Current date: 2026-09-09
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Number of records retrieved: 1300
Keyword score statistics
score 10 -- 1 abstracts
score 8 -- 2 abstracts
score 7 -- 2 abstracts
score 6 -- 1 abstracts
score 5 -- 5 abstracts
score 4 -- 6 abstracts
score 3 -- 17 abstracts
score 2 -- 34 abstracts
in total -- 68 abstracts
Articles that appeared on 2026-09-09
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[abstract 1 / 68] Wow! (score: 10)
- Title: Rapid radio variability in the $z\sim7$ BLAZAR VLASS J0410$-$0139: Indication of a hidden population of weak radio JETs at Cosmic DawnAuthors: Silvia Belladitta, Eduardo Bañados, Anniek J. Gloudemans, Timothy W. Shimwell, Emmanuel Momjian, Huib Intema, Chiara Mazzucchelli, Christian Fendt, Bhargav Vaidya, Fabian Walter,Comments: 16 pages, 3 figures, 3 tables, Accepted for publication in ApJSubjects: astro-ph.HE astro-ph.GACreated: 2026-09-04; Updated: 2026-09-09; Datestamp: 2026-09-09
Doppler boosting allows BLAZARs to be detected out to high-$z$, making them promising probes of the intergalactic medium through the 21 cm forest. We report 0.144$-$11 GHz observations of the most distant known BLAZAR, VLASS J041009.05$-$013919.88 at z$\sim$7, obtained with the upgraded Giant Metrewave Radio Telescope (uGMRT), the LOw Frequency ARray (LOFAR) and the Very Large Array (VLA). The first uGMRT epoch (300$-$820 MHz, April 2023) revealed an inverted radio spectrum which, combined with earlier (2021$-$2022) VLA data (1.5$-$11 GHz), unveiled a double-peaked spectrum potentially indicative of multi-epoch JET activity. A second uGMRT campaign (August 2023), simultaneous with new VLA observations (1.5$-$11 GHz), instead revealed a flat low-frequency and a peaked high-frequency spectrum, ruling out this interpretation. While limited by the two uGMRT epochs, variability analysis favors intrinsic JET processes, indicating a highly RELATIVISTIC, closely aligned JET ($θ<3$ deg, $δ>19.3$, $Γ>9.7$). The equipartition MAGNETic field ($> 1$ mG) exceeds the equivalent Cosmic Microwave Background field at $z\sim7$ (0.2 mG), indicating SYNCHROTRON losses dominate. The inferred Doppler boosting ($δ>19.3$) implies that J0410$-$0139 is intrinsically radio-weak. As a BLAZAR, it traces a much larger parent population of radio QUASARs at $z\sim7$, detectable only with deep ($\leq μ$Jy) next-generation radio observations. LOFAR 144 MHz observations (April and July 2024) yielded $\sim$2 mJy, well below the $\sim$8 mJy predicted from uGMRT epochs, confirming strong variability at rest-frame $\sim$1 GHz. Low-frequency monitoring will be crucial for identifying high radio intensity states suitable for future 21 cm forest studies.
[abstract 2 / 68] Wow! (score: 8) - Title: Hamiltonian variational reconstruction of the 3D MAGNETic geometry of RELATIVISTIC JETs: accuracy across GRMHD models and the fundamental sign degeneracyAuthors: Fabio Buffoli,Comments: 14 pages, 13 figures, 4 tablesSubjects: astro-ph.HECreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
Every resolved image of a RELATIVISTIC JET encodes its MAGNETic field, yet no image records which way the field points along the axis. Synchrotron intensity and linear POLARIZATION are blind to this: both probe the field only through even combinations of its components. We introduce H-MOG, a variational method that reconstructs the 3D field on a lattice from two projected observables, the JET width W(z) and the linear POLARIZATION p(z), regularized by a Hamiltonian prior and optimized with automatic differentiation. We apply H-MOG to ten GRMHD simulations spanning MAD and SANE states and five black-hole spins (a* = -0.94, -0.5, 0, +0.5, +0.94), and test three routes to break the intrinsic sign degeneracy of the reconstruction: a Faraday rotation-measure term, full 3D sampling, and a Blandford-Znajek spin prior. The unsigned field orientation is recovered at <|cos|> ~ 0.95-0.98, far above the random expectation of 0.5. The sense of the poloidal field, however, is not recovered, and we prove it cannot be: W and p are invariant under B -> -B. All three routes to break this degeneracy fail for distinct physical reasons; the spin-sense relation in these turbulent JETs is not monotonic, differing sharply between MAD and SANE. Recovering the sense requires a parity-odd observable: Faraday tomography or circular POLARIZATION.
[abstract 3 / 68] Wow! (score: 8) - Title: Chandra X-ray imaging and IC/CMB model for the inner JET of PKS 0637-752Authors: Jaya Maithil, Daniel A. Schwartz, Aneta Siemiginowska, Diana M. Worrall, Preeti Kharb,Comments: Accepted in ApJ. 21 pages, 10 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
We present the X-ray surface brightness maps of the JET from the QUASAR PKS 0637-752, using two epochs of archival Chandra observations (1999 and 2017). We present, for the first time, a model of the faint inner JET extending from 3.4 to 7 arcsec from the core, interpreting its X-ray emission as inverse Compton scattering of cosmic microwave background photons by the SYNCHROTRON-emitting RELATIVISTIC electrons. The inner JET contrasts with the bright outer part of the JET, dominated by several discrete knots for which upper limits to the FERMI gamma-ray flux rule out the inverse Compton mechanism. It is the first detailed inverse Compton model published for this inner JET. We examine three physically motivated scenarios, distinguished by the high-energy cutoff of the electron distribution, that can account for the observed radio, millimeter/submillimeter, and X-ray emission while remaining consistent with optical and gamma-ray upper limits. We also report for the first time X-rays from the radio lobe at the end of the receding JET.
[abstract 4 / 68] Wow! (score: 7) - Title: A Possible X-ray and Gamma-ray Quasi-Periodic Oscillation in GRB 241030AAuthors: Noel Klingler, Cecilia Chirenti, M. Coleman Miller, Amy Lien, Simone Dichiara,Comments: 18 pages, 13 figures, submitted to ApJSubjects: astro-ph.HECreated: 2026-09-04; Updated: 2026-09-09; Datestamp: 2026-09-09
Quasiperiodic oscillations (QPOs) in gamma-ray intensity have been reported from a few GAMMA-RAY BURSTs. These QPOs could be related to fundamental frequencies in the sources, which would lead to new insights about these systems. Here we report on our analysis of GRB~241030A, a several-minute-long burst with $\sim 10$ gamma-ray flares that have approximate periodicities at f ~ 0.04 Hz and f ~ 0.08 Hz. This quasi-periodicity is seen in X-rays with the SWIFT X-Ray Telescope (XRT) as well as in gamma-rays with the SWIFT Burst Alert Telescope (BAT) and the FERMI Gamma-ray Burst Monitor (GBM). Compared with a power spectral model that has only red noise, the Bayes factor in favor of a Lorentzian-shaped QPO is more than $10^{200}$, even when the red noise is described by segments with up to four different slopes. However, the interpretation of this power spectral feature as a QPO rather than as a fluctuation in red noise is complicated by the low frequency of the feature as well as the extremely large number of counts, which amplifies differences from smooth power spectral distributions. After discussing the properties of the apparent QPO, we discuss a few processes that could plausibly modulate the flux at this frequency. Among the mechanisms considered, we find the most plausible explanation to be a GRB JET passing through regularly spaced shells of circumburst material, possibly produced by binary interactions near periastron in an eccentric progenitor system.
[abstract 5 / 68] Wow! (score: 7) - Title: CoportSL: A Contribution-constrained Hybrid Slow-light Framework for Time-dependent Polarized GRMHD ImagingAuthors: Fan Zhou, Jiewei Huang, Yuehang Li, Minyong Guo, Bin Chen,Comments: 24 pages, 11 figures, 2 tablesSubjects: astro-ph.HE gr-qcCreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
Fast-light approximations neglect fluid evolution along rays, whereas slow-light modeling is indispensable for recovering the true MAGNETohydrodynamic state. However, full slow-light radiative transfer for extended general RELATIVISTIC MAGNETohydrodynamic (GRMHD) sources requires simultaneous access to many fluid snapshots and is memory-intensive. We introduce CoportSL, the first contribution-constrained hybrid slow-light framework for time-dependent full-Stokes imaging. It uses emission, absorption, and Faraday contributions to identify where fluid evolution must be retained, applies fast light elsewhere, and loads only snapshots spanning the relevant delays. Tests with M87*-like MAGNETically arrested disk GRMHD data show that the contribution-based region and delay-based snapshot restrictions each keep normalized full-image Stokes differences below $4\times10^{-3}$ relative to the corresponding complete calculation. At this accuracy, CoportSL requires 75.3% and 44.7% fewer snapshot layers for near-horizon and JET images, respectively; its per-frame slow-light transfer time remains comparable to fast light. For the two configurations, source-code estimates place the capacities of the principal data structures at 255-657 GiB for a fixed public ipole version and 20.2-37.3GiB for CoportSL, bringing both configurations within workstation-scale memory. Fast--slow comparisons further show close agreement in near-horizon variability, whereas JET variability follows similar overall trends but differs in local peaks and amplitudes; in both cases, fast light misses substantial full-Stokes spatial structure. As the next-generation Event Horizon Telescope (ngEHT) advances toward dynamical imaging and spatially resolved polarimetry, CoportSL provides a computationally practical way to model full-Stokes finite-light-travel-time signatures in extended BLACK HOLE systems.
[abstract 6 / 68] Yes (score: 6) - Title: A pilot submillimeter search for IceCube neutrino counterparts: JCMT follow-up and dusty-galaxy catalog associationsAuthors: Yuji Urata, Kuiyun Huang,Comments: 16 pages, 4 figures, 6 tables. Submitted to PASJSubjects: astro-ph.GA astro-ph.HECreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
The submillimeter band offers a complementary route to identifying electroMAGNETic counterparts of high-energy neutrinos, tracing RELATIVISTIC transients and persistent dust-obscured galaxies. We present a pilot search combining JCMT/SCUBA-2 follow-up of IceCube events with catalog searches for bright high-redshift dusty systems. Among nine rapidly observed IceCube fields, sources of particular interest were found in three: JCMT0402-0424 ("Shadow Blaster") in IC 210922A, a transient-like source following IC 220115A, and two known BLAZARs in IC 240105A. ALMA resolved the Shadow Blaster into a strongly lensed dusty star-forming galaxy at z=2.988 with a compact gas-rich starburst core. Motivated by this result, we cross-matched IceCube localizations with the Herschel Bright Sources (HerBS) and Planck High-Redshift Source Candidate (PHZ) catalogs. Among 51 historical IceCube events with A_bbox,90 <= pi deg^2, four fields contain at least one HerBS source, compared with 0.723 expected from right-ascension scrambling (fixed-cut p=4.18e-3). Scanning the localization-area threshold gives p_global,A=0.0135. Applying the same IceCube selection to PHZ gives four associated fields versus 3.544 expected (p=0.478). Because the focused HerBS selection followed a broader exploratory analysis with trials-corrected p_global=0.130, the focused result is suggestive rather than definitive. The four well-localized HerBS fields contain six high-redshift DSFGs with apparent L_IR~10^13 L_sun. ALMA imaging and published spectroscopy reveal compact or multiple-component morphologies, extreme molecular-gas kinematics, and possible obscured nuclear activity. These results support a hierarchical strategy: identify luminous submillimeter candidates through wide-field imaging and catalogs, then characterize them at high angular resolution to test for compact gas-rich calorimetric conditions and obscured AGN activity.
[abstract 7 / 68] Yes (score: 5) - Title: The Physics of Solar Energetic ParticlesAuthors: Donald V Reames,Comments: 33 pages, 12 figuresSubjects: astro-ph.SRCreated: 2026-09-04; Updated: 2026-09-09; Datestamp: 2026-09-09
Solar energetic particles (SEPs) are produced in two fundamental ways: at MAGNETic RECONNECTion sites in solar JETs and at collisionless shock waves driven by fast coronal mass ejections (CMEs). "Impulsive" SEP events, on open field lines from JETs, have signature abundance enhancements of 3He and of increasingly heavy elements, and their outward streaming electrons drive type-III radio bursts. Similar acceleration for particles trapped on closed loops energizes solar flares. In contrast, fast, wide, CME-driven shocks accelerate seed ions from the ambient corona that grow resonant Alfven waves as they stream outward. These waves can scatter and trap lower-rigidity ions near the shock, limiting outflow, and flattening low-energy spectra upstream at the "streaming limit." Downstream, a spatially-uniform "reservoir" of SEPs is shed by the expanding shock between it and the Sun. These trapped invariant SEP spectra decrease in intensity adiabatically as the volume of the reservoir expands. Ions from the reservoir can seed further acceleration in multi-shock event and energetic proton precipitation can prolong solar gamma-ray emission. Shocks are often additionally seeded by residual impulsive ions which dominate the SEP heavy-ion abundances with their signature enhancements. As samples of the corona, SEP abundances also probe differences with the photosphere that depend upon the first ionization potential (FIP) of the elements.
