Current date: 2026-05-11

Setting default datestamp limit: 0

Datestamp limit: 2026-05-11 (0 days ago)

Created/updated limit: 2026-05-04 (7 days ago)

Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics

Setting default set: physics

OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-05-11&until=2026-05-11&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 616

Keyword score statistics

score 10 -- 1 abstracts

score 8 -- 1 abstracts

score 7 -- 1 abstracts

score 6 -- 3 abstracts

score 5 -- 4 abstracts

score 4 -- 5 abstracts

score 3 -- 7 abstracts

score 2 -- 12 abstracts

in total -- 34 abstracts

Articles that appeared on 2026-05-11

[abstract 1 / 34] Wow! (score: 10)
arXiv:2601.01533 [pdf, ps, other]

Title: Diffuse neutrino flux from RELATIVISTIC RECONNECTion in AGN coronae

Authors: D. Karavola, M. Petropoulou, D. F. G. Fiorillo, A. Georgakakis, L. Comisso, L. Sironi,

Comments: 9 pages, 10 figures. Published on A&A The AGN coronal model used in this work (Karavola et al., JCAP04(2025)075) can be found as a python class on GitHub: https://github.com/Des0053/Coronal_neutrinos

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

IceCube observations point to Active Galactic Nuclei (AGN) as promising contributors to the observed astrophysical neutrino flux. Close to the central BLACK HOLE, protons can be accelerated through MAGNETic RECONNECTion to very high energies and subsequently interact with abundant X-ray photons in the source, leading to neutrino production. We investigate whether the diffuse neutrino flux observed by IceCube can originate, via proton acceleration, in RECONNECTion-powered coronae of non-JETted AGN. We create a library of neutrino spectral templates, over a large grid of values for the three key model parameters: the proton plasma MAGNETization of the corona $σ_{\rm p}$, the X-ray coronal luminosity, and the BLACK HOLE mass. Synchrotron cooling of pions and muons plays a significant role due to the large coronal MAGNETic fields. We couple the single-source model with a mock AGN catalog, consistent with the observed X-ray and mid-infrared AGN samples at redshifts $z=0-4$, to infer the diffuse neutrino flux. Coronal emission satisfactorily explains the most recent IceCube measurements of the diffuse neutrino flux up to energies of $\sim 1$~PeV, provided that $\sim$10\% of the AGN coronae have $σ_{\rm p} \sim 10^5$, while the rest are distributed over a range of lower MAGNETizations. Coronal emission is suppressed at higher energies by pion and muon cooling, so that another population is required, with JETted AGN being strong candidates.

[abstract 2 / 34] Wow! (score: 8)
arXiv:2604.27671 [pdf, ps, other]

Title: Long-term study of the gamma-ray emission of Cygnus X-3 with MAGIC and FERMI-LAT

Authors: K. Abe, S. Abe, J. Abhir, A. Abhishek, V. A. Acciari, A. Aguasca-Cabot, I. Agudo, I. Albanese, T. Aniello, S. Ansoldi, L. A. Antonelli, A. Arbet Engels, C. Arcaro, T. T. H. Arnesen, A. Babić, C. Bakshi, U. Barres de Almeida, J. A. Barrio, L. Barrios-Jiménez, I. Batković, J. Baxter, J. Becerra González, W. Bednarek, E. Bernardini, J. Bernete, A. Berti, J. Besenrieder, C. Bigongiari, A. Biland, O. Blanch, G. Bonnoli, P. Bordas, Ž. Bošnjak, E. Bronzini, I. Burelli, C. Campa, A. Campoy-Ordaz, A. Carosi, R. Carosi, M. Carretero-Castrillo, A. J. Castro-Tirado, D. Cerasole, G. Ceribella, A. Cerviño, A. Chilingarian, G. Chon, A. Cifuentes Santos, J. L. Contreras, J. Cortina, S. Covino, G. D'Amico, P. Da Vela, F. Dazzi, A. De Angelis, B. De Lotto, M. Delfino, J. Delgado, F. Di Pierro, R. Di Tria, L. Di Venere, A. Dinesh, D. Dominis Prester, A. Donini, D. Dorner, M. Doro, L. Eisenberger, D. Elsaesser, L. Foffano, L. Font, F. Frías García-Lago, S. Fröse, Y. Fukazawa, S. García Soto, M. Gaug, J. G. Giesbrecht Paiva, N. Giglietto, F. Giordano, P. Gliwny, N. Godinović, T. Gradetzke, R. Grau, J. G. Green, P. Günther, D. Hadasch, A. Hahn, G. Harutyunyan, T. Hassan, J. Herrera Llorente, D. Hrupec, D. Israyelyan, J. Jahanvi, I. Jiménez Martínez, J. Jiménez Quiles, S. Kankkunen, J. Konrad, P. M. Kouch, H. Kubo, J. Kushida, M. Láinez, A. Lamastra, E. Lindfors, S. Lombardi, F. Longo, R. López-Coto, M. López-Moya, A. López-Oramas, S. Loporchio, L. Lulić, E. Lyard, P. Majumdar, M. Makariev, G. Maneva, M. Manganaro, S. Mangano, M. Mariotti, M. Martínez, P. Maruševec, D. Mazin, S. Menchiari, J. Méndez Gallego, S. Menon, D. Miceli, J. M. Miranda, R. Mirzoyan, M. Molero González, E. Molina, H. A. Mondal, A. Moralejo, C. Nanci, A. Negro, V. Neustroev, M. Nievas Rosillo, C. Nigro, L. Nikolić, S. Nozaki, A. Okumura, J. Otero-Santos, S. Paiano, D. Paneque, R. Paoletti, J. M. Paredes, M. Peresano, M. Persic, M. Pihet, F. Podobnik, P. G. Prada Moroni, E. Prandini, W. Rhode, M. Ribó, J. Rico, A. Roy, N. Sahakyan, F. G. Saturni, F. Schiavone, K. Schmitz, T. Schweizer, A. Sciaccaluga, G. Silvestri, A. Simongini, J. Sitarek, D. Sobczynska, A. Stamerra, J. Strišković, D. Strom, M. Strzys, Y. Suda, R. Takeishi, J. Tartera Barberà, P. Temnikov, T. Terzić, M. Teshima, A. Tutone, S. Ubach, M. Vazquez Acosta, S. Ventura, G. Verna, I. Viale, A. Vigliano, C. F. Vigorito, E. Visentin, V. Vitale, M. Vorbrugg, I. Vovk, R. Walter, C. Walther, F. Wersig, P. K. H. Yeung, V. Bosch-Ramon,

Comments: 15 pages, 3 figures, accepted for publication in JHEAP

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Cygnus X-3 is a microQUASAR composed of a compact object of unknown nature closely orbiting around a Wolf-Rayet star. The particularities of this source make it a unique case among microQUASARs. This fact, together with its recent establishment as a PeV particle accelerator, makes Cygnus X-3 a very interesting target for the investigation of the physical processes leading to gamma-ray production. In this work, the TeV and GeV gamma-ray emission of Cygnus X-3 is studied in order to determine its origin and constrain the properties of the system. For that purpose, a point-like analysis of 130 h of data taken with the MAGIC telescopes between 2013 and 2024 was performed, which represents the largest available sample for Cygnus X-3 at $\sim$TeV energies. Additionally, contemporary data from FERMI-LAT were also analysed to better contextualize the MAGIC observations. For a more detailed investigation of the source physics, the data were divided into three subsets according to the flaring state of the source and orbital phase. No significant detection of Cygnus X-3 is found between 0.1 and 7 TeV for any of the datasets, and differential and integral flux upper limits are reported over the long-term monitoring of the source. The FERMI-LAT fluxes can be considered compatible with previous results, taking into account the different data samples used across studies. The MAGIC upper limits presented in this work represent the most constraining ones up to date at $\sim$TeV energies. An eventual detection of Cygnus X-3 at these energies would significantly constrain the source properties, and is not unreasonable to expect given that the source has already been detected in both the GeV and PeV regimes during flaring states. Further observations of Cygnus X-3 at energies above tens of GeV would be valuable for this purpose.

