be strongly damped and not describable by linear eigenmodes. Nevertheless, FMW are clearly observed in the wavelet helicity spectrogram, indicating that they are generated by nonlinear processes (e.g., parametric decay or phase steepening) and persist despite linear damping. The net energy flux ratio for FMW is close to $+1$ at low frequencies but decreases at higher frequencies, yet never reaches zero (net energy flow remains forward). These results demonstrate that ICW are linear, core-driven waves that transfer energy to the plasma, while FMW are heavily damped, nonlinearly generated waves.

[abstract 17 / 31] (score: 2)
arXiv:2512.14773 [pdf, ps, other]

Title: Achromatic, spin-odd Kerr EVPA as a null Frenet-Serret torsion integral on the photon ring

Authors: M. Baran Ökten,

Comments: 20 pages, 5 figures

Subjects: gr-qc astro-ph.GA astro-ph.HE

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

We compute the achromatic gravitational imprint that Kerr spacetime leaves on linear POLARIZATION at the photon ring. Recasting parallel transport in a null Frenet--Serret frame yields a single scalar evolution law for the electric-vector position angle. On the observer's screen, the Kerr-minus-Schwarzschild pattern on the direct critical curve is nonzero, strictly odd under spin reversal after a half-turn azimuth relabelling, and tightly confined to a thin annulus. Using backward-shot, Carter-separated geodesics with midpoint RK2 transport, we achieve second-order convergence and degree-scale amplitudes that grow monotonically with spin and inclination (RMS $\simeq 0.5$--$2^\circ$ for $a/M\gtrsim 0.8$, $i\gtrsim 60^\circ$). Three independent constructions -- Frenet--Serret line integral, explicit Levi--Civita transport of the POLARIZATION vector, and the phase of the Walker--Penrose constant -- agree ray by ray. We then define a parity-odd ring estimator that is intrinsically achromatic after standard wavelength-squared regression, symmetry-protected against common even-parity systematics, and compressed into low azimuthal modes. This yields a minimal two-parameter template (spin and inclination) for mm/sub-mm polarimetry of horizon-scale rings in sources such as M87$^\ast$ and Sgr~A$^\ast$. The pipeline enables either a detection of the strong-field parallel-transport phase induced by frame dragging or informative upper limits.

[abstract 18 / 31] (score: 2)
arXiv:2604.17524 [pdf, ps, other]

Title: Sachs Equations and Plane Waves VI: Penrose Limits

Authors: Jonathan Holland, George Sparling,

Comments: v2: 17 pages. Substantially revised: the canonical soldering theorem is sharpened by separating the intrinsic graded Penrose datum from its neighborhood realizations, which form a higher-order gauge torsor

Subjects: gr-qc

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

Let $(M,g)$ be a Lorentzian manifold whose local space $\mathcal N$ of unparametrized null geodesics is smooth. We show that its Penrose limits assemble into a smooth bundle of plane-wave germs with a canonical gauge-theoretic soldering to spacetime. The incidence correspondence $\mathcal U=\{(x,[γ]):x\inγ\}$ identifies the contact space modulo the tangent space to the sky of $x$ with the screen space at $x$, and identifies the contact line with the weight-two null quotient. These evaluation maps solder the associated-graded Penrose model. A first JET of contact scale fixes the affine scale and a Reeb representative of the weight-two direction. Above the resulting pullback of $J^1\mathcal S$, full neighborhood realizations form a torsor under the group $\mathscr G_>$ of weighted diffeomorphism germs with identity principal part. We also identify the sky-parabolic reduction and its further transverse-Lagrangian reduction to Rosen gauges. The reduction fails precisely where the chosen Lagrangian meets the moving sky, which is the Rosen caustic locus. The trace of the Grassmannian Schwarzian of the sky curve defines a conformally natural projective structure on each null geodesic, and its trace-free part is the Weyl tidal profile of the Penrose germ.