[abstract 8 / 68] Yes (score: 5) - Title: MEOW: The increase in the obscured AGN fraction in mid-infrared from 0 < z < 6 with JWST MIRIAuthors: Teodora-Elena Bulichi, Gene C. K. Leung, Anna-Christina Eilers, Pablo G. Perez-Gonzalez, Guillermo Barro, Steven L. Finkelstein, Micaela B. Bagley, Anton M. Koekemoer, Bren E. Backhaus, Mark Dickinson, Norman A. Grogin, Dale D. Kocevski, Ray A. Lucas, Fabio Pacucci, Nor Pirzkal, Elia Pizzati, Jan-Torge Schindler, Alberto Traina, Guang Yang,Comments: 19 pages (main text), 9 figures (+ 2 in the appendix), 3 tables (1 in the appendix). Published in ApJSubjects: astro-ph.GACreated: 2026-09-04; Updated: 2026-09-09; Datestamp: 2026-09-09
Obscured ACTIVE GALACTIC NUCLEi (AGN) are often invoked to explain the rapid emergence of young QUASARs at high redshift and are crucial for building a complete census of AGN activity and BLACK HOLE growth. The advent of the James Webb Space Telescope (JWST) extends the discovery space for obscured AGN into the mid-infrared (mid-IR) with unprecedented precision through reprocessed dust emission. In this work, we use deep JWST Mid-Infrared Instrument (MIRI) imaging from the MIRI Early Obscured AGN Wide Survey (MEOW), together with existing JWST Near Infrared Camera (NIRCam), spectroscopic, and Hubble Space Telescope imaging data, to identify a previously unrecognized population of obscured AGN out to z ~ 6. Using spectral energy distribution (SED) modeling of the MIRI-detected sources, we identify 883 AGN over an area of ~ 131 arcmin2 and construct the AGN bolometric luminosity function, including both obscured and unobscured sources, across five redshift bins. We find an excess in AGN abundance relative to UV-selected AGN luminosity functions, indicating a substantial obscured population missed by optical/UV surveys, with the inferred obscured fraction increasing with redshift and reaching ~ 98-99% in our highest-redshift bin, 4.5 < z < 6. We also find higher AGN abundances and obscured fractions than X-ray-based studies, consistent with a previously unrecognized population of heavily obscured, Compton-thick AGN revealed by mid-IR selection. These results suggest that a large fraction of supermassive BLACK HOLE growth at early times occurs during heavily obscured phases largely inaccessible at other wavelengths.
[abstract 9 / 68] Yes (score: 5) - Title: HAMCOR: A physics-driven Hamiltonian framework for inferring AGN coronal geometry from X-ray reverberation lagsAuthors: Fabio Buffoli,Comments: 11 pages, 7 figures, 5 tablesSubjects: astro-ph.HECreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
We present HAMCOR (Hamiltonian-based AGN Multi-constraint CORonal inference framework), a geometry-agnostic method for inferring the X-ray coronal structure of accreting BLACK HOLEs using reverberation-lag measurements. Unlike conventional template-fitting approaches, HAMCOR reframes coronal geometry inference as the ground-state selection of a physical Hamiltonian. The corona is represented as a discrete emissivity distribution over a cylindrical grid, and its geometry emerges from five competing physical constraints: MAGNETic coherence, lag consistency, illumination consistency, pair-production stability, and energy budget feasibility. Minimisation is performed via projected gradient descent with Armijo backtracking line search on the probability simplex. We validate HAMCOR on three synthetic geometries (lamppost, column, ring) using the same grid as the real-data fits, recovering spatial correlations rho = 0.24, 0.50, 0.12 and fractional lag errors below 24 per cent. A hyperparameter sensitivity analysis confirms robustness over more than one order of magnitude in the coupling constants. We apply HAMCOR to five sources spanning seven orders of magnitude in BLACK HOLE mass: four AGN observed with XMM-Newton (Mrk 335, 1H 0707-495, IRAS 13224-3809, MCG-6-30-15) and the stellar-mass BLACK HOLE binary Cyg X-1 (M_bh = 14.8 M_sun), recovering consistent extended disc-corona geometries across the full mass range. We further present a multi-epoch analysis of Mrk 335 across five XMM-Newton observations (2006-2019), revealing that the coronal centroid remains stable at (R_c, z_c) ~ (6.3, 0.5) r_g across flux states spanning a factor of ~15 in reverberation lag amplitude, arguing against a collapsing or expanding lamppost. Schwarzschild-Shapiro delay corrections amount to ~79 per cent of the flat-spacetime lag on average; the recovered spatial morphology is robust to this correction.
[abstract 10 / 68] Yes (score: 5) - Title: Multi-epoch Detection of an Ultra-fast Inflow in ESP 39607: Evidence for an Accretion CascadeAuthors: Alessandro Peca, Michael J. Koss, Roberto Serafinelli, C. Megan Urry, Claudio Ricci, Keigo Fukumura, Massimo Gaspari, Elias Kammoun, Alessia Tortosa, Giulia Cerini, Peter G. Boorman, Richard Mushotzky, Quirino D'Amato,Comments: Accepted for publication in ApJSubjects: astro-ph.HE astro-ph.GACreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
We present simultaneous XRISM, XMM-Newton, and NUSTAR observations of ESP 39607, a Seyfert 2 galaxy at $z = 0.201$. XRISM/Resolve reveals two absorption features near 4.7 and 4.9 keV in the observed frame, consistent with redshifted Fe XXV He-$α$/Fe XXVI Ly-$α$ absorption from gas inflowing at $v_{\rm in} \simeq 0.16c$. The high velocity identifies the absorber as an ultra-fast inflow (UFI), which is detected at $\sim 3$-$3.7σ$ across different methods and continuum models. Photoionization modeling yields $\log ξ/{\rm erg\,s^{-1}\,cm} \simeq 3.7$-$3.8$ and a column density $\log N_{\rm H,abs}/{\rm cm^{-2}} \simeq 23.2$-$23.8$, the latter depending on the assumed metallicity. The inflow velocity and line properties are consistent with those reported from two earlier NUSTAR epochs, indicating that similar inflowing material was present over a baseline of at least 2.2 yr in the source rest frame. Across all three epochs, the combined detection significance of the UFI is $5.3σ$. Given the dynamical timescale of a few days at the inferred radius, $R \simeq 49$-$77\,R_{\rm g}$, the multi-year evidence favors a scenario in which the inflow is continuously replenished, forming an accretion "cascade", rather than a single long-lived cloud. With an estimated mass inflow rate of $\dot{M}_{\rm in} \simeq 0.3$-$1.4\,M_\odot$ yr$^{-1}$, depending on metallicity, and a ratio $\dot{M}_{\rm in}/\dot{M}_{\rm acc} \simeq 0.2$-$1.0$, the inflow could supply a substantial fraction of the accretion needed to power the central ACTIVE GALACTIC NUCLEus.
[abstract 11 / 68] Yes (score: 5) - Title: Two-Phase Structure of Synchrotron-Cooling-Unstable Relativistic PlasmaAuthors: Agnieszka Wierzchucka, Pablo J. Bilbao, Robert J. Ewart, Dmitri A. Uzdensky, Alexander A. Schekochihin,Comments: 47 pages, 15 figuresSubjects: astro-ph.HE physics.plasm-phCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
Using analytic theory, radiative particle-in-cell (PIC) simulations, and fluid simulations, we show that RELATIVISTIC, SYNCHROTRON-cooling, collisionless, high-$β$ pair plasmas filament into a two-phase medium. This process occurs through the interplay of the SYNCHROTRON cooling instability (SCI) with the SYNCHROTRON firehose instability (SFHI). One phase has high plasma~$β$ and is infested with small-scale firehose fluctuations, which scatter particles and pin the pressure anisotropy to the firehose-marginal level. The other phase has much lower~$β$, causing the suppression of firehose modes and thus allowing large pressure anisotropies. We propose a fluid model for this two-phase plasma, which we use to study the linear and nonlinear evolution of the SCI and SFHI, and to predict the emergence time of the two-phase structure.
[abstract 12 / 68] Yes (score: 4) - Title: Diverse Morphologies of GRB X-Ray Plateaus within a Common Magnetar FrameworkAuthors: Xiao-Fei Dong, Yong-Feng Huang, Nurimangul Nurmamat, Chen Deng, Ze-Cheng Zou, Fan Xu, Abdusattar Kurban, Chen Du, Chen-Ran Hu, Jin-Jun Geng,Comments: 15 pages, 8 figures, 1 table. Submitted. Comments are welcomeSubjects: astro-ph.HECreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
The origin of the X-ray plateau phase in GAMMA-RAY BURSTs (GRBs) remains an open problem. In particular, it is unclear whether GRBs with different temporal morphologies (i.e., with a rising, flat, or decaying plateau) arise from a common underlying mechanism. Although MAGNETar energy injection is a leading explanation, previous studies have primarily inferred MAGNETar properties on a burst-by-burst basis and have not tested the model at the population level. Here we perform the first hierarchical population inference of MAGNETar parameters for a uniform sample of 185 long GRBs with X-ray plateaus within a conditional Poisson point-process framework. It is found that the observed plateau population is well reproduced by physically plausible MAGNETar populations. The inferred parameter distributions show no strong statistical separation among subclasses with different plateau morphologies. Nevertheless, all subclasses show a substantial intrinsic luminosity scatter, $σ_{L,\rm int}\sim0.5$--1.0 dex, whereas the intrinsic duration scatter remains considerably smaller. The results provide a population-level test of the MAGNETar interpretation of GRB X-ray plateaus, showing that the observed diversity of plateau morphologies does not require distinct MAGNETar populations.
[abstract 13 / 68] Yes (score: 4) - Title: ElectroMAGNETic filament coalescence as MAGNETic island merging with diaMAGNETic effectsAuthors: Souvik Mondal, N Bisai, Abhijit Sen, Indranil Bandyopadhyay,Comments:Subjects: physics.plasm-phCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
We investigate the nonlinear coalescence of two current-carrying ELM filaments using a three-dimensional electroMAGNETic fluid model. In the flat-density limit, the coalescence exhibits MAGNETic island-like RECONNECTion, characterized by X-point formation, current-sheet development, and Sweet-Parker-like resistive scaling. Introducing a blob-like density perturbation modifies the RECONNECTion dynamics: while the peak RECONNECTion rate remains nearly unchanged for weak perturbations, it decreases and is increasingly delayed for larger density amplitudes. Analysis of the induction equation reveals a transition from resistive to increasingly density-dependent advective dynamics. Finite density perturbations also enhance the post-compression rebound, or sloshing, of the filaments. The sloshing amplitude increases with the density-gradient pressure force, establishing density perturbation as an additional control parameter for both RECONNECTion and filament sloshing. These results highlight the coupled electroMAGNETic and pressure-driven dynamics governing the nonlinear evolution of ELM filaments in the tokamak edge.
[abstract 14 / 68] Yes (score: 4) - Title: LOFAR follow-up of sources in the First LHAASO CatalogueAuthors: Maria Arias, Timothy Shimwell, Martin Hardcastle, Roland Timmerman,Comments: Accepted in A&ASubjects: astro-ph.HECreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
The First LHAASO Catalogue lists 90 sources of very-high-energy gamma-ray emission, many without an established counterpart at other frequencies, reopening the question of which Galactic accelerators produce the highest-energy COSMIC RAYs. We search for low-frequency radio counterparts to the 55 1LHAASO sources that fall within the Galactic fields of the LOFAR Two-metre Sky Survey Data Release Three (LoTSS-DR3), using 144~MHz continuum maps at $6''$ and $20''$ resolution, complemented with archival data from other radio surveys where available. We present an overview of the radio emission towards all 55 sources, and identify the structures potentially associated with the gamma-ray emission. We report 24 new SUPERNOVA remnant (SNR) candidates, nine flat-spectrum radio shells with faint or no infrared counterpart, and six sources with no clear Galactic radio emission present in the LOFAR maps. A bootstrap analysis shows that 23 of the 50 sources in the Galactic plane footprint (46\%, for $|b| \leq 5$) overlap a catalogued SNR, whereas random placement yields only $10.0\pm2.8$ matches even if the underlying Galactic SNR population is ten times larger than currently catalogued; in the outer Galaxy, where chance alignment is rarest, 4 of 12 sources coincide with an SNR against a null expectation of $\lesssim2$. We estimate that at least a quarter, and up to half, of the 1LHAASO Galactic-plane sources genuinely reside in SNR environments, consistent with a population dominated by pulsar wind nebulae, SNR--PWN composites, and cosmic-ray-illuminated clouds. Individual results include a new SNR candidate inside the TeV shell HESS~J1912+101, a radio candidate for the SNR hypothesised to explain the GeV emission of 1LHAASO~J1945+2424, and the first proposed counterparts of 1LHAASO~JJ0056+6343u and 1LHAASO~J2200+5643u.
[abstract 15 / 68] Yes (score: 4) - Title: Correlation between X-ray and gamma data of SWIFT measurementsAuthors: Istvan I. Racz, Lajos G. Balazs, Istvan Horvath, Sandor Pinter,Comments: 9 pages, 5 figuresSubjects: astro-ph.HECreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
Several studies over the last two decades have used canonical correlation analysis (CCA) to study the relationships between main γ-ray (e.g. fluence, peak flux, and duration) and main X-ray (flux, decay and spectral index, and hydrogen column density) data from GAMMA-RAY BURSTs (GRBs). In this paper, we revisit this approach using a much larger dataset to identify potential new insights into these relationships. We used CCA to investigate the interrelationship of the aforementioned gamma-ray and X-ray parameters. Using the derived canonical variables, we calculated their correlations (canonical loadings) with the original data. Consistently with previous research, the analysis revealed that gamma-ray fluence and X-ray flux have the strongest correlation, while the X-ray decay index and spectral index have a lower contribution. Interestingly, our analysis of a much larger dataset reveals that the HI column density makes a significant contribution to the overall correlation. This finding, in the context of the collapsar model for long GRBs, could be interpreted as an indication that the progenitor star ejected an HI envelope during the GRB.
[abstract 16 / 68] Yes (score: 4) - Title: Interior Magnetic Fields in Magnetars and Radio PulsarsAuthors: Raj Kishor Joshi, Brynmor Haskell, William Cook, Sebastiano Bernuzzi,Comments: 12 Pages, 6 FiguresSubjects: astro-ph.HECreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
Magnetic fields are fundamental for neutron star physics and play a central role in powering the extreme phenomenology of MAGNETars, including Soft Gamma Repeaters and Anomalous X-ray Pulsars. However, the structure and stability of their internal MAGNETic fields remain largely unconstrained, as they cannot be directly probed by electroMAGNETic observations. Using 3D general-RELATIVISTIC MAGNETohydrodynamics simulations across a range of rotation rates and MAGNETic field strengths, we identify two distinct evolutionary regimes leading towards dynamically stable MAGNETic configurations. In rapidly rotating stars, the Alfvén crossing timescale exceeds the rotation period, allowing differential winding to amplify a strong toroidal MAGNETic component before the onset of instabilities, leading to long-lived, stable configurations. In contrast, in MAGNETically dominated stars, instabilities in the poloidal field drive rapid field decay, leaving only a comparatively weak toroidal component. These results imply that the internal MAGNETic structure of neutron stars depends sensitively on their rotational state: rotation-dominated stars like radio pulsars develop strong toroidal fields, while MAGNETars are characterized by predominantly poloidal configurations. Our findings therefore show that a neutron star's rotational history shapes its internal MAGNETic structure, providing a unifying physical picture that connects the observed diversity of neutron star classes to their hidden field configurations.