[abstract 3 / 34] Wow! (score: 7)
arXiv:2605.07235 [pdf, ps, other]

Title: Anisotropic Thermal Conduction as a Driver of Jet Collimation and Magnetic Field Amplification on Cold Fronts

Authors: Nana Matsuno, Takaaki Yokoyama, Mami Machida,

Comments:

Subjects: astro-ph.HE astro-ph.CO

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Galaxy clusters contain a hot, diffuse, and weakly MAGNETized plasma known as the intracluster medium (ICM). In this environment, how thermal conduction influences plasma dynamics and the conditions under which it operates efficiently remain open questions in cluster physics. Systems in which ACTIVE GALACTIC NUCLEi (AGN) JETs interact with cold fronts produced by cluster mergers provide a unique setting to examine the interplay between conduction, JET dynamics, and ordered MAGNETic fields. To interpret the detailed structures revealed by recent observations, it is therefore important, as a first theoretical step, to quantify how thermal conduction modifies AGN JET morphology and the surrounding MAGNETic-field configuration. We perform two-dimensional MAGNETohydrodynamic (MHD) simulations of an AGN JET in an ICM environment, incorporating anisotropic thermal conduction with varying efficiency. The simulations show that thermal conduction transports heat from the JET head backward along MAGNETic field lines into the inner cocoon. This process increases the inner cocoon pressure, enhancing JET collimation by a factor of $\sim 4$ compared to models without conduction. This stronger collimation stretches the MAGNETic fields along the cold-front surface, resulting in a maximum field strength up to a factor of $\sim 1.5$ larger. Jet collimation increases as the conduction efficiency increases, which is interpreted as a conductive collimation mechanism. These results suggest that anisotropic thermal conduction can operate effectively on JET scales in galaxy clusters, and that accounting for conduction may be important when interpreting JET morphology and MAGNETic field structure in merging cluster environments.

[abstract 4 / 34] Yes (score: 6)
arXiv:2605.07255 [pdf, ps, other]

Title: Resonant Inverse Compton Scattering and Hard X-ray Emission in Magnetar Magnetospheres

Authors: Kun Hu, Nicholas Rackers, Alexander Y. Chen,

Comments: 20 pages, 13 figures, submitted to ApJ

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Magnetars are a subclass of neutron stars with ultra-strong surface MAGNETic fields. Some MAGNETars exhibit persistent hard X-ray emission, characterized by power-law tails with photon indices around 1--1.5, extending from ${\sim}$10 keV to several hundred keV. The leading explanation for this hard X-ray component is resonant Compton scattering, in which the thermal seed photons are upscattered by RELATIVISTIC electron-positron pairs flowing along MAGNETic field lines in the MAGNETosphere. In this work, we adopt the pair outflow framework of the MAGNETar MAGNETosphere and calculate the resonant Compton scattering opacity, as well as the spectrum and POLARIZATION of the upscattered emission. We find that resonant cooling can substantially modify the MAGNETospheric plasma density and impose strong optical depth constraints on the hard X-ray emission regions. Under the viewing geometry inferred from IXPE, an equatorial twist near the stellar surface provides a viable configuration for the NUSTAR hard X-ray spectrum of 4U 0142+61, while a polar-twist geometry is disfavored. Joint spectral, timing, and polarimetric modeling will be essential for distinguishing between the MAGNETospheric scattering geometries and understanding the physical properties of the pair plasma.

[abstract 5 / 34] Yes (score: 6)
arXiv:2605.07680 [pdf, ps, other]

Title: Advance warning of $γ$-ray BLAZAR flares from \textit{FERMI}-LAT light curves: a strictly causal machine-learning backtest

Authors: Zahir Shah, Sikandar Akbar,

Comments:

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Long-term \textit{FERMI}-LAT monitoring makes it possible to ask whether a BLAZAR light curve shows signs of an upcoming flare before the flare becomes obvious in the $γ$-ray emission. We present a strictly causal machine-learning framework for forecasting $γ$-ray BLAZAR flares from 3-d binned LAT light curves. Flare intervals are identified with Bayesian Blocks, and each light curve is sampled with 365-d trailing windows from which 42 variability features are measured. We train separate WATCH and TRIGGER models: WATCH predicts whether flare activity will appear within the next 90 d, while TRIGGER predicts whether a new flare onset will occur within the next 45 d. To avoid temporal leakage, all scaling, calibration, threshold selection, and validation use only the pre-cutoff data before MJD 60000. We apply the method to the FSRQ 4FGL\,J1048.4$+$7143, using 13 bright BLAZARs as auxiliary training sources. Among logistic regression, polynomial logistic regression, and random forest classifiers, polynomial logistic regression gives the strongest held-out WATCH performance, with ROC AUC $=0.891$, average precision $=0.396$, and a block-permutation probability $p_{\rm perm}=0.006$. At the selected WATCH threshold, it recovers 18 of the 21 positive windows in the held-out WATCH set, corresponding to a recall of 0.86. The same model also gives the best held-out TRIGGER ranking, with TRIGGER AUC $=0.770$ and TRIGGER AP $=0.123$, although no reliable pre-onset TRIGGER alert is obtained. The WATCH state appears before both held-out flare episodes, with final alerts 4.5 and 2.5 d before onset. The corresponding broader WATCH-active periods begin 88.5 and 72.5 d before flare onset. These results suggest that long-term {\fermi} light curves contain useful predictive information about the build-up to BLAZAR flares.

[abstract 6 / 34] Yes (score: 6)
arXiv:2605.07777 [pdf, ps, other]

Title: Young Massive Star Clusters as TeV Emitters: Constraints from H.E.S.S. and LHAASO

Authors: Rowan Batzofin, Pierre Cristofari, Kathrin Egberts,

Comments: Accepted for publication in A&A 07 May 2026

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Young massive star clusters (YMSCs) have been proposed as excellent candidates for the main sources of Galactic COSMIC RAYs (CRs) up to the PeV range. The detection and study of gamma rays in the very-high-energy (E>100GeV) range has brought arguments in favour of this hypothesis. Current instruments have detected only a few YMSCs. Future observatories are expected to increase this number, providing a larger sample improving our ability to constrain the role of YMSCs in the origin of CRs. We study the population of TeV YMSCs detected and their properties, confronting simulations of the YMSC population to the observed sample, to address the fundamental questions concerning the spectrum of accelerated particles, the efficiency of CR production, and the fraction of the wind luminosity converted into turbulent MAGNETic fields. Using Monte Carlo methods, we simulate the Galactic population of YMSCs in the gamma-ray domain and confront our simulations to the catalogue of sources of the systematic survey of the Galactic plane performed by H.E.S.S. (HGPS) and the First LHAASO Catalogue of Gamma-Ray Sources. We systematically explore the parameter space of our model, including the slope of accelerated particles $α$, the CR efficiency $η_{\rm CR}$, the fraction of the wind luminosity converted into turbulent MAGNETic field $η_{\rm b}$, and the diffusion regime. We found 5 possible sets of parameters for which >75% of realisations agree with the combined data from the HGPS and LHAASO 1st catalogue. Certain regions of the parameter space are strongly disfavoured, such as Bohm diffusion. Our model successfully reproduces the YMSC population observed in both catalogues. With future systematic surveys, e.g. the Cherenkov Telescope Array Observatory (CTAO), this approach will help break degeneracies and improve our understanding of particle acceleration at YMSC shocks in the Galaxy.

