Current date: 2026-07-24

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Datestamp limit: 2026-07-24 (0 days ago)

Created/updated limit: 2026-07-17 (7 days ago)

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OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-07-24&until=2026-07-24&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 705

Keyword score statistics

score 9 -- 1 abstracts

score 8 -- 3 abstracts

score 7 -- 1 abstracts

score 5 -- 3 abstracts

score 4 -- 3 abstracts

score 3 -- 10 abstracts

score 2 -- 17 abstracts

in total -- 38 abstracts

Articles that appeared on 2026-07-24

[abstract 1 / 38] Wow! (score: 9)
arXiv:2607.19972 [pdf, ps, other]

Title: Constraints on the VHE counterpart of two binary BLACK HOLE mergers observed by the MAGIC and CTAO LST-1 telescopes

Authors: K. Abe, S. Abe, J. Abhir, A. Abhishek, V. A. Acciari, F. Acero, A. Aguasca-Cabot, I. Agudo, I. Albanese, D. Ambrosino, F. Ambrosino, T. Aniello, S. Ansoldi, L. A. Antonelli, C. Aramo, C. Arauner, A. Arbet-Engels, C. Arcaro, T. T. H. Arnesen, P. Aubert, A. Babić, C. Bakshi, A. Baktash, M. Balbo, A. Bamba, A. Baquero-Larriva, U. Barres-de-Almeida, J. A. Barrio, L. Barrios-Jiménez, I. Batkovic, J. Baxter, J. Becerra-González, W. Bednarek, E. Bernardini, J. Bernete, A. Berti, J. Besenrieder, C. Bigongiari, A. Biland, E. Bissaldi, O. Blanch, Ž. Bošnjak, G. Bonnoli, P. Bordas, L. Breton-Zaourat, A. Briscioli, E. Bronzini, G. Brunelli, J. Buces, A. Bulgarelli, I. Burelli, L. Burmistrov, C. Campa, A. Campoy-Ordaz, M. Cardillo, S. Caroff, A. Carosi, R. Carosi, R. Carraro, M. Carretero-Castrillo, F. Cassol, A. J. Castro-Tirado, D. Cerasole, G. Ceribella, A. Cerviño-Cortínez, Y. Chai, A. Chiavassa, A. Chilingarian, G. Chon, L. Chytka, G. M. Cicciari, A. Cifuentes Santos, J. L. Contreras, J. Cortina, H. Costantini, S. Covino, M. Croisonnier, G. D'Amico, P. Da-Vela, M. Dalchenko, F. Dazzi, A. De-Angelis, M. de-Bony-de-Lavergne, B. De-Lotto, R. de-Menezes, G. De-Palma, V. de-Souza, R. Del-Burgo, L. Del-Peral, M. Delfino, C. Delgado Mendez, J. Delgado-Mengual, D. della-Volpe, L. Di-Bella, C. Di-Domenico, A. Di-Piano, F. Di-Pierro, R. Di-Tria, L. Di-Venere, C. Díaz, A. Dinesh, E. Do Souto Espineira, D. Dominis-Prester, A. Donini, D. Dorner, M. Doro, L. Eisenberger, D. Elsässer, G. Emery, J. Escudero, L. Farina, L. Feligioni, F. Ferrarotto, A. Fiasson, L. Foffano, L. Font, F. Frías-García-Lago, Y. Fukazawa, S. Gallozzi, J. Garcia-Garcia, R. J. García López, S. Garcia-Soto, D. Gasparrini, S. Gasparyan, M. Gaug, J. G. Giesbrecht Paiva, N. Giglietto, F. Giordano, P. Gliwny, N. Godinovic, T. Gradetzke, R. Grau, J. Green, G. Grolleron, S. Gunji, P. Günther, D. Hadasch, A. Hahn, M. Hashizume, T. -Hassan, K. Hayashi, L. Heckmann, M. Heller, J. Herrera-Llorente, N. Hiroshima, D. Hoffmann, D. Horns, J. Houles, D. Hrupec, T. Inada, S. Inoue, K. Ioka, M. Iori, D. Israyelyan, A. Iuliano, J. Jahanvi, I. Jiménez-Martínez, J. Jiménez-Quiles, I. Jorge-Rodrigo, J. Jurysek, M. Kagaya, S. Kankkunen, V. Karas, H. Katagiri, T. Kayanoki, D. Kerszberg, M. Khachatryan, G. W. Kluge, Y. Kobayashi, K. Kohri, J. Konrad, P. Kornecki, P. M. Kouch, H. Kubo, J. Kushida, B. Lacave, M. Láinez, A. Lamastra, L. Lemoigne, E. Lindfors, M. Linhoff, S. Lombardi, F. Longo, R. López-Coto, M. López-Moya, A. López-Oramas, S. Loporchio, A. Lorini, J. Lozano-Bahilo, F. Lucarelli, H. Luciani, L. Lulić, P. L. Luque-Escamilla, P. Majumdar, M. Makariev, M. Mallamaci, D. Mandat, G. Maneva, M. Manganaro, S. Mangano, D. K. Maniadakis, G. Manicò, K. Mannheim, F. Marini, M. Mariotti, G. Marsella, J. Martí, D. Martin, G. Martínez, M. Martínez, O. Martinez, P. Maru\v{s, evec, M. Massa, D. Mazin, S. Menchiari, J. Méndez-Gallego, S. Menon, E. Mestre-Guillen, D. Miceli, T. Miener, J. M. Miranda, J. M. Miranda, R. Mirzoyan, M. Mizuno, M. Molero-Gonzalez, E. Molina, H. A. Mondal, T. Montaruli, A. Moralejo, S. Morales-Sanchez-De-Lozada, K. Morita, A. -Morselli, V. Moya, K. Mrakovčić, A. L. Müller, H. Muraishi, T. Nagata, S. Nagataki, T. Nakamori, C. Nanci, A. Negro, A. Neronov, V. Neustroev, D. Nieto-Castaño, M. Nievas-Rosillo, C. Nigro, L. Nikolić, K. Nilsson, K. Noda, V. Novotny, S. Nozaki, M. Ohishi, A. Okumura, R. Orito, L. Orsini, J. Otero-Santos, P. Ottanelli, S. Paiano, M. Palatiello, G. Panebianco, D. Paneque, R. Paoletti, J. M. Paredes, M. Pech, M. Pecimotika, M. Peresano, F. Perrotta, M. Persic, F. Pfeifle, E. Pietropaolo, M. Pihet, G. Pirola, C. Plard, F. Podobnik, M. Polo, C. Pozo-Gonzaléz, P. G. Prada Moroni, E. Prandini, S. Rainò, R. Rando, W. Rhode, M. Ribó, J. Rico, V. Rizi, G. Rodriguez-Fernandez, A. Roy, E. Ruiz-Velasco, N. Sahakyan, T. Saito, S. Sakurai, D. A. Sanchez, H. Sano, E. Santos-Moura, T. Šarić, Y. Sato, F. G. Saturni, V. Savchenko, F. Schiavone, K. Schmitz, F. Schussler, T. Schweizer, M. Seglar-Arroyo, U. Sharma, T. Siegert, G. Silvestri, A. Simongini, J. Sitarek, V. Sliusar, D. Sobczynska, I. Sofia, A. Stamerra, J. Strišković, D. Strom, M. Strzys, Y. Suda, A. Sunny, H. Tajima, M. Takahashi, R. Takeishi, S. J. Tanaka, J. Tartera Barberà, T. Tavernier, P. Temnikov, Y. Terada, K. Terauchi, T. Terzic, M. Teshima, M. Tluczykont, T. Tomura, D. F. Torres, F. Tramonti, P. Travnicek, G. Tripodo, A. Tutone, S. Ubach, M. Vacula, M. Vázquez-Acosta, S. Ventura, G. Verna, I. Viale, A. Viana, A. Vigliano, C. F. Vigorito, E. Visentin, V. Vitale, M. Vorbrugg, G. Voutsinas, I. Vovk, T. Vuillaume, R. Walter, C. Walther, L. Wan, P. Witczak, F. Wersig, T. Yamamoto, R. Yamazaki, Y. Yao, P. K. H. Yeung, T. Yoshida, T. Yoshikoshi, W. Zhang,

Comments: In press at PASP. Corresponding authors: Andrea Simongini, Juan Jiménez Quiles, Mario Pecimotika, Monica Seglar-Arroyo

Subjects: astro-ph.HE

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

We present very-high-energy gamma-ray observations of two binary BLACK HOLE merger candidates, GW240615_113620 and GW241125_010116, performed with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes and the first Large-Sized Telescope of the Cherenkov Telescope Array Observatory's (CTAO LST-1). GW240615_113620 was the best localized event of the fourth observing run of the LIGO-Virgo-KAGRA gravitational waves interferometers. GW241125_010116 was temporally and spatially coincident with a sub-threshold short-duration burst detected with the SWIFT-Burst Alert Telescope (BAT), the SWIFT-X-Ray Telescope (XRT) and the Einstein Probe Follow-up X-ray Telescope (FXT). We observed the two events in stereoscopic mode, taking advantage of the improved sensitivity of joint MAGIC+LST-1 observations. No detection was achieved in the GeV-TeV gamma-ray band for any of the two sources. The unfavourable observing conditions of both events posed a challenge for a standard analysis and therefore a non standard analysis was necessary for both objects. Owing to the small localization area and the association with a GRB-like burst respectively, these events represented an unprecedented opportunity to study in details the electroMAGNETic emission from binary BLACK HOLEs merger events and, in particular, we discussed two theoretical models that predict a detectable gamma-ray emission and the possible future applications.

