Current date: 2025-07-18
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Datestamp limit: 2025-07-18 (0 days ago)
Created/updated limit: 2025-07-11 (7 days ago)
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Number of records retrieved: 597
Keyword score statistics
score 12 -- 1 abstracts
score 11 -- 1 abstracts
score 10 -- 1 abstracts
score 7 -- 1 abstracts
score 6 -- 3 abstracts
score 5 -- 4 abstracts
score 4 -- 5 abstracts
score 3 -- 11 abstracts
score 2 -- 23 abstracts
in total -- 50 abstracts
Articles that appeared on 2025-07-18
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[abstract 1 / 50] Wow! (score: 12)
- Title: X-ray Spectral Variability as Probe of Multimessenger Emission in Blazar 5BZB J0630-24064Authors: Jose Maria Sanchez Zaballa, Sara Buson, Stefano Marchesi, Francesco Tombesi, Thomas Dauser, Joern Wilms, Alessandra Azzollini,Comments: 14 pages, 10 figuresSubjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
X-ray observations are essential for understanding the multimessenger emission mechanisms of ACTIVE GALACTIC NUCLEi (AGN). Blazars, a subset of AGN whose X-ray emission predominantly originates from RELATIVISTIC JETs, have been proposed as promising high-energy neutrino sources. In this work, we study the candidate neutrino-emitting BLAZAR 5BZB J0630-24064, which has been observed over multiple epochs with the XMM-Newton, NUSTAR, Neil Gehrels SWIFT-XRT, and eROSITA observatories. Analysis of the X-ray spectra in the 2.0-10.0 keV band shows significant variability, with high flux states adhering to a power-law model indicative of JET emission. However, during low-flux states, the spectrum reveals an additional component at hard-X-rays, indicating a transition from JET-dominated to multi-component X-ray emission, possibly associated with hadronic processes. To investigate this spectral evolution, we tested various models and found it to be consistent with corona emission or photoionised absorption processes typically observed in obscured AGN. The identification of the X-ray spectral variability in 5BZB J0630-24064, combined with its potential for neutrino production, opens new perspectives in multimessenger astrophysics of BLAZARs highlighting the synergies between the mechanisms of the JET and the nuclear environment.
[abstract 2 / 50] Wow! (score: 11) - Title: Looking into the Jet Cone of the Neutrino-Associated Very High Energy Blazar PKS 1424+240Authors: Y. Y. Kovalev, A. B. Pushkarev, J. L. Gomez, D. C. Homan, M. L. Lister, J. D. Livingston, I. N. Pashchenko, A. V. Plavin, T. Savolainen, S. V. Troitsky,Comments: 5 pages, 5 figures; accepted by A&A LettersSubjects: astro-ph.HE astro-ph.GACreated: 2025-07-11; Updated: 2025-07-18; Datestamp: 2025-07-18
The acceleration process of massive particles as well as the production of very high energy (VHE) photons and neutrinos remains a fundamental challenge in astrophysics. We investigate the parsec-scale JET structure and MAGNETic field of the BLAZAR PKS 1424+240, that has been selected on the basis of strong VHE gamma-ray emission and identified with one of the highest peaks in the IceCube 9-year neutrino sky. We analyze 15 GHz VLBA observations of this BL Lac object, stacking 42 POLARIZATION-sensitive images collected in 2009-2025 to enhance the signal and reveal persistent parsec-scale structure. Our observations uncover a rare scenario. The object is viewed inside the JET cone, very close to the axis of its RELATIVISTIC JET, with a viewing angle of <0.6 deg. This effectively maximizes Doppler boosting to values ~30 and enhances both electroMAGNETic and neutrino emission in the observer's direction. Based on polarimetric observations, we unambiguously detect a net toroidal component of the JET's MAGNETic field, indicating a current carrying JET flowing almost directly towards our line of sight. Blazars with very small JET viewing angles offer a solution to the longstanding mismatch between Doppler factors inferred from low VLBI apparent JET speed and those derived from VHE observations -- the so-called "Doppler factor crisis". We show that RELATIVISTIC beaming plays the critical role in the gamma-ray and neutrino emission of BLAZARs, with direct implications for models of their multi-messenger emission.
[abstract 3 / 50] Wow! (score: 10) - Title: Gamma-ray emission from the Seyfert galaxy NGC 4151: Multi-messenger implications for ultra-fast outflowsAuthors: Enrico Peretti, Giada Peron, Francesco Tombesi, Alessandra Lamastra, Francesco Gabriele Saturni, Matteo Cerruti, Markus Ahlers,Comments: 23 pages (1-column format), 11 figures, 4 tables; matches the version published in JCAPSubjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
The nuclear activity typical of Seyfert galaxies can drive powerful winds where high-energy phenomena occur. In spite of their high power content, the number of such non-JETted ACTIVE GALACTIC NUCLEi (AGN) detected in gamma rays is very limited. 4FGL J1210.3+ 3928, a source recently discovered by the FERMI-LAT telescope, is spatially consistent with the BLAZAR 1E 1217.9+3945 and NGC 4151, a Seyfert galaxy located at about 15.8 Mpc known for hosting ultra-fast outflows (UFOs) in its innermost core. We show that the localization of 4FGL J1210.3+3928 might be affected by fluctuations due to a superposition of the two nearby sources. We explore the possibility of NGC 4151 to be a high-energy source and we conclude that particle acceleration at the UFO wind termination shock can explain the luminosity and spectral shape of the observed gamma-ray flux, whereas the multiwavelength spectral energy distribution of 1E 1217.9+3945 disfavors it as the dominant GeV gamma-ray counterpart. Interestingly, NGC 4151 is also spatially coincident with a weak excess of neutrino events identified by the IceCube neutrino observatory. We compute the contribution of the UFO to such a neutrino excess and we discuss other possible emission regions such as the AGN nearest neighborhood.