[abstract 7 / 34] Yes (score: 5)
arXiv:2605.06917 [pdf, ps, other]

Title: X-ray spectroscopy mass constraints on V1674 Her: the fastest nova does not have a near-Chandrasekhar white dwarf

Authors: Tekeba Olbemo, Manel Errando, Andrea Gokus,

Comments: Accepted for publication in ApJ

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

Created: 2026-05-07; Updated: 2026-05-11; Datestamp: 2026-05-11

V1674 Her (Nova Her 2021) is the fastest classical nova ever recorded, with an optical decline time of $t_2 \sim 1$ day, typically interpreted as evidence for a white dwarf mass close to the Chandrasekhar limit. We present a broadband X-ray study of V1674 Her combining contemporaneous XMM-Newton and NUSTAR observations in quiescence to directly constrain the white dwarf mass and MAGNETic field strength. The hard X-ray emission is modeled using a physically motivated post-shock accretion column model that accounts for the temperature gradient in the flow and reflection from the white dwarf surface. Under the assumption that the accretion disk is truncated at the co-rotation radius, we obtain a white dwarf mass of $M = 1.09^{+0.07}_{-0.06}\,M_\odot$. An independent constraint derived from timing analysis of the X-ray power spectrum yields a consistent value of $M = 1.12 \pm 0.06\,M_\odot$. These values are significantly lower than those inferred from empirical decline-time relations, suggesting that such relations may overestimate white dwarf masses in extreme fast novae. From the inferred accretion rate and MAGNETospheric radius, we estimate a surface MAGNETic field strength of $B = 21.3^{+6.6}_{-5.7}\,(\mathrm{stat})^{+12.9}_{-8.1}\,(\mathrm{sys})\,\mathrm{MG}$, placing V1674 Her at the high end of the MAGNETic field distribution for intermediate polars. Our results demonstrate that even the fastest novae do not necessarily host near-Chandrasekhar white dwarfs, highlighting the importance of direct X-ray constraints and suggesting that additional parameters beyond white dwarf mass play a key role in setting nova timescales.

[abstract 8 / 34] Yes (score: 5)
arXiv:2605.07479 [pdf, ps, other]

Title: Diffuse gamma-ray emissions around the stellar cluster Berkeley 59

Authors: Ziwei Ou, Xiaolong Yang, Songpeng Pei,

Comments:

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

We report a detailed analysis on the young stellar cluster Berkeley 59 using FERMI-LAT. Using up-to-date source catalog and background models, we found significant extended GeV emission around Berkeley 59, which can be modeled by a radial disk of 1.02 degree radius with a significance of the extension of 10.6 sigma. We investigated the molecular, neutral and ionized gas content and the hadronic origin. The gamma-ray spectrum of Berkeley 59 has a photon index of 2.88. The derived gas mass from H2 and HII around Berkeley 59 is about 289 solar mass. We derived the relationship between COSMIC RAY acceleration efficiency and diffusion coefficient. Our results suggest that the extended gamma-ray emission originates from COSMIC RAYs accelerated by cluster winds interacting with surrounding gas.

[abstract 9 / 34] Yes (score: 5)
arXiv:2605.07684 [pdf, ps, other]

Title: The diverse morphologies and evolution of low-luminosity edge-brightened RADIO GALAXies

Authors: B. Barkus, J. H. Croston, B. Mingo, M. J. Hardcastle, G. Gürkan, V. H. Mahatma,

Comments: 16 pages, 7 figures, 8 tables. Accepted for publication in MNRAS

Subjects: astro-ph.GA

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Fanaroff-Riley class I (FRI) RADIO GALAXies show centre-brightened emission from disrupted lower power JETs, while traditionally more luminous class II (FRIIs), are edge-brightened, with RELATIVISTIC JETs terminating in hotspots. Population studies of radio-loud AGN (RLAGN) with low frequency, deep, wide-field surveys have revealed FRII-like radio structures at lower luminosities. We present the first high-resolution morphological investigation of a representative LOFAR-selected sample of low-luminosity FRIIs, to determine whether this new population is physically distinct from traditional high-luminosity FRIIs. Using new $1.5$-GHz Jansky Very Large Array (VLA) observations for a sample of 19 low-luminosity FRIIs, from the LOFAR Two Metre Sky Survey Data Release 1 (LoTSS DR1), with luminosities up to three orders of magnitude lower than the typical FR break ($L_{150} = 10^{26}$ W Hz$^{-1}$). We examine the compact features and perform spectral index analysis to identify hotspots, cores and signatures of restarting or remnant activity. We find a higher prevalence of cores and a comparable number of hotspots in the low-luminosity FRII sample compared to a randomly-selected sample of luminous ($L_{150}>10^{26}$ W Hz$^{-1}$) FRIIs selected from the same parent LOFAR sample. Approximately 32 per cent of low-luminosity FRIIs show restarting or remnant behaviour, while $\sim 32$ per cent are active FRIIs with compact hotspots. Our results show that FRII source dynamics occur at low radio luminosities, but reinforce earlier conclusions that the population of low-luminosity edge-brightened RLAGN is highly diverse. Binary morphological classifications should be used cautiously as a first step towards more nuanced investigations of the complexity of JET life cycles and evolution.

[abstract 10 / 34] Yes (score: 5)
arXiv:2605.07965 [pdf, ps, other]

Title: A Changing-Look Seyfert Discovered by eROSITA Reveals a Two-Component Broad-Line Region

Authors: Alex Markowitz, Mirko Krumpe, David Homan, Bożena Czerny, Mariusz Gromazdki, Hartmut Winkler, Joern Wilms, Steven Hämmerich, Georg Lamer, Tathagata Saha, David A. H. Buckley, Malte Schramm, Daniel E. Reichart, Mara Salvato, Pietro Baldini,

Comments: 29 pages; 10 figures. Accepted for publication in Astronomy & Astrophysics

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

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Extreme sudden changes in the flow of accreting gas onto SMBHs manifest themselves via large-amplitude continuum variability and changes to broad Balmer emission profiles, driving changing-look AGN. X-ray flux monitoring with SRG/eROSITA revealed that in the Seyfert AGN HE 1237-2252 the soft X-ray flux dipped abruptly, by a factor of 17 within 18 months. We initiated a follow-up campaign that caught the luminosity recovery after the dip, and enabled us to study how the various accretion components responded during this flux recovery. Our campaign included multiband photometry, X-ray spectroscopy, and optical spectroscopy. We tracked as the accretion rate relative to Eddington increased by a factor of 7 in 3 years. Based on broad Hbeta variability, HE 1237-2252 was subtype 1.0-1.2 in 2002, transitioned to subtype 1.8 by the time of the luminosity dip, and then transitioned back to subtype 1.0 within 3 months as luminosity recovered. Both transitions saw broad Hbeta integrated line flux change by factors of 4-6. The broad Balmer profile is decomposed into a broad Gaussian consistent with virialized gas at 27+/-3 lt-dy, plus a double-peaked profile, consistent with a diskline structure at more than roughly 5 lt-dy. The diskline component's relative contribution to the total profile increases as continuum flux rises. The lack of obscuration in the X-ray spectra, as well as the IR continuum dip, point to an intrinsic pause in the accretion rate as opposed to variable line-of-sight obscuration. Candidates for the underlying mechanisms include propagating cold and warm fronts in the accretion disk. The increased prominence of the diskline BLR component's emission could be due to evolution in the physical extent of the X-ray corona, and in the fraction of >13.6 eV photons intercepted by the diskline, as the accretion rate increases.