[abstract 19 / 31] (score: 2)
arXiv:2605.27953 [pdf, ps, other]

Title: Probing Effective Field Theory Corrections with Quasinormal Modes and Gravitational Lensing in Reissner-Nordström Black Holes

Authors: Takamasa Kanai,

Comments: 22 pages, 4 figures

Subjects: gr-qc hep-th

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

Effective field theory (EFT) provides a systematic framework for parametrizing possible higher-energy corrections to general relativity through higher-curvature interactions. In this work, we investigate gravitational lensing in both weak- and strong-field regimes for EFT-corrected Reissner-Nordström BLACK HOLE spacetimes, focusing on both weakly charged and near-extremal configurations. Using the strong deflection limit formalism, we derive the corresponding corrections to the deflection angle, photon sphere radius, critical impact parameter, and strong lensing coefficients induced by higher-derivative curvature-electroMAGNETic interactions. Our analysis is restricted to purely geometrical corrections associated with modifications of the background spacetime geometry, without including POLARIZATION-dependent corrections to the photon propagation law. We show that strong gravitational lensing observables in charged BLACK HOLE backgrounds can provide complementary probes of effective interactions between gravity and electroMAGNETic fields. These results suggest that future high-precision observations of strong lensing phenomena may place constraints on higher-curvature EFT couplings beyond general relativity.

[abstract 20 / 31] (score: 2)
arXiv:2606.26250 [pdf, ps, other]

Title: Prediction for IMAP: Revealing the Role of the Solar Magnetic Field in the Heliotail

Authors: M. Kornbleuth, M. Opher,

Comments: Submitted to ApJL

Subjects: astro-ph.SR

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

The classic paradigm of the heliosphere considered the solar MAGNETic field as having a passive role in the heliosheath, yet Opher et al. (2015) and Drake et al. (2015) suggested that the solar MAGNETic field plays an active role by collimating the solar wind plasma. Previous work has suggested that high-latitude lobes observed by IBEX-Hi energetic neutral atom (ENA) maps are solely due to the fast/slow solar wind profile, yet other works have found that the solar MAGNETic field may play a role in organizing the lobes as well. Here, using an MHD solution with and without the solar MAGNETic field, we find that the fast/slow wind profile largely dictates the ENA profile up to $\sim$10-18 keV. Beyond this energy, the collimation effects are more prominent and the fast/slow solar wind profile no longer organizes the maps. The collimation creates two high latitude lobes. By 80 keV, the heliosphere with collimation yields an enhancement of ENAs of the high-latitude tail lobes compared to the low-latitude region by a factor of $\gtrsim$ 1.3, whereas the uncollimated heliosphere yields a ratio $<$ 1. Therefore, IMAP should be able to identify whether the solar MAGNETic field collimates the solar wind in the deep heliotail.

[abstract 21 / 31] (score: 2)
arXiv:2607.07943 [pdf, ps, other]

Title: Nonlinear hydrodynamics in spinning neutron stars: Theoretical universal relations and equilibrium solutions

Authors: Hang Yu, Giorgio Nicolini, Shu Yan Lau, K. J. Kwon, Tejaswi Venumadhav, Nils Andersson, Pantelis Pnigouras, Fabian Gittins, Amlan Nanda,

Comments: 43 pages, 11 figures, to be submitted

Subjects: gr-qc astro-ph.HE

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

We study tides during the inspiral of a binary neutron star system, including nonlinear hydrodynamical interactions. Using an affine approximation that treats the perturbed neutron star (NS) as an ellipsoid, we analytically derive coupling coefficients among the quadrupolar f-modes and the radial mode to the four-wave order (next-to-next-to-leading order) in the Hamiltonian, allowing for arbitrary (aligned or anti-aligned) spin of the background star. Our model reveals a series of universal relations from first-principles arguments. We show that the three-wave (next-to-leading-order) interaction coefficients in a non-spinning star are fully determined by the properties of the linear tide. They do not probe new physics of the NS. Nonetheless, three-wave nonlinear tides are significant corrections to the gravitational waveform. We support this via a hybrid approach that simultaneously captures mode resonances expected in Newtonian hydrodynamics and is consistent with RELATIVISTIC calculations in the low-frequency expansion. The nonlinear tide in a single NS can cause a phase shift of around 1.8 radians accumulated up to merger compared to the linear tide model; for a binary, the phase shift is approximately doubled. In a low-frequency expansion, the nonlinear tide is degenerate with the finite-frequency correction of the linear tide, introducing systematic bias when ignored. Our calculation extends to four-wave interactions, which, for a slowly spinning neutron star, provide only small corrections. For a rapidly rotating neutron star, the nonlinear centrifugal drive of the f-mode provides a window to study the internal buoyancy that cannot be probed by the linear and three-wave f-mode tides in slowly spinning systems. The four-wave anharmonicity cannot lead to resonance locking of the f-mode.