[abstract 2 / 38] Wow! (score: 8)
arXiv:2607.20604 [pdf, ps, other]

Title: Revealing the Structure and Magnetization of GRB Jets with ALMA Polarization Observations

Authors: Tanmoy Laskar, Collin T. Christy, Noah Franz, Gavin Farley, Kate D. Alexander, Jonathan Granot, Ramandeep Gill, Tarraneh Eftekhari, Shiho Kobayashi, Hendrik van Eerten, Raffaella Margutti, Edo Berger,

Comments: Submitted to ApJ, comments welcome

Subjects: astro-ph.HE

Created: 2026-07-22; Updated: 2026-07-24; Datestamp: 2026-07-24

We present a systematic study of the currently available ALMA millimeter polarimetric sample of GAMMA-RAY BURST (GRB) afterglows. Our sample comprises 24 observations (20 new) of 11 long-duration GRBs spanning $\approx0.1$-87 days after the burst. We detect significant linear POLARIZATION in 8 observations across 6 events, with POLARIZATION degrees ranging from $Π_L\approx0.6\%$ to $2.4\%$. For the remaining observations, we place deep upper limits (median $Π_L\lesssim1\%$). Multi-epoch observations reveal diverse POLARIZATION evolution. GRB 190114C yields the best-sampled $Π_L$ for a radio afterglow to date, with early evolution favoring patchy MAGNETic fields in the reverse shock (RS) and later POLARIZATION broadly consistent with forward-shock (FS) models. GRB 220921A exhibits a rapid rise in POLARIZATION from $Π_L\lesssim0.4\%$ to $2.4\%$ over 1.9-6.8 days, inconsistent with toroidal RS MAGNETic-field models but broadly consistent with several FS random-field models. GRB 221009A yields the highest-significance POLARIZATION detections in the sample ($Π_L\approx1.4$-$1.6\%$), yet neither existing FS nor RS POLARIZATION models reproduce both the observed POLARIZATION evolution and the viewing geometry inferred from broadband afterglow modeling, with the exception of patchy fields in the RS. Deep upper limits for GRB 171205A rule out RS toroidal-field models for the published off-axis geometry, while a strong, single-epoch detection of GRB 190829A, if RS-dominated, requires a nearly on-axis geometry for toroidal-field configurations. Interpreting the observations within a patchy-field framework implies MAGNETic-field coherence scales of order $θ_B\sim10^{-3}$-$10^{-2}$ rad. These observations demonstrate the diagnostic power of radio/mm polarimetry for probing the MAGNETic-field structure, emission region, and viewing geometry of RELATIVISTIC GRB JETs.

[abstract 3 / 38] Wow! (score: 8)
arXiv:2607.20615 [pdf, ps, other]

Title: The Origin of the Magnetic Flux Driving TDE Jets

Authors: Nimrod Tripto, Julian Krolik, Tsvi Piran,

Comments: 19 pages, 2 figures, 2 tables

Subjects: astro-ph.HE

Created: 2026-07-22; Updated: 2026-07-24; Datestamp: 2026-07-24

Tidal Disruption Events (TDEs) occur when a star approaches a BLACK HOLE closely enough to be torn apart by tidal forces, after which the stellar debris begins to orbit the BLACK HOLE. Over the past decade, hundreds of TDEs have been identified, with many more expected from upcoming surveys. A small subset of these events launch transient, highly luminous RELATIVISTIC JETs (10^47-10^48 erg/s isotropic-equivalent). These are generally interpreted in terms of the Blandford--Znajek mechanism, implying the presence of substantial MAGNETic flux near the BLACK HOLE horizon. The question arises: What is the origin of this flux? In this paper, we investigate three candidate sources: stellar MAGNETic fields, MAGNETic flux from large radii around the BLACK HOLE (the Lasso mechanism), and MAGNETic flux stored in the inner portion of a pre-existing accretion disk. We find that: observed stellar MAGNETic fields are insufficient to power these JETs; the Lasso mechanism requires shallow radial MAGNETic field profiles and a mechanism to trap the MAGNETic flux brought by the debris in the vicinity of the BLACK HOLE; pre-existing MAGNETic flux near the BLACK HOLE in an accretion disk is the most plausible source.

[abstract 4 / 38] Wow! (score: 8)
arXiv:2607.20618 [pdf, ps, other]

Title: Polarization of impulsive RELATIVISTIC JETs propagating in a stratified medium

Authors: Gal Birenbaum, Paz Beniamini, Jonathan Granot,

Comments: 13 pages, 12 figures

Subjects: astro-ph.HE

Created: 2026-07-22; Updated: 2026-07-24; Datestamp: 2026-07-24

Gamma-ray bursts (GRBs) and at least some tidal disruption events (TDEs) are highly energetic transients involving impulsive RELATIVISTIC JETs. As these JETs propagate into their surrounding media, they drive a RELATIVISTIC forward shock into it, which radiates multi-wavelength polarized SYNCHROTRON emission, known as an afterglow. Analyzing the afterglow light curve along with its POLARIZATION curve can shed light on the geometrical properties of the GRB or TDE system such as the MAGNETic field structure behind the shock, the JET angular structure and even distinguish between proposed scenarios of delayed radio emission seen in some TDEs. While most afterglow POLARIZATION measurements are for long GRBs, whose massive star progenitor winds are expected to form a stratified external medium, the POLARIZATION from such environments is largely unexplored. Similarly, stratified media surround JETted TDEs. In this work we explore how shock propagation into a stratified medium affects the observed afterglow POLARIZATION from impulsive RELATIVISTIC JETs. We find that for both top hat and structured JETs, in most cases the POLARIZATION levels are reduced and its temporal signature evolves on longer time scales compared to a uniform external medium. The POLARIZATION peaks at times close to a geometrical break in the light curve, indicating measurements during this time probe the maximal levels of POLARIZATION possible for the system. In addition, observationally capturing the POLARIZATION evolution time scales can assist in constraining our viewing angle and the external medium stratification. Such composite models, that account for more realistic systems that are motivated by light curve fittings, will allow us to complement afterglow light curves better and promote joint modeling of these observables.

[abstract 5 / 38] Wow! (score: 7)
arXiv:2603.04533 [pdf, ps, other]

Title: Geometric masking in AGN JETs and its implications for unification and BLAZAR physics

Authors: Alberto Domínguez,

Comments: Published in Research Notes of the American Astronomical Society

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

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

I explore the theoretical implications of the Geometric Masking scenario for AGN Unification and the BLAZAR sequence. In PKS 2155$-$304, GeV spectral hardening appears locked to its $\sim 1.7$ yr quasi-periodic oscillation trough, suggesting high-flux states are dominated by a soft, geometrically amplified envelope that masks an underlying hard core. While this foundational mechanism builds on observations of coexisting emission regions (Madero & Domínguez 2026) and phase-locked spectral hardening (Domínguez et al. 2026), here I propose hypothetical extensions that fall outside the scope of those works. I propose that Doppler boosting preferentially enhances this soft component in closely aligned JETs. This visibility bias could extend AGN Unification and introduce a geometric modulation layer to the BLAZAR sequence. Under this speculative framework, low-flux states represent windows of geometric transparency, and misaligned systems act as naturally unmasked laboratories. Consequently, the intrinsic duty cycle of extreme acceleration in AGN JETs may be higher than inferred from flux-selected observations.

[abstract 6 / 38] Yes (score: 5)
arXiv:2605.13697 [pdf, ps, other]

Title: Guitar Nebula: extreme accelerator in extreme environment

Authors: Igor Nikolaevich Nikonorov, Maxim Vladimirovich Barkov, Maxim Lyutikov,

Comments: 11+9 pages, 4+2 figures, 4 tables. Accepted for publication in JHEAP

Subjects: astro-ph.HE

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Guitar nebula is a prime example of a class of bow-shock pulsar wind nebulae (PWNe), powered by a wind of a supersonically moving neutron star. Bow-shock PWNe can probe particle acceleration processes in RELATIVISTIC pulsar winds, as well as the structure of the interstellar medium (ISM). We demonstrate that the Guitar is an exceptional object in a number of ways. First, particles escaping the PWN and forming the X-ray ``kinetic JET'' need to be accelerated to the energies corresponding to the maximal electric potential of the neutron star $η_\text{acc}\gtrsim 3/4$ : it is another example of the class of extreme accelerators. Second, exceptionally bright H$_α$ emission requires that the central pulsar PSR J2225+6535 passes through a dense, low ionization ISM region. Bright X-ray emission of the ``kinetic JET'' then also requires exceptionally high MAGNETic field, $\sim 100~μ$G. We hypothesize that Guitar passes through the one of long-predicted, narrow dense shells of an old SUPERNOVA remnant, currently in the ``pressure-driven snowplow'' regime.

[abstract 7 / 38] Yes (score: 5)
arXiv:2607.20621 [pdf, ps, other]

Title: Time-evolving Diagnostic of the Ionized Absorbers in NGC 4051. II. High-throughput Time-resolved Spectroscopy

Authors: Alfredo Luminari, Fabrizio Nicastro, Roberto Serafinelli, Riccardo Middei, Yair Krongold, Elias Kammoun, Luigi Piro, Francesca Diaferia,

Comments: A&A accepted. 12 main pages, 14 figures. Abstract abridged

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

Created: 2026-07-22; Updated: 2026-07-24; Datestamp: 2026-07-24

Active Galactic Nuclei (AGNs) are one of the most powerful sources in the Universe. The accretion-liberated energy can strongly impact the surrounding environment, up to the host galaxy and beyond. Notwithstanding their ubiquitous presence, nuclear outflows are poorly characterised, mainly due to the degeneracy between their number density $n_e$ and radial location $r$, intrinsic in the photoionisation equilibrium models which are usually employed to fit the observations. This degeneracy prevents a self-consistent determination of the gas energetics and, therefore, of the efficiency in transporting the AGN energy outwards. We analyse a joint XMM-Newton and NUSTAR observation of the bright, highly-variable AGN NGC 4051. The high flux allows to perform time-resolved spectroscopy and, thus, to study the evolution of its three main ionised absorbers. Since the timescale of the gas ionisation variability depends on its number density, constraining it allows to break the density-distance degeneracy. We employ the Time-Evolving PhotoIonisation Device (TEPID) to model the temporal evolution of the outflows. We split the observation in 37 time-resolved spectra, each few kiloseconds long (total duration 160 ksec), and we fit them jointly with the time-resolved ionised spectra. We fully constrain $n_e=10^7 cm^{-3}$ and $r=10^4$ gravitational radii for the absorber with the highest opacity and intermediate ionisation. This distance is the same of the optical and UV Broad Line Region and of the soft X-ray emission lines. The fastest and most ionised absorber is at $r<600 r_G$, cospatial with the broad component of the Fe K$α$ line. The slowest and least ionised absorber is at $r \geq 3.8 \cdot 10^5 r_G$, the same distance of the cold torus and the narrow Fe K$α$. The total energy outflow rate is below $10^{-4} L_{bol}$, ruling out a meaningful mechanical impact on the host galaxy.