[abstract 11 / 34] Yes (score: 4)
arXiv:2511.20682 [pdf, ps, other]

Title: High-energy radiation from the pulsar Equatorial Current Sheet

Authors: Ioannis Contopoulos, Jerome Petri, Ioannis Dimitropoulos,

Comments: 9 pages, 5 figures, accepted for publication in Astronomy and Astrophysics

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Pulsars emit beams of radiation that reveal the extreme physics of neutron star MAGNETospheres. Yet, their understanding remains incomplete. Recent global Particle-in-Cell (PIC) simulations have raised several questions that led us to question their validity and their extrapolation to realistic particle Lorentz factors, electric and MAGNETic fields. We want to generate realistic sky maps of high-energy radiation from first principles. We propose a novel method to study the Equatorial Current Sheet (ECS) where most of the particle acceleration and the high-energy radiation is expected to originate. We first determine its shape and external MAGNETic field with a steady-state ideal force-free solution. Then, we consider the extra electric and MAGNETic field components that develop when dissipation is considered. Finally, we study the particle acceleration and radiation that is due to these extra field components for realistic field and particle parameters. We generate realistic sky maps of high-energy radiation and compare them with those obtained via PIC simulations. These sky maps may also be closely reproduced using the ECS of the split-monopole solution beyond the light cylinder. The ECS is probably stabilized by the normal MAGNETic field component that is due to the global MAGNETospheric RECONNECTion. Our method helps us better understand the origin of the pulsed high-energy radiation in the pulsar MAGNETosphere.

[abstract 12 / 34] Yes (score: 4)
arXiv:2603.07620 [pdf, ps, other]

Title: A JET formation model for astrophysical objects

Authors: Chun Xu,

Comments: 1 figure, 7 pages; resubmitted to MNRAS after major revision

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

We propose a unified model for JET formation applicable to ACTIVE GALACTIC NUCLEi, young stellar objects, and X-ray binaries. In this model, the binding energy released from the accretion disk is primarily stored as turbulence rather than being radiated away, leading to the formation of advection-dominated accretion flows. Near the central object, a thick accretion disk with funnel-like structures develops. Within the turbulent flows, the smallest stable blobs can be accelerated beyond the escape velocity through the combination of two mechanisms - the Gaussian-like velocity distribution within the turbulence and a mechanism involving the combined effects of inward pressure force and angular momentum conservation.These rapidly moving blobs may exit through the funnels, collectively forming two opposing JETs. This model predicts that JETs originate from the innermost region of the thick disk surrounding the central object. The formation of JET is directly related a parameter ηthat describes the energy fraction stored in turbulence in units of the binding energy of local Keplerian energy. η> 0.5 is a minimal condition for JET to form. This model can be extended to account for JET formation in ACTIVE GALACTIC NUCLEi, young stellar objects, X-ray binaries, and other analogous astronomical systems.

[abstract 13 / 34] Yes (score: 4)
arXiv:2605.06791 [pdf, ps, other]

Title: Hidden Monsters with SPHEREx I: A goldmine for heavily reddened QUASARs at cosmic noon

Authors: Matthew Stepney, Manda Banerji, Franz E. Bauer, Roberto J. Assef, Guodong Li,

Comments: Submitted to A&A 5th May 2026

Subjects: astro-ph.GA

Created: 2026-05-07; Updated: 2026-05-11; Datestamp: 2026-05-11

Heavily reddened QUASARs (HRQs) are luminous, dust-obscured broad-line QUASARs thought to represent a short-lived phase of intense BLACK HOLE growth and feedback. Previous studies have been limited by small sample sizes, restricting robust statistical analysis. We expand the sample of the most luminous HRQs to enable population-level studies, connecting their spectral energy distributions (SEDs) to other QUASAR populations and placing them within an evolutionary sequence of massive galaxy and BLACK HOLE formation. We assemble multiwavelength broadband photometry for the brightest HRQ candidates (K$_{AB}$ < 18 mag) and select AGN with red near-infrared colours (J-K)$_{AB}$ > 1.6. Using SPHEREx spectrophotometry, we confirm HRQs and determine redshifts. Detailed SED fitting allows comparison with other luminous QUASARs, including a control sample of hyper-luminous, unobscured Quaia QUASARs and luminous Hot Dust-Obscured Galaxies (Hot DOGs). We confirm 77 new HRQs with redshifts 1.5 < z < 3.9, dust-corrected optical continuum luminosities log$_{10}(λL_λ(3000A)$ [erg/s])>47.0, and line-of-sight extinctions 0.4 < E(B-V) < 1.6 (A$_V$ mag). This more than doubles the known HRQs at z > 1.5, including the first seven at z > 3. A UV excess consistent with scattered QUASAR emission is detected in 76% of HRQs. We show that HRQs are hot-dust poor compared to blue QUASARs of similar luminosity and redshift. Their 6um continuum luminosities are systematically fainter at fixed 3000A continuum luminosity relative to blue Quaia QUASARs, indicating deficiency in both hot and warm dust. These results support a scenario in which HRQs represent a blow-out phase, where strong feedback begins clearing obscuring material from central regions.

[abstract 14 / 34] Yes (score: 4)
arXiv:2605.06794 [pdf, ps, other]

Title: The study of the circumnuclear environment of accreting supermassive BLACK HOLEs with realistic X-ray spectral models

Authors: Georgios Dimopoulos, Claudio Ricci, Stéphane Paltani,

Comments: 18 pages, 9 figures, the models are available: https://www.astro.unige.ch/reflex/xspec-models

Subjects: astro-ph.HE

Created: 2026-05-07; Updated: 2026-05-11; Datestamp: 2026-05-11

X-ray spectral modeling is a powerful tool for studying the immediate environment of accreting objects, including supermassive BLACK HOLEs. Several models, either phenomenological or physically driven, have been developed over the past decade to study X-ray spectra, delivering important insights into the properties of circumnuclear material of ACTIVE GALACTIC NUCLEi (AGN). Despite the fact that these models are able to reproduce the data well, they often lack realistic geometries, and most of them consist of simplified configurations such as a slab or a torus. We use the ray-tracing code \textsc{RefleX} to generate new spectral models that cover a wide energy range in the X-ray band, adopting a realistic configuration for the surrounding material. We introduce two new table models that are publicly available: 1) the RXToPo model, which features an X-ray source along with a dusty torus and a polar hollow cone; 2) the RXagn1 model, which includes, besides the torus and polar cone, also the accretion disk and the broad line region. Both models were applied to the X-ray spectrum of NGC 424, demonstrating their potential to study sources whose X-ray emission is dominated by reprocessed radiation.

[abstract 15 / 34] Yes (score: 4)
arXiv:2605.07889 [pdf, ps, other]

Title: Investigating Pre-flare Signatures in Spectroscopic Observations of an X9-class Solar Flare

Authors: Louis Seyfritz, Maria Kazachenko, Ryan French,

Comments: 16 pages, 5 figures; accepted for publication in Solar Physics

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

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

On October 3rd, 2024, the Sun emitted an X9.0-class flare from active region NOAA 13842. The event was recorded by multiple space-based instruments, beginning hours before the eruption, granting a unique opportunity to provide insight into the flare's pre-flare phase. In this study, we employ analysis of Interface Region Imaging Spectrograph (IRIS) spectroscopic data to investigate pre-flaring phenomena associated with this flare. We present time-series and wavelet analysis of non-thermal velocity, Doppler velocity, and line intensity quantities of the IRIS Si IV 1403 angstrom line. We find two ranges of periodic oscillations during the pre-flare phase: ~7-10 min and ~18-21 min oscillations, with local enhancements occurring near the polarity inversion line. We also find a steady rise in Si IV line parameters beginning 3 hours before the flare in the same region, transitioning into strong non-thermal velocities and blueshifts ~15 minutes before onset. These findings are consistent with a slow destabilization of the coronal MAGNETic field, possibly driven by the gradual activation of a flux rope, followed by a rapid shift to intense RECONNECTion activity leading to flare onset.