[abstract 4 / 50] Wow! (score: 7) - Title: Three-dimensional Dynamics of Strongly Magnetized Ion-Electron Relativistic ReconnectionAuthors: Fabio Bacchini, Gregory R. Werner, Camille Granier, Jesse Vos,Comments:Subjects: astro-ph.HE physics.plasm-phCreated: 2025-07-16; Updated: 2025-07-18; Datestamp: 2025-07-18
We present 3D simulations of semiRELATIVISTIC collisionless MAGNETic RECONNECTion, where upstream ions are subRELATIVISTIC while electrons are ultraRELATIVISTIC. We employ the realistic proton-to-electron mass ratio and explore a range of upstream ion MAGNETization spanning two orders of magnitude, with our highest-MAGNETization run achieving unprecedentedly large domain sizes. Through a parameter scan, we find that as the system transitions from mildly to trans- and ultraRELATIVISTIC regimes the qualitative behavior of RECONNECTion becomes strongly influenced by 3D effects mediated by drift-kink and flux-rope kink dynamics. As a result, MAGNETic-energy dissipation at high MAGNETizations, and the subsequent nonthermal particle acceleration, can become less efficient, contrary to general expectations for 3D RELATIVISTIC RECONNECTion. Our results have important implications for understanding RECONNECTion in MAGNETized astrophysical scenarios, such as the surroundings of BLACK HOLEs and neutron stars.
[abstract 5 / 50] Yes (score: 6) - Title: FERMI-GBM Observations of GRB 230307A: An Exceptionally Bright Long-Duration Gamma-ray Burst with an Associated KilonovaAuthors: S. Dalessi, P. Veres, C. M. Hui, S. Bala, S. Lesage, M. S. Briggs, A. Goldstein, E. Burns, C. A. Wilson-Hodge, C. Fletcher, O. J. Roberts, P. N. Bhat, E. Bissaldi, W. H. Cleveland, M. M. Giles, M. Godwin, R. Hamburg, B. A. Hristov, D. Kocevski, B. Mailyan, C. Malacaria, O. Mukherjee, L. Scotton, A. von Kienlin, J. Wood,Comments: 17 Pages, 10 figuresSubjects: astro-ph.HECreated: 2025-07-16; Updated: 2025-07-18; Datestamp: 2025-07-18
On March 7th, 2023 the \textit{FERMI} Gamma-ray Burst Monitor observed the second highest fluence GAMMA-RAY BURST (GRB) ever, GRB~230307A. With a duration beyond 100~s, GRB~230307A contains a multitude of rapidly-varying peaks, and was so bright it caused instrumental effects in the GBM detectors. The high fluence of this burst, (6.02 $\pm$ 0.02)$\times$10$^{-3}$ erg cm$^{-2}$, prompted rapid follow-up across the electro MAGNETic spectrum including the discovery of an associated kilonova. GRB~230307A is one of a few long GRBs with an associated compact merger origin. Three main temporal regions of interest are identified for fine time-resolution spectral analysis: triggering pulse, main emission, and late emission, and the parameter evolution is traced across these regions. The high flux of the burst allowed for the statistical preference of a more complex, physically-motivated model, the Double Smoothly Broken Power Law, over typical spectral fitting functions for GRBs. From this model the evolution of the parameters was found to be in accordance with those expected for SYNCHROTRON radiation in the fast-cooling regime. Additionally, it was found that the flux experiences a steep decline in late time intervals, a feature which is often attributed to high-latitude emission, which follows the dissipation episodes. Furthermore, GRB~230307A was found to have one of the highest inferred bulk Lorentz factors of $Γ= 1600$. GRB~230307A is a noteworthy burst in terms of flux alone, but additionally provides a unique insight into the possible temporal and spectral characteristics of a new long merger class of GRBs.
[abstract 6 / 50] Yes (score: 6) - Title: The Physical Origin and Time Lag of Multi-Frequency Flares from SgrA*Authors: Hong-Xuan Jiang, Yosuke Mizuno, Indu K. Dihingia, Feng Yuan, Xi Lin, Christian M. Fromm, Antonios Nathanail, Ziri Younsi,Comments: 20 pages, 12 figures, accepted by ApJSubjects: astro-ph.HE gr-qcCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Sagittarius~A$^*$, the supermassive BLACK HOLE at the center of our galaxy, exhibits flares across various wavelengths, yet their origins remain elusive. We performed 3D two-temperature General Relativistic Magnetohydrodynamic (GRMHD) simulations of MAGNETized accretion flows initialized from multi-loop MAGNETic field configuration onto a rotating BLACK HOLE and conducted General Relativistic Radiative Transfer (GRRT) calculations considering contributions from both thermal and non-thermal SYNCHROTRON emission processes. Our results indicate that the polarity inversion events from the multi-loop MAGNETic field configurations can generate $138\,\rm THz$ flares consistent with observations with the help of non-thermal emission. By tracing the intensity evolution of light rays in GRRT calculations, we identify the precise location of the flaring region and confirm that it originates from a large-scale polarity inversion event. We observe time delays between different frequencies, with lower-frequency radio flares lagging behind higher frequencies due to plasma self-absorption in the disk. The time delay between near-infrared and 43 GHz flares can reach up to $\sim 50$ min, during which the flaring region gradually shifts outward, becoming visible at lower frequencies. Our study confirms that large-scale polarity inversion in a Standard And Normal Evolution (SANE) accretion flow with a multi-loop initial MAGNETic configuration can be a potential mechanism driving flares from Sgr~A$^*$.