[abstract 8 / 38] Yes (score: 5)
arXiv:2607.20945 [pdf, ps, other]

Title: Using horizon shadows to distinguish a BLACK HOLE and a white hole

Authors: Chengyu Bi, Zhoujian Cao,

Comments: 11 pages, 14 figures. Extended work of Chinese Physics C,49(2):025109 (2025)

Subjects: gr-qc astro-ph.HE

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Within theoretical frameworks such as loop quantum gravity, BLACK HOLEs may evolve into white holes through a quantum bounce. This paper uses general RELATIVISTIC ray-tracing techniques to calculate the ray-traced imaging of accretion disks from the previous cosmic stage during the Kerr BLACK HOLE and post-bounce Kerr white hole phases. Calculations show that the BLACK HOLE image presents a crescent emission ring and a central shadow. In contrast, after radiation from the previous universe penetrates the rotating white hole, eccentric and asymmetric nested intensity ring structures form in the synthetic image due to frame-dragging and lensing effects. We analyze the influence of spin parameters, observation inclinations, and accretion disk geometric configurations on the distribution of this nested ring structure using synthetic images and intensity profiles. Building upon this, we introduce polarized ray-tracing calculations for radiation across evolutionary stages. This process results in the POLARIZATION image features after the POLARIZATION vector is subjected to the gravitational field and spacetime spin dragging during the photon propagation through the white hole horizon and internal spacetime. The spatial rotation patterns and concentric interference fringes in the white hole POLARIZATION images exhibit a distinct inter-ring POLARIZATION discontinuity. This phenomenon differs from the POLARIZATION behavior of BLACK HOLEs. The intensity ring structures and POLARIZATION inter-ring discontinuity features provide multi-band and polarimetric interferometry baselines to overcome morphological observational degeneracies. This provides theoretical guidance for future very-long-baseline interferometry (VLBI) to distinguish BLACK HOLEs and white holes.

[abstract 9 / 38] Yes (score: 4)
arXiv:2607.20609 [pdf, ps, other]

Title: Black hole-neutron star binaries with high spins and large mass asymmetries: III. Properties of the ejected material and its electroMAGNETic signatures

Authors: Konrad Topolski, Samuel D. Tootle, Paramvir Singh, Mattia Bulla, Luciano Rezzolla,

Comments: 29 pages, 18 figures, comments are welcome

Subjects: gr-qc astro-ph.HE

Created: 2026-07-22; Updated: 2026-07-24; Datestamp: 2026-07-24

Compact binary systems consisting of a BLACK HOLE (BH) and a neutron star (NS) are expected to provide detectable signals both in the gravitational wave and in the electroMAGNETic channels, thus representing excellent sources for multi-messenger astronomy. In this third paper in a series, we report on the geometric and thermodynamic properties of the purely dynamical ejecta component modeled in our general-RELATIVISTIC MAGNETohydrodynamical simulations of BHNS systems over a comprehensive binary parameter space consisting of large mass ratio and high BH spin. The tidal disruption and dynamical mass ejection is studied by monitoring the transfer of energy and angular momentum to matter for the particular case of a highly unequal-mass binary with large BH spin, extending known results for low-mass-ratio, irrotational BHNS binaries. By varying the binary parameters, we investigate their influence on the geometric, thermodynamic, and kinematic properties of the ejected matter. Furthermore, we employ the nuclear-reaction network SkyNet to obtain the elemental abundances resulting from the r-process active in the ejecta and study how they depend on the properties of the progenitor objects. Finally, using the radiative-transfer code POSSIS, we compute the kilonova light-curves from the results of our simulations, discuss their bolometric and optical/near-infrared evolution, and compare them with the AT2017gfo data and upper-limits for S190814bv, finding overall consistency.

[abstract 10 / 38] Yes (score: 4)
arXiv:2607.21316 [pdf, ps, other]

Title: Spirited Away: Advective Loss of Cosmic Rays into the Milky Way's Circumgalactic Medium Explains the Large Magellanic Cloud's Low Gamma-ray Luminosity

Authors: Taaseen Islam, Hilay Shah, Mark R. Krumholz, Roland Crocker,

Comments: 15 pages, 7 figures, submitted to the Open Journal of Astrophysics

Subjects: astro-ph.HE

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Models of galactic-scale COSMIC RAY production and transport have successfully reproduced the radio and $γ$-ray spectra of many galaxies; however, one notable exception is the Large Magellanic Cloud (LMC), where models that successfully fit other galaxies consistently overestimate its $γ$-ray flux. Here we investigate this discrepancy by applying the CRIPTIC COSMIC RAY transport code to recent MAGNETohydrodynamic simulations of the LMC's interactions with the Milky Way circumgalactic medium that accurately reproduce observations of the LMC's MAGNETic field structure. We recover a simulated $γ$-ray luminosity that is close to the observed luminosity for a wide range of COSMIC RAY transport models, while our control simulations of an isolated LMC not interacting with the Milky Way show the same over-prediction problem as previous investigations. Simulations including the CGM interaction yield lower $γ$-ray luminosities because in them COSMIC RAYs escape the galaxy primarily via advection, significantly decreasing the emission from collisional processes and changing the dominant $γ$-ray emission mechanism from pion decay to inverse Compton emission. Comparisons of the detailed spectral shape show that our interacting LMC models match the observed $γ$-ray spectrum at photon energies below $\sim 10$ GeV, but still slightly overestimate the flux at higher energies, suggesting either more strongly energy-dependent transport than the models we have explored, or a COSMIC RAY injection spectrum steeper than the $p^{-2.2}$ that we adopt.

[abstract 11 / 38] Yes (score: 4)
arXiv:2607.21587 [pdf, ps, other]

Title: XMM-Newton and SWIFT Unveil Another X-Ray Transient in NGC 4945, XMM J130514.64-493311.27

Authors: Ryan W. Pfeifle, Kimberly A. Weaver, Jenna M. Cann, Murray Brightman, Miranda McCarthy,

Comments: 10 pages, 5 figures, 1 table. Resubmitted to ApJ

Subjects: astro-ph.HE

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

NGC 4945 hosts a Compton-thick, low luminosity AGN and a nuclear starburst in its core and has been the subject of many previous X-ray investigations of the AGN emission structure, nuclear starburst properties, and ultraluminous X-ray (ULX) source populations. Indeed, NGC 4945 has proven to be a rich system for ULX and X-ray transients, with at least four X-ray transients being reported over the last 15 years. Here we report the detection of an X-ray transient source, XMM J130514.64-493311.27, in NGC 4945 in the latest and deepest XMM-Newton observation of NGC 4945 to-date. The source lies $\sim5.5'$ south of the nucleus and was not detected in any previous XMM-Newton or Chandra imaging, but the source was detected by SWIFT-XRT in 2008, 2019, and in 2022, the latter of which coincides roughly with our new XMM-Newton imaging; we are therefore tracing the most recent outburst of this object with XMM-Newton. The source is soft with $Γ\approx3$, and our spectroscopic analysis suggests the source is best characterized by a multicolor disk + power law model or, alternatively, a multicolor disk + thermal plasma model, with a 0.3-10 keV X-ray luminosity of $\sim2.2-2.3\times10^{38}$. We find no evidence for a counterpart in the optical, near-infrared, ultraviolet, or in the radio, but we identify a candidate counterpart in NEOWISE mid-IR light curves. We propose that this X-ray source is an X-ray binary within NGC 4945 caught during its most recent active phase.

[abstract 12 / 38] (score: 3)
arXiv:2512.09017 [pdf, ps, other]

Title: Viscously Spreading Accretion Disks around Black Holes: Implications for TDEs, LFBOTs and other Transients

Authors: Mila Winter-Granic, Eliot Quataert,

Comments: 17 pages, 11 figures. Published The Open Journal of Astrophysics

Subjects: astro-ph.HE

Created: 2026-07-22; Updated: 2026-07-24; Datestamp: 2026-07-24

We present a simple time-dependent model of viscously spreading accretion disks around BLACK HOLEs (BHs) with masses between $10-10^8M_\odot$. We apply the results to observations of late-time emission in tidal disruption events (TDEs) and luminous fast blue optical transients (LFBOT) such as AT2018cow. Our model generalizes previous work by incorporating outflows during super-Eddington accretion, non-conservation of mass and angular momentum in TDE circularization, irradiation of the outer disk by the inner accretion flow, and a range of viscous stress models. We show that many late-time plateaus in TDEs can be explained by disks formed with a large spread in angular momentum due to redistribution during circularization. Viscous spreading on year timescales is not required, although it is also compatible with the data. The collapse of radiation pressure dominated thin disks to the stable gas-pressure dominated phase greatly underpredicts TDE plateau luminosities, strongly favoring thermally stable MAGNETically dominated disk models. Irradiation of the outer disk in TDEs due to misalignment of the stellar orbit and BLACK HOLE spin increases plateau luminosities and durations by factors of a few. Continued study of late-time TDE emission provides a unique opportunity to constrain the physics of disk formation and circularization, disk warps, angular momentum transport, and other poorly understood aspects of disk physics. The models we develop can also explain the late-time optical-UV emission in the LFBOT AT2018cow for BH masses of ~$10-100M_\odot$. The faint X-ray emission at late times in AT2018cow is likely due to ongoing absorption. Our models predict that late-time X-rays should eventually be detectable again, and that HST/JWST observations of AT2018cow may detect a break in the SED at near-IR-optical wavelengths, providing a powerful probe of outer accretion disk thermodynamics.

[abstract 13 / 38] (score: 3)
arXiv:2601.14370 [pdf, ps, other]

Title: Hunting the first Cosmic Giants: formation and detectability of Direct Collapse Black Holes around high-redshift QUASARs

Authors: Alessandro Trinca, Alessandro Lupi, Zoltán Haiman, Marta Volonteri, Rosa Valiante, Raffaella Schneider, Roberto Decarli,

Comments: Accepted for publication in MNRAS. 19 pages, 8 figures, 2 appendices. Replaced with the accepted version

Subjects: astro-ph.GA

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

The rapid emergence of supermassive BLACK HOLEs (SMBHs) in the early Universe poses a challenge to current models of BLACK HOLE growth. One promising formation pathway is the direct collapse BLACK HOLE (DCBH) scenario, in which gas in pristine, low-metallicity halos forms supermassive (or quasi-) stars leading to massive BLACK HOLEs seeds under specific environmental conditions. In this work, we investigate the potential host environments of DCBHs by coupling a semi-analytic model tracing BH formation and galaxy co-evolution with high-resolution N-body DARK MATTER merger trees. This allows us to trace the population of DCBHs formed during the hierarchical assembly of a $\sim 10^{12} ~\rm M_\odot$ DARK MATTER halo hosting a bright $10^9 ~\rm M_\odot$ QUASAR at redshift $z \approx 7$. We find that, when accounting for local fluctuations in the UV radiation field within this early cosmic structure, massive BH seeds can form via direct collapse as early as $z \approx 22$. Even under more stringent conditions for heavy seed formation, tens of DCBHs are predicted to emerge within the simulated overdensity down to $z \sim 14$, at which point metal enrichment of the intergalactic medium inhibits further episodes of direct collapse. A significant fraction of the massive BLACK HOLE population formed at $z > 14$ is expected to survive in satellite galaxies that do not merge with the central halo down to $z \approx 7$. We show that the existence of such a population of ungrown heavy BH seeds can be probed through deep JWST observations targeting regions surrounding bright high-redshift QUASARs, and we discuss tailored observational strategies to detect and identify these elusive systems.