[abstract 17 / 68] Yes (score: 4) - Title: A New Sample of $\sim$ 100 Intermediate-mass Black Holes Reaching $z \approx 1$Authors: Wen-Juan Liu, Luis C. Ho, Su Yao, Xiao-Bo Dong, Yaqi Zhao,Comments: 21 pages, 8 figures, and 3 tables. Submitted to AAS JournalsSubjects: astro-ph.GA astro-ph.HECreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
We present a systematic search for intermediate-mass BLACK HOLE (IMBH) ACTIVE GALACTIC NUCLEi (AGNs) at $0.5 < z \lesssim 1$ using DESI DR1 spectroscopy.We identify 98 broad-line IMBH AGNs with BLACK HOLE masses $M_\mathrm{BH}<10^6$ $M_{\odot}$ through quantitative spectral decomposition and broad-H$β$ selection. This sample spans $M_\mathrm{BH}=10^{5.5}-10^{6.0}$ $M_{\odot}$ and Eddington ratios from 1.2 to 9.0 extending systematic IMBH AGN searches to intermediate redshift. Compared with a consistently selected $z<0.6$ IMBH sample, the $0.5
[abstract 18 / 68] (score: 3) - Title: Hidden in Pixels. I. Discovery of dual "little red dots" indicates excess clustering on kilo-parsec scalesAuthors: Takumi S. Tanaka, John D. Silverman, Kazuhiro Shimasaku, Junya Arita, Hollis B. Akins, Feige Wang, Kohei Inayoshi, Xuheng Ding, Masafusa Onoue, Zhaoxuan Liu, Caitlin M. Casey, Erini Lambrides, Vasily Kokorev, Shuowen Jin, Andreas L. Faisst, Jianwei Lyu, Jan-Torge Schindler, Yunjing Wu, Nicole Drakos, Yue Shen, Junyao Li, Mingyang Zhuang, Qinyue Fei, Kei Ito, Wei Leong Tee, Weizhe Liu, Wenke Ren, Tomokazu Kiyota, Zi-Jian Li, Suin Matsui, Makoto Ando, Shun Hatano, Michiko S. Fujii, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Daizhong Liu, Henry Joy McCracken, Jason Rhodes, Brant E. Robertson, Maximilien Franco, Koki Kakiichi, Jinyi Yang, Romain A. Meyer, Irham T. Andika, Aidan P. Cloonan, Xiaohui Fan, Ghassem Gozaliasl, Santosh Harish, Christopher C. Hayward, Marc Huertas-Company, Darshan Kakkad, Tomoya Kinugawa, Mingyu Li, Namrata Roy, Marko Shuntov, Margherita Talia, Sune Toft, Aswin P. Vijayan, Yiyang Zhang,Comments: 21 pages, 11 figures, and 3 tablesSubjects: astro-ph.GACreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
``Little Red Dots'' (LRDs) are an abundant high-redshift population newly discovered by the James Webb Space Telescope (JWST) and considered to be an early growth phase of supermassive BLACK HOLEs (SMBHs). Using a method of pixel-by-pixel color selection and relaxing the compactness criteria, we identify four dual LRD candidates in the COSMOS-Web survey with projected separations of $0.\!\!^{\prime\prime}2$-$1.\!\!^{\prime\prime}2$. A comparison between existing LRD samples and mock data reveals that the projected separations of these dual LRD candidates are unlikely to result from chance projections of objects at different redshifts. Furthermore, two of the four systems are covered by COSMOS-3D slitless spectroscopy, and a single-line detection at the same observed wavelength for each LRD in a pair strongly supports that they are at identical redshifts. Assuming that the detected lines are H$α$ based on their high equivalent width and broad profile, the spectroscopic redshifts of $z=5.822$ and $5.464$ for the two pairs are consistent with their photometric redshifts, yielding projected separations of $1.64$ and $7.36\,{\rm kpc}$. These discoveries suggest that the angular auto-correlation function (ACF) of LRDs exhibits an excess ($\sim20$-$30$ times) on sub-arcsec (kilo-parsec) separations compared to an extrapolation of a power-law ACF of JWST-found AGNs measured over $10^{\prime\prime}$-$100^{\prime\prime}$. Our sample is likely to represent precursors of mergers between LRDs, and such mergers may be one of the mechanisms that can drive the rapid growth of SMBHs in their early evolutionary stages.
[abstract 19 / 68] (score: 3) - Title: A coordinate-free expression of plasma theoryAuthors: Michael E. Glinsky,Comments: 24 pages, 18 figures, 146 equationsSubjects: physics.plasm-phCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
The theory of plasmas, that is collectives of charged particles, is developed using the coordinate-free and geometric methods of exterior calculus. This dramatically simplifies the algebra and gives a geometric physical interpretation. The fundamental foundation on which the theory is built is the conservation of phase space volume expressed by the Generalized Liouville Equation in terms of the Lie derivative. The theory is expanded both in the order of the correlation and in the weakness of the correlation. This gives a Generalized BBGKY (Bogoliubov-Born-Green-Kirkwood-Yvon) Hierarchy. The derivation continues to give a new generalized formula for the Variational Theory of Reaction Rates (VTRR). Pullbacks of the generalized formulas to generic canonical coordinates and Poisson brackets are done. Where appropriate, the canonical coordinates are assumed to be "action-angle" coordinates that are generated by the solution to the Hamilton-Jacobi equation, the action. Finally, generalized forms of all the common kinetic equations are derived: the Vlasov Equation, the Boltzmann Equation, the Master Equation, the Fokker-Planck Equation, the Vlasov-Fokker-Planck (VFP) Equation, the Fluid Equations, and the MagnetoHydroDynamic (MHD) Equations. Specific examples are given of these equations. The application of the VTRR to three-body recombination in a strong MAGNETic field is shown.
[abstract 20 / 68] (score: 3) - Title: Decoding FRB Energetics and Frequency Features Hidden by Observational IncompletenessAuthors: Chen-Ran Hu, Yong-Feng Huang, Jin-Jun Geng, Chen Deng, Ze-Cheng Zou, Xiao-Fei Dong, Yi-Dan Wang, Pei Wang, Fan Xu, Lang Cui, Song-Bo Zhang, Xue-Feng Wu,Comments: ApJS in pressSubjects: astro-ph.HECreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
Fast radio bursts (FRBs) are millisecond-duration extragalactic radio flashes likely powered by MAGNETars, yet their radiation mechanism remains unknown. Limited sensitivity and finite observing bandwidth inevitably lead to observational truncation, biasing our understanding of intrinsic burst properties. Assuming Gaussian-like spectra, we present a general inverse-modeling framework that reconstructs the intrinsic frequency and energy characteristics of repeating FRBs directly from truncated data, without spectral profile fitting. In our approach, detected bursts are classified as in-band (affected only by the sensitivity cutoff) or band-chipped (affected by both sensitivity and operating-band cutoffs) events. For in-band events, observed and intrinsic quantities are linked through a set of equations. For band-chipped bursts, with spectral peaks possibly outside the telescope's operating band, a population-based method is used to infer individual burst properties from the statistical properties of the entire sample. Applied to 2,223 bursts from FRB 20121102A, it is found that intrinsically energetic bursts tend to have narrower spectra than weak ones. We further quantify, for the first time, the number of out-of-band bursts, and reveal distinct frequency-evolution behaviors across active periods and frequency bands. Comparisons between reconstructed and original samples show that the sensitivity cutoff barely affects burst energy but biases the observed bandwidth, whereas the operating-band cutoff may cause severe energy leakage and bandwidth underestimation, suggesting that the energy release of some repeaters may be underestimated, with potential implications for the energy supply beyond the MAGNETar MAGNETosphere. Our methodology transforms incomplete archival observations into physically meaningful probes, bridging instrumental readouts and intrinsic FRB physics.
[abstract 21 / 68] (score: 3) - Title: The Physical Origin of Periodic Density Structures in the Solar Wind: Coronal Streamers as Magnetohydrodynamic ResonatorsAuthors: Olena Podladchikova,Comments: Withdrawn by the author following a reassessment of the original full-streamer resonator interpretation. A broader framework informed by MHD waveguide theory and coronal seismology separates reconnection-driven plasma release from its possible MHD modulation. The revised analysis, accepted by The Astrophysical Journal on 4 September 2026, has been submitted as an update to arXiv:2511.04850Subjects: astro-ph.SRCreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
We present a comprehensive physical model explaining the origin of Periodic Density Structures (PDS) observed in white-light coronagraphs with characteristic periods of approximately 45, 80, and 120 minutes. Through systematic investigation of potential resonant cavities in the solar atmosphere, we demonstrate that traditional large-scale cavities yield fundamentally incompatible periods: photosphere-transition region (3.3 minutes), transition region-sonic point (10.3 hours), and transition region-heliopause (7.7 years). We establish that coronal streamers act as natural MAGNETohydrodynamic resonators, with calculated harmonic periods of 122, 61, and 41 minutes that precisely match observations. The physical mechanism involves slow MAGNEToacoustic standing waves that create periodic density enhancements through wave compression, with the streamer resonator having quality factor Q ~ 10-100, enabling natural amplification of broadband coronal noise. At streamer cusps, these density enhancements trigger MAGNETic RECONNECTion, releasing plasma blobs into the solar wind at resonant periods. The model provides complete energy budget calculations, wave amplitude estimates, and explains all key observational features including spatial localization, period coherence, and the relationship between remote sensing and in situ measurements. This work establishes streamer resonators as fundamental structures shaping solar wind variability and provides a new framework for understanding the emergence of coherent structures in turbulent astrophysical plasmas.
[abstract 22 / 68] (score: 3) - Title: Can MHD Oscillations Modulate Quasi-Periodic Plasma Release from Coronal Streamers?Authors: Olena Podladchikova,Comments: Accepted for publication in The Astrophysical Journal (ApJ) on 4 September 2026. Substantially revised following peer review; title and abstract changed. 9 pages, 4 figuresSubjects: astro-ph.SRCreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
Periodic density structures in the slow solar wind are associated with quasi-periodic plasma release from coronal streamer and open-closed boundary regions, but the origin of their organization remains uncertain. We distinguish the process that releases plasma from the process that sets or modifies its cadence. In the proposed source-modulator framework, S-Web, interchange, cusp, or current-sheet RECONNECTion releases the plasma, while structured MHD responses may modulate density or release rate. An observation-informed parameter-space analysis gives compact slow-mode periods of about 22-231 min; reproducing 80-130 min requires an effective path length of 0.35-1.20 solar radii. In a classical top-hat cylinder with L/a = 5-50 and rho_i/rho_e = 1.6-2.5, the fundamental fast sausage mode is not trapped and the minimum trapped harmonic is approximately n = 4-50. A transverse fast-timescale benchmark based on a = 0.10-0.45 solar radii and outer-coronal fast speeds of 250-530 km/s gives 5.7-55 min. A corresponding fast-interface proxy gives 4.4-93 min, but is not a current-sheet eigenmode solution. Kink responses are constrained empirically rather than by inserting observer-frame propagation speeds into a standing-mode formula: one COR1 event showed an approximately 25 min pulse, whereas a LASCO/COR2 survey found global streamer-wave periods of 2-8 hr, observer-frame speeds of 360-740 km/s, and typically only one or two visible cycles. Among the candidates considered here, compact slow modes are the best-constrained stable compressive modulators; confirming their role requires constraints on longitudinal reflection and damping. Surface/current-sheet responses remain high-priority coupling candidates but require a sheet-specific dispersion relation; kink responses are transient geometric candidates; and tearing/plasmoid formation remains a strong intrinsic RECONNECTion-driven alternative.
[abstract 23 / 68] (score: 3) - Title: Investigating IceCube Neutrino Alerts with the HAWC $γ$-Ray ObservatoryAuthors: The HAWC Collaboration, R. Alfaro, C. Alvarez, A. Andrés, E. Anita-Rangel, M. Araya, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, E. Belmont-Moreno, A. Bernal, K. S. Caballero-Mora, T. Capistrán, F. Carreón, S. Casanova, J. Cotzomi, S. Coutiño de León, C. de León, E. De la Fuente, P. Desiati, N. Di Lalla, R. Diaz Hernandez, M. A. DuVernois, J. C. Díaz-Vélez, K. Engel, C. Espinoza, N. Fraija, S. Fraija, A. Galván-Gámez, J. A. García-González, F. Garfias, N. Ghosh, A. Gonzalez Muñoz, M. M. González, J. A. González, J. A. Goodman, D. Guevel, J. Gyeong, J. P. Harding, S. Hernández-Cadena, I. Herzog, J. Hinton, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, A. Iriarte, S. Kaufmann, D. Kieda, K. Leavitt, J. Lee, W. H. Lee, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, P. E. Mirón-Enriquez, E. Moreno, M. Mostafá, M. Najafi, A. Nayerhoda, L. Nellen, M. U. Nisa, R. Noriega-Papaqui, N. Omodei, M. Osorio-Archila, E. Ponce, Y. Pérez Araujo, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, M. Roth, H. Salazar, D. Salazar-Gallegos, A. Sandoval, M. Schneider, J. Serna-Franco, M. Shin, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, E. Varela, L. Villaseñor, X. Wang, Z. Wang, I. J. Watson, H. Wu, S. Yu, H. Zhou,Comments:Subjects: astro-ph.HECreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
Neutrino emission from astrophysical sources has long been considered a signature of cosmic-ray acceleration. The IceCube neutrino observatory has observed a diffuse flux of TeV-PeV neutrinos, but very few confirmed sources have emerged. With the recent publication of IceCube Event Catalog (IceCat-1), IceCube has released a list of the most promising astrophysical neutrino events since May 2011. Using the archival data from the High Altitude Water Cherenkov (HAWC) Gammma-ray observatory, we perform a coincidence search for gamma rays and neutrinos using a Bayesian Block algorithm with the public IceCube alerts from IceCat-1, along with additional alerts issued later. In this work, we consider 368 alerts, up to July 8, 2025, that are within HAWC's field of view. We observe approximately a 5\% coincident detection rate, which is consistent with expectations from background. Two of these detections contain the Active Galactic Nuclei (AGN) Markarian 421 and Markarian 501. We discuss the likelihood that the neutrino/$γ$-ray coincidences are false positives and a brief overview of the results.