[abstract 7 / 50] Yes (score: 6) - Title: The pulsar wind nebula around B1853+01 in X-raysAuthors: Xiying Zhang, Pol Bordas, Samar Safi-Harb, Kazushi Iwasawa,Comments:Subjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
We report on the results of a comprehensive analysis of X-ray observations carried out with \textit{Chandra}, \textit{XMM-Newton} and \textit{NUSTAR} of the pulsar wind nebula (PWN) associated with PSR B1853+01, located inside the W44 SUPERNOVA remnant (SNR). Previous X-ray observations unveiled the presence of a fast-moving pulsar, PSR B1853+01, located at the southern edge of the W44 thermal X-ray emission region, as well as an elongated tail structure trailing the pulsar. Our analysis reveals, in addition, the presence of an ``outflow'' feature ahead of the pulsar extending for about 1 \arcmin ($\sim$ 1.0 pc at the distance of 3.2 kpc). At larger scales, the entire PWN seems to be surrounded by a faint, diffuse X-ray emission structure. The southern part of this structure displays the same unusual morphology as the ``outflow'' feature ahead of the pulsar, and extends along $\sim 6$ \arcmin ($\sim$ 5 pc) in the direction of the pulsar proper motion. In this report, a spatially-resolved spectral analysis for the different extended regions around PSR B1853+01 is carried out. For an updated value of the column density of $0.65_{+0.46}^{-0.42} \times 10^{22} ~\textrm{cm}^{-2}$, a power-law fit to the ``outflow'' region yields a spectral index $Γ\approx 1.24_{+0.23}^{-0.24}$, which is significantly harder than that of the pulsar ($Γ\approx 1.87_{+0.48}^{-0.43}$) and the pulsar tail ($Γ\approx 2.01_{+0.39}^{-0.38}$). We argue that both the ``outflow'' structure and the surrounding halo-like X-ray emission might be produced by high-energy particles escaping the PWN around PSR B1853+01, a scenario recently suggested also for other Bow-shock PWNe with JET-like structures and/or TeV halos.
[abstract 8 / 50] Yes (score: 5) - Title: Dynamics of Reconnection NanoJETs in Eruptive and Confined Solar FlaresAuthors: Annu Bura, Arpit Kumar Shrivastav, Ritesh Patel, Tanmoy Samanta, Sushree S Nayak, Ananya Ghosh, Shanwlee Sow Mondal, Vaibhav Pant, Daniel B. Seaton,Comments: 13 pages, 5 Figures, 2 Tables, Accepted for publication in The Astrophysical Journal LettersSubjects: astro-ph.SRCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Recent observations reveal small-scale RECONNECTion-driven plasma ejections, often termed nanoJETs, triggered by MAGNETic field interactions at slight misalignment angles. These fast, collimated plasma ejections are $\sim$1.5 Mm long and $\sim$0.5 Mm wide. In this study, we analyze two high-resolution extreme ultraviolet imaging datasets from the Extreme Ultraviolet Imager onboard the Solar Orbiter mission, corresponding to an eruptive (M7.6) and a confined (C1.2) flare, to investigate the dynamics of nanoflare ejections and, for the first time, compare their properties in distinct MAGNETic environments. We identified 59 nanoflare ejections: 44 in the eruptive flare and 15 in the confined flare event. Our analysis reveals that these events form two distinct classes: confined events exhibit lower speeds (41--174 kms$^{-1}$) and lower kinetic energies ($10^{20}$--$10^{22}$ erg), placing them closely in or near the picoflare energy regime, while eruptive events show higher speeds (131--775 kms$^{-1}$) and higher kinetic energies ($10^{22}$--$10^{24}$ erg), falling within the nanoflare regime. Furthermore, MAGNETic field extrapolations reveal a highly sheared arcade with greater twist and higher MAGNETic energy density in the eruptive event, compared to the less twisted configuration in the confined event. We infer that this sheared arcade configuration in the eruptive event creates favorable conditions for higher speeds and kinetic energies, unlike the less braided structure in the confined event. Our findings highlight the crucial role of the surrounding MAGNETic environment in regulating the energetics of nanoflare ejections in the solar atmosphere.
