Current date: 2026-08-28

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Created/updated limit: 2026-08-21 (7 days ago)

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OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-08-28&until=2026-08-28&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 751

Keyword score statistics

score 11 -- 2 abstracts

score 8 -- 1 abstracts

score 7 -- 3 abstracts

score 6 -- 2 abstracts

score 4 -- 3 abstracts

score 3 -- 6 abstracts

score 2 -- 6 abstracts

in total -- 23 abstracts

Articles that appeared on 2026-08-28

[abstract 1 / 23] Wow! (score: 11)
arXiv:2603.10122 [pdf, ps, other]

Title: The baryon content of MAGNETically arrested BLACK HOLE disks and JETs

Authors: Anthony Chow, Lorenzo Sironi, Bart Ripperda, Amir Levinson,

Comments: 16 pages, 17 figures. Accepted for publication in MNRAS

Subjects: astro-ph.HE

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

We study the transport of baryons in MAGNETically arrested accretion flows and RELATIVISTIC JETs using general RELATIVISTIC MAGNETohydrodynamic simulations that incorporate a passive Eulerian tracer. The tracer allows us to reconstruct a proxy for the physical baryon density supplied by the accretion disk while excluding the mass injected numerically to maintain stability in highly MAGNETized, low-density regions. Applying this method to axisymmetric BLACK HOLE simulations with varying spin, we show that baryon loading of the JET is intrinsically episodic and regulated by MAGNETic flux eruption cycles occurring in the inner accretion flow. Each eruption evacuates baryons from the innermost equatorial region, drives RECONNECTion in extended current sheets, and expels moderately MAGNETized disk material along the funnel wall, establishing a recurrent mass-loading channel. In spinning BLACK HOLEs, shear-driven waves along the JET boundary further enhance baryon entrainment, whereas this mechanism is suppressed in the non-spinning case. For parameters representative of the BLACK HOLE accretion flow in M87, we map the global structure and time evolution of the Goldreich-Julian screening boundary, defined as the surface separating regions where the plasma density is sufficient to supply the charges required to screen electric fields parallel to the MAGNETic field from regions that are charge starved. For spinning BLACK HOLEs, we find that the electroMAGNETic power of the JET is predominantly carried by baryon-poor plasma, with extended time intervals of charge starvation. Our results provide a framework for diagnosing JET composition, charge starvation, and RECONNECTion-driven mass loading in MAGNETically arrested BLACK HOLE systems, with direct implications for particle acceleration and non-thermal emission in low-luminosity accretion flows.

[abstract 2 / 23] Wow! (score: 11)
arXiv:2608.27078 [pdf, ps, other]

Title: Source models of ultrahigh-energy COSMIC RAYs

Authors: Bing Theodore Zhang,

Comments: Proceedings of the 7th International Symposium on Ultra High Energy Cosmic Rays (UHECR2024), 17-21 November 2024, Malargüe, Argentina

Subjects: astro-ph.HE

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

We investigate potential sources of ultrahigh-energy COSMIC RAYs (UHECRs) and their acceleration mechanisms, focusing on astrophysical phenomena associated with massive stellar deaths and supermassive BLACK HOLEs. These phenomena include GAMMA-RAY BURSTs (GRBs), engine-driven SUPERNOVAe/hypernovae, MAGNETars, newly born pulsars, binary neutron star mergers (BNS), tidal disruption events (TDEs), and ACTIVE GALACTIC NUCLEi (AGN). While high-luminosity GRBs (HL GRBs) are constrained as UHECR sources by high-energy neutrino observations, low-luminosity GRBs (LL GRBs) and engine-driven SUPERNOVAe remain promising candidates, with intermediate-mass nuclei as the dominant components. Compact binary mergers and $r$-process nucleosynthesis in neutron-rich environments may also contribute to ultraheavy UHECRs. The composition of UHECRs from TDEs depends on the properties of the disrupted stars. AGN, particularly RADIO GALAXies, remain promising sources, with acceleration occurring in their large-scale JETs and lobes. Shear acceleration mechanisms have been proposed as a viable alternative for accelerating UHECRs, involving the re-acceleration of low-energy COSMIC RAYs and being compatible with the observed spectrum and composition. Future multi-messenger observations, especially from upcoming observatories, are expected to provide critical data to refine our understanding of UHECR origins, test existing models, and explore new acceleration mechanisms.

[abstract 3 / 23] Wow! (score: 8)
arXiv:2608.25552 [pdf, ps, other]

Title: Energy Partition in AGN-driven Bubbles of NGC 4438: From Nuclear Bubbles to a Galaxy-scale Outflow

Authors: Luan Luan, Jiang-Tao Li, Jianghui Xu, Yang Yang, Guilin Liu, Fulai Guo, Q. Daniel Wang,