[abstract 24 / 68] (score: 3) - Title: Do little red dots really form a distinct class of astronomical objects?Authors: Jean-Baptiste Billand, David Elbaz, Maximilien Franco, Fabrizio Gentile, Emanuele Daddi, Mauro Giavalisco, Dale D. Kocevski, Joseph S. W. Lewis, Benjamin Magnelli, Valentina Sangalli, Maxime Tarrasse,Comments: Accepted for publication in A&ASubjects: astro-ph.GACreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
JWST observations have identified a class of enigmatic sources known as little red dots (LRDs), interpreted as a distinct class of ACTIVE GALACTIC NUCLEi (AGNs) and host galaxies, whose BLACK HOLE masses, AGN emissivities, stellar masses, and possible quasi-stars or BLACK HOLE stars (BH*) suggest a previously unidentified class of extragalactic objects. However, two questions remain: is there a clear discontinuity between LRDs and field galaxies at the same epochs, and do LRDs form a homogeneous population? We address these issues with a continuous metric of the "LRDness" of galaxies, measuring their compactness (delta_compact), the sharpness of the V-shaped spectral energy distribution (delta_v-shape), and the strength of the broad Balmer emission. This approach, which avoids a binary "on-off" view, was applied to 48,000 (5,000) galaxies with photometric (spectroscopic) data over 750 arcmin^2. V-shape prominence correlates strongly with morphology, with no clear transition at the usual LRD threshold: the compact fraction rises with V-shape intensity. Similarly, broad H-alpha strength increases with V-shape sharpness and compactness. The [N II] deficit is not exclusive to LRDs, but a global property of compact, metal-poor galaxies. Only a minority of LRDs (the 3% most extreme) show a prominent Balmer break (greater than 3) of potentially non-stellar origin. LRDs and non-LRDs follow a similar Balmer decrement versus V-shape trend, suggesting a common origin consistent with dust attenuation, reinforced by the agreement between observed Balmer ratios and attenuated Case B predictions. The inferred dust mass (4-7 x 10^4 M_sun) is low enough to explain ALMA non-detections. We conclude that most LRDs are not a separate class, but rather the extreme tail of a continuous distribution of galaxies and broad H-alpha emitters, consistent with a classical broad-line region and dust component.
[abstract 25 / 68] (score: 3) - Title: Halo-driven Origin and Evolution of Overmassive Black Holes and Little Red DotsAuthors: Ritik Sharma, Mahavir Sharma,Comments: 11 pages, 7 figures, revised version, comments welcomeSubjects: astro-ph.GA astro-ph.CO astro-ph.HECreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
We present a theoretical model in which the recently detected overmassive BLACK HOLEs (OBHs), and potentially Little Red Dots (LRDs), arise during a halo-driven transient phase preceding the established coevolution of supermassive BLACK HOLEs (SMBHs) and their host galaxies. In this model, halo gravity drives an early phase of rapid BLACK HOLE growth, leading to systems in high-redshift haloes that lie above the local scaling relations. As the halo evolves, a transition in halo thermodynamics leads to the onset of a hot, pressure-supported medium that suppresses accretion, reducing the BLACK HOLE growth rate and driving the system toward the local BLACK HOLE mass$-$stellar mass relation. LRDs may represent an observational manifestation of the rapid, halo-driven growth phase, while OBHs trace its direct mass signature. Our model thus provides a unified framework in which these systems form and evolve toward the regulated coevolution observed in the local Universe.
[abstract 26 / 68] (score: 3) - Title: Multi-messenger View of White Dwarf Tidal Disruption Events by Intermediate-Mass Black Holes: I. Gravitational Waves and Disk Photon and Neutrino EmissionsAuthors: Jin-Hong Chen, Lixin Dai, Bing Zhang,Comments: 25 pages, 22 figures, Accepted for publication in ApJSubjects: astro-ph.HE astro-ph.GACreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
White dwarf (WD) tidal disruption events (TDEs) provide a unique window onto intermediate-mass BLACK HOLEs (IMBHs). We present a multi-messenger view of these systems in two papers. In this paper, we develop an accretion-disk model for WD--TDEs in which the bound debris accretes at extremely super-Eddington rates, $\sim 10^5$--$10^9$ times higher than in typical (main-sequence) TDEs. The model includes MAGNETic pressure, nuclear-burning heating, wind mass loss, and neutrino production via $e^{\pm}$ pair annihilation. At such high accretion rates, the gas and radiation temperatures of the inner flow can reach $T\gtrsim 10^9\,\mathrm{K}$, enabling prolific pair production and MeV neutrino emission. We find that the disk is predominantly advection dominated over a broad range of accretion rates, while disk winds can partially cool the flow and reduce the inner temperature. The predicted thermal EM emission is nearly insensitive to the fallback rate in the super-Eddington regime: the luminosity only mildly exceeds the IMBH Eddington luminosity and the spectrum peaks at $\sim 0.1$--$1\,\mathrm{keV}$, implying detectability with current X-ray facilities such as Einstein Probe. For low-mass IMBHs ($\sim 10^3\,M_{\odot}$), the disk can also produce a burst of MeV neutrinos with luminosities up to $\sim 10^{47}\,\mathrm{erg\,s^{-1}}$ for ONeMg WD--TDEs, although detectability with current neutrino detectors (e.g., Super-Kamiokande and JUNO) is limited to Galactic distances. Finally, we estimate the GW burst produced during the final passage prior to disruption, which peaks at $\sim 0.1$--$1\,\mathrm{Hz}$, placing WD--TDEs in the target band of proposed decihertz detectors and motivating coordinated GW+EM+neutrino searches. We also present a first exploration of GWs from a precessing WD--TDE disk; this signal is much weaker, with a detection horizon $\lesssim 1\,\mathrm{Mpc}$ for these missions.
[abstract 27 / 68] (score: 3) - Title: Instabilities in Cylindrical Geometry Using the Minimalist Approach: Formalism and Rotational InstabilitiesAuthors: Nektarios Vlahakis,Comments: Accepted for publication in UniverseSubjects: physics.plasm-ph astro-ph.HE astro-ph.SR physics.flu-dynCreated: 2026-09-02; Updated: 2026-09-09; Datestamp: 2026-09-09
The minimalist approach for linear stability analysis is applied to fluids and MAGNETized ideal plasmas in cylindrical geometry. In this approach, the dispersion relation is obtained by integrating a single first-order differential equation - referred to as the principal equation - subject to appropriate boundary conditions. We first derive the principal equation for a general unperturbed state with radially varying density and pressure, axial and azimuthal components of both the velocity and MAGNETic field, and a radially directed gravitational field. We then use this formulation to analyze rotating flows with axial MAGNETic fields, addressing both wall-bounded and interface-driven axisymmetric instabilities. In addition to exact results for selected unperturbed states, we obtain approximate dispersion relations using the WKBJ method in the incompressible and compressible limits. The analysis encompasses centrifugal, MAGNETorotational, and buoyancy-driven instabilities as special cases, and it clarifies how compressibility modifies their stability properties.
[abstract 28 / 68] (score: 3) - Title: An HLLD Implementation for General Relativistic Magnetohydrodynamics in AthenaKAuthors: Jacob Fields, George N. Wong, James M. Stone,Comments: 19 pages, 15 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
We present an implementation of an HLLD approximate Riemann solver for the AthenaK astrophysics code with support for full general RELATIVISTIC MAGNETohydrodynamics via a tetrad frame transformation. Our implementation uses an initial guess for the HLLD iterative solve which eliminates the need for an additional conserved-to-primitive inversion, which greatly accelerates performance without affecting accuracy. Additionally, by coupling the method with a first-order flux correction, we are able to use the method reliably even when the MAGNETization exceeds $10^4$, which we achieve in a SANE accretion disk. Our SANE disk shows that HLLD leads to a more strongly MAGNETized funnel and more accurate horizon fluxes when compared with HLLE. We further apply the new HLLD implementation to an equal-mass binary neutron star merger. For our long-lived remnant, HLLD enhances the MAGNETic shear stresses in the outer layers and leads to weaker differential rotation. However, due to weaker gravitational wave emissions in the post-merger phase, the remnant is consistently less compact while producing more dynamical ejecta and a more massive disk. The cost of this new solver is relatively modest thanks to the improved initial guess: our accretion disk tests are only ${\sim}10-25\%$ slower than HLLE, and for our binary neutron star runs with a microphysical equation of state, we find that HLLD is only ${\sim}3\%$ slower than HLLE across all runs.
[abstract 29 / 68] (score: 3) - Title: The First Multi-Messenger Nova: External Shocks, TeV Photons, and Neutrinos in the Next Eruption of T CrBAuthors: E. Aydi, P. Craig, K. V. Sokolovsky, L. Chomiuk, C. C. Cheung, L. Izzo, J. D. Linford, B. D. Metzger, S. Mohamed, I. Molina, K. Mukai, K. J. Shen, J. L. Sokoloski,Comments: 10 pages, 1 figure, 1 table (submitted to MNRAS)Subjects: astro-ph.HE astro-ph.SRCreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
T Coronae Borealis is the most compelling anticipated Galactic recurrent nova and one of the best opportunities to test whether nova eruptions can become genuine multi-messenger transients. Recent observational work on classical novae has shown that the GeV $γ$-ray luminosity correlates strongly with the differential velocity between interacting outflows, suggesting that shock power depends strongly on velocity contrast. We apply this empirical framework to T CrB and compare it with the 2021 eruption of RS Ophiuchi, the only nova securely detected at TeV energies. We argue that T CrB may lie at the extreme high-$Δv$ end of the nova population and that its strongest shock should arise at the external interaction between the nova ejecta and the slow circumbinary medium. This makes the external shock the most likely site of any TeV emission, while the GeV signal may contain contributions from both internal, if present, and external shocks. Because T CrB is substantially closer than RS Oph, it is an especially favorable target for TeV detection. The neutrino case is promising but more uncertain because it depends sensitively on the density and structure of the circumbinary material. We also revisit the recurrence time of T CrB. Using the observed scatter of better-sampled recurrent novae, we infer a representative population-scale recurrence of $T_{\rm rec}\simeq80\pm12$ yr. Taken together, its proximity and potentially extreme shock velocities make T CrB perhaps the best opportunity for a nova to become the first securely established multi-messenger nova.
[abstract 30 / 68] (score: 3) - Title: Distinguishing lensing and precessional modulation in binary black-hole inspiral waveformsAuthors: Tien N. Nguyen-Vo, Tamanjyot Singh, Benjamin McKallip, Michael Kesden, Lindsay King,Comments: 19 pages, 11 figures, submitted to PRDSubjects: gr-qc astro-ph.COCreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
Binary BLACK HOLEs (BBHs) emit gravitational waves (GWs) as they inspiral towards merger. These GWs can be gravitationally lensed by large-scale structure along the line of sight, potentially creating multiple images of the same source with fixed time delays determined by the lensing geometry. As the BBHs inspiral, the GW frequency increases, leading to successive constructive and destructive interference between the multiple images. BBHs also have spins $\mathbf{S}_i$ that may be misaligned with their orbital angular momentum $\mathbf{L}$. As the BBHs inspiral, these misaligned spins cause $\mathbf{L}$ to precess about the total angular momentum $\mathbf{J}$, modulating the GW emission similar to pulsar emission resulting from a misaligned JET rotating in and out of the line of sight. We investigate the ability of a single L-shaped GW detector to distinguish between these two sources of modulation. We find that precessional modulation can mimic the lensing modulation between two images with comparable magnifications when the time delay between the images is short enough that fewer than three interference fringes occur during the time the GW signal spends in the sensitivity band of the detector. As strong lensing is rare for GW sources at moderate redshift while misaligned spins are common for BBHs produced in certain formation channels, ruling out precessional modulation is essential to identifying genuinely lensed systems.
[abstract 31 / 68] (score: 3) - Title: Timing Gravity with Pulsars in the Strong FieldAuthors: Riccardo Della Monica, Ivan de Martino,Comments: 6 pages, 2 figures. Matches version published in The Astrophysical Journal LettersSubjects: astro-ph.HE gr-qcCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
We propose a novel approach for the timing of pulsars orbiting a supermassive BLACK HOLE, which implements the fully RELATIVISTIC calculations of the photon travel time into a robust timing model. We generate realistic mock catalogues of pulsar times-of-arrival for several putative pulsars on tight orbits around the Galactic Center supermassive BLACK HOLE, Sagittarius A* (Sgr A*). Then, we perform a proof-of-concept sensitivity analysis to forecast the accuracy that future observational facilities, like the Squared Kilometer Array, will achieve in the characterization of the parameters of our timing model. Our analysis shows how the observation of pulsars at the Galactic Center will open an incredibly promising avenue for the characterization of the physical properties of Sgr A*, which can improve by at least three orders of magnitude the current constraints on the BLACK HOLE's mass achieved with the S-stars and event-horizon scale observations.
[abstract 32 / 68] (score: 3) - Title: Binary Black Holes in Einstein-Maxwell-Dilaton Theory: Second Post-Newtonian Dynamics from Effective Field TheoryAuthors: Pawan Kumar Gupta,Comments: 25 pages, and 8 figuresSubjects: gr-qcCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
The detection of gravitational waves from compact binary coalescences provides a powerful opportunity to test general relativity in the strong-field regime and to search for signatures of alternative theories of gravity. In this work, we consider Einstein-Maxwell-Dilaton (EMd) theory, in which BLACK HOLEs can carry both electric and scalar (dilatonic) charges. We employ the effective field theory approach, together with a temporal Kaluza-Klein decomposition of the metric in terms of non-RELATIVISTIC gravitational fields, to derive the conservative two-body Lagrangian for charged black-hole binaries in EMd theory through second post-Newtonian (PN) order. Our calculation extends the previously known conservative dynamics at 1PN order and includes the gravitational, electroMAGNETic, and dilaton interactions at 2PN order. We verify the result in the appropriate Einstein-Maxwell, scalar-tensor, and general RELATIVISTIC limits, and perform an independent test-body-limit check of the static 2PN sector. These results provide the conservative dynamics needed for developing higher-accuracy waveform models and testing EMd theory with gravitational-wave observations.