[abstract 16 / 34] (score: 3)
arXiv:2405.09739 [pdf, ps, other]

Title: Are all models wrong? Falsifying binary formation models in gravitational-wave astronomy

Authors: Lachlan Passenger, Eric Thrane, Paul D. Lasky, Ethan Payne, Simon Stevenson, Ben Farr,

Comments: 11 pages, 5 figures, 1 table

Subjects: astro-ph.HE gr-qc

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

As the catalogue of gravitational-wave transients grows, several entries appear "exceptional" within the population. Tipping the scales with a total mass of $\approx 150 M_\odot$, GW190521 likely contained BLACK HOLEs in the pair-instability mass gap. The event GW190814, meanwhile, is unusual for its extreme mass ratio and the mass of its secondary component. A growing model-building industry has emerged to provide explanations for such exceptional events, and Bayesian model selection is frequently used to determine the most informative model. However, Bayesian methods can only take us so far. They provide no answer to the question: does our model provide an adequate explanation for the data? If none of the models we are testing provide an adequate explanation, then it is not enough to simply rank our existing models - we need new ones. In this paper, we introduce a method to answer this question with a frequentist $p$-value. We apply the method to different models that have been suggested to explain GW190521: hierarchical mergers in ACTIVE GALACTIC NUCLEi and globular clusters. We show that some (but not all) of these models provide adequate explanations for exceptionally massive events like GW190521.

[abstract 17 / 34] (score: 3)
arXiv:2507.01294 [pdf, ps, other]

Title: A Gaussian process framework for testing general relativity with gravitational waves

Authors: Lachlan Passenger, Shun Yin Cheung, Nir Guttman, Nikhil Kannachel, Paul D. Lasky, Eric Thrane,

Comments: 17 pages, 11 figures, 1 table

Subjects: gr-qc astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Gravitational-wave astronomy provides a promising avenue for the discovery of new physics beyond general relativity as it probes extreme curvature and ultra-RELATIVISTIC dynamics. However, in the absence of a compelling alternative to general relativity, it is difficult to carry out an analysis that allows for a wide range of deviations. To that end, we introduce a Gaussian process framework to search for deviations from general relativity in gravitational-wave signals from binary BLACK HOLE mergers with minimal assumptions. We employ a kernel that enforces our prior beliefs that - if gravitational waveforms deviate from the predictions of general relativity - the deviation is likely to be localised in time near the merger with some characteristic frequency. We demonstrate this formalism with simulated data and apply it to events from Gravitational-Wave Transient Catalog 3. We find no evidence for a deviation from general relativity. We limit the fractional deviation in gravitational-wave strain to as low as 7% (90% credibility) of the strain of GW190701_203306.

[abstract 18 / 34] (score: 3)
arXiv:2512.19056 [pdf, ps, other]

Title: On the Diversity of Pulsar's Frequency-Dependent Circular Polarization

Authors: Shunshun Cao, Yanjun Guo, Jinchen Jiang, Kejia Lee, Weiyang Wang, Renxin Xu,

Comments: 13 pages, 10 figures, accepted by A&A

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

The nature of coherent radio emission is still challenging even after more than half a century of pulsar discovery, but it is generally a consensus that single-pulse observations are essential for probing the MAGNETospheric dynamics, especially with the largest single-dish telescope FAST (Five-hundred-meter Aperture Spherical radio Telescope). This paper aims to explain the observed diversity of single pulse circular POLARIZATION, and to constrain the multiplicity and Lorentz factor of pulsar MAGNETospheric plasma, with the mode coupling model in the limiting POLARIZATION region. Assuming that circular POLARIZATION comes only from wave mode coupling, we apply a Bayesian analysis to the FAST observed single pulse circular POLARIZATION spectra, involving numerical solving of wave mode coupling equations, and analyze the posterior probability distribution functions of the parameters. Although the model fails to quantitatively fit most circular POLARIZATION spectra, circular POLARIZATION of different frequency evolution is reproduced. For three chosen pulsars, the Bayesian analysis constrains the multiplicity to be approximately $10^{0}\sim10^{2}$, and the Lorentz factor to be approximately $10^{0.5}\sim10^{2}$. Pulsar circular POLARIZATION could be induced by wave mode coupling. The plasma flow responsible for coherent radio emission carries only a very small fraction of the pulsar spin-down energy loss.

[abstract 19 / 34] (score: 3)
arXiv:2601.04953 [pdf, ps, other]

Title: Triaxial Magnetars as Sources of Fast Radio Bursts

Authors: J. I. Katz,

Comments: 5 pp; much revised Published in Open Journal of Astrophysics

Subjects: astro-ph.HE

Created: 2026-05-07; Updated: 2026-05-11; Datestamp: 2026-05-11

Some of the mysterious temporal properties of Fast Radio Bursts (FRB) may be explained if they are produced by dynamically triaxial MAGNETars. If the bursts are narrowly collimated along open field lines, then observed repeating FRB are those few whose rotation axis, open field lines and infrequent radiation (analogous to pulsar giant pulses) point nearly to the observer. In apparently non-repeating FRB these are misaligned and the directions of the open field lines and infrequent radiation wander across the sky as they rotate, reducing their observed duty factors by several orders of magnitude. In repeaters a triaxial moment tensor moves the radiation pattern into or out of the line of sight on long (precessional) time scales, explaining periods of greater or lesser (or absent) activity. The dynamics of triaxial bodies may thwart the coherent integration of gravitational signals from rotating neutron stars.

[abstract 20 / 34] (score: 3)
arXiv:2603.09674 [pdf, ps, other]

Title: Fast X-ray Transients produced by Off-axis Jet-Cocoons from Long Gamma-Ray Bursts

Authors: Jian-He Zheng, Wenbin Lu,

Comments: 15 pages, 14 figures, Accepted

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Fast X-ray transients (FXTs) have been detected for over a decade, yet their origins are still enigmatic. The observed association between FXTs and broad-lined Type Ic SUPERNOVAe (SNe Ic-BL) suggests that some may share the same progenitor with Long Gamma-Ray Bursts. In this work, we numerically simulate the long-term evolution of a RELATIVISTIC JET propagating from inside the progenitor star up to the photon diffusion radius of the cocoon. Then we post-process the hydrodynamic results and calculate the cocoon cooling emission for various viewing angles from the JET axis. We find that, for viewing angles $θ_{\rm v}=10^{\circ}$-$20^{\circ}$, the off-axis cocoon emission can produce FXTs with luminosity $L_{\rm X}\simeq 10^{47-48} {\rm\, erg\,s^{-1}}$ and duration $t_{\rm X}\simeq 10$-$100\,$s. The observed spectra are quasi-thermal with the peak energy $E_{\rm peak}\simeq0.8$ keV. These properties naturally explain observational features of { a fraction of FXTs}, including their high luminosity, soft spectra, and lack of gamma-ray counterparts. The Rayleigh-Jeans tail of the FXT spectra extends to the UV, producing an early UV flash simultaneously. As the cocoon expands and cools, the emission peak shifts to UV and optical bands, resulting in a bright optical plateau lasting for $\sim1$ day with color temperature $T_{\rm UV/opt} \simeq (1{-}3)\times10^{4}\,$K and bolometric luminosity $L_{\rm bol}\simeq10^{41-42} {\rm\, erg\,s^{-1}}$, before the emergence of SUPERNOVA emission. Although our model underpredicts the UV/optical luminosity at $\sim1$ day for some events (e.g. EP 240414a), it still provides useful diagnostics for identifying the origins of FXTs.