[abstract 22 / 31] (score: 2)
arXiv:2607.27730 [pdf, ps, other]

Title: eRASSU J043115.8-711730 :the first pulsating symbiotic super-soft X-ray source in the Magellanic Bridge

Authors: Tathagata Saha, Chandreyee Maitra, Philip Charles, Frank Haberl, David Kaltenbrunner, Andrzej Udalski, David Buckley, Itumeleng Monageng, Lee Townsend, Manami Sasaki, Sara Saeedi, Mara Salvato,

Comments: Accepted for publication in MNRAS. in press

Subjects: astro-ph.HE

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

The Magellanic Bridge stellar population is a relic of the tidal interaction between the Large and Small Magellanic Clouds. A comprehensive view of the evolution of the Bridge stellar population requires probing the compact remnants of stellar evolution, otherwise hidden at optical wavelengths. The all-sky survey conducted by the eROSITA instrument on-board the Spectrum Roentgen Gamma observatory has discovered a significant population of compact-object-powered systems in the Bridge using X-ray. The candidate super-soft source eRASSU J043115.8-711730 (hereafter J0431-71) was discovered as a part of this campaign, and we present here a deeper study of this source using XMM-Newton and SALT spectroscopy, long-term optical-infrared photometry using OGLE, ATLAS, ASAS-SN, WISE, and GAIA data. J0431-71 is a highly variable super-soft X-ray source, classified as a red giant with the GAIA color-magnitude diagram. The source exhibits: (a) a thermal X-ray spectrum with a temperature of kT$\sim$30 eV and a bright state luminosity of $3.2\times10^{37}$~erg~s$^{-1}$ in the 0.15-1 keV band, (b) Balmer emission lines, [Fe X] coronal line, HeII emission, and the Bowen fluorescence blend, (c) an optical and infrared periodicity of $\sim$500-560 days in phase with the X-ray-UV emission, (d) a 'redder-when-brighter' trend in the stellar emission with a $\sim$520 day period indicating a pulsating donor star. We argue that the observed spectral and temporal properties in J0431-71 are consistent with a high-accretion rate onto a white-dwarf via Roche-lobe overflow, making J0431-71 the first symbiotic source discovered in the Bridge.

[abstract 23 / 31] (score: 2)
arXiv:2608.13656 [pdf, ps, other]

Title: Abundant Heavy Black Hole Seeds from Moderate Lyman-Werner Radiation

Authors: Ryan Hazlett, Eli Visbal, Greg L. Bryan, Mihir Kulkarni,

Comments: 31 pages, 10 figures, submitted to JCAP

Subjects: astro-ph.GA astro-ph.CO

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

The existence of high-redshift QUASARs may indicate that massive BLACK HOLE seeds formed via supermassive Population III stars in atomic-cooling halos with large gas inflow rates; however, the dependence of this process on halo assembly rate and radiative background remains poorly constrained. We present a large suite of 65 high-resolution cosmological zoom-in simulations of 15 pristine halos spanning a wide range of Lyman-Werner radiation backgrounds and halo assembly histories. We introduce a novel method to estimate the final Population III stellar mass from radial gas infall profiles at the onset of runaway collapse and validate it against simulations from the literature that explicitly follow protostellar accretion with sink particles, reproducing protostellar masses to within a factor of $\sim2$. We find a clear transition in gas inflow rates between halos exposed to $J_{\rm 21} \lesssim 1$ and $J_{\rm 21} \gtrsim 10$, with the latter frequently sustaining inflow rates above the adopted threshold for supermassive STAR FORMATION and producing estimated stellar masses up to $10^{5} \, M_{\odot}$. In contrast, the halo assembly timescale, $M_{\rm Halo}$/$\dot{M}_{\rm Halo}$, shows no statistically significant correlation with predicted stellar mass, despite halo assembly rates spanning $0.01$-$7 \, M_{\rm \odot} \, {\rm yr}^{-1}$. The Lyman-Werner radiation field therefore is a stronger predictor of sustained high accretion within our parameter space. Finally, a semi-analytic model applied to cosmological volumes shows that halos exposed to intermediate Lyman-Werner backgrounds ($1 \lesssim J_{\rm 21} < 10$) are orders of magnitude more common than those in the high-$J_{\rm 21}$ tail. If sustained high accretion extends into this intermediate regime, heavy BLACK HOLE seeds may form in substantially more common environments than required by classical direct-collapse scenarios.