Comments: 20 pages, 7 figures, Accepted by ApJ, comments welcome

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

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

Jets launched by accreting supermassive BLACK HOLEs represent a major mode of ACTIVE GALACTIC NUCLEus (AGN) feedback. However, how their energy is divided among bulk kinetic motion, thermal gas, MAGNETic fields, COSMIC RAYs (CRs), and radiation - and how this distribution changes with spatial scale - remains poorly constrained. NGC 4438 provides a unique laboratory for probing this evolution, hosting two 200-pc-scale nuclear bubbles and a lopsided ~10 kpc galaxy-scale outflow plausibly associated with the same AGN. We present a multi-wavelength analysis to investigate the morphology, radiation mechanisms, and energetics of these structures. Joint radio-X-ray modeling shows that the non-thermal emission in the nuclear bubbles may require two distinct populations of cosmic-ray electrons, suggesting that in addition to shock acceleration at the bubble rim, the highest-energy particles may be linked to acceleration processes closer to the unresolved central engine. A spatially resolved energy inventory reveals that bulk kinetic energy dominates the current energy budget of the nuclear bubbles, while roughly half of the injected energy has already been transformed into thermal, CR, and MAGNETic energy, as well as radiative losses. Across all bubble sizes, the thermal and MAGNETic pressures are consistent within the uncertainties, implying that MAGNETic fields remain dynamically significant on all examined spatial scales. Furthermore, the empirical correlation between radio luminosity and JET power, established for kiloparsec-scale JET bubbles (MerloniHeinz2007), matches the energetics of the galaxy-scale outflow but substantially overestimates the power of the 200-pc-scale nuclear bubbles, underscoring the scale dependence of JET energy dissipation.

[abstract 4 / 23] Wow! (score: 7)
arXiv:2512.18323 [pdf, ps, other]

Title: On Lorentz Variability of Magnetically Dominated Relativistic Outflows

Authors: V. I. Berezhiani, N. L. Shatashvili, A. G. Tevzadze,

Comments: 16 pages, 2 figures. Accepted for publication in Physica Scripta

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

Created: 2026-08-26; Updated: 2026-08-28; Datestamp: 2026-08-28

We show that MAGNETized RELATIVISTIC outflows can exhibit a RELATIVISTIC effect in which Lorentz transformation maps spatially extended MAGNETic field structure into apparent temporal variability in the observer's frame. Using a force-free Beltrami configurations as representative equilibria of MAGNETically dominated outflows, we demonstrate that Lorentz mapping of stationary helical MAGNETic field produces quasi-periodic modulation of observable electroMAGNETic signatures, without invoking intrinsic plasma variability. The same mechanism naturally generates temporal evolution of the observed POLARIZATION properties, producing smooth, generally aperiodic POLARIZATION-angle swings in the observer's frame. This effect may be described as an aberration of force-free MAGNETic fields under Lorentz transformation. The characteristic frequency of the time variability is determined by the helical wave-number of the MAGNETic field, the viewing angle, and the bulk Lorentz factor of the JET outflow, and scales linearly with $Γ$. This establishes a purely kinematic RELATIVISTIC origin of variability and introduces the concept of MAGNETic Lorentz seismology: the inference of MAGNETic field structure in RELATIVISTIC outflows directly from observed temporal variability.

[abstract 5 / 23] Wow! (score: 7)
arXiv:2604.20768 [pdf, ps, other]

Title: Primordial Magnetogenesis and Gravitational Waves from ALP-assisted Phase Transition

Authors: Pankaj Borah, P. S. Bhupal Dev, Anish Ghoshal,

Comments: 42 pages, 7 figures. Minor revision and references added. Version accepted for publication in JCAP

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

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

Sufficiently strong first-order phase transitions (FOPTs) in the early Universe can simultaneously produce an observable stochastic gravitational wave background (SGWB) and a large-scale primordial MAGNETic field (PMF). The recent $3.8σ$ evidence for a non-zero intergalactic MAGNETic field from anisotropic pair-halo searches using \textit{FERMI}-LAT data further motivates a cosmological origin. We investigate an FOPT-origin of both cosmic signatures, namely, PMF and SGWB, and their correlation, within a minimal axion-like particle (ALP) framework in which a global $U(1)$ symmetry is spontaneously broken through radiative corrections, with the ALP sector coupled to the Standard Model (SM) via a Higgs-portal. We compute the present-day PMF amplitude and coherence length for both maximally helical and non-helical configurations, accounting for inverse cascade effects. For maximally helical configurations, we find peak field strengths up to $B_0 \sim 10^{-9}$ G at coherence length $λ_0 \sim 10^{-3}-10^{-1}$ Mpc, consistent with lower bounds on the IGMF inferred from BLAZAR observations by MAGIC, H.E.S.S. and {\it FERMI}-LAT. We show that the ALP parameter region consistent with $γ$-ray BLAZAR data (assuming maximally helical fields) simultaneously produces stochastic GW signals detectable at future space-based interferometers, such as LISA, etc., over the ALP decay constant range $10^3~\text{GeV} \lesssim f_a \lesssim 10^5~\text{GeV}$. We demonstrate that these correlated constraints can be directly mapped onto effective ALP couplings to SM particles, e.g., photons, gluons, and fermions. This establishes a multi-messenger complementarity between cosmological observables and laboratory/astrophysical ALP searches, with combined constraints preferring relatively heavy ALPs, $m_a \gtrsim 0.1~\text{GeV}$, accessible to next-generation intensity and energy-frontier experiments.