[abstract 9 / 50] Yes (score: 5) - Title: Energy Extraction via Magnetic Reconnection in Kerr-Sen-AdS$_{4}$ Black Hole: Circular Plasma and Plunging PlasmaAuthors: Xiao-Xiong Zeng, Ke Wang,Comments: 22 pages, 22 figuresSubjects: gr-qcCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
In this paper, we investigate the power and efficiency of energy extraction through MAGNETic RECONNECTion in the Kerr-Sen-AdS$_{4}$ BLACK HOLE, with a primary focus on both the circular orbit and plunging region. We plot the allowed regions for energy extraction and present corresponding power and efficiency values, comparing them with those of the Blandford-Znajek (BZ) mechanism. Our analysis reveals that energy extraction remains feasible even at a spin parameter as low as 0.5, significantly below previously reported thresholds, and the extracted power can exceed that of the BZ process under certain conditions. Furthermore, the dilatonic scalar charge $b$ and the AdS radius $l$ collectively contribute to lowering the spin threshold for energy extraction. The energy extraction process in the plunging region was further examined by analyzing the permissible energy extraction region, as well as the corresponding power output and efficiency. One can find that the energy extraction is possible even at a spin as low as 0.25. Crucially, parameter $b$ actively lowers the energy extraction spin threshold, while parameter $l$ exerts a counteracting effect, impeding such reduction. This trend shows a marked contrast with circular orbit behavior. Additionally, both power and efficiency in the plunging region consistently surpass those in the circular orbit region, indicating superior energy extraction capability in plunging region.
[abstract 10 / 50] Yes (score: 5) - Title: Hadronic acceleration in the young star cluster NGC 6611 inside the M16 region unveiled by FERMI-LAT: constraints on the acceleration efficiencyAuthors: Giada Peron, Stefano Menchiari, Giovanni Morlino, Elena Amato,Comments: Prepared for submission to A&ASubjects: astro-ph.HE astro-ph.GA astro-ph.SRCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Context. Young Massive Star Clusters, long considered as potentially important sources of galactic COSMIC RAYs, have recently emerged as gamma-ray emitters up to very high energies. Aims. In order to quantify the contribution of this source class to the pool of Galactic CRs, we need to estimate the typical acceleration efficiency of these systems. Methods. We search for emission in the GeV band, as most of the energy is emitted in this band. We perform an analysis of FERMI-LAT data collected towards the M16 region, a star-forming region also known as the Eagle Nebula, which hosts the Young Massive Star Cluster NGC 6611. We model the acceleration at the stellar wind termination shock and the propagation through the wind-blown bubble to derive the energetics of the process and interpret the GeV observations. Results. We find significant GeV emission in correspondence of a molecular cloud associated to the Young Massive Star Cluster NGC 6611. We interpret this as hadronic emission associated to particle accelerated at the cluster wind termination shock and propagated through the low-density wind-excavated bubble to the cloud. Our modeling allows us to put firm constraints on the acceleration efficiency in NGC 6611, assessing it between $\sim$ 1 % and $\sim$ 4 %.
[abstract 11 / 50] Yes (score: 5) - Title: First Evidence for a QPO Triplet and Its Relativistic Precession Origin in RE J1034+396Authors: Ruisong Xia, Yongquan Xue, Jialai Wang, Hao Liu,Comments: 8 pages, 5 figures, accepted for publication in ApJSubjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Quasiperiodic oscillations (QPOs) in ACTIVE GALACTIC NUCLEi (AGNs) provide a powerful tool for probing the structure of the innermost accretion flow and corona around supermassive BLACK HOLEs. RE~J1034+396, the most prominent AGN known to host an X-ray QPO, exhibits both short-term and long-term QPO evolution, offering a unique opportunity to investigate accretion disk and corona physics through its temporal behavior. We report a possible long-term ($\sim 92.2$ days) cyclic evolution of the QPO in RE~J1034+396, joining the detected QPO ($\sim 3730$ s) and its short-term ($\sim 17$ ks) modulation to form a possible QPO triplet, which is potentially the first such structure identified in an AGN. By applying the RELATIVISTIC precession model to the QPO triplet, we constrain the BLACK HOLE mass to $1.7^{+0.9}_{-0.8} \times 10^{6}\ M_\odot$, consistent with independent estimates, and find a low dimensionless BLACK HOLE spin of $0.017^{+0.028}_{-0.012}$. We propose an exploratory model that involves a quasiperiodic ultra-fast outflow (UFO) within the framework of the RELATIVISTIC precession model, explaining the QPO lag reversal, the modulation of hard-band QPO amplitude by soft-band flux, and the long-term evolution of timing properties. Supporting evidence includes blueshifted emission and absorption lines indicating a strong UFO at $\sim 0.3c$. This work provides new insights into the inner regions of AGN accretion disks and motivates further efforts in both numerical modeling and high-cadence timing observations.
[abstract 12 / 50] Yes (score: 4) - Title: Putting all the X in one basket: Updated X-ray constraints on sub-GeV Dark MatterAuthors: Marco Cirelli, Nicolao Fornengo, Jordan Koechler, Elena Pinetti, Brandon M. Roach,Comments: 17 pages, 9 figures. v3: corrected use of XMM-Newton data and updated corresponding boundsSubjects: hep-ph astro-ph.CO astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Sub-GeV DARK MATTER particles can annihilate or decay producing e^\pm pairs which upscatter the low-energy photon fields in the Galaxy and generate an X-ray emission (via the Inverse Compton effect). Using X-ray data from XMM-Newton, INTEGRAL, NUSTAR and SUZAKU, we derive new constraints on this class of DARK MATTER (DM). For annihilating DM, they are significant for m_DM > 100 MeV, and dominant if DM is p-wave annihilating. For decaying DM, they are the most stringent to date in the range m_DM ~400 MeV - 3 GeV$.