[abstract 33 / 68] (score: 3) - Title: Irreducible-Mass Balance for Magnetized Null Horizons with an Internal Current SheetAuthors: Remo Ruffini, Giorgio Sonnino,Comments: 6 pagesSubjects: astro-ph.GACreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
We begin with a general question: how does the irreducible mass of a MAGNETized BLACK HOLE change when the horizon is not stationary? The null Raychaudhuri equation gives an exact area balance for any smooth null horizon, without assuming stationarity or axisymmetry. When the horizon is axisymmetric and admits an integrable quasilocal Hamiltonian, this geometrical identity becomes an energy balance. The equation keeps area growth, rotational and electroMAGNETic work, nonstationary focusing, canonical-flux corrections, and internal-boundary terms separate. We then turn to Wang's self-gravitating split-monopole Blandford-Znajek engine. In the weak-field and slow-rotation regime, P/M_H\ll1 and a/M_H\ll1, our general balance reproduces Wang's mass- and angular-momentum loss rates. The irreducible mass, M_{irr}=\sqrt{A_H/(16π)}, reveals what those rates do not show by themselves. It measures the part of the rotational work absorbed irreversibly by the horizon. At fixed MAGNETic flux and under impedance matching, half of the instantaneous rotational work leaves as electroMAGNETic power. The other half increases the horizon area and M_{irr}. The assumptions behind this reduction are derived explicitly. A minimal nondissipative world-volume action makes the current-sheet contribution vanish through O(p^2ε^2). Direct power counting of Wang's perturbative fields, together with a compatible canonical-flux prescription, gives a relative focusing and canonical correction of O(p^2)+O(ε^2). These estimates mark the range in which the reduced Blandford-Znajek trajectory remains controlled. Extending that trajectory to high spin requires an additional extrapolation. Relating the quasilocal horizon loss to energy measured at infinity requires a separate asymptotic flux calculation.
[abstract 34 / 68] (score: 3) - Title: Bridging the Population Synthesis of Supermassive Binary Black Holes and the Gravitational Wave BackgroundAuthors: Kanyuni Iemoto, Boris Goncharov, Gabriela Sato-Polito, Xiaoming Bi,Comments: 13 pages, 5 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
Pulsar Timing Arrays (PTAs) constrain population properties of supermassive binary BLACK HOLEs (SMBHBs) through the observation of the gravitational wave background (GWB). Unlike other approaches that interpolate population-synthesis libraries or only consider the mean of the strain spectrum, here we capture its full strain probability density directly from semi-analytic population models. We apply our new method to the semi-analytic SMBHB population model, independently reproducing the parameter estimation for this model performed by the NANOGrav Collaboration with their 15-yr data. We also show the extent to which discrete SMBHB contributions to the GWB resolve degeneracies in the population parameter space. Finally, using the source-count intensity as the intermediate product in our calculation, we map PTA observations, as a proof of principle, to the SMBHB model based on the galaxy merger prescriptions from numerical hydrodynamical simulations "Illustris". We find the effect of delay times $τ$ between kiloparsec and subparsec SMBHB separations following galaxy mergers, finding $h_{\rm c}$ spanning $(1$-$6)\times10^{-16}$ and $N_{\rm c}$ spanning $(0.3$-$7.1)\times10^{-3}$ for $τ$ up to 8 Gyr.
[abstract 35 / 68] (score: 2) - Title: Energy Loss of Newborn Magnetars by Schwinger ProcessAuthors: Chul Min Kim, Sang Pyo Kim, Remo Ruffini, Yu Wang, Shurui Zhang,Comments: Accepted for publication in the Journal of High Energy AstrophysicsSubjects: astro-ph.HECreated: 2026-09-02; Updated: 2026-09-09; Datestamp: 2026-09-09
We investigate electron--positron pair creation through the Schwinger process in newborn MAGNETars with millisecond spin periods and surface dipole fields close to or above the QED critical field, $B_{\rm Q} = 4.414\times10^{13}\,\mathrm{G}$. In the unscreened field scenario, we derive the analytical global pair creation flux and recast it into a compact form with accurate analytic approximations. For a fiducial model with $B_{\rm p} = 10^{14}\,\mathrm{G}$ and $P_0 = 1\,\mathrm{ms}$, the Schwinger channel exceeds the classical Goldreich--Julian particle supply by many orders of magnitude and becomes the dominant source of charges at the earliest stage of the MAGNETar. The associated discharge removes about $90\%$ of the initial rotational energy within 30 ms, suppresses the gravitational-wave loss channel, and implies that the observable millisecond phase is extremely short in this unscreened scenario. The rapid energy release over such a short timescale may also provide a viable power source for astrophysical transients. Extending the same fiducial model to $10^4\,\mathrm{yr}$ gives spin periods of order seconds, linking newborn millisecond MAGNETars to the mature MAGNETar population.
[abstract 36 / 68] (score: 2) - Title: Stages of turbulence generation and decay in a T-shaped mixerAuthors: Mohammad Mehdi Zamani Asl, Marc Avila,Comments:Subjects: physics.flu-dynCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
The T-shaped mixer is widely used in fundamental studies of chemical engineering. Its transitional regime is well understood, whereas the turbulent dynamics has received scarce attention so far. Here we perform direct numerical simulations of the turbulent regime for Reynolds numbers up to $Re=2000$ at Schmidt number $Sc=1$. Our analysis reveals two distinct stages along the mixing channel prior to relaxation toward duct flow. Near the junction, a JET-like flow forms and exhibits the approximately self-similar behaviour of transitional planar JETs. Subsequently, a decay region characterised by power-law decay of turbulent kinetic energy, dissipation and scalar variance emerges. For the velocity field, the observed exponents are consistent with those of decaying turbulence in bounded domains, whereas the scalar-variance exponent is consistent with that of unbounded turbulence. We argue that this apparent discrepancy is a consequence of the mixing process progressing from the center of the channel toward the side walls in the decay region, while turbulence already fills the channel cross-section entirely at the end of the JET region.The time-averaged mixing state presents error-function profiles of the scalar in the transverse direction, similar to the laminar cases, and is quantified here through a stream-wise evolving effective diffusion coefficient.
[abstract 37 / 68] (score: 2) - Title: Long-lived intermittent accretion disks in the jittering JETs explosion mechanism (JJEM) of core-collapse SUPERNOVAeAuthors: Noam Soker,Comments: Accepted by Revista Mexicana de Astronomia y AstrofisicaSubjects: astro-ph.HECreated: 2026-09-04; Updated: 2026-09-09; Datestamp: 2026-09-09
Motivated by observations of core-collapse SUPERNOVA (CCSN) remnants that suggest cases where one to three energetic pairs of JETs dominate the CCSN remnant morphology and, hence, the CCSN explosion energy, I examine the formation of long-lived intermittent accretion disks that launch such pairs of energetic JETs in the framework of the jittering-JETs explosion mechanism (JJEM). In the JJEM, pairs of JETs explode all CCSNe. In most CCSNe, stochastic angular momentum fluctuations in the convective zones of the pre-collapse core seed instabilities above the newly born neutron star that lead to the formation of intermittent accretion disks. These disks launch several to about twenty pairs of JETs that explode the star. CCSNRs with signatures of 1-3 very energetic pairs of JETs require long-lived, intermittent accretion disks. I quantitatively show that viscosity-driven angular momentum transport in the disk can prolong its lifetime even when material with zero angular momentum continues to feed the disk. Other effects that I do not study here can also prolong the disk lifetime somewhat: JETs might prevent matter from accreting from the polar direction, and angular momentum fluctuations can, in some cases, add up to a positive angular momentum. The viscosity mechanism I study here, along with these other effects, can prolong the lifetime of 1-3 intermittent accretion disks (or none), which then launch energetic JET pairs. This study adds to the wide variety of morphologies that the JJEM can explain, somewhat supporting the claim that the JJEM is the primary explosion mechanism of CCSNe.
[abstract 38 / 68] (score: 2) - Title: Population-Level Verification of the Black-Hole Area Law with First- and Second-Generation Black HolesAuthors: Shao-Peng Tang, Yin-Jie Li, Yi-Zhong Fan,Comments: 25 pages, 9 figures, 3 tables, added non-parametric and common-growth analysesSubjects: astro-ph.HE gr-qcCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
Hawking's area theorem states that the total event-horizon area of classical BLACK HOLEs can never decrease. Gravitational-wave tests of this law have so far focused on individual loud mergers, thus probing only a sparse subset of binary parameter space. Here we perform the \emph{first} population-level test. We exploit the decomposition of the coalescing BLACK HOLEs in the latest gravitational-wave catalogue into a low-spin subpopulation of stellar-collapse origin and a high-spin subpopulation assembled through hierarchical mergers of the former. If the high-spin BLACK HOLEs are merger remnants, the area theorem requires their horizon areas to exceed the total pre-merger areas of the low-spin binaries. Using parameter estimation restricted to the inspiral of 241 events, so that no merger-ringdown information enters the inference, we find that both peaks of the horizon-area distribution of second-generation BLACK HOLEs lie above their first-generation counterparts. The displacement is significant at each peak ($2.1$--$3.7σ$), and when we tie the two subpopulations with a single common shift, an area decrease is excluded decisively ($\gtrsim5.0σ$). The second law of black-hole mechanics thus holds statistically across the quasicircular, moderately spinning mergers that dominate current catalogues, which in turn underpins the robustness of our classification of stellar-collapse and hierarchical-merger BLACK HOLEs.
[abstract 39 / 68] (score: 2) - Title: Sub-Second Collisionless Gyrokinetic Eigenvalue Solutions via Orbit-Invariant DecompositionAuthors: Anrui Luo, Jingyi Yu, Huasheng Xie, Jian Bao,Comments: 15 pages, 9 figures, v2 including fully electromagnetic effectsSubjects: physics.plasm-phCreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
Fast analysis of microscopic drift-wave instabilities based on linear gyrokinetic simulations is desirable for modeling anomalous transport in fusion devices. In this work, we present an orbit-invariant decomposition method for solving collisionless gyrokinetic eigenvalue problems. By discretizing velocity space along orbit invariants using particle energy and MAGNETic moment, the full eigenvalue matrix is separated into independent orbit blocks that couple with each other through the field equation, greatly reducing both matrix dimension and computational cost without sacrificing physics. Based on this method, we extend the MGK code [Phys.\ Plasmas 24, 072106 (2017)] with both CPU and GPU implementations, supporting collisionless electrostatic and electroMAGNETic linear simulations in $s$--$α$ and Miller equilibrium models. For kinetic ion temperature gradient (ITG) and trapped electron mode (TEM) eigenvalue problems, the solver reduces single-solution times to the 0.01--0.1~s range---more than three orders of magnitude faster than CGYRO on the same hardware---enabling efficient large-scale parameter scans. For fully electroMAGNETic KBM cases, it also achieves a speedup of three orders of magnitude over CGYRO and HD7. The eigenfrequencies and mode structures are verified by comparing with CGYRO results. The method is generally applicable to all collisionless gyrokinetic eigenvalue formulations and has been extended to fully electroMAGNETic simulations. [Python code available at: https://github.com/FusionAlpha/mgk]
[abstract 40 / 68] (score: 2) - Title: Revisiting candidates for non-pulsating stars located in the Cepheid instability strip in the Large Magellanic CloudAuthors: W. Narloch, C. Galan, G. Pietrzynski, B. Pilecki, W. Gieren, R. Smolec, H. Netzel, P. Wielgorski,Comments: 17 pages, 10 figures, 6 tables, Accepted for publication in A&ASubjects: astro-ph.SRCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
We analyzed photometric and spectroscopic data for 11 candidates for non-pulsating stars located in the Cepheid instability strip (IS) of the Large Magellanic Cloud (LMC) in order to investigate the reasons for the lack of pulsations. We used available temperature calibrations based on photometric colors to estimate the effective temperatures of the candidates, which served as initial parameters for the spectroscopic analysis. We also applied surface brightness-color relations calibrated for Cepheid variables, giants, and supergiants to estimate stellar radii. The spectral analysis was performed using the spectral synthesis method to determine the atmospheric parameters; namely, the effective temperature, metallicity, surface gravity, microturbulent velocity, projected rotational velocity, and chemical abundances for up to ~30 elements. For most objects, only a single spectrum was available. However, no significant variations in radial velocities were detected among the stars with repeat observations; therefore, all stars were treated as single object in the analysis. Two stars exhibit broad spectral lines, which may indicate high rotational velocities or possible binarity; however, additional spectra are required to confirm this interpretation. One of these objects also shows asymmetric line profiles, which might be related to the presence of non-radial pulsation modes causing line-shape variations. A common feature among all analyzed candidates is an enhancement of barium-peak s-process elements compared to solar values. This may indicate past mass transfer from a companion during its post-asymptotic giant branch phase. This study provides an insight into the physical parameters of candidates for non-pulsating stars residing within the Cepheid IS in the LMC, although the lack of pulsations remains a mystery and challenges pulsation theory.
[abstract 41 / 68] (score: 2) - Title: Constraints on Buchdahl-Inspired Gravity from Future Pulsar Timing near Sgr A*Authors: Jian-Ming Yan, Tao Zhu, Zong-Kuan Guo, Zhao Li,Comments:Subjects: astro-ph.HE gr-qcCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
Future pulsar timing observations near Sgr~A* offer a unique probe of gravitational physics in the vicinity of a supermassive BLACK HOLE. We forecast the ability of such measurements to constrain a Buchdahl-inspired $R^2$ gravity, parameterized by a single deviation parameter $ε$, using a timing framework that self-consistently integrates orbital dynamics with light-propagation delays and preserves the full timing solution across the observing span. Through Fisher-matrix forecasts for a representative pulsar, we systematically isolate how the precision on $ε$ depends on orbital geometry. We find that shorter orbital periods and higher eccentricities significantly enhance sensitivity, consistent with a substantial contribution from observations near periastron. As a benchmark comparison, we further consider a hypothetical pulsar on an S2-like orbit ($P_b=16~{\rm yr}$, $e=0.88$) and obtain a statistical sensitivity of $σ_ε\sim 10^{-4}$ within the adopted weak-field, static, and spherically symmetric timing model. This sensitivity is comparable to the natural order-of-magnitude truncation scale of the 1PN expansion and should not be interpreted as a complete forecast for the real Sgr~A* system. Under the adopted idealized assumptions, the characteristic statistical scale is several orders of magnitude below the current S2 95\% confidence interval half-width ($|ε|_{\rm S2}^{\rm 95\%}\approx 0.56$), though this comparison is heuristic given the differing confidence levels. These trends provide quantitative guidance for target selection and campaign design in future Galactic-center pulsar searches.