[abstract 6 / 23] Wow! (score: 7)
arXiv:2608.27197 [pdf, ps, other]

Title: Testing Narrow-JET Gamma-Ray Bursts as Sources of Ultrahigh-Energy Cosmic Rays

Authors: Saikat Das, Soebur Razzaque, Justin D. Finke, Siyao Xu,

Comments: 7 pages, 3 figures

Subjects: astro-ph.HE

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

Gamma-ray bursts (GRBs) have long been considered candidate sources of ultrahigh-energy COSMIC RAYs (UHECRs) due to their large energy release and RELATIVISTIC outflows. The detection of multi-TeV $γ$-rays from GRB~221009A and its rarity have renewed interest in this connection and motivate considering an additional narrow-JET long GRB population in the local Universe. We investigate whether such a local narrow-JET population can contribute to the observed diffuse UHECR energy spectrum. We also examine the associated cosmogenic neutrino and cascade $γ$-ray emissions to assess the multimessenger viability of this scenario. We fit the observed UHECR spectrum and mass composition data using three source-evolution models: a uniform comoving source emissivity, a standard-JET GRB population tracing the STAR FORMATION rate (SFR), and a standard + narrow-JET GRB population tracing SFR. We propagate a mixed-composition UHECR injection and calculate the cosmogenic neutrino and cascade $γ$-ray fluxes. The standard + narrow JET model fits the observed UHECR spectrum and composition, with the highest-energy flux dominated by the narrow-JET population confined to $z\le z_{\max,*}\simeq0.36$. This low-redshift dominance lowers the cosmogenic neutrino flux compared to the standard-JET GRB population. For the narrow-JET GRB population, the fit implies a baryon loading factor $ξ_{\rm CR}^{\rm nj}\simeq10$. Such a locally enhanced long-GRB population can therefore explain the highest-energy UHECR flux without violating current multimessenger constraints. Future UHE searches can further probe this scenario through the associated cosmogenic fluxes.

[abstract 7 / 23] Yes (score: 6)
arXiv:2606.06213 [pdf, ps, other]

Title: Probing a new subclass of llGRB-SN transients: Insights from EP250304a and its associated SUPERNOVA

Authors: L. Cotter, A. Martin-Carrillo, R. A. J. Eyles-Ferris, L. Izzo, D. B. Malesani, Y. Julakanti, G. Corcoran, A. Saccardi, P. G. Jonker, A. J. Levan, F. Carotenuto, P. T. O'Brien, J. H. Gillanders, J. N. D. van Dalen, M. E. Ravasio, S. Schulze, N. Sarin, F. E. Bauer, M. Fraser, J. Quirola-Vasquez, A. P. C. van Hoof, S. J. Smartt, C. Gall, A. Rest, C. T. Murphey, N. Tanvir, T. -W. Chen, Q. Wu, Y. Yin, S. Campana, C. Ashall, J. P. Anderson, J. A. Chacon, F. J. Cowie, V. D'Elia, L. Galbany, C. P. Gutierrez, D. H. Hartmann, P. Jakobsson, S. Kobayashi, A. H. Kong, P. Mazalli, T. E. Muller-Bravo, M. De Pasquale, L. Rhodes, A. Rossi, J. Sanchez-Sierras, J. Sollerman, A. Andersson, A. Aryan, T. de Boer, J. S. Bright, K. C. Chambers, M. Gromadzki, M. E. Huber, C. Inserra, T. Lowe, P. Minguez, G. S. Narayan, M. Nicholl, G. S. H. Paek, A. Sedgewick, K. W. Smith, J. W. Tweddle, S. Yang,

Comments: 23 pages, 22 figures

Subjects: astro-ph.HE

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

With the advent of the Einstein Probe (EP) mission, we are entering a new era in the study of GAMMA-RAY BURSTs (GRBs), enabling the detection of faint, low-luminosity transients that would previously have gone undetected. EP250304a was an event discovered by EP associated with the broad-lined type Ic SUPERNOVA (SN) SN 2025fhm located at z = 0.2. Despite no gamma-ray emission being detected at the time of the EP trigger, we identify evidence for a RELATIVISTIC outflow consistent with a GRB-like JET across multiple wavelengths. We present a detailed spectral and photometric analysis of EP250304a/SN 2025fhm, including multi-band light curve modelling performed with the Redback Python package. We find that this event closely resembles low-luminosity GRB-SNe (llGRB-SNe) such as GRB 060218/SN 2006aj, GRB 100316D/SN 2010bh, and GRB 171205A/SN 2017iuk, all of which exhibit early-time emission consistent with a thermal shocked cocoon. These similarities suggest that EP250304A/SN 2025fhm may belong to an emerging subclass of shocked cocoon-dominated llGRB-SNe, representing the low-luminosity end of a broader continuum of engine-driven GRB-SN explosions.