[abstract 13 / 50] Yes (score: 4) - Title: Preferential acceleration of heavy ions in MAGNETic RECONNECTion: Hybrid-kinetic simulations with electron inertiaAuthors: Neeraj Jain, Jörg Büchner, Miroslav Bárta, Radoslav Bučík,Comments: Published in A&ASubjects: physics.plasm-ph physics.space-phCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Solar energetic particles (SEPs) in the energy range 10s KeV/nucleon-100s MeV/nucleon originate from Sun. Their high flux near Earth may damage the space borne electronics and generate secondary radiations harmful for the life on Earth and thus understanding their energization on Sun is important for space weather prediction. Impulsive (or ${}^{3}$He-rich) SEP events are associated with the acceleration of charge particles in solar flares by MAGNETic RECONNECTion (MR) and related processes. The preferential acceleration of heavy ions and the extra-ordinary abundance enhancement of ${}^3$He in the impulsive SEPs are not understood yet. We study heavy-ion acceleration and their abundance enhancements by MR, an established acceleration source for impulsive SEPs in which heavy-ion enhancement is observed. We simulate MR using a 2-D hybrid-kinetic plasma model (kinetic ions and inertial electron fluid) with all the ions species treated self-consistently. We find that heavy ions are preferentially accelerated to energies many times larger than their initial thermal energies by a variety of acceleration mechanisms operating in MR. Most efficient acceleration takes place in the flux pileup regions of MR. Heavy ions with sufficiently small values of charge to mass ratio ($Q/M$) can be accelerated by pickup mechanism in outflow regions even before any MAGNETic flux is piled up. The energy spectra of heavy ions develop a shoulder like region, a non-thermal feature, as a result of the acceleration. The spectral index of the power law fit to the shoulder region of the spectra varies approximately as $(Q/M)^{-0.64}$. Abundance enhancement factor, defined as number of particles above a threshold energy normalized to total number of particles, scales as $(Q/M)^{-α}$ where $α$ increases with the energy threshold. We discuss our simulation results in the light of the SEP observations.
[abstract 14 / 50] Yes (score: 4) - Title: Wobbling around the clock: MAGNETically-driven quasi-periodic oscillations in pulsating ultraluminous X-ray sourcesAuthors: M. Veresvarska, M. Imbrogno, R. Amato, G. L. Israel, S. Scaringi, P. Casella, D. de Martino, F. Fürst, A. Gúrpide Lasheras, C. Knigge, M. J. Middleton,Comments: 10 pages, 3 figures. Accepted for publication on MNRAS in July 2025Subjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Ultraluminous X-ray sources (ULXs) are X-ray binary systems containing an accreting neutron star (NS) or BLACK HOLE emitting at luminosities above the Eddington limit of a $10M_{\odot}$ BLACK HOLE. Approximately 1900 (either confirmed or candidate) ULXs have been identified to date. Three systems have been confirmed to exhibit coherent signals consistent with NS spin frequencies and quasi-periodic oscillations (QPOs) in the mHz range. Several interpretations for generating such QPOs have been proposed, including general RELATIVISTIC frame-dragging effects. In this work, we test if an alternative model in which MAGNETically-driven precession of the inner accretion flow can self-consistently reproduce the observed NS spin and QPO frequencies for reasonable values for accretion rates and NS MAGNETic field strengths. For a range of parameters, we recover family of solutions with accretion rates $\approx10^{-7}$--$10^{-5}$\,M$_{\odot}$\,yr$^{-1}$ and surface MAGNETic fields $\gtrsim10^{12}$\,G, in agreement with previous estimates. If validated, this interpretation could reconcile several observed properties of pulsating ULXs, including QPO frequencies and the observed high luminosities of these systems, in a self-consistent framework without requiring general RELATIVISTIC effects and/or strong beaming due to specific viewing angles. Although the predictive power of the model is currently limited by parameter degeneracies and uncertainties, searching for and discovering more pulsating ULX systems will allow to further test or refute the proposed model.
[abstract 15 / 50] Yes (score: 4) - Title: Gravitational Torques from a Lopsided Young Stellar Component Sustain High Black Hole Accretion Rates in NGC 4593Authors: Nico Winkel, Knud Jahnke, Juan Antonio Fernández-Ontiveros, Timothy A. Davis, Françoise Combes, Massimo Gaspari, Justus Neumann, Mainak Singha, Jacob S. Elford, Vardha N. Bennert, Matthew A. Malkan,Comments: Revised version after language editing. 14 pages, 8 figures, accepted for publication in A&ASubjects: astro-ph.GACreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Supermassive BLACK HOLEs (SMBHs) grow primarily through gas accretion, observed as ACTIVE GALACTIC NUCLEi (AGNs). While mergers can drive luminous AGN episodes, secular processes may fuel a substantial portion of cosmic BH growth. Whether these mechanisms can sustain high BH accretion rates remains uncertain. This study aims to identify the secular mechanism driving high BH accretion rates, by targeting a galaxy with moderately massive SMBH, high central gas densities, accretion rates of a few percent of the Eddington limit, and gas kinematics resolved close to BLACK HOLE-dominated scales. A blind search led to the identification of NGC 4593, which is representative of the AGN population driving BH mass density growth since $z=1$. A prominent single-arm ("$m=1$") molecular gas spiral with ${\rm log}\,M_{\rm mol}/{\rm M}_\odot=8.1\pm0.3$ extends from 1.3$\,$kpc down to the SMBH's sphere of influence ($1.7^{+0.5}_{-0.2}\,{\rm pc}$). Star formation in the spiral is inefficient (${\rm SFR} = 4.9 \times 10^{-2} \,{\rm M}_\odot {\rm /yr}$, $\langle t_{\rm dep}\rangle=3.9 \pm 0.6\,\rm{Gyr}$), whereas inflow rate exceeds the SFR by two orders of magnitude and is sufficient to sustain the current BH accretion rate for $\geq$35$\,$Myr, enabling $\sim$10% SMBH growth. A young, lopsided stellar component (${\rm log}\,M_\star/{\rm M}_\odot=7.5-9.3$) exerts torques on the molecular gas, likely driving the gas inflow. This young stellar component may serve as both a cause and a product of sustained gas funnelling towards the SMBH. These findings provide evidence for the sustained secular $m=1$ feeding mode at high BH accretion rates, linking kpc-scale gas dynamics to the BLACK HOLE's sphere of influence. This mechanism, consistent with simulation predictions, may represent a key contributor to SMBH growth in luminous AGNs since cosmic noon.