[abstract 42 / 68] (score: 2) - Title: Rapid Growth of Intermediate-Mass Black Holes through Disk-induced Stellar DisruptionsAuthors: Mengye Wang, Yiqiu Ma, Qingwen Wu, Boyuan Liu, Zijian Wang, Zhili Wang,Comments: 14 pages, 8 figures. Submitted to ApJSubjects: astro-ph.GA astro-ph.HECreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
Dense nuclear star clusters provide unique environments for studying the dynamical interactions between stars and massive BLACK HOLEs. When an accretion disk is present, dissipative star--disk interactions can capture surrounding stars, drive their inward migration, and ultimately lead to disk-induced tidal disruption events\,(dTDEs). The long-term feeding rate from this process, however, cannot be inferred from single-orbit migration estimates alone, as it depends on the coupled evolution of disk capture, collisional relaxation, stellar depletion and replenishment, and physical mergers within the star cluster. In this work, we use high-performance direct $N$-body simulations combined with analytic prescriptions for star--disk interactions to follow this coupled evolution for intermediate-mass BLACK HOLEs\,(IMBHs) with accretion disks embedded in dense stellar clusters. The simulations track the formation of the stellar cusp, the capture of stars by repeated disk crossings, their subsequent orbital damping and migration, and their eventual consumption by the central IMBH. We find that dTDEs can sustain stellar mass supply rates of $\sim10^{-3}\,M_\odot \,\mathrm{yr}^{-1}$, which exceeds the Eddington-limited gas accretion rate for IMBHs with $M_\bullet<10^5\,M_\odot$. These results identify dTDEs as an efficient stellar feeding channel for IMBHs in gas-rich dense stellar systems. As one possible application, this mechanism may help transform $\sim10^3\,M_\odot$ IMBHs into more massive black-hole seeds, provided that compact stellar clusters and accretion disks persist for $>30$ Myr.
[abstract 43 / 68] (score: 2) - Title: Coherent multipath wave response on Reissner-Nordström analogue surfaceAuthors: Peng-Yu Chen, Sen Guo, Qing-Quan Jiang, Yu Liang, Kai Lin,Comments: 25 pages, 9 figuresSubjects: gr-qcCreated: 2026-09-02; Updated: 2026-09-09; Datestamp: 2026-09-09
To uncover how the intrinsic metric of a RELATIVISTIC compact object governs macroscopic wave phenomena, we establish a theoretical framework mapping the charge dependent spatial geometry of a Reissner-Nordström (RN) BLACK HOLE onto the coherent response of an analogue curved surface. By solving an exact spatial geodesic boundary value problem on an isometrically embedded equatorial slice, we extract the discrete multi-loop path-length spectrum and convert this geometric backbone into a physical wave field via a finite-path surface Huygens-Fresnel construction. We analytically compute the arbitrary order winding trajectories alongside their high winding accumulation limits, demonstrating that the analogue charge acts as a precise physical dial that reconfigures the event horizon throat and fundamentally reorganizes the discrete path sequence. Furthermore, we find that this underlying geometric deformation uniquely dictates the macroscopic interference, revealing that steady state spatial fringes, spectral resonance combs, and transient temporal echo ladders are intrinsically unified physical projections of a single charge controlled path spectrum. This systematic parameter to response methodology establishes a rigorous theoretical bridge between strong field gravitational lensing and tabletop transformation optics, providing a highly tunable blueprint for future multi domain analogue gravity experiments.
[abstract 44 / 68] (score: 2) - Title: LOFAR radio properties of QUASARs hosting Extremely High Velocity OutflowsAuthors: Amy L. Rankine, Paola Rodríguez Hidalgo,Comments: 8 pages, 5 figures. Submitting to MNRAS, comments welcomeSubjects: astro-ph.GACreated: 2026-09-04; Updated: 2026-09-09; Datestamp: 2026-09-09
Quasar winds are a potential contributor to the radio emission observed in the so-called 'radio-quiet' QUASARs. Extremely High Velocity Outflows (EHVOs), with bulk velocities >0.1c, represent some of the most energetic of these winds. In this work, we investigate the radio properties of QUASARs hosting EHVOs in order to assess whether such high-velocity winds contribute to the observed radio emission. We cross-match the catalogue of EHVOs from the Sloan Digital Sky Survey with the high-sensitivity Low-Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS) Data Release 3. We find that EHVO QUASARs exhibit a significantly higher radio-detection fraction of 38 per cent compared to an underlying parent QUASAR population at 24 per cent. By constructing control samples using nearest-neighbour matching, we show that matching the C IV emission line blueshift alone is sufficient to reproduce the elevated radio-detection fraction in a global sense; however, differences still remain in the radio-detection fraction as a function of C IV emission blueshift between the EHVO distribution and any matched sample, suggesting that some additional mechanism is at play. Furthermore, composite spectra reveal no significant differences in the ultraviolet absorption profiles between radio-detected and radio-undetected EHVOs, although we identify a mild positive correlation between maximum outflow velocity and radio luminosity. Our results suggest that EHVOs likely represent a subset of the QUASARs which host fast winds that are observed along particular lines-of-sight, and that radio emission associated with such winds remains a plausible mechanism.
[abstract 45 / 68] (score: 2) - Title: Novel approach to general curvilinear coordinates for plasma fluid applicationsAuthors: Federico D. Halpern Tess N. Bernard, Oleksandr Koshkarov, Ronald E. Waltz,Comments:Subjects: physics.plasm-phCreated: 2026-09-04; Updated: 2026-09-09; Datestamp: 2026-09-09
In general geometry, plasma fluid equations include nonlinear geometric sources associated with fictitious forces, which pose significant challenges to computer simulations. We reformulate the plasma fluid hierarchy to rigorously preserve geometry and conservation properties critical to numerical simulations, while concealing the geometric sources. In their discrete form, the reformulated models conserve mass, angular momentum, and energy naturally, by simple analogy with the continuum equations. These conservation properties have minimal requirements in discrete space, namely, the anti-symmetry of the first derivative and the orthogonality of the scalar and cross products. By decoupling MAGNETic geometry, coordinate systems, and numerical discretization, this enables maximum flexibility while preserving physics fidelity. As a testbed, we apply the novel representation to the resistive MAGNETohydrodynamic system, which involves a complete set of curvilinear operations. We verify the correctness of the approach using steady state liquid metal flows and the classic Orszag-Tang vortex.
[abstract 46 / 68] (score: 2) - Title: Magnetically Confined Mountains on Accreting White DwarfsAuthors: Pedro H. B. Rossetto, Manoel F. Sousa, Diego A. Falceta-Gonçalves,Comments: 16 pages, 8 figuresSubjects: astro-ph.SR astro-ph.HECreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
The hydroMAGNETic structure of MAGNETically confined mountains on accreting white dwarfs is computed, alongside the effects of accretion on the reduction of the star's MAGNETic field. The equilibrium structure of the mountain is obtained by numerically solving the Grad-Shafranov equation with a self-consistent scheme that enforces MAGNETic flux freezing. For characteristic system parameters, it is shown that MAGNETic field lines are significantly deformed and dragged equatorwards by mountains with masses $\sim10^{-3}M_\odot$ that have a characteristic height of $\sim10^5\,\mathrm{cm}$. A mathematical relation is obtained for the maximum mass that a white dwarf can confine MAGNETically given the star's MAGNETic field and temperature. It is found that the accretion buries the star's MAGNETic field by reducing it by up to $10\%$ of its pre-accretion value. The star's MAGNETic field remains dominantly dipolar, but with added multipolar components.
[abstract 47 / 68] (score: 2) - Title: Thin accretion disk and gravitational capture cross sections of a quantum Oppenheimer--Snyder BLACK HOLE immersed in an external MAGNETic fieldAuthors: Anuar Idrissov, Hernando Quevedo,Comments: 14 pages, 13 figures, 2 tablesSubjects: gr-qcCreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
We study a geometrically thin, optically thick Novikov--Thorne accretion disk and the gravitational capture cross sections of a quantum Oppenheimer--Snyder BLACK HOLE immersed in an external, asymptotically uniform MAGNETic field. The exterior geometry carries a single quantum parameter, and we work over its entire admissible range, which contains a two-horizon BLACK HOLE, an extremal configuration and a horizonless compact object, and which ends where the photon sphere disappears. Since the spacetime is static, the Wald potential is purely axial, so the field acts on the disk only through the Lorentz force on weakly charged accreting matter and all of its effects are controlled by a single MAGNETic coupling. We compute the charged circular orbits, the innermost stable circular orbit, the radiative flux, the effective temperature, the redshift factor, the differential and spectral luminosity and the radiative efficiency, together with the marginally bound orbit and the capture cross sections of massless, massive and charged particles. The construction is checked against the exact Schwarzschild limit and against the identity that relates the bolometric luminosity to the efficiency. The quantum parameter changes the disk observables only weakly, whereas the MAGNETic coupling raises the efficiency, the peak flux and the height of the spectral peak by large factors and shifts that peak to higher frequency. The two parameters act with opposite signs on absorption. The quantum parameter shrinks every capture cross section, while the MAGNETic coupling enlarges the one for massive particles and leaves the photon cross section unchanged, so that within this test-field model shadow observables respond to the quantum parameter alone. For charged particles the uniform field confines the motion, and no particle reaches the hole from beyond a MAGNETic shielding radius.
[abstract 48 / 68] (score: 2) - Title: Stacking HI in the dark: Towards detecting the reionization-epoch 21 cm signal in Lyman-$α$ dark gapsAuthors: Barun Maity, Frederick B. Davies,Comments: Prepared for submission to A&A, 12 pages, 15 figures, Comments welcomeSubjects: astro-ph.COCreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
The detection of the redshifted 21 cm signal from neutral hydrogen during the epoch of reionization remains one of the central challenges in contemporary cosmology. Although upcoming radio interferometers are expected to measure 21 cm fluctuations at a few percent precision, an independent confirmation is essential to ensure robustness against instrumental systematics and foreground contamination. In this work, we propose a novel real-space stacking technique to detect the 21 cm signal, guided by the presence of dark gaps in QUASAR absorption spectra during the late stages of reionization ($z \sim 5.0$-$6.1$). Using a semi-numerical reionization model, we show that stacking 21 cm images on long dark gaps (length, $L > 32~h^{-1}\mathrm{cMpc}$ and threshold flux, $F_{\mathrm{th}} < 0.005$) should reveal a strong emission signal with a peak mean-subtracted 21 cm brightness temperature of $δ\tilde{T}_b \sim 2-3~ mK$ for a volume-weighted average neutral fraction of $x_{\mathrm{HI}} \sim 0.1$ at $z = 5.9$. We further extend our analysis to realistic reionization lightcones, incorporating thermal noise and foreground avoidance effects, generated for two different reionization histories. In an optimistic foreground avoidance scenario (wedge field of view $θ< 20^\circ$), a sample of roughly 100 dark gaps is sufficient to achieve a combined root-sum-square signal-to-noise ratio exceeding 10 for both reionization models, while a more conservative wedge avoidance may require more dark gaps for a solid detection. Given the large number of QUASARs known at $z > 6$, a detection of this stacked signal may thus already be within reach of existing optical (i.e., VLT, Keck) and 21 cm observatories (i.e., HERA, SKA). This synergistic approach offers a promising pathway towards a direct and statistically robust detection of the cosmological 21 cm signal.
[abstract 49 / 68] (score: 2) - Title: Physics-based phenomenological modeling of binary BLACK HOLE hierarchical formation 1: Synthetic universes from globular cluster simulations for GWTCAuthors: R. O'Shaughnessy, R. Mechum, M. Qazalbash, Z. Rosenberg, M. Zeeshan,Comments: 34 pages, 17 figuresSubjects: gr-qc astro-ph.HECreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
We iteratively model the GWTC-5.0 binary-black-hole census with three components. First, a physically normalized population from Rapster globular-cluster simulations spans cluster mass, metallicity, formation redshift, compactness, and natal black-hole spin. Hierarchical mergers reproduce higher-mass events and their larger effective-spin dispersion, provided BLACK HOLEs are born with zero natal spin. Second, a phenomenological field (isolated-binary) channel supplies the low-mass, preferentially aligned population. Its inclusion flattens the cluster compactness likelihood, permitting ordinary dense globular-cluster birth radii without requiring nuclear-cluster-like conditions. Finally, residual tension at $15$--$30 M_\odot$ motivates an intermediate-mass isotropic component representing field remnants reprocessed in clusters. This is a hypothesis, not a detection: current numerical support precludes a reliable evidence comparison. Physical normalization converts the high-mass rate into $\hat{f}_{\rm GC}\simeq0.39\%$, with local rates $R_{\rm cl}\simeq9.1$ and $R_{\rm field}\simeq16.0$ Gpc$^{-3}$ yr$^{-1}$. The model predicts linked mass-spectrum breaks near $35$ and $70 M_\odot$, a $q\simeq0.5$ feature from first-plus-second-generation pairings, and a symmetric effective-spin distribution that broadens sharply above $45 M_\odot$. These correlated, mass-resolved predictions can be tested as the gravitational-wave census grows.