[abstract 8 / 23] Yes (score: 6)
arXiv:2608.26290 [pdf, ps, other]

Title: Synchrotron self-Compton Reverse Shock in Energy-Injection and Radiative Scenarios

Authors: Fraija Nissim, Betancourt-Kamenetskaia Boris, Galván Antonio, Dainotti Maria Giovanna,

Comments: 43 pages, 7 tables, 13 figures. The Astrophysical Journal, Volume 1006, Issue 2, id.227

Subjects: astro-ph.HE

Created: 2026-08-26; Updated: 2026-08-28; Datestamp: 2026-08-28

Gamma-ray bursts (GRBs) are among the most energetic extragalactic transients, providing a unique laboratory to investigate the physical origin of the diverse morphologies observed in high-energy light curves and spectra. These morphologies, interpreted through SYNCHROTRON and SYNCHROTRON self-Compton (SSC) closure relations (CRs), may depend on the circumburst density profile, energy injection, and the dynamical evolution of the reverse shock in the adiabatic or radiative regime. We derive the SSC closure relations produced in the reverse-shock region for both thick- and thin-shell cases, considering constant-density and stratified circumburst media. The analysis assumes two power-law (PL) distributions for the electron spectral index and includes scenarios with and without energy injection from the progenitor. We show that, depending on the physical parameters, SSC emission from the reverse shock can reproduce the initial steep-decay and plateau phases commonly observed in GRB afterglows. We then compare the predicted spectral and temporal indices with those derived from PL and broken power-law (BPL) fits reported in the Second FERMI-LAT Gamma-ray Burst Catalog (2FLGC). Our results indicate that PL (BPL) light-curve fits preferentially favor scenarios with (without) energy injection. In scenarios with energy injection, the data preferentially support a constant-density environment over a stellar-wind profile.

[abstract 9 / 23] Yes (score: 4)
arXiv:2608.01750 [pdf, ps, other]

Title: AGNI: A differentiable MHD stability solver & optimizer for MAGNETic confinement fusion devices

Authors: Rahul Gaur, Sanket Patil, Prateek Gupta, Djin Patch, Tony Qian,

Comments: 28 pages, 8 figures, added AI use declaration, link to source code, improved readability

Subjects: physics.plasm-ph

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

The existence of an ideal MagnetoHydroDynamic (MHD) equilibrium does not guarantee its stability. Finite toroidal mode number (n) instabilities degrade performance in both tokamaks and stellarators and differentiable stability optimization tools to date have operated only in the infinite-n limit. We present AGNI (Analysis of Global Normal modes in Ideal MHD), a GPU-accelerated, automatically differentiable finite-n ideal MHD stability solver and optimizer. AGNI discretizes the ideal MHD energy principle pseudospectrally in real space using differentiation matrices and geometric coefficients from a DESC equilibrium, giving a variational eigenvalue problem for the plasma displacement, and efficiently finds the most unstable modes. Built on JAX, AGNI yields reverse-mode gradients of the growth rate with respect to boundary-shape and profile parameters without re-solving the equilibrium. We benchmark AGNI against the initial-value code NIMSTELL for a modified Landreman-Buller-Drevlak quasi-helically symmetric equilibrium, recovering the dominant m = n = 4 interchange mode with agreement in both growth rate and eigenfunction structure, and verify the automatic differentiation gradients against central finite differences. We quantify CPU and GPU cost for eigenvalue and gradient evaluation, establish the finite-precision limit on resolving near-marginal eigenvalues, and present a robust scheme to impose incompressibility compatible with gradient-based optimization. AGNI will allow us to optimize tokamaks, stellarators, and mirrors against ideal MHD instabilities.

[abstract 10 / 23] Yes (score: 4)
arXiv:2608.26243 [pdf, ps, other]

Title: Radio Monitoring of the Changing-look AGN Mrk 590 I: VLA Observations Reveal A Bow-shock Driven Radio Brightening Event

Authors: Gregory Walsh, Marianne Vestergaard, Daniel Lawther, Sandra Raimundo, Jun Yi Koay,

Comments: 11 pages, 3 figures, 3 tables

Subjects: astro-ph.HE

Created: 2026-08-26; Updated: 2026-08-28; Datestamp: 2026-08-28

Mrk 590 is a changing-look AGN (CLAGN) that slowly faded from a Seyfert Type 1 to near quiescence over a few decades before re-igniting in 2017. Monitoring in the optical/UV/X-ray wavebands has revealed accretion-driven variability signatures, but the response of the radio source to the changing-look events that drove its fading and re-ignition is unknown. We present multi-frequency (1-17~GHz), A-configuration, Karl G. Jansky Very Large Array (VLA) observations of Mrk 590 over four epochs from 2015 to 2017. The radio source is dominated by a faint, compact component, absent of any notable extended structures. We identify a variable radio spectrum over this period, both in amplitude and in shape, and implement a Bayesian inference modeling routine to constrain the mechanism driving the radio variability. Our routine favors radio variability powered by a bow shock produced through an interaction of a radio JET with the interstellar medium, which drives the radio brightening in later epochs. This demonstrates that the radio variability we observed is not correlated with the variable accretion event that led to the re-brightening of the AGN at higher energy wavebands. While correlated variability between the radio and accretion-driven emission has been observed in other CLAGN, the lack of correlated variability in Mrk 590 shows the diversity of changing-look AGN populations and the mechanisms driving their behavior.