[abstract 16 / 50] Yes (score: 4) - Title: A Torus Remnant Revealed by the Infrared Echo of TDE AT2019qiz: Implications for the Missing Energy and QPE FormationAuthors: Mingxin Wu, Ning Jiang, Jiazheng Zhu, Di Luo, Liming Dou, Tinggui Wang,Comments:Subjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
AT2019qiz is the first standard optical tidal disruption event (TDE) with detection of X-ray quasi-periodic eruptions (QPEs), providing strong evidence for TDE-QPE association. Moreover, it belongs to the rare subset of optical TDEs with prominent infrared (IR) echoes revealed by the multi-epoch photometry from the Wide-field Infrared Survey Explorer (WISE). The IR light curve shows an early bump, followed by a steady rise until the second-to-last epoch, after which it appears to enter a plateau phase. The dust temperature decreased until the fourth epoch and remains approximately constant for the subsequent five epochs. We have fitted the last five epochs using a convex dust ring model, resulting in an inner radius $>1.2$ pc. Such a large radius greatly exceeds the inner radius of the ACTIVE GALACTIC NUCLEi (AGN) torus for a $10^6\,M_{\odot}$ BLACK HOLE and thus could be a torus remnant with the inner part having vanished, further supporting the unified scenario of recently faded AGNs, TDEs, and QPEs. Consequently, a connection between QPEs and IR-bright TDEs is naturally expected. Moreover, the echo requires at least a peak bolometric luminosity of $(6.6, 9.5, 1.0)\times 44 \,\text{erg}\,\text{s}^{-1}$ assuming silicate, silicon carbide, and graphite dust grains, respectively, all of which are significantly higher than the peak optical blackbody luminosity. It adds to the accumulating evidence that the missing energy of TDEs may lie in the unobservable extreme UV. This work highlights the unique value of IR echoes in the study of TDEs and QPEs, and a promising prospect in the era of the Near-Earth Object (NEO) Surveyor, the successor to WISE.
[abstract 17 / 50] (score: 3) - Title: Theoretical Radio Signals from Radio-Band Gravitational Waves Converted from the Neutron Star Magnetic FieldAuthors: Wei Hong, Zhen-Zhao Tao, Peng He, Tong-Jie Zhang,Comments: 40 pages, 19 figures, 4 tables. Accepted for publication in ApJ. We infer two novel types of the converted radio signals: transient and persistent signals. Considering the mass and spin of the graviton, the expected spectral line shape of the graviton is derived. FAST is the most sensitive telescope to detect VHFGWs in a single-dish telescope. In addition, SKA2-MID has greater detection potentialSubjects: astro-ph.HE astro-ph.CO gr-qcCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Gravitational waves (GWs) can convert into electroMAGNETic waves in the presence of a MAGNETic field via the Gertsenshtein-Zeldovich (GZ) effect. The characteristics of the MAGNETic field substantially affect this conversion probability. This paper confirms that strong MAGNETic fields in neutron stars significantly enhance the conversion probability, facilitating detectable radio signatures of very high-frequency (VHF, $\left(10^6-10^{11}\mathrm{~Hz}\right)$) gravitational waves. We theoretically identify two distinct signatures using single-dish telescopes (FAST, TMRT, QTT, GBT) and interferometers (SKA1/2-MID): transient signals from burst-like gravitational wave sources and persistent signals from cosmological background gravitational wave sources. These signatures are mapped to graviton spectral lines derived from quantum field theory by incorporating spin-2 and mass constraints, resulting in smooth, featureless profiles that are critical for distinguishing gravitational wave signals from astrophysical foregrounds. FAST attains a characteristic strain bound of $h_c<10^{-23}$, approaching $10^{-24}$ in the frequency range of $1-3\mathrm{~GHz}$ with a 6-hour observation period. This performance exceeds the $5 σ$ detection thresholds for GWs originating from primordial BLACK HOLEs (PBHs) and nears the limits set by Big Bang nucleosynthesis. Additionally, projections for SKA2-MID indicate even greater sensitivity. Detecting such gravitational waves would improve our comprehension of cosmological models, refine the parameter spaces for primordial BLACK HOLEs, and function as a test for quantum field theory. This approach addresses significant deficiencies in VHF GW research, improving detection sensitivity and facilitating the advancement of next-generation radio telescopes such as FASTA and SKA, which feature larger fields of view and enhanced gain.