[abstract 14 / 38] (score: 3)
arXiv:2601.14497 [pdf, ps, other]

Title: The failed failed-SUPERNOVA scenario of M31-2014-DS1

Authors: Noam Soker,

Comments: Published in the Open Journal of Astrophysics

Subjects: astro-ph.HE

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

I examine a recently proposed failed-SUPERNOVA scenario for the fading of the yellow supergiant event M31-2014-DS1, and find that it requires unlikely fine-tuned parameters to work, if at all. In the failed-SUPERNOVA scenario, most of the yellow supergiant collapsed to form a BLACK HOLE. Due to the energy carried by neutrinos from the cooling, collapsing core, gravity decreases, leading to the ejection of a small fraction of the outer envelope, some of which remains bound. The fallback accreted gas possesses large angular-momentum fluctuations due to the pre-collapse envelope convection. The fallback material forms intermittent accretion disks around the BLACK HOLE that launch JETs (or disk wind), which unbind most of the bound material. The failed-SUPERNOVA scenario for M31-2014-DS1 requires that only <1% of the bound material be accreted by the BLACK HOLE, but the JETs do not shut down the backflow for over 10 years. I find this fine-tuned requirement unlikely. I also find that, due to the rapid radiative cooling of the outflow interaction zone with the outer gas, the expected radiation is about an order of magnitude or more above the observed value. These, as well as earlier challenges raised against the failed-SUPERNOVA scenario, make the alternative type II intermediate-luminosity optical transient scenario, in which fading is due to dust ejection in a violent binary interaction, more likely. The fading event M31-2014-DS1 does not support the failed-SUPERNOVA scenario predicted by the neutrino-driven explosion mechanism of core-collapse SUPERNOVAe.

[abstract 15 / 38] (score: 3)
arXiv:2603.25065 [pdf, ps, other]

Title: Fitting the light curves of tidal disruption events with non-parabolic model

Authors: Shiyan Zhong, Chenxi Shang, Xiaowei Liu,

Comments: Accepted for publication in Research in Astronomy and Astrophysics

Subjects: astro-ph.HE

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Tidal disruption events (TDEs) are powerful probes of supermassive BLACK HOLE (SMBH) properties and accretion physics. The existing light curve fitting tools assume that the disrupted stars are on parabolic orbits, which may introduce systematic biases in derived parameters. In this work, we extend the model of Zhong (2025) to construct a non-parabolic TDE model that incorporates orbital energy of the disrupted star as a free parameter ($\tildeε_{\rm orb}$) to modify the debris mass distribution and mass fallback rate. We apply this model to 30 TDEs from the ZTF-I survey and compare the results with those from a standard parabolic model. We find that neglecting orbital energy leads to biased BLACK HOLE mass estimates: for eccentric (hyperbolic) orbits, parabolic models systematically underestimate (overestimate) the BLACK HOLE mass. Additionally, we measure orbital eccentricities ($e$) and penetration factors ($β$) of the disrupted stars in this sample, enabling an investigation of their origins via the $e$-$β$ parameter space. Most events (24/30) are consistent with production via two-body relaxation in spherical nuclear star clusters, but six outliers with high $β$ and $e<1$ suggest alternative mechanisms. Our results highlight the importance of accounting for orbital energy in TDE modeling to improve the accuracy of SMBH mass measurements and to better understand the dynamical origin of the disrupted stars.

[abstract 16 / 38] (score: 3)
arXiv:2604.14535 [pdf, ps, other]

Title: Ultrahigh-energy cosmogenic neutrino emissions in the high-redshift universe

Authors: Shigeru Yoshida, Maximilian Meier,

Comments: 8 pages, 3 figures: The version accepted for publication in PRD Letters

Subjects: astro-ph.HE

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

The James Webb Space Telescope (JWST) revealed a large population of ACTIVE GALACTIC NUCLEi (AGN) with redshifts greater than five. We show that if they emit ultrahigh-energy protons with energies up to $\lesssim 10^{19}$ eV, the cosmogenic neutrino production in the high-redshift CMB field yields a neutrino flux with a bump at around 50 PeV. This flux is potentially consistent with the current neutrino intensity estimate by the IceCube Neutrino Observatory within the parameter space allowed from the AGN luminosity and number density estimates by JWST. Future neutrino observations that confirm the 50-PeV bump and constrain the small-scale anisotropy will infer ultra-high energy cosmic-ray emissions in the early universe.

[abstract 17 / 38] (score: 3)
arXiv:2607.20614 [pdf, ps, other]

Title: Gravitational Lensing Predictions from Wave Simulations of Fuzzy Dark Matter

Authors: Jiajun Zhou, Zhengxiang Li, Amruth Alfred, Ran Gao, Jeremy Lim, Zong-Hong Zhu,

Comments: 18 pages, 9 figures; Comments are welcome

Subjects: astro-ph.CO

Created: 2026-07-22; Updated: 2026-07-24; Datestamp: 2026-07-24

In the cold DARK MATTER paradigm, ultra-light particles are emerging as strong contenders to conventional massive particles. A unique prediction of DARK MATTER comprising such ultra-light particles, known as fuzzy DARK MATTER (FDM), is the presence of strong density modulations throughout galactic halos due to wave interference, which -- when approximated by a Gaussian random field (GRF) -- have been proposed to account for the inability to reproduce the observed positions (when measured at sufficient precisions) and flux ratios of multiply-lensed images of QUASARs. Here, we predict for the first time the properties of gravitationally lensed images generated from 3-D density fields obtained by wave simulations that directly evolve the Schrödinger--Poisson equations. Using a novel framework to project these evolved density fields along various axes of the 3-D halo, we obtain the distribution of perturbations to the positions of lensed images. As an exacting test, we find that particles of mass $10^{-22}$ eV can reproduce the positions of the quadruply-lensed radio JETs in system HS 0810+2554 to a level better than that of either the GRF approximation or, to a greater extent, an NFW best-fit solution, both of which rely on accurately capturing the global 3-D density field of DARK MATTER halos. Our work highlights the importance of wave simulations for making accurate FDM lensing predictions and the potential for high-resolution observations of lensed systems to serve as a direct probe of the nature of DARK MATTER.

[abstract 18 / 38] (score: 3)
arXiv:2607.20617 [pdf, ps, other]

Title: A dust-free hierarchically nested supermassive-star model for James Webb Space Telescope Little Red Dots

Authors: Pau Amaro Seoane,

Comments: Accepted for publication ApJ Letters

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

Created: 2026-07-22; Updated: 2026-07-24; Datestamp: 2026-07-24

Observations by the James Webb Space Telescope reveal a population of high-redshift objects, the little red dots. These sources exhibit optical reddening alongside blue ultraviolet continua, host broad Balmer lines indicative of active BLACK HOLEs, and lack detectable x-ray emission. Their cosmic abundance at early epochs exceeds standard Eddington-limited growth timescales. Prevailing models invoke specific dust geometries to reconcile these traits. We propose a dust-free physical framework. We evaluate the concept that the dust-poor subset of little red dots represents the observational manifestation of hierarchically nested supermassive stars. A primary radiation-dominated envelope traps a nuclear star cluster. Plunging stars drive a MAGNETic dynamo that inflates the envelope. This produces the red optical continuum. Unobscured infalling stars yield the blue ultraviolet excess. Trapped stellar debris sediments to form a high-density secondary core within this Compton-thick host. This nested topology thermalizes x-rays and powers the broad hydrogen $α$ features. The central seed accretes at the global radiation limit of the host envelope. This kinetic bypass shortens the assembly timescale from hundreds of millions of years to tens of millions of years.

[abstract 19 / 38] (score: 3)
arXiv:2607.20671 [pdf, ps, other]

Title: A multi-band radio flux density catalog of ICRF3 sources using the Onsala Twin Telescopes

Authors: Alva Kinman, Rüdiger Haas, Karine Le Bail, Jun Yang, Eskil Varenius,

Comments: 21 pages, 17 figures (including Appendix). Submitted to A&A

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

Created: 2026-07-22; Updated: 2026-07-24; Datestamp: 2026-07-24

The VLBI Global Observing System (VGOS) is the next generation system for geodetic and astrometric Very Long Baseline Interferometry (VLBI). To optimize the observing time for each source in geodetic schedules, a flux density catalog is needed for the sources that are observed at the VGOS frequencies. The aim of this work is to monitor the flux densities of geodetic sources in the VGOS bands. The obtained flux density time series can be used for more effective scheduling of geodetic and astrometric VLBI experiments, as well as probing ACTIVE GALACTIC NUCLEi (AGN) physics. The Onsala Twin Telescopes have been used as a single baseline interferometer to measure flux densities of AGN that are part of the International Celestial Reference System (ICRF3). The telescopes observed at 3.2, 5.5, 6.6 and 10.4 GHz simultaneously. Both locally planned flux monitoring sessions and international geodetic experiments were analyzed. The data were calibrated using the Common Astronomy Software Applications (CASA). The possibility of predicting geodetic signal-to-noise ratios (S/N) using the measured flux densities was also tested. Simultaneous light curves in up to four frequencies have been obtained for 361 sources. The majority of the sources vary significantly in flux density during the measurement period. Most sources have a flat or inverted spectrum, with only 6 % having a steep spectrum. Furthermore, the flux densities from this work were shown to more precisely predict geodetic signal-to-noise ratios compared to the standard VGOS flux density catalog, especially for the most variable sources. Flux density variation needs to be taken into account to obtain the most optimal VGOS schedules. The flux density catalog presented here is expected to be of use for both astronomy and geodesy. We plan to continue the monitoring program.