[abstract 11 / 23] Yes (score: 4)
arXiv:2608.26654 [pdf, ps, other]

Title: Spectro-Polarimetric Properties of CHIME FRB Sources

Authors: Dengke Zhou, Yi Feng, Jiaying Xu, Chenyuan Xu, Jianhua Fang,

Comments:

Subjects: astro-ph.HE

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

Fast radio bursts (FRBs) are enigmatic millisecond-duration radio transients whose POLARIZATION properties offer crucial insights into their origins and environments. In particular, low-frequency dePOLARIZATION---quantified by the parameter \(σ_{\mathrm{RM}}\)---probes the complex MAGNETo-ionic medium surrounding the progenitor, and has been observed across a population of repeating FRBs. We present a systematic spectro-polarimetric analysis of repeating and non-repeating FRBs using observations from the Canadian Hydrogen Intensity Mapping Experiment (CHIME). For 28 repeating FRBs, we measure \(σ_{\mathrm{RM}}\), expanding the known sample from 14 to 36 sources (an increase by a factor of 2.6). The kernel density estimate (KDE) of the repeating population peaks at \(1.3\ \mathrm{rad\,m^{-2}}\), with approximately 70\% of the sources showing \(σ_{\mathrm{RM}} \gtrsim 1\ \mathrm{rad\,m^{-2}}\), implying that most reside in complex MAGNETo-ionic environments. For 70 non-repeating FRBs, we investigate four spectro-polarimetric models; no source exhibits significant dePOLARIZATION with \(σ_{\mathrm{RM}} \gtrsim 5\ \mathrm{rad\,m^{-2}}\). Roughly half of the non-repeaters are consistent with a constant linear POLARIZATION fraction across frequency. We caution, however, that these results may be affected by the limited frequency coverage of CHIME. Future ultra-wideband polarimetry, spanning widely separated frequencies, will overcome current observational biases, enable precise \(σ_{\mathrm{RM}}\) measurements, and substantially deepen our understanding of FRB environments.

[abstract 12 / 23] (score: 3)
arXiv:2608.24292 [pdf, ps, other]

Title: The First X-Ray Polarimetry of the Typical Accretion Disk Corona Source 4U 1822-37

Authors: WanYun Wu, Fei Xie, YuShan Ling,

Comments: 10 pages, 8 figures, 5 tables. Accepted for publication in MNRAS

Subjects: astro-ph.HE

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

We report the first Imaging X-ray Polarimetry Explorer (IXPE) observations of the typical accretion disk corona (ADC) source 4U 1822-37, covering 44 orbital cycles, together with simultaneous SWIFT-XRT data. The POLARIZATION degree (PD) of this source is found to be higher than typical low-mass X-ray binary (LMXB) values and exhibits a significant energy dependence. Within the 2--5~keV and 5--8~keV bands, PD remains constant, with average values of \(5.6\pm0.8\%\) and \(11.6\pm1.7\%\), respectively, and the difference is significant (\(>3σ\)). Orbital phase-resolved analysis reveals that during the companion eclipse, the PD in the 2--5~keV band drops from a significantly non-zero value to a level consistent with zero, while the POLARIZATION angle (PA) remains unchanged. In contrast, the PD in the 5--8~keV band shows a marginal rising trend, reaching \(21.3\pm6.1\%\), and the PA exhibits a periodic rotation of \(30^\circ\) before the eclipse. In addition, the PA rotates by \(40^\circ\) with increasing neutral absorption on a three-day timescale. These results suggest that the soft and hard emission in the 2--8~keV band may originate from regions with different spatial distributions, with the high PD implying a scattering contribution. The PA rotation is likely linked to scattering geometry asymmetries caused by a bulge or clumps.

[abstract 13 / 23] (score: 3)
arXiv:2608.26356 [pdf, ps, other]

Title: Apokamp-type Gas Discharge Phenomenon: Experimental and Theoretical Backgrounds

Authors: Vasily Yu. Kozhevnikov, Andrey V. Kozyrev, Aleksandr O. Kokovin, Aleksey G. Sitnikov, Eduard A. Sosnin, Victor A. Panarin, Victor S. Skakun, Victor F. Tarasenko,

Comments:

Subjects: physics.plasm-ph physics.ao-ph physics.comp-ph

Created: 2026-08-26; Updated: 2026-08-28; Datestamp: 2026-08-28

The apokamp discharge is an atmospheric-pressure plasma JET generated at the bending point of the discharge channel between high-voltage and floating-potential electrodes. The JET propagates perpendicularly to the interelectrode discharge channel without convection. In ambient air, the apokamp length reaches several centimeters, and the temperature of its tip is 100-250 °C. The typical apokamp propagation speed ranges from 100 to 220 km/s. The proposed time-dependent theoretical model explains the phenomenon. The discharge modeling confirms the tendencies observed in various experiments on the problem.

[abstract 14 / 23] (score: 3)
arXiv:2608.26567 [pdf, ps, other]

Title: FRB 121102: No SUPERNOVA-like ejecta or MAGNETar power, hinting at a binary WD merger

Authors: Eli Waxman, Eran O. Ofek, Doron Kushnir,

Comments:

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

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

We use measurements of the time-dependent dispersion measure of the repeating FRB 121102, together with earlier radio observations of its associated persistent radio source (PRS), to derive stringent constraints on its underlying ``engine.'' The energy held by the RELATIVISTIC PRS plasma is $>10^{49.5}$ erg, and its age is $\approx60$ yr, corresponding to an underlying source power exceeding $10^{40}$ erg s$^{-1}$. If the underlying source is a neutron star, this implies a rotational rather than a MAGNETic energy source, consistent with a $\sim10$ ms, $\sim10^{12.5}$ G neutron star. Alternatively, accretion may also be a viable energy source. The velocity and the kinetic energy of the cold plasma confining the RELATIVISTIC PRS plasma are inconsistent with it being typical SUPERNOVA ejecta (unless a significant fraction of the ejecta mass is carried by high-density clumps of $\approx10^{-2.5}$ fractional size)- its expansion speed is limited to a few hundred km/s, which also implies that it was ejected from the source more than $\approx 10^3$ yr preceding the onset of RELATIVISTIC PRS plasma emission. These constraints may be satisfied by a white dwarf binary merger progenitor system, where a fraction of a solar mass was ejected at a slow speed during and after the merger, and a rapidly rotating neutron star was formed after $\sim10^3$ yr thermal evolution period of the merger remnant.

[abstract 15 / 23] (score: 3)
arXiv:2608.26627 [pdf, ps, other]

Title: Investigating the disappearance of a type-C QPO in BLACK HOLE X-ray binary SWIFT J151857-572147 with AstroSat

Authors: Biki Ram, Manoneeta Chakraborty, Mayukh Pahari,

Comments: 16 pages, 12 Figure. Accepted for Publication in JHEAP

Subjects: astro-ph.HE

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

We present a timing and broadband spectral study of the AstroSat observation of the BLACK HOLE low mass X-ray binary SWIFT J151857.0--572147, focusing on its evolution across two temporal segments, S1 and S2. During the first segment S1 lasting $\sim$ 50.6 ks, the source shows a clear type-C QPO at $\sim8.02$ Hz and a low-frequency bump (LFB) in the power density spectrum. By the later segment S2, the strength of the QPO feature decreases significantly and is no longer consistent with a coherent QPO, along with the simultaneous disappearance of the LFB. An energy-dependent analysis reveals that both the RMS amplitude and the time lag of the QPO in S1 increase monotonically with energy, suggesting a low inclination nature of the source. The QPO and LFB centroid frequencies show a strong positive correlation across orbital segments, with a Pearson coefficient of 0.98. Our variability analysis and hardness-intensity diagram reveal a spectral state transition of the source coincident with the turn-off of the QPO and the LFB, a conclusion supported by the evolution of broadband spectral parameters. Notably, the orbit-resolved spectral analysis reveals that the non-thermal parameters, photon index, and electron temperature of the corona exhibit significant deviation as the source traverses from S1 to S2, whereas the thermal parameters scatter without any systematic variation between the two segments. The simultaneous turn-off of the type-C QPO and the low-frequency broadband noise component, both originating from the hot inner flow, indicates a rapid reorganization of the inner accretion geometry. Our results strongly suggest a coronal origin for the QPO and demonstrate that the disappearance of both features reflects a substantial transformation of the Comptonizing region across the spectral transition.

[abstract 16 / 23] (score: 3)
arXiv:2608.26857 [pdf, ps, other]

Title: A Bayesian Framework for Constraining Magnetar Magnetic Fields from Repeating FRB Statistics

Authors: Can-Min Deng, Hao-Hao Chen,

Comments: 16 pages, 1 figures

Subjects: astro-ph.HE

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

Fast radio bursts (FRBs) are widely considered to be associated with MAGNETars, motivated by the detection of an FRB-like radio burst from the Galactic MAGNETar SGR~1935+2154. However, constraining the MAGNETic field strength of extragalactic FRB sources remains challenging. In this work, we develop a Bayesian framework that models FRB time--energy sequences as a marked point process, combining burst waiting-time statistics with energy distributions to quantify the MAGNETic field strengths required to sustain the observed bursting activity under the MAGNETar powered scenario. Applying this method to a sample of repeating FRBs, we derive constraints on their MAGNETic fields by incorporating an empirical prior on the radio emission efficiency calibrated from the Galactic event. Under a conservative assumption for the activity duty cycle, most sources require MAGNETic energy reservoirs consistent with MAGNETar strength fields, with characteristic field strengths of order $10^{13}$--$10^{15}$ G, although the constraints remain sensitive to the poorly known efficiency and duty-cycle parameters. FRB~20200120E provides an interesting case with a substantially lower field requirement, highlighting the importance of source environment and evolutionary history in interpreting FRB activity. Our framework provides a statistical approach for connecting transient burst properties with MAGNETic energy reservoirs, with potential applications to FRBs and other MAGNETically powered transients.

[abstract 17 / 23] (score: 3)
arXiv:2608.27192 [pdf, ps, other]

Title: Optimal transport regularized dynamic radio interferometric reconstruction

Authors: Andy Nilipour, Kotaro Moriyama, Shiro Ikeda, Kazunori Akiyama, Mareki Honma,

Comments: 13 pages, 7 figures, submitted to A&A

Subjects: astro-ph.IM

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

We propose a new technique for dynamic video reconstruction of radio interferometric data using the optimal transport (OT) distance as a regularizer within the regularized maximum likelihood (RML) framework. Compared to other commonly used regularization terms in RML and related prior-based approaches, the OT distance more naturally captures information including physical motion and promotes coherent dynamics. This property makes the OT regularization particularly suitable for dynamic imaging of astrophysical phenomena on minute timescales. We perform a series of tests on simulated very long baseline interferometric (VLBI) observations of Sagittarius A$^\ast$ (SgrA*), the supermassive BLACK HOLE at the Galactic Center, with the Event Horizon Telescope (EHT), using both geometric and general RELATIVISTIC MAGNETohydrodynamic models. We demonstrate that adding an OT regularization term yields significant improvements in dynamic reconstructions compared to those without it, as quantified by better recovery of orbital motion and higher dynamic cross-correlation metrics. Continued developments in OT theory across various fields, proposed extensions to the EHT network, and broad applicability to other VLBI networks make it so that OT regularization for dynamic radio interferometric reconstructions will continue to be utilized and improved in the future.