[abstract 24 / 31] (score: 2)
arXiv:2608.13683 [pdf, ps, other]

Title: Generalized space-charge solver for three-dimensional converging or diverging beams

Authors: Ji Qiang,

Comments:

Subjects: physics.acc-ph

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

Nonlinear space-charge effects play a critical role in the dynamics of high-intensity, high-brightness beams. While conventional space-charge forces scale inversely with the square of the RELATIVISTIC Lorentz factor ($γ$) as beam energy increases, this suppression may not apply to all components of the electroMAGNETic force. In this paper, we present a generalized space-charge solver that accounts for contributions from transverse currents in three-dimensional (3D) converging or diverging beams. We demonstrate that these additional forces from transverse currents lack an explicit dependence on $γ$, potentially rendering them significant in specific high-energy applications. We provide a semi-analytical solution for a 3D converging or diverging beam with the Gaussian density distribution and identify the regimes in which these transverse current forces become comparable to conventional space-charge forces. Furthermore, we present a numerical solution for the generalized model applicable to arbitrary density distributions. Finally, we evaluate the impact of these forces on strongly converging electron beams within the interaction regions of the FCC-ee and ILC, as well as the second bunch compressor of LCLS-II-HE; our results indicate that these extra forces do not significantly alter the final electron beam quality in these specific cases.

[abstract 25 / 31] (score: 2)
arXiv:2608.13814 [pdf, ps, other]

Title: Time-dependent multi-energy neutrino emission from symbiotic recurrent novae: the role of accretion disks

Authors: Rui Xu, Yudong Cui, Yihan Shi, Lili Yang,

Comments: 13 pages, 7 figures, version accepted by PRD

Subjects: astro-ph.HE

Created: 2026-08-13; Updated: 2026-08-17; Datestamp: 2026-08-17

Symbiotic recurrent novae provide a unique laboratory for studying thermonuclear explosions, shock evolution, and nonthermal particle acceleration in dense circumstellar environments. In this work, we develop a time-dependent, multi-energy framework to describe neutrino emission from such systems, consistently incorporating both MeV neutrinos produced during thermonuclear runaway and GeV neutrinos generated through hadronic interactions in nova-driven shocks. Using RS Oph as a benchmark source, we model the evolution of the shock interacting with both the red giant wind and a dense accretion disk surrounding the white dwarf. We show that the resulting neutrino signal exhibits a characteristic two-component temporal structure: an early, rapidly rising MeV component tracing nuclear burning, followed by a delayed GeV component governed by shock propagation and particle acceleration. The presence of an accretion disk can significantly enhance the early-time GeV neutrino emission by providing a dense target for proton-proton interactions. This leads to a pronounced neutrino flux within the first few hours after eruption, a feature absent in wind-dominated scenarios. We further evaluate the detectability of these signals and find that while the MeV component remains below current detection thresholds, the GeV neutrino emission from nearby systems may become accessible to next-generation detectors. Our results highlight the critical role of the circumstellar structure in shaping nova neutrino emission and demonstrate that symbiotic recurrent novae are promising targets for future multi-messenger observations.

[abstract 26 / 31] (score: 2)
arXiv:2608.14009 [pdf, ps, other]

Title: X-ray Activity of the RS CVn-type Star σ Gem with the First-Year Observations of Einstein Probe

Authors: Xuan Mao, Giuseppina Micela, Fabio Favata, Weimin Yuan, He-yang Liu, Huaqing Cheng,

Comments: 16 pages, 17 figures, 6 tables. Accepted for publication in Astronomy & Astrophysics