[abstract 50 / 68] (score: 2) - Title: The accuracy of merger times in hierarchical BLACK HOLE triplesAuthors: Giulia Fumagalli, Alejandro Vigna-Gómez,Comments: 10 pages, 5 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
Orbit-averaged equations are widely used to model the gravitational-wave-driven evolution of compact binaries. Their validity relies on the radiation-reaction timescale being much longer than the orbital period, an assumption that can break down for highly eccentric systems. In this work, we investigate the impact of orbit averaging on merger-time estimates by comparing orbit-averaged and non-orbit-averaged prescriptions. We apply our analysis to two different astrophysically motivated populations of BLACK HOLE binaries in hierarchical triple systems, where von Zeipel-Lidov-Kozai oscillations can drive the inner binary eccentricities close to unity. We find that merger-time estimates obtained with orbit-averaged equations remain remarkably accurate across a wide range of eccentricities, even when the orbital timescale exceeds the radiation-reaction timescale. Significant discrepancies arise only for the most extreme and compact binaries, simultaneously characterized by very high eccentricities and small semi-latus recta. In this regime, the merger time becomes strongly dependent on the initial orbital phase, with different phases yielding predictions that can differ by several orders of magnitude. We also compare our results with an orbit-averaged merger-time prescription specifically developed for hierarchical triple systems and find substantial differences between this prescription and both the generic orbit-averaged and non-orbit-averaged calculations in the high-eccentricity regime. While these results demonstrate the robustness of orbit-averaged merger-time estimates for most systems, they also highlight the potential importance of non-orbit-averaged effects when merger times are used to infer compact-binary delay-time distributions and formation channels.
[abstract 51 / 68] (score: 2) - Title: Connecting the little dots in polarized lightAuthors: Piero Madau, Roberto Maiolino, Francesco D'Eugenio,Comments: 12 pages, 6 figures, submittedSubjects: astro-ph.GA astro-ph.HECreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
Recent observations of the local Little Red Dot (LRD) analog SDSS~J1025+1402 have revealed that the optical continuum is polarized at the ~1.5% level, while broad Halpha has lower POLARIZATION (~0.7%) and a different POLARIZATION angle. We explain these properties in a scenario in which LRDs are dust-obscured Little Blue Dots (LBDs) viewed at high inclination and powered by super-Eddington accretion. In this framework, electron scattering in the geometrically thick inner accretion flow produces intrinsic continuum POLARIZATION, while unpolarized emission from the outer thin disk dilutes the signal, particularly at optical wavelengths. A circumnuclear dust screen contributes dichroic POLARIZATION to both the continuum and broad-line emission. Broad Halpha lacks the intrinsic disk component and therefore has lower POLARIZATION and a different position angle. We show that this model quantitatively reproduces the observed POLARIZATION properties, although degeneracies between accretion rate and inclination remain. These results illustrate the potential of spectropolarimetry as a probe of accretion-flow geometry and orientation in the little-dot population, complementary to spectral-energy-distribution fitting and line diagnostics.
[abstract 52 / 68] (score: 2) - Title: Interstellar Complex Organic Molecules and Molecular Outflows in NGC 1333 IRAS 4B and 4B' Observed Using NOEMAAuthors: C. C. Sarver, M. M. Giese, D. C. Lis, S. L. Widicus Weaver,Comments: 43 pagesSubjects: astro-ph.GA astro-ph.SRCreated: 2026-09-05; Updated: 2026-09-09; Datestamp: 2026-09-09
We present interferometric observations with the Northern Extended Millimeter Array (NOEMA) of NGC 1333 IRAS 4B and 4B', two young stellar objects (YSOs) within the Perseus molecular cloud. YSOs, especially Class 0 protostars, are rich in gas-phase interstellar complex organic molecules (iCOMs), but relatively little is known about the spatial distribution of these important prebiotic molecules. Various molecules were imaged within IRAS 4B and the surrounding area in the 145 GHz spectral range, revealing hundreds of molecular transitions within the warm inner envelope of IRAS 4B. This work provides derived physical parameters (rotational temperature, column density, velocity shift with respect to local standard of rest, and full-width at half-maximum spectral line width) for 11 molecules toward IRAS 4B including methanol (CH$_3$OH and isotopologues), methyl formate (HCOOCH$_3$), dimethyl ether (CH$_3$OCH$_3$), acetaldehyde (CH$_3$CHO), ethanol (C$_2$H$_5$OH), glycolaldehyde (CH$_2$OHCHO), acetone (CH$_3$COCH$_3$), and isocyanic acid (HNCO). Out of these molecules, 10 are iCOMs (excluding HNCO) that trace the inner envelope of IRAS 4B and mark it as a rich source of organic material. There is a strong spatial correlation between the continuum emission of IRAS 4B and iCOM molecular emission and among various iCOMs with each other. Physical parameter and integrated intensity maps show that IRAS 4B is a binary protostar system that drives a JET in a north-south orientation and an outflow in a northwest-southeast orientation. IRAS 4B' also drives a west-east outflow but shows no evidence of molecular emission cospatial with its continuum emission.
[abstract 53 / 68] (score: 2) - Title: IPHAS J190812.63+045728.1: A deeply eclipsing, X-ray bright cataclysmic variable with frequent outburstsAuthors: Raimundo Lopes de Oliveira, Albert Bruch, Koji Mukai, A. S. de Araujo, Guilherme P. Guimarães, Ted Leandro de Almeida,Comments: Accepted by ApJSubjects: astro-ph.SR astro-ph.HECreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
We present a multi-wavelength characterization of IPHAS J190812.63+045728.1. Independently discovered by us after being serendipitously observed by XMM-Newton, followed up with optical photometry with SPARC4/OPD and spectroscopy with GMOS/Gemini South, and exploring archival TESS and ZTF observations, we reveal the system to be an eclipsing accreting white dwarf (WD) system with an orbital period of 5.073 h. The deep optical and flat-bottomed X-ray eclipses completely occult the WD and the accretion disk, providing a model-independent, uncontaminated view of the donor star which we classify as an M2.3 dwarf with a mass of $\sim 0.50\,M_\odot$. The system is a modestly luminous (L$_{x;0.3-10 keV} \sim$ 1.7 $\times$ 10$^{32}$ erg s$^{-1}$) hard thermal (consistent with a shock-heated plasma cooling down from $k$T $\sim$ 26 keV) X-ray source. While these X-ray properties are typical of low luminosity intermediate polars (IPs), long-term archival photometry reveals frequent, large-amplitude outbursts ($Δm \sim 2$ mag in the ZTF $zr$ band) that are the typical characteristics of DWARF NOVAe, and would be unusual for IPs. The weakness of the HeII $λ$4686 emission line does not allow us to decide between the IP and the DWARF NOVA scenarios. On the other hand, the optical and X-ray light curves do not exhibit periodic variations caused by the WD rotation. If the system is indeed an IP, the accretion geometry is likely unusual while the DWARF NOVA-like outbursts indicating disk instabilities would make IPHAS J190812.63+045728.1 a benchmark for testing disk instability models in the presence of MAGNETically truncated accretion disks. Otherwise, the system is a DWARF NOVA with X-ray properties at the extreme end of its class.
[abstract 54 / 68] (score: 2) - Title: Incoherent scattering of highly ultraRELATIVISTIC channeled particles on electronsAuthors: Victor V. Tikhomirov,Comments: 32 pages, 4 figuresSubjects: physics.acc-phCreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
This article systematically examines the effects that must be taken into account when modeling the dechanneling of highly ultraRELATIVISTIC charged particles caused by incoherent scattering by electrons of crystal atoms. Changes in the particle electroMAGNETic field that occur in condensed matter at highly ultraRELATIVISTIC energies are taken into account. The excitation of both collectivized electrons and inner-shell electrons of atoms is considered, taking into account thermal vibrations and the inhomogeneous periodic distribution of atoms in crystals. Differences in the calculations of stopping power and mean square scattering angle by electron of channeled particles are described. The need to separate both of them into diffuse processes, accompanied by the transmission of a transverse momentum which does not exceed the transverse momentum of the channeled particles, and instantaneous dechanneling processes with a greater transmitted momentum, the variation range of which reaches several orders of magnitude, is substantiated. The main result of the present work is expressions for the mean square projected scattering angles per unit length in planes parallel and perpendicular to the atomic plane, which also allow for the introduction of effective minimum momenta for incoherent scattering. Expressions of both types take into consideration completely the nonlocal effects of momentum transfer from crystal electrons to particles moving along classical trajectories, and allow for the formulation of simple methods for modeling the incoherent scattering of ultraRELATIVISTIC positively charged particles.
[abstract 55 / 68] (score: 2) - Title: Magnetic island structures in RELATIVISTIC LASER-driven plasma channelsAuthors: Dongchi Cai, Zheng Gong, Guanqi Qiu, Deji Liu, Yinren Shou, Xueqing Yan,Comments:Subjects: physics.plasm-ph physics.acc-phCreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
We develop a theoretical model for self-generated MAGNETic islands in RELATIVISTIC LASER-driven channels in near-critical-density plasmas. The islands arise from the nonlinear superposition of the quasi-static MAGNETic fields generated by the longitudinal channel current $j_x$ and the LASER-front driven transverse current $j_y$. By deriving the critical conditions among LASER depletion, transversely symmetric channel formation, and MAGNETic-island formation, we identify the LASER-plasma parameter window in which the MAGNETic island structures can exist. Within this window, the balance between the LASER ponderomotive force and the charge-separation force, expressed through an effec tive electron density $n_\mathrm{eff}$, determines the transverse island width $H$, whereas the mismatch between the LASER group and phase velocities determines the longitudinal period $L$. Large-scale particle-in-cell simulations over a broad range of LASER intensities and plasma densities validate the resulting scaling laws. The model turns the island geometry from a qualitative feature of the channel field into a predictable quantity, providing a basis for tailoring electron transport, particle acceleration, high-energy radiation, and novel fusion ignition schemes in RELATIVISTIC LASER-plasma interactions.
[abstract 56 / 68] (score: 2) - Title: Possible Sources of Iron Nuclei in Ultra-High-Energy Cosmic RaysAuthors: Anna Uryson,Comments: 10 pages, 2 figuresSubjects: astro-ph.HECreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
The origin of a COSMIC RAY particle with an ultra-high energy of 2.44 x 10^20 eV recorded by the Telescope Array is discussed by assuming that it is a heavy nucleus, namely an iron or silicon nucleus. Iron is chosen as a heaviest element in COSMIC RAYs, while silicon is chosen to find out how much the theoretical results obtained vary with the mass of the heavy nucleus. Assuming extragalactic origin of the particle with such energy, the constraints on the distances to possible sources are analysed using a routine calculation of the COSMIC RAY propagation in extragalactic space. These possible sources are discussed.
[abstract 57 / 68] (score: 2) - Title: Shadows and Thin-Disk Images of Kerr-Newman Black Holes in a Bertotti-Robinson Magnetic FieldAuthors: Xi Wan, Haiyu Wang, Zhenyu Zhang, Zelin Zhang, Bin Chen,Comments: 25 pages, 4 figures, 2 tablesSubjects: gr-qcCreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
In this paper, we investigate the optical properties of Kerr-Newman-Bertotti-Robinson (KN-BR) BLACK HOLEs. We use the separability of null geodesics to analyze unstable spherical photon orbits and determine the radial extent of the photon shell. Because the spacetime is not asymptotically flat, we construct the critical curve on the screen of a finite-distance zero-angular-momentum observer. We then perform backward ray tracing for a geometrically thin and optically thin disk that extends from the outer region to the event horizon, and examine the resulting images, intensity profiles, critical-curve areas, and inner-shadow areas. We find that the genuine neutral Kerr-BR$_0$ and specially charged Kerr-BR$_s$ configurations have nearly identical optical appearances. It is remarkable that for the KN-BR BLACK HOLEs increasing the electric charge reduces the characteristic image size in the Kerr-Newman limit but enlarges it in the MAGNETized configurations considered here. We also find that the external MAGNETic field strongly increases the apparent image scale, while the observer inclination affects the inner-shadow area more significantly than the critical-curve area. These results may provide useful theoretical insight for future observations aimed at identifying such exotic MAGNETized BLACK HOLEs.
[abstract 58 / 68] (score: 2) - Title: Physics-based phenomenological modeling of binary BLACK HOLE hierarchical formation 2: Autodifferentiable functional inference of hierarchical compact-binary populationsAuthors: R. O'Shaughnessy, M. Zeeshan, M. Qazalbash,Comments: 30 pages, 12 figures; main paper onlySubjects: gr-qc astro-ph.HECreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
The gravitational-wave (GW) census contains mass and spin structure consistent with contributions from BLACK HOLEs assembled through repeated mergers in dense environments. Connecting that structure to formation physics requires models that are both physically interpretable and tractable within population inference. We construct an autodifferentiable, physics-based phenomenological model in which each dense environment is represented by a coagulation response and a population of such environments produces an observable merger-rate density. Embedded in the gwkokab Poisson-likelihood framework, this model enables joint inference of natal-population and interaction parameters from the GW census. Applied to GWTC-5.0, the framework shows why simple pairwise coagulation models struggle to reproduce the observed high-mass, comparable-mass population and tests alternative interaction structures against the data, while retaining an explicitly modeled natal component.
[abstract 59 / 68] (score: 2) - Title: Particle pinch in global tokamak edge simulationsAuthors: Ben Zhu,Comments: 32 pages, 16 figuresSubjects: physics.plasm-phCreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
The inward particle flux, or particle pinch, is routinely observed in MAGNETically confined fusion experiments, yet its mechanism is not fully understood. We study the particle pinch in the tokamak edge with the flux-driven global turbulence model GDB. Starting from a flat density profile fueled only near the last closed flux surface, the simulation develops a strong inward particle flux that builds a centrally peaked density profile over $O(10)$ ms. The pinch coexists with the usual outward turbulent heat transport; two distinct mechanisms carry it. In the early stage, when density and temperature gradients oppose each other ($η_α=L_n/L_{T_α}<0$), drift-wave turbulence drives the inward flux through electron thermal diffusion. In the late stage, once the density profile has flattened, a persistent inward equilibrium $E\times B$ flux, carried by the poloidally asymmetric density and electrostatic potential, drives the central peaking. While the Pfirsch--Schlüter neoclassical transport sets the amplitude of the up-down asymmetric density, classical theory predicts no net radial flux from this asymmetry at leading order. The observed flux flows in a separate non-ideal channel, opened by parallel resistivity, electron inertia, and electroMAGNETic induction in the equilibrium electron force balance. This channel shifts the equilibrium potential poloidally against the density by $δ_s\simeq-0.08π$ and supplies the late-phase density build-up. These results show that a flux-driven global edge simulation can self-consistently produce a centrally peaked density profile without ad hoc assumptions, and bear on longstanding edge questions such as density pedestal formation.