[abstract 20 / 38] (score: 3)
arXiv:2607.21026 [pdf, ps, other]

Title: The Extended Ultrahigh-energy Gamma-Ray Emission in the Vicinity of PSR J2238+5903

Authors: Zhen Cao, F. Aharonian, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, J. Blunier, A. V. Bukevich, C. M. Cai, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, E. S. Chen, G. H. Chen, H. K. Chen, L. F. Chen, Liang Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen, S. H. Chen, S. Z. Chen, T. L. Chen, X. B. Chen, X. J. Chen, X. P. Chen, Y. Chen, N. Cheng, Q. Y. Cheng, Y. D. Cheng, M. Y. Cui, S. W. Cui, X. H. Cui, Y. D. Cui, B. Z. Dai, H. L. Dai, L. X. Dai, Z. G. Dai, Danzengluobu, Y. X. Diao, A. J. Dong, X. D. Duan, J. H. Fan, Y. Z. Fan, J. Fang, J. H. Fang, K. Fang, C. F. Feng, H. Feng, L. Feng, S. H. Feng, X. T. Feng, Y. Feng, Y. L. Feng, S. Gabici, B. Gao, Q. Gao, W. Gao, C. Ge, M. M. Ge, T. T. Ge, L. S. Geng, G. Giacinti, G. H. Gong, Q. B. Gou, M. H. Gu, W. M. Gu, F. L. Guo, J. Guo, K. J. Guo, X. L. Guo, Y. Q. Guo, R. P. Han, O. A. Hannuksela, M. Hasan, H. H. He, H. N. He, J. Y. He, X. Y. He, Y. He, S. Hernández-Cadena, C. Hou, X. Hou, H. B. Hu, S. C. Hu, D. H. Huang, F. Huang, J. J. Huang, X. L. Huang, X. T. Huang, X. Y. Huang, Y. Huang, Z. J. Huang, A. Inventar, X. L. Ji, H. Y. Jia, K. Jia, H. B. Jiang, K. Jiang, X. W. Jiang, Z. J. Jiang, M. Jin, S. Kaci, M. M. Kang, I. Karpikov, D. Khangulyan, D. Kuleshov, W. H. Lei, Cheng Li, Cong Li, D. Li, F. Li, H. B. Li, H. C. Li, Jian Li, Jie Li, K. Li, L. Li, R. L. Li, T. Y. Li, W. L. Li, X. R. Li, X. Y. Li, Y. Li, Zhe Li, Zhuo Li, E. W. Liang, Y. F. Liang, S. J. Lin, B. Liu, C. Liu, D. Liu, D. B. Liu, H. Liu, J. Liu, J. L. Liu, J. R. Liu, M. Y. Liu, R. Y. Liu, S. M. Liu, T. Liu, W. Liu, Y. Liu, Y. Liu, Y. N. Liu, Y. Q. Lou, Q. Luo, Y. Luo, H. K. Lv, B. Q. Ma, L. L. Ma, X. H. Ma, I. O. Maliy, J. R. Mao, Z. Min, W. Mitthumsiri, Y. Mizuno, G. B. Mou, A. Neronov, K. C. Y. Ng, S. C. -Y. Ng, M. Y. Ni, L. Nie, L. J. Ou, Z. W. Ou, P. Pattarakijwanich, Z. Y. Pei, D. Y. Peng, J. C. Qi, M. Y. Qi, J. J. Qin, H. L. Qu, A. Raza, C. Y. Ren, M. Q. Ruan, D. Ruffolo, A. Sáiz, D. Savchenko, D. Semikoz, L. Shao, O. Shchegolev, Y. Z. Shen, X. D. Sheng, F. W. Shu, H. C. Song, Yu. V. Stenkin, Y. Su, C. Y. Sun, D. X. Sun, H. Sun, J. X. Sun, M. Sun, Q. N. Sun, X. N. Sun, Z. B. Sun, N. H. Tabasam, J. Takata, P. H. T. Tam, H. B. Tan, Q. W. Tang, R. Tang, Z. B. Tang, W. W. Tian, C. N. Tong, L. H. Wan, C. Wang, D. H. Wang, G. W. Wang, H. G. Wang, J. C. Wang, J. F. Wang, J. S. Wang, K. Wang, Kai Wang, Kai Wang, L. P. Wang, L. Y. Wang, W. Wang, X. G. Wang, X. J. Wang, X. Y. Wang, Y. Wang, Y. D. Wang, Z. H. Wang, Z. X. Wang, Zheng Wang, D. M. Wei, J. J. Wei, Y. J. Wei, T. Wen, S. S. Weng, C. Y. Wu, H. R. Wu, Q. W. Wu, S. Wu, X. F. Wu, Y. S. Wu, S. Q. Xi, J. Xia, G. M. Xiang, D. X. Xiao, G. Xiao, Y. F. Xiao, B. H. Xie, Y. L. Xin, H. D. Xing, Y. Xing, D. R. Xiong, B. N. Xu, C. Y. Xu, D. L. Xu, R. X. Xu, S. S. Xu, L. Xue, D. H. Yan, T. Yan, C. Y. Yang, F. F. Yang, L. L. Yang, M. J. Yang, R. Z. Yang, W. X. Yang, Z. H. Yang, Z. G. Yao, X. A. Ye, L. Q. Yin, N. Yin, X. H. You, Z. Y. You, Y. H. Yu, Q. Yuan, H. Yue, H. D. Zeng, T. X. Zeng, W. Zeng, X. T. Zeng, M. Zha, B. Zhang, B. B. Zhang, B. T. Zhang, C. Zhang, H. Zhang, H. M. Zhang, H. Y. Zhang, J. L. Zhang, J. Y. Zhang, L. Y. Zhang, Li Zhang, P. F. Zhang, R. Zhang, R. Y. Zhang, S. R. Zhang, S. S. Zhang, S. Y. Zhang, W. Zhang, X. Zhang, X. L. Zhang, X. P. Zhang, Yi Zhang, Yong Zhang, Z. P. Zhang, J. Zhao, L. Zhao, L. Z. Zhao, X. H. Zhao, F. Zheng, T. C. Zheng, B. Zhou, H. Zhou, J. N. Zhou, L. Zhou, M. Zhou, P. Zhou, R. Zhou, X. X. Zhou, X. X. Zhou, B. Y. Zhu, C. G. Zhu, F. R. Zhu, H. Zhu, K. J. Zhu, Y. F. Zhu, Z. F. Zhu, Y. C. Zou, X. Zuo,

Comments:

Subjects: astro-ph.HE

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

We present a comprehensive analysis of the recently discovered TeV gamma-ray source, LHAASO J2238+5900. Based on data collected from the LHAASO, our fitting results suggest that the source is significantly extended with an angular extension of 0.54° \pm 0.01° and is spatially coincident with the pulsar PSR J2238+5903. Its spectrum is characterized by a power-law with a cutoff at 41.0\pm 3.5 TeV. Additionally, the source exhibits a significant signal of 7.9σabove 100 TeV, implying that it is a PeVatron candidate. While the gamma-ray emission is consistent with a pulsar wind nebula (PWN) scenario, the relatively large extension size also allows for a halo interpretation, potentially caused by electron-positron pairs escaping from the PWN.

[abstract 21 / 38] (score: 3)
arXiv:2607.21385 [pdf, ps, other]

Title: Ultra-High-Energy Particle Production in Binary Mergers Endowed with Magnetic Fields

Authors: Carlos H. Coimbra-Araujo, Rita C. Anjos, Jonas P. Pereira, Jaziel G. Coelho,

Comments: 16 pages, 4 figures. Accepted for publication in Physical Review D

Subjects: astro-ph.HE astro-ph.CO gr-qc hep-ph hep-th

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

We study the production of ultra-high-energy particles via the Bañados--Silk--West (BSW) mechanism in the pre-merger phase of binary systems detected by LIGO-Virgo-KAGRA. By solving the geodesic equations for charged particles in MAGNETized Kerr spacetime with fields of $B \sim 10^{12}$--$10^{14}$~G, we demonstrate that collisions near the horizon can achieve center-of-mass energies $E_{\mathrm{cm}} \sim 10^{18}$-- $10^{20}$~eV, placing them firmly in the ultra-high-energy cosmic-ray (UHECR) range. We systematically explore the parameter space of merger remnants, varying BLACK HOLE mass ($M \sim 20$--$150\,M_\odot$, characteristic of the binary BLACK HOLE population), dimensionless spin ($χ_f \sim 0.7$--$0.9$), MAGNETic field strength, and particle angular momenta. Our analysis reveals three distinct acceleration regimes: a gravity-dominated regime ($B < 10^{12}$~G) with negligible MAGNETic enhancement; a transition regime ($10^{12}~\text{G} \lesssim B \lesssim 10^{13}~\text{G}$) where gravitational and MAGNETic effects compete; and a MAGNETic-dominated regime ($B > 10^{13}$~G) where fields amplify collision energies by nearly an order of magnitude. For the 34 gravitational-wave events with high remnant spins ($χ_f > 0.7$), we compute the maximum achievable energies, finding that systems with $χ_f \gtrsim 0.85$ and $M \gtrsim 100\,M_\odot$ can reach $E_{\mathrm{max}} \sim 10^{20}$~eV. Our results establish MAGNETized binary mergers, particularly BLACK HOLE--neutron star systems and postmerger BLACK HOLE remnants formed in binary neutron star coalescences, as promising sources of UHECRs and provide quantitative predictions linking gravitational-wave observables to particle acceleration efficiency.

[abstract 22 / 38] (score: 2)
arXiv:2506.18151 [pdf, ps, other]

Title: Inferring Neutron Star Nuclear Properties from Gravitational-Wave and Gamma-Ray Burst Observations

Authors: Hsin-Yu Chen, Ore Gottlieb,

Comments: ApJ accepted version

Subjects: astro-ph.HE gr-qc nucl-ex

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Recent discoveries of long GAMMA-RAY BURSTs accompanied by kilonova emission prompted interest in understanding their progenitors. If these long-duration bursts arise from neutron star mergers, similar to short GAMMA-RAY BURSTs, it raises the question of which physical properties govern burst duration. The mass of the merger stands out as a key factor, strongly influencing the lifetime of the merger remnant, which in turn determines the burst duration: lighter mergers that form long-lived remnants produce short bursts, whereas more massive mergers result in short-lived remnants that collapse into BLACK HOLEs, powering longer bursts. In this paper, we compare merger rates from gravitational-wave observations of LIGO-Virgo-KAGRA with the rates of kilonova-associated long and short GAMMA-RAY BURSTs, to identify a characteristic total neutron star mass that separates the two burst classes at $1.36^{+0.08}_{-0.09}$ times of the neutron star Tolman-Oppenheimer-Volkoff (TOV) mass (median and 68% confidence interval). This result suggests that massive neutron stars could survive an extended period after merger. Our findings are robust against substantial observational uncertainties and model assumptions. Moreover, we identify a correlation between the characteristic mass and the neutron star TOV mass, allowing constraints on the characteristic mass to be directly mapped to upper limits on the TOV mass. This establishes a novel, independent method for constraining the neutron star TOV mass and their equation of state using gravitational-wave and GAMMA-RAY BURST observations.