Subjects: astro-ph.HE astro-ph.SR

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

Context. Stellar flares are energetic events driven by the sudden release of MAGNETic energy in the stellar atmosphere. Studying these flares is crucial for understanding their impact on exoplanets, the circumstellar environment, and stellar evolution itself. The launch of the Einstein Probe (EP) offers a unique opportunity to systematically detect such events. Aims. We present a systematic analysis of the flaring activity of the active RS CVn-type binary σ Gem, utilizing the first-year monitoring data from the Wide-field X-ray Telescope (WXT) aboard EP. Our goals are to demonstrate the unique capability of EP in monitoring stellar X-ray activity and detecting flares, by identifying and characterizing extreme X-ray flares on σ Gem and estimating their occurrence rate. Methods. We developed a data-processing pipeline to select and extract EP-WXT observations, producing a background-subtracted, vignetting-corrected light curve. We employed the Bayesian Blocks method to detect significant flares in the long-term X-ray light curve. For each identified flare, we performed light curve and spectral fitting to derive the flare parameters. Results. Between October 2024 and April 2025, WXT detected 6 distinct flares from σ Gem. Their durations ranged from 21 hours to 3 days, with peak X-ray luminosities (0.5-4 keV) of 3.7 * 10^31 to 7.0 * 10^32 erg/s and total energies of 1.1 * 10^36 to 4.4 * 10^37 erg, placing them among the "superflare" class. Conclusions. Using σ Gem as a case study, we demonstrate an analysis process for flare detection and analysis with EP-WXT data, which provides new statistical constraints on its flaring behavior. Applying this methodology to the growing EP stellar archive promises to yield a vast sample of X-ray flares, which will significantly advance our understanding of stellar MAGNETic activity.

[abstract 27 / 31] (score: 2)
arXiv:2608.14056 [pdf, ps, other]

Title: Neural network maximum entropy framework for distribution reconstruction in heavy-ion collisions

Authors: Qian-Ru Lin, Fu-Peng Li, YiGe Huang, Long-Gang Pang,

Comments: 9 pages, 6 figures

Subjects: nucl-th hep-ph

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

We develop a neural-network maximum-entropy (NN+MaxEnt) framework for reconstructing probability distributions from limited observables in heavy-ion collisions. The method combines flexible neural-network representations with Shannon-entropy regularization, preserving positivity and normalization without assuming a fixed analytic form. After validation with Gaussian, Poisson, and mixed-Poisson closure tests, we apply the framework to two physics-motivated inverse problems: an effective multiplicity reconstruction constrained by functional renormalization group cumulants, used as a closure test, and the conditional JET-energy-loss distribution extracted from single-inclusive JET $R_{AA}$ data in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$~TeV. For the fRG closure test, NN+MaxEnt accurately reproduces the imposed cumulants and yields distributions consistent with conventional MaxEnt solutions. For JETs, the reconstructed energy-loss distributions reproduce the measured $R_{AA}$; at an initial JET momentum $x=50~\mathrm{GeV}$, the conditional mean energy loss is $\langleΔp_T\rangle\simeq11.8~\mathrm{GeV}$, with a central $16\text{--}84\%$ interval of $9.0\text{--}15.0~\mathrm{GeV}$. The extracted energy-loss profile is qualitatively consistent with Bayesian MCMC and LBT results. NN+MaxEnt thus provides a flexible, less ansatz-dependent framework for regularized distribution reconstruction from observables connected to the underlying distribution through differentiable forward maps.

[abstract 28 / 31] (score: 2)
arXiv:2608.14137 [pdf, ps, other]

Title: Enhancement of axial MAGNETic field generation during RELATIVISTIC self-channeling of LASER radiation propagating along thin films

Authors: Vitalia A. Kuleshova, Artem V. Korzhimanov,

Comments: 11 pages, 7 figures; to be published in JETP Letters

Subjects: physics.plasm-ph

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

Within the framework of a stationary model of RELATIVISTIC self-focusing, it is shown that the addition of a thin layer of denser plasma on the propagation axis of a circularly polarized beam increases the axial MAGNETic field generated by it via the inverse Faraday effect by more than a factor of 10 compared to the case of a homogeneous plasma. The magnitude of the axial field in this case can exceed the MAGNETic field of the LASER wave, which makes it possible, at radiation intensities $\sim 10^{26}$~W/cm$^2$ potentially achievable in the near future, to approach the level of teragauss quasi-stationary fields.