[abstract 18 / 23] (score: 2)
arXiv:2407.15953 [pdf, ps, other]

Title: A universal relation between intermittency and dissipation within and beyond homogeneous isotropic turbulence

Authors: F. Schmitt, A. Fuchs, J. Peinke, M. Obligado,

Comments:

Subjects: physics.flu-dyn

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

Fundamental quantities of turbulent flows, such as the dissipation \Vsix{parameter} $C_\varepsilon$ and the intermittency \Vsix{parameter} $μ$, are examined in relation to each other for a broad class of inhomogeneous turbulent flows. In the context of the energy cascade, it is known that $C_\varepsilon$ reflects its basic overall properties, while $μ$ quantifies the intermittency \Vsix{of} the cascade. Using an extensive hot-wire dataset of turbulent wakes, grid-generated turbulence, and an axisymmetric JET, we individually analyze these quantities as one-dimensional surrogates of the energy cascade, considering only data that exhibit consistent scaling behavior. We find that $μ$ is inversely proportional to $C_\varepsilon$, offering a new empirical principle that bridges the gap between large and small scales in arbitrary turbulent flows. The generalized framework presented here recovers the established values and trends reported for homogeneous isotropic turbulence, and expands them to cover inhomogeneous situations.

[abstract 19 / 23] (score: 2)
arXiv:2603.20676 [pdf, ps, other]

Title: Generalized JMN Naked Singularity Models

Authors: Jay Verma Trivedi, Pankaj S. Joshi,

Comments: 14 pages, 9 figures

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

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

We construct a generalized class of Joshi-Malafarina-Narayan (JMN) naked singularity spacetimes that arise as equilibrium end states of gravitational collapse with non-vanishing tangential pressure. The generalization introduces density inhomogeneity through a radially dependent mass function $F(r)=(M_0+M_n r^n)r^3$, leading to a two-parameter family of solutions matched smoothly to an exterior Schwarzschild spacetime. The observational properties of the spacetime are then examined through shadow formation and thin accretion disk emission. We find that when the photon sphere lies in the exterior Schwarzschild region, the shadow is identical to that of a Schwarzschild BLACK HOLE. Accretion disk spectra show enhanced high-frequency emission compared to Schwarzschild, while deviations from the original JMN model remain small due to strong constraints on the inhomogeneity parameter. These results indicate that the generalized model effectively serves as a small perturbation of the JMN spacetime, demonstrating the robustness of JMN-type naked-singularity geometries.

[abstract 20 / 23] (score: 2)
arXiv:2607.07793 [pdf, ps, other]

Title: Tracing BLACK HOLE and galaxy growth across environments since cosmic noon

Authors: Emma Jane Weller, Priyamvada Natarajan, Colin J. Burke, Shashank Dattathri,

Comments: 17 pages, 11 figures. Published in ApJ

Subjects: astro-ph.GA

Created: 2026-08-26; Updated: 2026-08-28; Datestamp: 2026-08-28

The distribution of systems in the BLACK HOLE (BH) mass-stellar mass ($M_\mathrm{BH}-M_\star$) plane encodes both the integrated growth of galaxies and their central BLACK HOLEs, and the processes that shape their evolution. Using the ASTRID and TNG300 cosmological simulations, we track massive BHs from cosmic noon ($z=2$) to $z=0.5$. TNG300 repositions BHs to the centers of their host galaxies at every time step, while ASTRID instead advances them under the resolved gravitational forces plus a subgrid dynamical friction model, allowing BHs to wander off-center when orbital decay is inefficient. We follow the BHs rather than their original host galaxies, thereby capturing central BHs, BHs in satellites, and wandering BHs. We find that central BHs in both simulations evolve along a tight, nearly redshift-invariant $M_\mathrm{BH}-M_\star$ relation that is broadly consistent with local empirical constraints. Departures from this relation trace distinct evolutionary channels in which mergers play a key role. Major galaxy mergers drive BH-BH coalescence that dominates the growth of the most massive central BHs. These BHs subsequently quench their hosts through ACTIVE GALACTIC NUCLEus (AGN) kinetic feedback. Minor mergers tidally strip satellites to lower $M_\star$ at nearly fixed $M_\mathrm{BH}$, producing weakly accreting, overmassive central BHs in gas-poor systems. In ASTRID, satellite accretion and inefficient dynamical friction generate wandering BHs that are undermassive relative to their new hosts and experience minimal accretion or merger-driven growth. A BH's location in the $M_\mathrm{BH}-M_\star$ and specific BH accretion rate-specific STAR FORMATION rate planes is therefore a fossil record of its dynamical, accretion, merger, and feedback history.