[abstract 21 / 34] (score: 3)
arXiv:2605.02996 [pdf, ps, other]

Title: Wave interference as the origin of the cyclic MAGNETorotational dynamo in accretion disks: insights from weakly nonlinear theory and local shearing box simulations

Authors: Uddipan Banik, Amitava Bhattacharjee, James M. Stone,

Comments: 22 pages main text + 9 pages appendices, 12 figures, comments welcome

Subjects: astro-ph.HE astro-ph.EP astro-ph.SR physics.flu-dyn physics.plasm-ph

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Long-period cyclic reversals of the large-scale MAGNETic field are a prominent feature of the dynamo associated with the MAGNETorotational instability (MRI) in accretion disks, but their physical origin remains unclear. We develop a quasilinear theory (QLT) of the MRI dynamo where the electromotive force (emf) is computed from the linear eigenfunctions under the WKB approximation. The emf depends on the mean field $\mathbf{B}$ more generally than standard mean-field closures allow. In the unstratified case, the leading order contribution to the large-scale dynamo is the shear-current effect: the emf depends on the current $\mathbf{J}$ as $\pmb{\varepsilon} = \pmbβ\cdot\mathbf{J}$, with a tensor $\pmbβ(\mathbf{B},t)$ that oscillates with time $t$ and whose off-diagonal components generate the mean field. The oscillations arise from beats between the two branches of eigenfrequencies. Since the beat frequency varies only weakly with wavenumber, the beats remain coherent and drive the long-period butterfly cycle seen in local shearing box simulations. We predict a dominant cycle period $\sim 30{\left(1+a^2\right)}^{1/2}\,t_{\rm orb}$, with $a$ the vertical-to-radial aspect ratio and $t_{\rm orb}$ the orbital period, and an amplitude scaling $\sim a^2$ before saturation at $a\gtrsim 5$. Both trends agree with zero-net-flux unstratified shearing box simulations with Athena++. A carrier-envelope analysis of the simulation spectra shows that the same interference mechanism extends beyond strict QLT, through higher-order linear combinations of the eigenfrequencies, with observed cycles arising from pairwise beats within this spectral network. These results identify coherent interference between nearly degenerate eigenfrequencies as a key mechanism behind large-scale cyclic dynamos, with implications for MAGNETic variability in protoplanetary disks, X-ray binaries, and AGNs.

[abstract 22 / 34] (score: 3)
arXiv:2605.06767 [pdf, ps, other]

Title: Complex organic molecules and COSMIC RAY ionisation rate towards the massive protostar Cepheus A HW2

Authors: Emma W. Nielsen, Anna Punanova, Eva Wirström, Brandt Gaches, A. O. Henrik Olofsson, Paola Caselli, Prasanta Gorai, Jonathan C. Tan,

Comments: Submitted to A&A, comments are welcome. 20 pages, 18 figures

Subjects: astro-ph.GA

Created: 2026-05-07; Updated: 2026-05-11; Datestamp: 2026-05-11

Cosmic rays (CRs) are important drivers for molecular chemistry in star-forming regions, and laboratory experiments have shown that CRs can stimulate the release of complex organic molecules (COMs) such as methanol. Observationally, this has primarily been tested in cold, low-mass cores, so studying how CRs affect COM formation in a high-mass star-forming environment is of great interest. We performed a high-sensitivity wide-band spectral line survey with the Onsala 20 m telescope towards the high-mass protostar Cepheus A HW2, which is known to host an ionised JET. Consistent with previous studies, two primary velocity components ($-11$ km s$^{-1}$ and $-5$ km s$^{-1}$) were identified. Column densities and relative abundances of the detected ions and COMs were estimated from rotational diagrams, single transitions and RADEX grid searches (CH$_3$OH: $1.6\times10^{-9}$, CH$_3$CN: $5.9\times10^{-11}$, t-HCOOH: $7.9\times10^{-11}$, H$_2$CCO: $1.7\times10^{-11}$, CH$_3$CHO: $1.9\times10^{-11}$, CH$_3$OCHO: $7.6\times10^{-10}$ at $-11$ km s$^{-1}$). Deuterium fractions were also estimated (in range $0.002-0.3$ at $-11$ km s$^{-1}$), and the volume density of molecular hydrogen ($2.6\times10^5$ cm$^{-3}$ at $-11$ km s$^{-1}$) was constrained from the RADEX grid searches. Electron fractions and CR ionisation rates (CRIR, $6.8\times10^{-17}$ s$^{-1}$ at $-11$ km s$^{-1}$, $\leq9.2\times10^{-19}$ s$^{-1}$ at $-5$ km s$^{-1}$) were estimated through analytic chemistry using different ions as probes. The gas-grain chemical code Nautilus reproduced the observed abundances of CH$_3$OH, CH$_3$CN, HCO$^+$, N$_2$H$^+$ at the observed density, temperature and CRIR within the uncertainty of the model. The results indicate that the CR ionisation rate of the kinematic component associated with most of the COMs' emission in the region is locally enhanced.

[abstract 23 / 34] (score: 2)
arXiv:2412.20091 [pdf, ps, other]

Title: Gamma-Ray Burst Light Curve Reconstruction: A Comparative Machine and Deep Learning Analysis

Authors: A. Manchanda, A. Kaushal, M. G. Dainotti, A. Deepu, S. Naqi, J. Felix, N. Indoriya, S. P. Magesh, H. Gupta, K. Gupta, A. Madhan, D. H. Hartmann, A. Pollo, M. Bogdan, J. X. Prochaska, N. Fraija, D. Debnath,

Comments: 37 pages, 10 figures (105 panels), 5 Tables, Accepted in ApJ

Subjects: astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Gamma-Ray Bursts (GRBs), observed at high-z, are probes of the evolution of the Universe and can be used as cosmological tools. Thus, we need correlations with small dispersion among key parameters. To reduce such a dispersion, we mitigate gaps in light curves (LCs), including the plateau region, key to building the two-dimensional Dainotti relation between the end time of plateau emission (Ta) and its luminosity (La). We reconstruct LCs using nine models: Multi-Layer Perceptron (MLP), Bi-Mamba, Fourier Transform, Gaussian Process-Random Forest Hybrid (GP-RF), Bidirectional Long Short-Term Memory (Bi-LSTM), Conditional GAN (CGAN), SARIMAX-based Kalman filter, Kolmogorov-Arnold Networks (KANs), and Attention U-Net. These methods are compared to the Willingale model (W07) over a sample of 521 GRBs. MLP and Attention U-Net outperform other methods, with MLP reducing the plateau parameter uncertainties by 37.2% for log Ta, 38.0% for log Fa, and 41.2% for alpha (the post-plateau slope in the W07 model), achieving the lowest 5-fold cross-validation (CV) mean squared error (MSE) of 0.0275. Attention U-Net achieved the lowest uncertainty of parameters, a 37.9% reduction in log Ta, a 38.5% reduction in log Fa and a 41.4% reduction in alpha, but with a higher MSE of 0.134. Although Attention U-Net achieves the largest uncertainty reduction, the MLP attains the lowest test MSE while maintaining comparable uncertainty performance, making it the more reliable model. The other methods yield MSE values ranging from 0.0339 to 0.174. These improvements in parameter precision are needed to use GRBs as standard candles, investigate theoretical models, and predict GRB redshifts through machine learning.