[abstract 29 / 31] (score: 2)
arXiv:2608.14382 [pdf, ps, other]

Title: Jet functions for next-to-leading power factorization

Authors: Robin van Bijleveld, Jaco ter Hoeve, Eric Laenen, Coenraad Marinissen, Leonardo Vernazza, Guoxing Wang,

Comments: Proceeding of "Loops and Legs in Quantum Field Theory" 2026, 14 pages

Subjects: hep-ph

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

We discuss the factorization of scattering processes near partonic threshold at next-to-leading power (NLP) in the threshold variable $1-z$, with $z \equiv q^2/\hat{s}$. We review the general structure of power-suppressed contributions both in Soft-Collinear Effective Theory (SCET) and in a direct QCD approach, and discuss the definition of NLP JET functions as gauge-invariant operator matrix elements in QCD. As a controlled check of the resulting factorization formula, we verify it explicitly at one and two loops for the massive electroMAGNETic form factor in the limit $m^2 \ll s$, using the method of regions. We conclude by outlining the two challenges that remain for a systematic resummation of NLP logarithms: the treatment of endpoint divergences in SCET convolutions, and the extension of JET functions to radiative processes capable of describing an arbitrary number of soft-gluon emissions -- the latter being the last missing ingredient for exponentiation, given that the purely soft sector is already understood in terms of generalised webs via the replica trick.

[abstract 30 / 31] (score: 2)
arXiv:2608.14521 [pdf, ps, other]

Title: Limitations of post accelerating ion beams using the snowplow field in a near-critical density target

Authors: Davide Terzani, Stepan S. Bulanov, Lieselotte Obst-Huebl, Carlo Benedetti, Franklin Dollar, Eric Esarey, Axel Huebl, Aodhan McIlvenny, John Palastro, Jessica Shaw, Carl B. Schroeder, Douglass Schumacher, Mingsheng Wei, Louise Willingale,

Comments:

Subjects: physics.plasm-ph physics.acc-ph

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

Laser-matter interaction at RELATIVISTIC intensities is central to almost every scientific case for multi-PW LASER facilities. In particular, the progress in LASER-driven ion acceleration brings this interaction closer to multiple applications, ranging from material science to biomedical research. One of the most important questions regarding ion acceleration is how to obtain high charge ion beams with RELATIVISTIC energies. Increasing LASER energy and intensity usually leads to a number of limitations on maximum achievable ion energies rooted in the fundamental properties of charged particle interaction with strong electroMAGNETic fields. Following advances in staged LASER-plasma electron acceleration, staged ion acceleration could offer a path to RELATIVISTIC energies. Here, such scheme is explored and the possibility of scaling the acceleration of ion beams to RELATIVISTIC energies is discussed.

[abstract 31 / 31] (score: 2)
arXiv:2608.14549 [pdf, ps, other]

Title: Blazar Boosted Dark Matter in IceCube

Authors: Alberto M. Gago, Jaime Hoefken Zink, Joel Jones-Pérez, Gabriel D. Zapata,

Comments: 21 pages, 6 figures

Subjects: hep-ph astro-ph.HE

Created: 2026-08-14; Updated: 2026-08-17; Datestamp: 2026-08-17

We study the sensitivity of IceCube to BLAZAR-boosted DARK MATTER in a fermionic DARK MATTER model with a massive vector mediator coupling to QUARKs. To this aim, we compute the diffuse flux arising from a sample of 324 BLAZARs with proton spectra inferred from multiwavelength observations, adopting conservative DARK MATTER spike profiles around the central supermassive BLACK HOLEs and consistently accounting for attenuation effects during propagation through the Earth. The DARK MATTER-nucleon scattering cross section is evaluated by including elastic, resonant single pion production, and deep inelastic contributions, with particular emphasis on resonant single-pion production channels in order to smoothly cover the transition between the elastic and deep inelastic regimes. Using IceCube neutrino data, we derive constraints on the parameter space of the model and show that this detection strategy can surpass the sensitivity of conventional direct-detection experiments for DARK MATTER masses below $\sim 1$ GeV. We find that the signal is dominated by deep inelastic scattering and is therefore more sensitive to comparatively heavy mediators, while resonance processes provide a reduction of the event rate, reaching up to about $9\%$ near the experimental threshold. Our results demonstrate that IceCube constitutes a powerful probe of sub-GeV DARK MATTER scenarios through the observation of BLAZAR-boosted DARK MATTER.