[abstract 21 / 23] (score: 2)
arXiv:2608.26296 [pdf, ps, other]

Title: The mass ejected by a bubble bursting from a free drop

Authors: Alfonso M. Ganan-Calvo,

Comments: 7 pages, 5 figures

Subjects: physics.flu-dyn

Created: 2026-08-26; Updated: 2026-08-28; Datestamp: 2026-08-28

A bubble bursting at a flat liquid surface ejects droplets only below a critical Ohnesorge number Oh$_c\simeq0.043$. We ask how much it ejects when the bath is a drop of finite size. We solve the axisymmetric Navier--Stokes equations for a bubble of radius $R_0$ tangent internally to a free drop of radius $λR_0$, punctured at $t=0$, over liquid-to-gas volume ratios $Λ=V_{\rm liq}/V_{\rm gas}=λ^3-1$ from $1/16$ to $512$ and Oh from 0.005 to 0.11. Ejection ceases at Oh$_1=Oh_c(1+2β/λ)$ with $β\cong 0.83$, so confinement extends ejection to liquids too viscous, or bubbles too small, to eject at a flat surface. Two effects of first order in $1/λ$ produce the shift: the added Laplace overpressure of the outer surface, and the reduced inertia of the liquid shell. Our main result concerns the ejected mass $M_e$, which unlike the droplet count converges under mesh refinement. It obeys $M_e=C\,δ\,V_{\rm gas}V_{\rm liq}/(V_{\rm gas}+V_{\rm liq})$, with $δ=1-Oh/Oh_1$ and $C\simeq 0.013$, for $Λ\gtrsim0.2$: the two volumes combine as a reduced volume. When liquid is abundant this reduces to $M_e=C\,δ\,V_{\rm gas}$, a fixed fraction of the bubble volume, in agreement with classical JET-drop measurements; when gas is abundant, to $M_e=C\,δ\,V_{\rm liq}$. The fraction of liquid ejected spans four orders of magnitude, exceeding one third in the thinnest shells, where a distinct twin-JET mechanism takes over. Since hollow drops are generic in breaking waves, confinement includes bubbles that a flat surface would exclude and fixes what each delivers: two essential ingredients of sea-spray source functions.

[abstract 22 / 23] (score: 2)
arXiv:2608.26933 [pdf, ps, other]

Title: Anisotropy-driven constraints on the transition from Galactic to extragalactic cosmic-ray sources

Authors: Teresa Bister, Foteini Oikonomou, Damiano F. G. Fiorillo,

Comments:

Subjects: astro-ph.HE

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

The spatial distribution of the cosmic-ray (CR) flux above $8\,\mathrm{EeV}$ exhibits a significant dipole in agreement with expectations from extragalactic sources following the large-scale structure. At the ankle, the direction changes suddenly and is compatible with the Galactic center for energies $\lesssim4\,\mathrm{EeV}$. We leverage the direction and strength of the dipole anisotropy as diagnostics of the possible sources of the intermediate-mass nuclei below the ankle that cannot be associated with the continuation of the Peters cycle of lower-energy Galactic CRs. Using 3D-simulations of CR propagation in up-to-date Galactic MAGNETic field models, we show that the dipole anisotropy of both continuous and transient individual Galactic sources and source distributions exceeds the measurements by $>3σ$. An extragalactic origin of the intermediate nuclei below the ankle instead agrees with all data, where the observed change in dipole direction is guided by the fading heavy Galactic component dominant at the second knee.

[abstract 23 / 23] (score: 2)
arXiv:2608.27293 [pdf, ps, other]

Title: Electric and MAGNETic Penrose processes, charged-particle collisions and superradiance around a Lorentz-violating dyonic BLACK HOLE

Authors: Fernando M. Belchior, Edilberto O. Silva,

Comments: 25 pages

Subjects: gr-qc

Created: 2026-08-27; Updated: 2026-08-28; Datestamp: 2026-08-28

This paper is aimed at investigating electroMAGNETic energy extraction, charged-particle collisions, charged-field superradiance, and horizon stability in a Lorentz-violating dyonic Kalb-Ramond BLACK HOLE. The geometry differs from the dyonic Reissner-Nordström solution through a modified asymptotic normalization and an effective charge combining electric and MAGNETic sectors. We derive the dynamics of electrically and MAGNETically charged probes, including monopole-induced conical motion, and formulate electric and MAGNETic Penrose processes as decay or collision mechanisms in which a negative-energy fragment falls into the horizon while another escapes with enhanced energy. The electric and MAGNETic channels are controlled by \(Φ_H=Q/[(1-\ell)r_+]\) and \(Ψ_H=p/[(1-2\ell)r_+]\), respectively. Negative-energy states arise from electroMAGNETic canonical energy rather than from a geometrical ergoregion. We also obtain escape conditions for the outgoing products, test the possibility of overcharging or overMAGNETizing the BLACK HOLE, and analyze the center-of-mass energy of charged-particle collisions. Nonextremal same-direction collisions remain finite, whereas head-on or near-critical configurations can become large. In the extremal limit, electrically or MAGNETically critical particles may generate the Bañados-Silk-West divergence when the radial reachability condition is fulfilled.