[abstract 18 / 50] (score: 3) - Title: Collisionless shocks having RELATIVISTIC velocities in RELATIVISTICally hot plasmasAuthors: Kamiido Kazuki, Ohira Yutaka,Comments: 9 pages, 7 figuresSubjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Shocks in RELATIVISTICally hot plasmas are thought to exist in various high-energy astrophysical phenomena, but it is not clear how RELATIVISTIC collisionless shocks are formed, whether particles are accelerated by the shock as in the case of cold upstream. In this work, collisionless shocks with a RELATIVISTIC shock velocity in RELATIVISTICally hot unMAGNETized electron-positron plasmas are investigated by two-dimensional particle-in-cell simulations. It is shown that the upstream flow is dissipated by the Weibel instability, so that the RELATIVISTIC collisionless shock is formed as in the case of cold upstream. The density and MAGNETic field structures around the shock front are almost independent of the upstream temperature when the spatial scale is normalized by the inertial length scale which takes into account the RELATIVISTIC temperature. This can be understood by considering the pressure anisotropy, which asymptotically approaches a finite value due to the RELATIVISTIC beaming effect, even as the temperature becomes RELATIVISTICally hotter and hotter. In addition, as long as the shock velocity is RELATIVISTIC, some particles are accelerated, forming a power-law energy spectrum similar to that in the cold upstream.
[abstract 19 / 50] (score: 3) - Title: GPU-Accelerated Gravitational Lensing & Dynamical (GLaD) Modeling for Cosmology and GalaxiesAuthors: Han Wang, Sherry H. Suyu, Aymeric Galan, Aleksi Halkola, Michele Cappellari, Anowar J. Shajib, Miha Cernetic,Comments: 20 pages, 11 Figures, 4 Tables, accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.COCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Time-delay distance measurements from strongly lensed QUASARs provide a robust, independent method for determining the Hubble constant ($H_0$). This approach cross-checks $H_0$ estimates from the distance ladder in the late universe and the cosmic microwave background in the early universe. However, the mass-sheet degeneracy in lensing models introduces systematic uncertainty, limiting precision. Dynamical modeling complements strong lensing by constraining the mass distribution with independent observational data. We develop a methodology and software framework for joint modeling of stellar kinematics and lensing data. Using simulated data for the lensed QUASAR RXJ1131$-$1131, we demonstrate that high-quality kinematic data can achieve $\sim$4% precision on $H_0$. Through extensive modeling, we examine the impact of the presence of a supermassive BLACK HOLE in the lens galaxy and potential systematic biases in kinematic data on $H_0$ measurements. Our results show that imposing priors on BLACK HOLE mass and orbital anisotropy, or excluding central kinematic bins, mitigates biases in $H_0$ estimates. By testing on mock kinematic data with systematic biases, we highlight the need for sub-percent control of kinematic systematics, which is achievable with current technology. Additionally, we leverage GPU parallelization to accelerate Bayesian inference, reducing a previously month-long process by an order of magnitude. This pipeline offers significant potential for advancing cosmological and galaxy evolution studies with large datasets.
[abstract 20 / 50] (score: 3) - Title: Little Red Dots from Ultra-Strongly Self-Interacting Dark MatterAuthors: M. Grant Roberts, Lila Braff, Aarna Garg, Stefano Profumo, Tesla Jeltema,Comments: 16 pages, 2 figures, updated references and acknowledgment, submitted to JCAPSubjects: astro-ph.GACreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
We investigate the possibility that the recently identified population of high-redshift, obscured QUASARs - known as "Little Red Dots" (LRDs) - originates from early BLACK HOLE seed formation driven by ultra-strongly self-interacting DARK MATTER (uSIDM). In this framework, DARK MATTER halos undergo gravothermal core collapse due to large self-interaction cross sections, resulting in the rapid formation of massive BLACK HOLE (BH) seeds with masses $\gtrsim 10^{5} M_\odot$ at redshifts $z \gtrsim 5$. We develop a semi-analytic model that tracks the evolution of the DARK MATTER halo population, the redshift of collapse $z_{\rm coll}$, and the corresponding BH mass function. Black hole growth is modeled stochastically via a log-normal Eddington ratio distribution and a finite duty cycle. We find that the uSIDM scenario naturally reproduces key observed properties of LRDs, including their abundance, compactness, and characteristic BH masses, while offering a mechanism for early, obscured BLACK HOLE formation that is difficult to achieve in standard CDM-based models. The predicted SMBH mass function at $z \sim 5$ shows excellent agreement with LRD observational data and SIDM merger-tree simulations, particularly at the high-mass end $(m_{\rm BH} \gtrsim 10^{7} M_\odot)$. These results suggest that LRDs may serve as powerful observational tracers of exotic dark sector physics and that SMBH formation in the early universe could be significantly shaped by non-gravitational DARK MATTER interactions.