[abstract 23 / 38] (score: 2)
arXiv:2510.20319 [pdf, ps, other]

Title: Vortex ring-cylinder interactions: regimes, RECONNECTion, and the role of topology

Authors: Andres Herrera-Gómez, Juan Ángel Tendero-Ventanas, Rodolfo Ostilla-Mónico,

Comments:

Subjects: physics.flu-dyn

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

We investigate the interaction between vortex rings and cylindrical obstacles using direct numerical simulations across a wide range of geometric and dynamical parameters. The flow is characterized in terms of the diameter ratio between ring and object $T_D = d/D$, the Reynolds number based on circulation $Re_Γ$, and the slenderness ratio $Λ$. By systematically varying $T_D$ and $Re_Γ$, we identify three distinct interaction regimes: the wire, cutting, and wall regimes. In the wire regime ($T_D \lesssim 0.05$), the primary vortex ring survives the interaction with limited deformation and carries a weak lobe of secondary vorticity generated by the object's boundary layer. As $T_D$ increases, the interaction transitions to the cutting regime, where the ring is split into two secondary structures formed through the RECONNECTion between boundary-layer and ring vorticity. For sufficiently large obstacles ($T_D \gtrsim 0.8$), the wall regime emerges, in which boundary-layer vorticity dominates and the primary ring is deflected and stretched along the obstacle surface. The transition between regimes depends primarily on $T_D$, while increasing $Re_Γ$ enhances vortical dynamics producing additional small-scale and tertiary structures. Finally, by modifying the topology of the obstacle, we demonstrate that RECONNECTion and recovery of the primary ring depend critically on the topology of the secondary vorticity. These results provide a unified framework for interpreting vortex-body interactions, bridging the gap between vortex ring, tube, and wall collision dynamics.

[abstract 24 / 38] (score: 2)
arXiv:2603.20371 [pdf, ps, other]

Title: Radial Velocity Orbital Solutions for Candidate Black Hole and Neutron Star Binary Systems in the Gaia Data Release 3 Catalog

Authors: Joshua D. Simon, Casey Y. Lam, Kareem El-Badry, Henrique Reggiani, Sukanya Chakrabarti, Puragra Guhathakurta, Ian B. Thompson, Nidia Morrell, Daniel Huber, Benjamin J. Fulton, Lauren M. Weiss,

Comments: 26 pages, 16 figures, 4 tables. Accepted for publication in ApJ

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

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

We present spectroscopic followup observations of binary systems from the Gaia Data Release 3 (DR3) binary catalog that were selected to have large enough mass functions for their companions to be BLACK HOLEs or neutron stars. The selection includes 20 stars that are astrometric and/or spectroscopic binaries, as well as 11 stars with large accelerations both in the plane of the sky and along the line of sight but no DR3 orbital solution. We provide classifications for this entire sample, including radial velocity orbital solutions for 12 binaries. Apart from the previously published binaries Gaia BH1, Gaia BH2, and Gaia NS1, we show that the Gaia orbits are incorrect for all of the stars with candidate dark companions above 2 Msun. We suggest more conservative cuts on the significance and goodness of fit parameters that may be useful for identifying reliable orbital solutions in the tail of the binary star distribution. Although we find no new confirmed BLACK HOLE or neutron star companions, one accelerating system has a minimum companion mass of 1.16 +/- 0.01 Msun that is likely to be a neutron star or an ultramassive white dwarf. The acceleration catalogs may therefore provide a largely unexplored source of additional wide binaries containing compact objects.

[abstract 25 / 38] (score: 2)
arXiv:2605.19653 [pdf, ps, other]

Title: Evidence for Intermediate-Mass Black Holes From Microlensing Signatures in CHIME/FRB catalog 2

Authors: Huan Zhou, Zhengxiang Li, Cheng-Gang Shao, Xi-Jing Wang, Kai Liao, He Gao, Zong-Hong Zhu,

Comments: 12 pages, 5 figures, 1 table

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

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Intermediate-mass BLACK HOLEs (IMBHs) are the missing link in the cosmic hierarchy of BLACK HOLEs, bridging the gap between stellar-mass BLACK HOLEs and supermassive ones. They also serve as unique laboratories for testing strong-field gravity and are prime targets for future multi-messenger observations. However, IMBHs are a population that has remained notoriously difficult to detect. The microlensing effect of fast radio bursts (FRBs) can serve as a clean and powerful method to probe IMBHs. In this work, we develop a pipeline to search for microlensed FRBs based on their dynamic spectra and apply it to the CHIME/FRB Catalog 2. Two microlensing signatures have been identified in two separate sources, i.e. FRB~20190131D and FRB~20211115A. The inferred lens masses for these two signatures are $\sim[280-467]~M_{\odot}$ and $\sim[539-609]~M_{\odot}$, respectively. Here we interpret them as evidence for IMBHs. If there are no intervening structures-such as galaxies or clusters-along the line of sights for these two sources, the two identified IMBHs might be isolated and of primordial origins. In that case, we obtain primordial BLACK HOLEs (PBHs) within these two mass ranges would constitute $\sim4\%$ of DARK MATTER. Moreover, if these two candidates are not genuine lensing signatures, the abundance of intermediate-mass PBHs with masses $>300,M_{\odot}$ is constrained to be $\sim13\%$ at $95\%$ confidence level. Therefore, more comprehensive observational information for FRBs, together with a deeper understanding of whether the intrinsic emission mechanisms of FRBs can produce lensing-like signals, will be crucial for establishing this effect as a powerful tool for probing (primordial) IMBHs.

[abstract 26 / 38] (score: 2)
arXiv:2606.00498 [pdf, ps, other]

Title: Suppression of boosted relic neutrinos by photon backgrounds during ultra-high-energy COSMIC RAY propagation

Authors: Gabriel Azeredo, Vitor de Souza,

Comments: 18 pages, 5 figures

Subjects: astro-ph.HE hep-ph

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Constraining the cosmic neutrino background (C$ν$B) represents a major experimental challenge in cosmology. Recent studies have suggested that relic neutrinos boosted by ultra-high-energy COSMIC RAYs (UHECRs) may generate observable diffuse neutrino fluxes. Previous estimates have not effectively propagated the primary COSMIC RAYs, often neglecting crucial energy losses and the unavoidable, competing interactions with diffuse photon backgrounds. Here we revisit these expectations using a realistic Monte Carlo propagation framework. This approach allows us to consistently incorporate COSMIC RAY energy losses, nuclear photodisintegration, and production of secondary neutrinos. We show that interactions with diffuse photon backgrounds strongly suppress the boosted relic neutrino flux predicted in simplified propagation scenarios. Furthermore, we demonstrate that to produce any observable suppression on the UHECR energy spectrum at Earth, or for the boosted C$ν$B component to become comparable to the cosmogenic neutrino flux, the C$ν$B density must be enhanced by a factor, the so-called overdensity, of extreme magnitude ($η\gtrsim 10^{8}$).

[abstract 27 / 38] (score: 2)
arXiv:2606.17141 [pdf, ps, other]

Title: Chemical enrichment of the Perseus cluster core seen by XRISM/Resolve

Authors: XRISM Collaboration, Marc Audard, Hisamitsu Awaki, Ralf Ballhausen, Aya Bamba, Ehud Behar, Rozenn Boissay-Malaquin, Laura Brenneman, Gregory V. Brown, Lia Corrales, Elisa Costantini, Renata Cumbee, Maria Diaz Trigo, Chris Done, Tadayasu Dotani, Ken Ebisawa, Megan E. Eckart, Dominique Eckert, Satoshi Eguchi, Teruaki Enoto, Yuichiro Ezoe, Adam Foster, Ryuichi Fujimoto, Yutaka Fujita, Yasushi Fukazawa, Kotaro Fukushima, Akihiro Furuzawa, Luigi Gallo, Javier A. García, Liyi Gu, Matteo Guainazzi, Kouichi Hagino, Kenji Hamaguchi, Isamu Hatsukade, Katsuhiro Hayashi, Takayuki Hayashi, Natalie Hell, Edmund Hodges-Kluck, Ann Hornschemeier, Yuto Ichinohe, Daiki Ishi, Manabu Ishida, Kumi Ishikawa, Yoshitaka Ishisaki, Jelle Kaastra, Timothy Kallman, Erin Kara, Satoru Katsuda, Yoshiaki Kanemaru, Richard Kelley, Caroline Kilbourne, Shunji Kitamoto, Shogo Kobayashi, Takayoshi Kohmura, Aya Kubota, Maurice Leutenegger, Michael Loewenstein, Yoshitomo Maeda, Maxim Markevitch, Hironori Matsumoto, Kyoko Matsushita, Dan McCammon, Brian McNamara, François Mernier, Eric D. Miller, Jon M. Miller, Ikuyuki Mitsuishi, Misaki Mizumoto, Tsunefumi Mizuno, Koji Mori, Koji Mukai, Hiroshi Murakami, Richard Mushotzky, Hiroshi Nakajima, Kazuhiro Nakazawa, Jan-Uwe Ness, Kumiko Nobukawa, Masayoshi Nobukawa, Hirofumi Noda, Hirokazu Odaka, Shoji Ogawa, Anna Ogorzałek, Takashi Okajima, Naomi Ota, Stephane Paltani, Robert Petre, Paul Plucinsky, Frederick S. Porter, Katja Pottschmidt, Kosuke Sato, Toshiki Sato, Makoto Sawada, Hiromi Seta, Megumi Shidatsu, Aurora Simionescu, Randall Smith, Hiromasa Suzuki, Andrew Szymkowiak, Hiromitsu Takahashi, Mai Takeo, Toru Tamagawa, Keisuke Tamura, Takaaki Tanaka, Atsushi Tanimoto, Makoto Tashiro, Yukikatsu Terada, Yuichi Terashima, Yohko Tsuboi, Masahiro Tsujimoto, Hiroshi Tsunemi, Takeshi Tsuru, Ayşegül Tümer, Hiroyuki Uchida, Nagomi Uchida, Yuusuke Uchida, Hideki Uchiyama, Shutaro Ueda, Yoshihiro Ueda, Shinichiro Uno, Jacco Vink, Shin Watanabe, Brian J. Williams, Satoshi Yamada, Shinya Yamada, Hiroya Yamaguchi, Kazutaka Yamaoka, Noriko Yamasaki, Makoto Yamauchi, Shigeo Yamauchi, Tahir Yaqoob, Tomokage Yoneyama, Tessei Yoshida, Mihoko Yukita, Irina Zhuravleva, Elena Bellomi, Ian Drury, Annie Heinrich, Julie Hlavacek-Larrondo, Julian Meunier, Konstantinos Migkas, Lior Shefler, Phillip C. Stancil, Nhut Truong, Benjamin Vigneron, Congyao Zhang, John ZuHone,

Comments: 16 pages, 10 figures. Accepted for publication in Astronomy & Astrophysics

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

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

The intracluster medium (ICM) is rich in chemical elements, produced by core-collapse (SNcc) and Type Ia SUPERNOVAe (SNIa) over the last $\sim$12 Gyr. Whereas cluster outskirts are uniformly enriched with Fe at $\sim$0.3 solar - strongly suggesting that the gas had been pre-enriched during or before the assembly of galaxies into clusters, the Fe abundance is known to centrally increase in the core of relaxed clusters. The origin of these central Fe peaks however, as well as the apparent presence of mysterious drops previously reported in the very centre of a number of systems, remain to be clarified. In this paper, we address these two questions by measuring the spatial distribution of Fe and its relative Si/Fe, S/Fe, Ar/Fe, Ca/Fe, Cr/Fe, Mn/Fe, and Ni/Fe ratios in the X-ray bright, nearby Perseus cluster. We take advantage of the unprecedented spectral resolution ($\sim$5 eV) offered by the Resolve microcalorimeter on board XRISM, which observed four distinct pointings of Perseus out to $\sim$250 kpc ($\sim$0.2$r_{500}$) during its Performance Verification phase. Although the presence of an X-ray bright AGN challenges a precise quantification of absolute abundances in the very core, our baseline analysis rules out a strong drop with $>$2$σ$ confidence, at variance with previous CCD measurements. In addition, we find a remarkable spatial uniformity of X/Fe ratios, supporting the idea of negligible late SNIa enrichment from the brightest cluster galaxy NGC 1275. We also compare the overall chemical composition of the Perseus ICM with SNcc and SNIa nucleosynthesis yield models, finding that the co-existence of two separate SNIa enrichment channels is not needed to reproduce the ICM ratios satisfactorily.