[abstract 24 / 34] (score: 2)
arXiv:2601.10472 [pdf, ps, other]

Title: From Weibel seeds to collisionless dynamos beyond pair-plasmas

Authors: Lise Hanebring, James Juno, Ammar Hakim, Jason M. TenBarge, Istvan Pusztai,

Comments:

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

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Bridging the spatiotemporal scales of MAGNETic seed field generation and subsequent dynamo amplification in the weakly collisional intracluster medium presents an extreme numerical challenge. We perform collisionless turbulence simulations with initially unMAGNETized electrons that capture both MAGNETic seed generation via the electron Weibel instability and the ensuing dynamo amplification. Going beyond existing pair-plasma studies, we use an ion-to-electron mass ratio of 100 for which we find electron and ion dynamics are sufficiently decoupled. These simulations are enabled by the 10-moment collisionless fluid solver of Gkeyll, which evolves the full pressure tensor for all species. The electron heat-flux closure regulates pressure isotropization and effectively sets the MAGNETic Reynolds number. We investigate how the strength of the closure influences the transition between a regime reminiscent of previous kinetic pair-plasma simulations and a regime exhibiting dynamo behavior qualitatively similar to MAGNETohydrodynamics.

[abstract 25 / 34] (score: 2)
arXiv:2604.07256 [pdf, ps, other]

Title: Revisiting the sphaleron and axion production rates in QCD at high temperatures

Authors: Sayak Guin, Sayantan Sharma,

Comments: v2; Discussions mainly in Section IV B updated and references added

Subjects: hep-lat astro-ph.CO hep-ph hep-th

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

We report our new lattice results for the sphaleron rate calculated within a thermal effective field theory of soft SU(N) gluons whose momenta are below the MAGNETic scale, where $N=2,3$, for a wide range of temperatures spanning from $0.6$-$10^{15}$ GeV at sufficiently large volumes. Comparing these results with sphaleron rates in a non-thermal SU(N) plasma where the infrared gluons are over-occupied, we estimate the typical thermalization time for these ultra-soft soft gluons during the early stages of reheating after inflation. We also calculate the thermal production rate of RELATIVISTIC axions due to these non-perturbatively interacting soft gluons which shows a significant deviation from its perturbative estimate even at the electroweak scale.

[abstract 26 / 34] (score: 2)
arXiv:2604.13162 [pdf, ps, other]

Title: Investigating the Circumgalactic Medium through Mg II absorption coincidence

Authors: Paryag Sharma, Raghunathan Srianand, Hum Chand, Labanya Kumar Guha,

Comments: Published in MNRAS. This version matches the published article

Subjects: astro-ph.GA

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

We present a statistical measurement of the transverse coherence of Mg II $λ\lambda2796,2803$ absorption using a large sample of 9204 absorber-centric QUASAR sightline pairs from the Sloan Digital Sky Survey. We quantify the probability that an Mg II absorber detected along one sightline is also present along a nearby sightline, and measure how this coincidence probability varies with projected separation from $\sim$50 kpc to $\sim$1 Mpc. The resulting coincidence curve exhibits a clear two-regime structure: the coincidence probability rises steeply to $\sim$5-8% at separations below $\sim$100 kpc, but declines rapidly beyond this scale and settles into a low plateau of $\sim$1--2% out to $\sim$1 Mpc. A simple geometrical single-halo model reproduces the enhanced probability at $\lesssim$100 kpc, while the large-scale plateau is well explained by the expected contribution from galaxy clustering, confirmed using both photometric galaxy counts and the two-point correlation function. A complementary stacking analysis reveals a significant excess in Mg II equivalent width in paired sightlines lacking individual detections, implying a coherence scale of $\sim$100-200 kpc for the cool, metal-enriched CGM. Together, these results identify the transition from a halo-dominated coherence regime at small separations to a clustering-dominated regime at large scales, bridging the gap between small-scale lensing constraints and megaparsec-scale absorber clustering studies.

[abstract 27 / 34] (score: 2)
arXiv:2605.04158 [pdf, ps, other]

Title: Emergent gravity from nonlinear perturbation of spherical accretion with variable adiabatic index

Authors: Rohit Ghosh, Souvik Ghose, Biplab Raychaudhuri, Apashanka Das, Tapas K. Das,

Comments: 10 pages, 1 figure, revetex class

Subjects: gr-qc astro-ph.HE

Created: 2026-05-07; Updated: 2026-05-11; Datestamp: 2026-05-11

The main aim of the present work is to demonstrate that the analogue gravity phenomena are not an artifact of linear perturbation, rather gravity-like effects emerge through the non linear higher order perturbation of transonic fluid as well. To establish that fact, a spherically accreting astrophysical system has been considered where the hydrodynamic accretion with a RELATIVISTIC, multi-component equation of state with position dependent adiabatic index onto compact astrophysical objects has been considered. By extending the acoustic metric formalism beyond the linear regime, it has been shown that the aforementioned perturbations satisfy a covariant wave equation in an effective acoustic spacetime with non-linear corrections, making the analogue geometry dynamical. As a consequence, the acoustic horizon can shift (inward or outward), depending on the relative amplitudes of density, temperature, and mass accretion-rate fluctuations. This provides a more realistic framework to investigate the dynamics of the non-linear analogue spacetime in astrophysically relevant accretion flows.

[abstract 28 / 34] (score: 2)
arXiv:2605.05362 [pdf, ps, other]

Title: Constraining Lorentz symmetry breaking in bumblebee gravity with extreme mass-ratio inspirals

Authors: Sheng Long, Zhong-wu Xia, Huajie Gong, Zhoujian Cao, Qiyuan Pan, Jiliang Jing,

Comments:

Subjects: gr-qc

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Extreme mass-ratio inspirals (EMRIs), with their long-lived and highly RELATIVISTIC orbital evolution, can probe strong-field spacetime geometry and provide an important means to test general relativity. In this work, we investigate EMRI waveforms in a Schwarzschild-like BLACK HOLE spacetime arising in bumblebee gravity, where Lorentz symmetry breaking (LSB) is characterized by a dimensionless parameter $\ell$. We construct EMRI waveforms within the Augmented Analytic Kludge (AAK) framework using the modified orbital frequencies and fluxes. We find that $\ell$ significantly affects the orbital evolution and thereby modifies the waveform. These modifications grow with increasing $\ell$ and are further enhanced for more eccentric orbits. Furthermore, using Bayesian analysis, we obtain the posterior distributions of EMRI with the parameter $\ell$ included. Our results show that all injected source parameters are recovered within their $1\,σ$ credible intervals. We find that the bumblebee parameter $\ell$ can be constrained with an uncertainty of order $\mathcal{O}(10^{-4})$ by LISA.