[abstract 60 / 68] (score: 2) - Title: A scaling theory for the macroturbulence of weakly supercritical planetary atmospheresAuthors: Ryan Eusebi, Tapio Schneider, Andy Thompson,Comments: Submitted to Journal of the Atmospheric SciencesSubjects: physics.ao-phCreated: 2026-09-06; Updated: 2026-09-09; Datestamp: 2026-09-09
A theory for the general circulation of the atmosphere must be based on a theory of its macroturbulence. A central component is the near-surface eddy heat flux, which is closely tied to the mass transport of the surface branch of the circulation. Existing scaling theories are largely formulated within the two-layer quasi-geostrophic framework, which assumes supercritical states and an inverse cascade of kinetic energy---conditions that are frequently not satisfied in planetary atmospheres, including Earth's. Nevertheless, such theories have shown some empirical success, including that the Rhines scale is associated with the mixing length even in the absence of any inverse energy cascade. Here, we analyze hundreds of idealized, dry general circulation model simulations spanning wide ranges of rotation rates, meridional temperature gradients, vertical stratification, and seasonality. Most simulations reside in the marginally critical regime where strongly nonlinear scaling theories fail. We propose a new theory that captures both domain-averaged and local eddy heat flux behavior across all simulations. The theory uses scaling arguments for the zonal momentum balance and accounts for kinematic effects on eddy mixing. The scaling depends on a non-dimensional thermal Rossby number and implicitly accounts for the role of nonlinear eddy momentum fluxes across JETs. We demonstrate the skill of the proposed scaling in explaining global near-surface temperature distributions across a wide range of climate states in a simple energy balance model. Implications for general circulation theory and extending the scalings to moist atmospheres are discussed.
[abstract 61 / 68] (score: 2) - Title: Catching Up with the Fastest Star in the Galaxy: A Two-Passage GRAVITY+ Campaign to Detect S301's Schwarzschild PrecessionAuthors: Joseph Catanzarite,Comments: 9 pages, 4 figures; submitted to Monthly Notices of the Royal Astronomical Society (MNRAS)Subjects: astro-ph.GA astro-ph.SRCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
S301 is the fastest known star in the Galaxy. It orbits Sgr A* every 8.68 yr on an e = 0.9832 orbit that carries it within 136 Schwarzschild radii at 25,600 km/s (GRAVITY Collaboration 2026). An orbit like that must precess, by the same Schwarzschild effect that turns Mercury's perihelion, whatever the spin of the BLACK HOLE. We ask whether an astrometry-only GRAVITY+ campaign covering the 2031.8 and 2040.5 periapsis passages can catch it. We validate a RELATIVISTIC light-curve model, design a 131-epoch Fisher-optimal cadence with a periapsis floor, fit a seven-parameter orbit including the light-travel-time delay, and build a systematic error budget. With white noise at the 207 microarcseconds achieved on S301, the fit recovers the injected rate, 0.2307 deg/yr, as 0.2324 +/- 0.0023 deg/yr (+/-0.0012 at the forecast 100 microarcseconds). Real astrometric noise is not white. We add per-run calibration offsets and a wandering Sgr A* photocentre at GRAVITY's published amplitudes, marginalize over the reference zero point, mass and distance, add the bounded systematics in quadrature, and inflate by the excess scatter of real GRAVITY orbit fits. What survives is 0.0074 deg/yr, a 31 sigma detection. The Sun hides the first periapsis for 153 d, at a cost to the period and periapsis epoch but not to the precession rate. Radial velocities are out of reach at S301's magnitude; photometry only validates the light-curve model. The spin of Sgr A* could shift the rate by 5.17-5.74 per cent and cannot be bounded, so the campaign is a spin-agnostic test of general relativity, and a forecast until the star comes round.
[abstract 62 / 68] (score: 2) - Title: Recovering Large-Scale Clustering of Missing Galaxies for Galaxy--Gravitational-Wave Cross-correlationsAuthors: Tathagata Ghosh, Surhud More,Comments: 11 pages, 6 figuresSubjects: astro-ph.COCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
We present a framework for completing galaxy catalogs from flux-limited surveys which reconstructs the missing galaxy population while preserving its clustering properties. This is particularly important for cosmological analyses using gravitational-wave (GW) dark sirens without electroMAGNETic counterparts, such as binary BLACK HOLE mergers, which constitute the majority of GW detections. As GW detectors probe increasingly larger distances, galaxy catalogs become progressively incomplete owing to survey flux limits. Current state-of-the-art statistical host identification methods typically account for this incompleteness by assuming that the missing galaxies are uniformly distributed in comoving volume. While this approximation can mitigate biases due to incompleteness, it neglects the clustering of galaxies within the cosmic web. Since galaxies and GW sources are both expected to trace the underlying large-scale structure, their spatial distributions are correlated, making a homogeneous reconstruction physically unrealistic, a shortcoming which our framework addresses. As a proof of concept, we apply the method to simulated galaxy catalogs with different flux limits and observational selection functions. Our approach provides a significantly more realistic completion of incomplete galaxy catalogs than the commonly adopted homogeneous-in-comoving-volume approximation, enabling more robust cosmological inference from gravitational-wave dark sirens.
[abstract 63 / 68] (score: 2) - Title: An Eccentric Massive Protobinary Assembled via a Core-merger Parabolic EncounterAuthors: Yao Wang, Yichen Zhang, Rubén Fedriani, Kei E. I. Tanaka, Viviana Rosero, Kai Yang, Morten Andersen, Maria T. Beltrán, Mélisse Bonfand, Yu Cheng, James M. De Buizer, Yihuan Di, Guido Garay, Prasanta Gorai, Zhi-Yun Li, Yao-Lun Yang, Jonathan C. Tan,Comments: 51 pages, 23 figures, 5 tables. Published in Nature AstronomySubjects: astro-ph.SR astro-ph.GACreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
Most massive stars form in binary systems, which profoundly influence their subsequent evolution. However, how such systems form remains poorly understood, with several competing scenarios proposed, including disk fragmentation, core fragmentation and capture. Determining the orbital architectures of massive binaries, particularly during their earliest embedded phases, is therefore crucial for distinguishing among these formation pathways, but direct measurements of their three-dimensional motions have remained exceptionally challenging. Here we present high-resolution, multi-epoch sub-millimeter-to-centimeter ALMA and JVLA observations of the massive protobinary IRAS 07299$-$1651, complemented by JWST and VLT infrared imaging. We detect orbital proper motion of the binary components, enabling a full three-dimensional orbital reconstruction. Combining orbital fitting, multi-wavelength continuum modelling, hydrogen recombination line kinematics and JET observations, we find that the preferred orbital solutions are highly eccentric and close to parabolic, while both circumstellar disks are strongly misaligned with the orbital plane. These properties are naturally explained by a ``core-merger'' scenario in which the two protostars originated independently from initially unbound cores that recently underwent a near-parabolic encounter, producing an eccentric binary with a current separation of about 200 au. These findings suggest that the core-merger process may represent an important pathway for forming eccentric massive binaries.
[abstract 64 / 68] (score: 2) - Title: Oblique Collision of a Relativistic Cold Shell with an Ideal Reflecting WallAuthors: Jonathan Granot, Prasanta Bera, Michael Rabinovich, Paz Beniamini,Comments: 17 pages, 21 figures, submitted to Physics of FluidsSubjects: astro-ph.HECreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
Relativistic flows are common in astrophysics and often form shocks when different parts of the flow collide at RELATIVISTIC relative velocities. Such collisions are often oblique, forming two shocks whose shocked fluids are separated by a contact discontinuity, which is treated here as an ideal reflecting ``wall'' where the flow on either side is modeled separately. The latter is modeled in the lab frame $S$ as a uniform cold planar shell propagating into vacuum at velocity $v_1=β_1c$ normal to its vacuum interface, colliding with the wall at an incidence angle $α_1$. The collision point $P$ moves along the wall at a velocity $v_p=v_{1}/\sinα_1$, and a boost along the wall at $v_p$ leads to a steady-state frame $S'$ where this problem is highly simplified. However, a ``super-luminal'' regime exists where $v_p>c\Leftrightarrow\tanα_1<Γ_{1}β_{1}=(1-β_{1}^2)^{-1/2}β_1$ and no steady-state frame $S'$ exists. It corresponds to only very small $α_1$ in the Newtonian regime, but nearly all $α_1$ in the RELATIVISTIC regime. We solve this problem \textit{\textbf{fully analytically}} using integral conservation laws, in the attachmrnt region where point $P$ is attached to the wall. This region of parameter space is bound at high $α_1$ by the detachment line, which coincides with the sonic line for a cold initial shell. A weak-shock solution exist in all this region, while a strong-shock solution exists only in the sub-luminal attachment region -- between the luminal line and the detachment/sonic line where the two solutions coincide and beyond which point $P$ detaches from the wall and shocked fluid spills into the vacuum.
[abstract 65 / 68] (score: 2) - Title: Thermodynamics and phase transitions of spherically symmetric AdS regular BLACK HOLEsAuthors: Qi-Quan Li, Yu Zhang, Hoernisa Iminniyaz,Comments: 9 pages, 6 figuresSubjects: gr-qcCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
We obtain the singular ''mother'' BLACK HOLE solution by solving the coupling between Einstein gravity with a cosmological constant and a nonlinear electroMAGNETic field. The thermodynamic quantities of the ''mother'' BLACK HOLE are first derived in the unconstrained phase space $(S, q, α, P)$, after which the regularity condition $M = q^3/α$ is imposed to obtain the thermodynamic quantities of a class of spherically symmetric AdS regular BLACK HOLEs self-consistently. We distinguish two categories of thermodynamic quantities: fundamental conjugate variables defined by the first law, and thermodynamic response functions constructed from them. For response functions involving second-order derivatives -- in particular the heat capacity -- we show that the order of constraint imposition and derivative calculation cannot be interchanged, and the correct procedure is to first impose the constraint and then construct the response function. Within this framework, we find that when $P
[abstract 66 / 68] (score: 2) - Title: Approximating the statistics of a gravitational wave backgroundAuthors: Mikel Falxa,Comments: 13 pages, 7 figuresSubjects: astro-ph.IM astro-ph.GA astro-ph.HECreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
The astrophysical origin of the gravitational wave background (GWB) reported by pulsar timing array (PTA) collaborations has yet to be confirmed. A GWB signal made of the sum of individual gravitational wave (GW) from the population of supermassive BLACK HOLE binaries (SMBHB) would show the imprint of a discrete Poissonian statistics in its spectral properties. In this work, we propose a tool based on the saddlepoint approximation method to estimate the distribution of characteristic strain for any given population model. This tool can be used for Bayesian inference or for a quick visualization of the statistics of the GWB from the output of more realistic semi-analytical models. We introduce the general family of variance mixture Gaussian distributions that models heavy-tailed behavior distributions that is expected for a non-Gaussian GWB signal. We show that setting the correct hierarchical priors to a Gaussian free spectrum PTA likelihood is effectively equivalent to a non-Gaussian likelihood. Using ideal simulations, we compare the performance of the saddlepoint approximation with a log-Normal distribution to infer the parameters of the astrophysical model from the statistics of the GWB and show that correctly modeling higher order moments is essential. Future PTA analyses should include the statistics of the GWB in their pipelines.
[abstract 67 / 68] (score: 2) - Title: Thresholdless IBW Emission and Alpha-to-Thermal-Ion Energy Channeling via Pole Resonance of Fusion-Product IonsAuthors: Hong Qin, Nathaniel J. Fisch,Comments: 7 pages, 4 figuresSubjects: physics.plasm-phCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
Fusion reactions can release a substantial fraction, and in aneutronic reactions nearly all, of their energy as the kinetic energy of fusion-product ions. In MAGNETized plasmas, these energetic ions can form ring distributions in velocity space. Such distributions can drive Dory-Guest-Harris (DGH) electrostatic instabilities, but these self-instabilities require a finite energetic-ion density and can be stabilized by a thermal background. We show that the same background can instead enable a distinct instability mechanism: a cyclotron pole of the minority energetic-ion susceptibility destabilizes a stable ion Bernstein wave (IBW) eigenmode. When the energetic-ion harmonic is distinct from the thermal-ion harmonics, exact root-pole resonance is thresholdless in the ideal collisionless limit. A species-resolved power balance shows that the energetic ions supply the free energy while the thermal plasma receives it. In the LAPD proton--alpha example, $99.96\%$ of the alpha-particle power loss enters the coherent proton response. This self-excited, ion-directed transfer provides a possible linear building block for alpha-particle energy channeling in proton-Boron11 fusion.
[abstract 68 / 68] (score: 2) - Title: Hamiltonian Particle Dynamics in Fusion Plasmas: Orbital Tomography and Spectrum Analysis for Energy and Momentum Transport under Resonant Non-Axisymmetric PerturbationsAuthors: Yiannis Antonenas,Comments: PHD ThesisSubjects: physics.plasm-ph nlin.CDCreated: 2026-09-07; Updated: 2026-09-09; Datestamp: 2026-09-09
This thesis investigates the impact of resonant mode-particle interactions on transport and confinement in toroidal fusion plasmas. Using analytical and numerical approaches, we study how intrinsic and externally applied MAGNETic perturbations affect plasma particles with different kinetic characteristics, focusing on resonant interactions with guiding-center motion. We develop a novel, computationally efficient method based on Action-Angle variables to identify resonance locations and characterize resonances in guiding-center phase space, including the number of islands in resonance chains and the formation of transport barriers. Using the drift center (DC) approximation, we derive analytical expressions for orbital frequencies and the kinetic $q$ factor for large-aspect-ratio (LAR) equilibria. These results provide the conditions for mode-particle resonances, which can strongly influence particle, momentum, and energy transport and, consequently, plasma confinement. The analytical results are validated against numerical simulations, demonstrating an efficient tool for predicting transport barriers and energetic-particle behavior under non-axisymmetric perturbations. We further extend the orbital-frequency analysis from LAR equilibria to numerically reconstructed, realistic equilibria using a computationally efficient, semi-analytical geometrical method applicable to arbitrary unperturbed equilibria. Finally, for the LAR equilibrium, we extend the analysis to time-dependent perturbations and demonstrate the emergence of Arnold diffusion in guiding-center phase space, highlighting the role of the Arnold web in particle transport. Overall, this work advances the understanding of mode-particle resonant interactions and provides computational tools for predicting transport and confinement in realistic fusion configurations.
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