[abstract 28 / 38] (score: 2)
arXiv:2607.17338 [pdf, ps, other]

Title: Constraints on Primordial Black Hole Dressed by Dark Matter Halo from Microlensing Effect of Fast Radio Bursts

Authors: Hong-Rui Tao, Huan Zhou, Cheng-Gang Shao, Xiao-Long Gong, Zheng-Xiang Li,

Comments: 12 pages, 4 figures

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

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Primordial BLACK HOLEs (PBHs) are not only considered as a candidate for DARK MATTER, but also as potential sources of gravitational waves from binary BLACK HOLE mergers by the LIGO-Virgo-KAGRA and as seeds for the supermassive BLACK HOLEs observed by the James-Webb Space Telescope, thereby remaining intense interest in cosmology and astrophysics. Fast radio bursts (FRBs) are bright millisecond-duration radio transients whose physical origin remains elusive, which have rapidly developed into one of the most active and rapidly evolving fields in astronomy. The microlensing effect of FRBs offers a clean and powerful probe of PBHs, especially in the mass range above stellar-mass window. In this work, we derive a complete transformation that converts any upper limit on the abundance of PBHs originally derived for `bare' PBHs with monochromatic mass distribution, into the corresponding constraint on `dressed' PBHs with arbitrary extended mass distributions. Based on this framework, we estimate the future constraints on the dressed PBH abundance \(f_{\mathrm{PBH}}\) from FRB observations assuming an expected sample of \(10^5\) FRBs accumulated over the next decade well within the projected detection capabilities of SKA. Our results indicate that including halo enhancement tightens the upper limits on \(f_{\mathrm{PBH}}\) by approximately one order of magnitude, with the most stringent constraint reaching \(\sim10^{-4}\) for the typical mass range from stellar-mass to intermediate-mass BLACK HOLEs.

[abstract 29 / 38] (score: 2)
arXiv:2607.19619 [pdf, ps, other]

Title: Probing the matter-dominated expansion with multi-redshift Lyman-$α$ BAO from DESI DR2

Authors: Hiram K. Herrera-Alcantar, Julien Guy, Alma X. Gonzalez-Morales, Eric Armengaud, Edwin L. Pérez-Ochoa, Cristhian Garcia-Quintero, J. Aguilar, S. Ahlen, F. Beutler, D. Bianchi, A. Brodzeller, D. Brooks, E. Chaussidon, T. Claybaugh, A. Cuceu, K. S. Dawson, A. de la Macorra, Arjun Dey, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, G. Gutierrez, C. Hahn, K. Honscheid, D. Huterer, M. Ishak, T. Karim, R. Kehoe, D. Kirkby, A. Kremin, O. Lahav, A. Lambert, M. Landriau, L. Le Guillou, M. Manera, P. Martini, A. Meisner, R. Miquel, J. Moustakas, A. Muñoz-Gutiérrez, S. Nadathur, G. Niz, E. Paillas, N. Palanque-Delabrouille, W. J. Percival, C. Poppett, F. Prada, I. Pérez-Ràfols, C. Ravoux, G. Rossi, R. Ruggeri, L. Samushia, E. Sanchez, C. Saulder, D. Schlegel, M. Schubnell, H. Seo, J. Silber, G. Tarlé, B. A. Weaver, C. Yèche, R. Zhou,

Comments: 35 pages, 15 figures

Subjects: astro-ph.CO

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

We present a multi-redshift Baryon Acoustic Oscillations (BAO) analysis of the DESI Data Release 2 (DR2) Lyman-$α$ (Ly$α$) forest, splitting the forest auto-correlation and its cross-correlation with QUASARs into three redshift bins. We obtain BAO measurements at effective redshifts $z_{\rm eff} = 2.13$, $2.40$, and $2.81$ with $\sim2.0$--$2.5\%$ precision per bin in the radial and transverse directions, corresponding to $\sim1.1$--$1.2\%$ precision for the isotropic BAO measurement. Using the same data products and modeling framework as the DESI DR2 Ly$α$ BAO analysis, we validate the pipeline on $400$ synthetic datasets and find unbiased BAO recovery with well-calibrated uncertainties. The measurements show an increase in the isotropic dilation parameter $D_V/r_d$ from $30.26\pm0.39$ to $32.22\pm0.47$ and in the Alcock-Paczyński parameter $D_M/D_H$ from $3.96\pm0.15$ to $5.63^{+0.22}_{-0.24}$. The Hubble distance $D_H/r_d$ decreases from $9.40\pm0.20$ to $7.22\pm0.17$, providing a direct measurement of the expansion history consistent with $Λ$CDM and the expected matter-dominated scaling, with $H(z)\propto(1+z)^n$ giving $n=1.34\pm0.16$. The redshift split also provides a self-consistent measurement of clustering evolution: the Ly$α$ forest bias evolves as $(1+z)^γ$ with $γ_α=3.05\pm0.16$, the RSD parameter has a redshift evolution described by $γ_β=-0.97\pm0.26$, and the QUASAR bias evolves with $γ_Q=1.56\pm0.23$, consistent with independent QUASAR clustering measurements. Combining these three-bin BAO measurements with DESI DR2 galaxy and QUASAR BAO measurements yields cosmological constraints consistent with the single-bin Ly$α$ BAO analysis in flat $Λ$CDM and $w_0w_a$CDM and improves curvature constraints by $\sim12\%$ in $Λ$CDM$+Ω_\mathrm{K}$.

[abstract 30 / 38] (score: 2)
arXiv:2607.20568 [pdf, ps, other]

Title: Gravitational Effects on Light Propagation in Linear Magnetoelectrics and Plasmas

Authors: Elda Guzmán-Herrera, Vitorio A. De Lorenci, Renato Klippert,

Comments: 10 pages, 6 figures

Subjects: physics.gen-ph physics.plasm-ph

Created: 2026-07-21; Updated: 2026-07-24; Datestamp: 2026-07-24

A covariant formalism for electroMAGNETism is used to investigate the effects of light propagation within certain material systems under the influence of a background gravitational field. Specifically, dielectric media described by linear constitutive relations, as well as MAGNETized plasma media, such as the MAGNETosphere of neutron stars, are examined. Estimates for detecting gravitational effects through precise refractive index measurements within these scenarios are provided.

[abstract 31 / 38] (score: 2)
arXiv:2607.20659 [pdf, ps, other]

Title: A Single-Trace Surface Integral Equation Solver for Simulation of Open Bianisotropic Metasurfaces Described by Generalized Sheet Transition Conditions

Authors: Sebastian Celis Sierra, Junze Shao, Ran Zhao, Rui Chen, Partha Mondal, Hakan Bagci,

Comments:

Subjects: physics.comp-ph

Created: 2026-07-22; Updated: 2026-07-24; Datestamp: 2026-07-24

A single-trace surface integral equation (SIE) solver incorporating generalized sheet transition conditions (GSTCs) is presented for the simulation of three-dimensional (3D) open bianisotropic metasurfaces. The metasurface is modeled as an infinitesimally thin, non-enclosing sheet across which the GSTCs enforce the electroMAGNETic field discontinuities through four surface susceptibility tensors. The proposed solver uses a single set of equivalent surface currents on the sheet, in place of the two sets used by prior multi-trace formulations. The scattered fields on both faces of the sheet, expressed through SIE operators acting on these currents, are substituted into the GSTCs. The resulting system of equations is then discretized using Rao--Wilton--Glisson basis functions. This solver models an open metasurface directly, without an artificial closure, and applies to both planar and curved geometries. It is validated against analytical solutions for POLARIZATION rotation and perfect reflection, and is used to model a realistic broadband absorber whose susceptibility tensors are retrieved from full-wave simulation data. A direct comparison shows that the single-trace formulation attains lower error than a multi-trace formulation while using significantly fewer unknowns.

[abstract 32 / 38] (score: 2)
arXiv:2607.20978 [pdf, ps, other]

Title: Relativistic Oblique Shocks at Finite Temperature: Detachment Angle, Shock Polars, and the Turning Parameter

Authors: Rushikesh Ashok Sonkusale, Anshuman Verma, Ritam Mallick,

Comments: 14 pages, 11 figures

Subjects: astro-ph.HE

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Oblique shocks are ubiquitous in high-energy astrophysical environments, yet a systematic analytical treatment of how finite upstream temperature influences the maximum deflection angle has been lacking. We address this problem by developing a unified thermodynamic framework based on a novel dimensionless quantity, the turning parameter, which encapsulates the equation of state, upstream Mach number, and thermal state of the flow into a single variable. Starting from the RELATIVISTIC Rankine-Hugoniot conditions and the Taub adiabat, we derive a compact turning relation and a first-order perturbative expansion in the upstream thermal parameter. We show that any finite upstream temperature monotonically suppresses the maximum deflection angle relative to the cold-fluid limit, implying that cold models systematically overestimate shock attachment. In the combined ultra-thermal and ultra-RELATIVISTIC limit, the turning parameter saturates to a universal value, yielding an asymptotic detachment angle that depends only on the equation of state. Numerical shock-polar calculations validate the analytical results and reveal a non-monotonic dependence of the detachment angle on the Mach number at intermediate temperatures, arising from the competition between thermal pressure and bulk kinetic energy-a distinctly RELATIVISTIC thermal effect absent in both the cold and ultra-hot limits. As an illustrative astrophysical application, we apply the framework to the Crab pulsar wind nebula, demonstrating how finite-temperature effects modify the termination-shock morphology and the observed torus geometry.