[abstract 29 / 34] (score: 2)
arXiv:2605.06872 [pdf, ps, other]

Title: On the origin of the rotation of massive stars

Authors: André Oliva, Facundo D. Moyano, Luca Sciarini, Sylvia Ekström, Patrick Eggenberger, Georges Meynet,

Comments: Accepted for publication in Astronomy & Astrophysics

Subjects: astro-ph.SR astro-ph.GA

Created: 2026-05-07; Updated: 2026-05-11; Datestamp: 2026-05-11

We explore the origin of the rotation rates of massive stars. Contrary to their low-mass siblings, most massive stars do not have detectable MAGNETic fields, so that star-disk interaction models used for the formation of rotating low-mass stars do not apply. We investigate whether the MAGNETic fields of protostellar JETs present in the parent molecular cloud prevent the protostar from reaching the critical angular velocity. Starting from the gravitational collapse of a molecular cloud, we run two two-dimensional radiation-gravito-MAGNETohydroynamical simulations to study the formation of an accretion disk and the launching of MAGNETically-driven protostellar outflows (of particular interest is the formation of a MAGNETocentrifugal JET originating from the protostar and inner disk). We then study the angular momentum transfer from the disk and JET onto the protostar. Finally, we compute one-dimensional stellar evolution models of the pre-main sequence including our results from the disk-JET simulations and follow the angular momentum redistribution within the structure of the protostar. We find that the angular momentum transported outwards by the MAGNETically-driven protostellar outflows is sufficient for keeping the protostar below the critical speed at all times. Moreover, we are able to link the strength of the JET, and thus the rotation rate at the end of the accretion epoch, to the initial conditions for STAR FORMATION. Our results show that the JET strength produces a variety of stellar rotation rates, suggesting that protostellar JETs fix the rotation rate of massive stars.

[abstract 30 / 34] (score: 2)
arXiv:2605.06896 [pdf, ps, other]

Title: $Ab$ $initio$ modeling of Galactic dust polarized CMB foreground

Authors: Alexei G. Kritsuk, Ka Wai Ho, Ka Ho Yuen, Raphael Flauger,

Comments: 4 pages, 3 figures, contribution to the 2026 Cosmology session of the 60th Rencontres de Moriond

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

Created: 2026-05-07; Updated: 2026-05-11; Datestamp: 2026-05-11

We present the analysis of high-resolution synthetic dust POLARIZATION maps derived from large-scale simulations of MAGNETized multiphase interstellar turbulence carried out with the AthenaK code on the $Frontier$ exascale supercomputer at the Oak Ridge National Laboratory. Our turbulence model accurately captures spectral properties of the $E$- and $B$-modes measured by $Planck$ at 353 GHz. The simulations provide new insights into the physical origins of the observed $E/B$ asymmetry and positive $TE$ signal, facilitating the development of advanced models of Galactic foreground emission for current and future CMB experiments.

[abstract 31 / 34] (score: 2)
arXiv:2605.07616 [pdf, ps, other]

Title: Probing the Inert Doublet Dark Matter with Stellar-Mass Black Hole Mini-Spikes

Authors: Rameswar Sahu,

Comments: 15 Pages, 2 Figures, 1 Table

Subjects: hep-ph astro-ph.HE

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

The nature of DARK MATTER remains a central unresolved problem in contemporary physics, motivating the exploration of well-defined extensions of the Standard Model. Among these, the Inert Doublet Model provides a minimal and theoretically consistent framework accommodating a viable weakly interacting massive particle DARK MATTER candidate. In this work, we investigate the IDM parameter space through an analysis of FERMILAT observations of DARK MATTER mini-spikes surrounding stellar-mass BLACK HOLEs. Owing to the strong gravitational compression of DARK MATTER in the vicinity of these systems, the resulting annihilation signal can be significantly enhanced, rendering such environments exceptionally sensitive probes of DARK MATTER interactions. We find that substantial regions of the IDM parameter space, particularly in the high-mass regime, are subject to stringent constraints extending into the multi-TeV range. These results underscore the increasingly important role of indirect detection in probing particle DARK MATTER scenarios beyond the reach of current COLLIDER and direct detection experiments.

[abstract 32 / 34] (score: 2)
arXiv:2605.07778 [pdf, ps, other]

Title: Scalar memory from compact binary coalescences

Authors: Jann Zosso, Silvia Gasparotto, Llibert Aresté Saló, Daniela D. Doneva, Stoytcho S. Yazadjiev,

Comments: 17 pages, 5 figures

Subjects: gr-qc

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Gravitational memory provides a distinctive low-frequency probe of gravity, but explicit merger studies beyond general relativity remain limited. In this work, we investigate memory from binary BLACK HOLE mergers in Ricci-coupled scalar-Gauss-Bonnet gravity, a natural extension of scalar-Gauss-Bonnet theory that admits an additional scalar breathing POLARIZATION. Based on numerical-relativity waveforms of binary BLACK HOLE coalescences, we show that the change in the scalar charge of the system across merger generates a significant scalar-memory contribution. For a GW150914-like system, this effect modifies the memory signal in a gravitational-wave detector on the same observable timescale and by an amount comparable to the pure scalar-Gauss-Bonnet correction to tensor memory. Thus, it can substantially enhance the total deviation from the general-relativity prediction over a broad range of source and detector configurations. We argue that this identifies a general mechanism: whenever a compact-binary merger changes the asymptotic charge of an additional gravitational field, and that field sources an observable extra POLARIZATION, the resulting memory can provide a leading low-frequency signature of new gravitational physics.

[abstract 33 / 34] (score: 2)
arXiv:2605.07822 [pdf, ps, other]

Title: Pair creation as a source of longitudinal chiral MAGNEToconductivity

Authors: J. L. Acosta Avalo, S. Montesino Castillo, E. E. García Reynaldo,

Comments: 12 pages and 4 figures. arXiv admin note: text overlap with arXiv:2402.16859, arXiv:1602.01402

Subjects: hep-ph

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

We demonstrate that chiral transport in a strongly MAGNETized electron-positron plasma can arise dynamically from dissipative pair-creation processes encoded in the imaginary part of the photon POLARIZATION tensor within one-loop finite-temperature quantum electrodynamics (QED). In the kinematic region corresponding to longitudinal photon absorption, real electron-positron pair production induces axial charge nonconservation and generates an electric current parallel to the MAGNETic field, without requiring the introduction of an external chiral chemical potential. This provides a microscopic mechanism for chiral MAGNETic transport, offering an alternative to hydrodynamic or anomaly-based effective descriptions in which chirality imbalance is typically introduced as an external input. We derive an explicit expression for the longitudinal MAGNEToconductivity associated with this process and show that it exhibits an approximately quadratic dependence on the MAGNETic field only within a restricted intermediate regime. This behavior emerges from the dominance of the lowest Landau levels as a characteristic of negative longitudinal MAGNEToresistance. We further analyze how Pauli blocking regulates the pair-creation phase-space and demonstrate that the dynamically generated chiral imbalance is suppressed at high frequencies, revealing a transition between chiral-active and non-chiral-active regimes. Our results connect microscopic QED processes with anomaly-related transport phenomena in strongly MAGNETized RELATIVISTIC plasmas, where pair creation provides a dynamical source for chiral imbalance.

[abstract 34 / 34] (score: 2)
arXiv:2605.07845 [pdf, ps, other]

Title: Warm Topological Langmuir Cyclotron Wave

Authors: Virginia Billings, Hong Qin, Chuang Ren, J. B. Marston,

Comments: 16 pages, 4 figures

Subjects: physics.plasm-ph

Created: 2026-05-08; Updated: 2026-05-11; Datestamp: 2026-05-11

Finite-temperature effects in MAGNETized electron plasmas create a new Weyl-point degeneracy between the warm Langmuir and right-circularly polarized waves. The associated topological charge at this warm Weyl point is found to be 1, which, by the index theorem, predicts a gap-traversing topological edge mode. Solving the full warm-fluid eigenmode problem In a 1D inhomogeneous equilibrium, we numerically identify this anticipated mode as the warm topological Langmuir-cyclotron wave, which is absent in the cold limit and occurs in a parameter regime relevant to the LArge Plasma Device (LAPD) at UCLA.