[abstract 33 / 38] (score: 2)
arXiv:2607.20985 [pdf, ps, other]

Title: Accurate Extragalactic Magnetic Fields from Faraday Rotation with Optimal Dispersion Measure Estimators

Authors: Hilay Shah, Mark Krumholz, Naomi McClure-Griffiths, Zipeng Hu,

Comments: 22 pages, 10 figures, under review MNRAS

Subjects: astro-ph.GA

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Faraday rotation measures (RMs) are one of our few observational tools for measuring MAGNETic field strengths in extragalactic systems, but converting an RM to a MAGNETic field estimate requires knowledge of the electron column density -- the dispersion measure (DM) -- to the RM source. Because DMs are difficult to measure for most extragalactic RADIO GALAXies, observers have adopted a range of strategies to estimate them from more easily measured quantities, but the accuracy of these approaches is poorly known. To address this, we carry out simulated observations of high-resolution MAGNETohydrodynamic simulations of a range of galactic environments to explore the performance of various possible DM estimators. We obtain the best results using an estimator $\mathrm{DM} \propto \mathrm{EM}^α \ N_\mathrm{Hi}^β$, where EM is the emission measure and $N_\mathrm{Hi}$ is the atomic hydrogen column density, with exponents $α\approx 0.2-0.4$ and $β\approx 0-0.1$ depending on galactic environment (e.g., galaxy centres versus outskirts, and dwarfs versus spirals). We show that the variation of these exponents with environment can be understood in terms of simple physical arguments. Based on our tests, we provide recommended best practices for extracting galactic MAGNETic fields from RM data as a function of galactic environment and of proxy data availability, and show that using these methods one can obtain field measurements that are accurate to a few tenths of a dex. This work therefore represents an important step toward making use of RM data from next-generation surveys with the SKA.

[abstract 34 / 38] (score: 2)
arXiv:2607.21029 [pdf, ps, other]

Title: Dissecting the multiple-component outflow in NGC 5548 with absorption-line Variability

Authors: Yaqi Chen, Zhicheng He, Guilin Liu,

Comments:

Subjects: astro-ph.GA

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

AGN-driven outflows are routinely invoked as a key agent of supermassive BLACK HOLEs to regulate the evolution of galaxies. The radial distance from the central engine is a crucial parameter for evaluating the impact of these outflows on the host galaxy. In this work, we estimate the radial distances of ultraviolet (UV) outflow components in NGC 5548 using the most up-to-date absorption-line variability method, combined with multi-epoch HST/COS spectroscopy from the 2014 AGN STORM campaign and archival data observed in 2013. The recombination timescale (tr) of the absorbers are measured by analyzing the detection rate curves of absorption-line variability. In particular, the detection rate curves of the absorption troughs showing blended multiple velocity components are featured by distinct ``multi-step' profiles, allowing for measuring tr for individual components. Among the 6 identified outflow components, four are found to be a few pc from the center and two are 30-40 pc away. Our results agree well with the more reliable results in the literature on components 1 and 4, and show overall consistency with previous works, demonstrating the power of our new methodology especially when it is aided by densely sampled HST spectra.

[abstract 35 / 38] (score: 2)
arXiv:2607.21122 [pdf, ps, other]

Title: MIGHTEE: The Host-Galaxy Associated Catalogue of the Radio Sources in MIGHTEE Continuum Data Release 1

Authors: C. L. Hale, J. Hamlett, I. H. Whittam, M. J. Jarvis, M. J. Hardcastle, S. L. Jung, N. Stylianou, R. G. Varadaraj, M. Vaccari, L. Barchiesi, P. N. Best, K. K. L. Charlton, E. Malefahlo, E. Moravec, J. P. Moss, M. Rakototafika, T. F. Rarivoarinoro, F. Sinigaglia, M. N. Tudorache, S. I. Loubser, L. Heino, A. Saintonge, A. Mazumder, N. Netshiavha, D. J. B. Smith, L. Verdes-Montenegro, J. Delhaize, H. Pan, F. Pozzi, Z. Randriamanakoto, L. Stockenstroom, A. A. Vărăşteanu, E. Vardoulaki, W. L. Williams, R. A. A. Bowler, L. Marchetti, A. Matthews,

Comments: 23 pages, 13 figures, Accepted for publication in MNRAS

Subjects: astro-ph.GA

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Radio continuum surveys provide samples of ACTIVE GALACTIC NUCLEi (AGN) and star forming galaxies (SFGs) to high redshifts, free of biases due to dust obscuration. However, radio detected sources require multi-wavelength counterparts to understand their intrinsic properties (e.g. redshift, stellar mass) and to study the evolution of STAR FORMATION and AGN activity. In this work we present host galaxy counterparts for the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey continuum Data Release 1 in regions with the best ancillary data (totalling 7.5 sq. deg). We combine statistical cross-matching and visual inspection to identify Ks-band selected host galaxies, and additionally combine multiple radio components into single physical objects, where needed. This results in a combined radio catalogue of ~66 000 sources, with host counterparts and redshifts identified for ~95 per cent of sources in the COSMOS field, ~91 per cent in XMM-LSS and ~90 per cent in CDFS-DEEP. This includes a significant fraction of sources with spectroscopic redshifts within the COSMOS field (~50 per cent), with ~30 and ~20 per cent in the XMM-LSS and CDFS-DEEP fields respectively. Using the cross-matched catalogue, we make an initial identification of radio-excess and star forming galaxies based on comparisons of the radio luminosities to host STAR FORMATION rates. Using this split as a proxy for radio loud AGN or SFGs, we present expectations for the redshift distributions of these sources, finding broad agreement with those from deep radio luminosity functions and simulated catalogues.

[abstract 36 / 38] (score: 2)
arXiv:2607.21247 [pdf, ps, other]

Title: Contribution to the 2026 Cosmology session of the 60th Rencontres de Moriond: Galactic moments: Understanding polarized foregrounds complexity in the quest for CMB primordial $B$ modes with LiteBIRD

Authors: S. Vinzl, J. Aumont, L. Vacher, R. T. Génova-Santos, D. Adak, A. Rizzieri, for the LiteBIRD Collaboration,

Comments:

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

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

Accurate modeling of polarized Galactic emission has become a major challenge for current and next-generation cosmic microwave background (CMB) $B$-mode experiments. Ignoring the spectral complexity of thermal dust and Galactic SYNCHROTRON emission when integrating along the line of sight and over large sky fractions inevitably leads to biases in CMB POLARIZATION analyses. In this work, we review how the future LiteBIRD satellite, which will benefit from an increased number of bands and sensitivity with respect to past CMB experiments such as Planck, will exploit its broader frequency coverage to characterize the spectral properties of interstellar medium emission across the three-dimensional structure of the Milky Way. We show that the canonical description of foreground spectral behavior will reach its limits for LiteBIRD, and that this challenge can be addressed using the moment expansion formalism.

[abstract 37 / 38] (score: 2)
arXiv:2607.21313 [pdf, ps, other]

Title: Collisionless stationary states of a stratified plasma in an expanding MAGNETic tube with stochastic heating

Authors: Luca Barbieri, Pascal Démoulin, Daniel Verscharen,

Comments: 24 pages, 5 figures

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

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

We investigate the collisionless kinetic structure of the upper solar atmosphere in the presence of an expanding MAGNETic field. We consider a stationary two-component plasma confined within an expanding MAGNETic flux tube and subject to gravity, self-electrostatic interactions, the Pannekoek-Rosseland electric field, and MAGNETic moment conservation. Starting from the Vlasov equation, we derive fully analytical expressions for the particle distribution functions, density profiles, and the parallel, perpendicular, and total temperature profiles. We show that the combined conservation of energy and MAGNETic moment generates a loss-cone distribution, reducing the density with respect to the corresponding unMAGNETized atmosphere and producing a pronounced temperature anisotropy. For a single-temperature boundary condition, the competition between MAGNETic moment conservation and gravity causes the parallel temperature to develop a maximum. We derive analytical scaling laws for its location and amplitude and validate them against numerical calculations. We further show that the anisotropy persists independently of the temperature distribution at the lower boundary. In the regime of rare but intense heating events, gravitational filtering enhances the contribution of the hottest particle populations at coronal heights, while MAGNETic moment conservation further amplifies the resulting velocity-space anisotropy. This work provides a fully analytical kinetic description of the combined effects of gravitational filtering and MAGNETic moment conservation in an expanding coronal MAGNETic flux tube undergoing stochastic heating at its base. These results establish a theoretical framework for investigating the role of MAGNETic-field expansion in shaping the density and temperature structure of weakly collisional stellar coronae.

[abstract 38 / 38] (score: 2)
arXiv:2607.21364 [pdf, ps, other]

Title: Rapid Orbital Decay of Supersoft X-Ray Source WX Cen: a Surrounding Circumbinary Disk

Authors: Zhi-Qiang Liu, Wei-Min Liu, Wen-Cong Chen,

Comments: 11 pages, 7 figures, 1 table. ApJ in press

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

Created: 2026-07-23; Updated: 2026-07-24; Datestamp: 2026-07-24

WX Cen is most likely a candidate of compact binary supersoft X-ray sources, which consists of a white dwarf (WD) and a donor star that fills the Roche lobe. Recently, this source was detected to be experiencing a rapid orbital decay at a rate of $\dot{P} =-(4.4\pm0.4)\times10^{-7}~ \rm days~\rm{yr}^{-1}$. According to the mass function and optical eclipses, the donor-star mass can be constrained to be $0.41-0.44$, $0.47-0.50$, and $0.55-0.59~M_\odot$ when the WD mass is $0.7$, $0.9$, and $1.2~M_\odot$, respectively. The observed orbital period derivative cannot be produced by the angular momentum loss due to mass loss during the accretion of the WD, MAGNETic braking (MB) mechanisms, including standard MB, convection and rotation-enhanced MB, and anomalous MB prescriptions. We propose that the rapid orbital decay of WX Cen is caused by the tidal torque that originates from the resonant interaction between the binary and a surrounding circumbinary (CB) disk. Detailed stellar evolution models indicate that a WD binary with a $2.5 \times 10^{-7}~M_{\odot}$ CB disk can evolve toward a WX Cen-like system, which has an orbital period derivative of $\dot{P}=-4.0\times10^{-7}~ \rm days~\rm{yr}^{-1}$ and a relatively high mass-transfer rate of $5.3\times10^{-7}~M_\odot\rm yr^{-1}$ that can trigger a stable hydrogen burning process on the surface of the WD.