[abstract 21 / 50] (score: 3) - Title: Spherical Orbital Dynamics and Relativistic Precession in Kerr-MOG SpacetimeAuthors: Hui-Min Wang,Comments: 14 pages, 6 figuresSubjects: gr-qc astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
We study the dynamics and RELATIVISTIC precessions of massive particles on spherical orbits around Kerr-MOG BLACK HOLEs in scalar-tensor-vector gravity (STVG). By employing the Hamilton-Jacobi formalism, we derive conserved quantities and analyze how the MOG parameter $α$ and orbital tilt angle $ζ$ influence the innermost stable spherical orbits (ISSOs) and orbital stability. We compute the nodal and periastron precession frequencies, finding that nodal precession increases monotonically with both BLACK HOLE spin and MOG parameter, while periastron precession exhibits a more complex behavior: MOG amplifies curvature-induced effects, which can be partially counteracted by spin. Furthermore, to complement the orbital analysis, we examine the Lense-Thirring spin precession of a gyroscope and demonstrate its sensitivity to the MOG parameter, spin, and orbital tilt angle. These results reveal distinctive signatures of modified gravity in orbital dynamics and provide a potential observational probe to test deviations from general relativity near rotating BLACK HOLEs.
[abstract 22 / 50] (score: 3) - Title: Epicyclic oscillations and accretion disk around a special Buchdahl-inspired spacetimeAuthors: Mirzabek Alloqulov, Mubasher Jamil, Sanjar Shaymatov, Qiang Wu, Mustapha Azreg-Aïnou,Comments: 10 pages, 10 figures, Accepted for publication in JHEAPSubjects: gr-qcCreated: 2025-07-14; Updated: 2025-07-18; Datestamp: 2025-07-18
In this paper, we consider the Buchdahl-inspired spacetime metric and investigate its aspects using the quasiperiodic oscillations and the accretion disk due to the accreting matter. First, we focus on analyzing the geodesics of particles around the Buchdahl-inspired spacetime, together with the conserved quantities such as specific energy and angular momentum for massive particles orbiting on the innermost stable circular orbits (ISCOs). We show that the effect of the Buchdahl parameter $\tilde{k}$ increases as the radii of the ISCO orbits decrease, resulting in shifting orbits toward the central object compared to the Schwarzschild BLACK HOLE case. We also consider astrophysical epicyclic oscillations and derive their general expressions using implications of circular motion of massive particles around the Buchdahl-inspired spacetime. Further, we explore the astrophysical implications of observational higher-frequency QPOs of the selected galactic microQUASARs of X-ray binary systems to obtain the best-fit constraints on the Buchdahl-inspired spacetime parameters. Finally, we consider the accretion disk around the Buchdahl-inspired spacetime using implications of the ISCO parameters that define the accretion disk's inner edge. We explore radiation properties of the accretion disk and redshifted image and intensity of a lensed accretion disk around the Buchdahl-inspired spacetime.
[abstract 23 / 50] (score: 3) - Title: The halo MAGNETic field of a spiral galaxy at z=0.414Authors: Timea Orsolya Kovacs, Sui Ann Mao, Aritra Basu, Yik Ki Ma, B. M. Gaensler,Comments: 16 pages, 5 figures, Accepted for publication in A&ASubjects: astro-ph.GACreated: 2025-07-16; Updated: 2025-07-18; Datestamp: 2025-07-18
Even though MAGNETic fields play an important role in galaxy evolution, the redshift evolution of galactic-scale MAGNETic fields is not well constrained observationally. In this paper we aim to provide an observational constraint on the time-scale of the mean-field dynamo, and derive the MAGNETic field in a distant galaxy at $z=0.414$. We obtained broadband spectro-polarimetric $1-8$ GHz Very Large Array observation of the lensing system B1600+434, which is a background QUASAR gravitationally lensed by a foreground spiral galaxy into two images. We apply Rotation Measure (RM) synthesis and Stokes $QU$ fitting to derive the RM of the two lensed images, which we use to estimate the lensing galaxy's MAGNETic field. We measured the RM difference between the lensed images, and detected Faraday dispersion caused by the MAGNETo-ionic medium of the lensing galaxy at $z=0.414$. Assuming that the RM difference is due to the large-scale regular field of the galaxy's halo, we measure a coherent MAGNETic field with a strength of $0.2 - 3.0\,μ$G at 0.7 kpc, and $0.01 - 2.8 \,μ$G at 6.2 kpc vertical distance from the disk of the galaxy. We derive an upper limit on the dynamo e-folding time: $τ_{\rm dynamo} < 2.9~\times 10^8$~yr. We find turbulence on scales below 50 pc, and a turbulent field strength of $0.2 - 12.1 \, μ$G. We measure the MAGNETic field in the halo of a spiral galaxy, and find turbulence on scales of $<50$ pc. If the RM difference is due to large-scale fields, our result follows the expectation from mean-field dynamo theory, and shows that galaxies at $z \simeq 0.4$ already have MAGNETic field strengths similar to present-day galaxies. However, we note the caveat of the possibility of the turbulent field of the lensing galaxy contributing to the observed RM difference.
[abstract 24 / 50] (score: 3) - Title: Supermassive Stars Match the Spectral Signatures of JWST's Little Red DotsAuthors: Devesh Nandal, Abraham Loeb,Comments: 10 pages, 6 figuresSubjects: astro-ph.GA astro-ph.SRCreated: 2025-07-16; Updated: 2025-07-18; Datestamp: 2025-07-18
The James Webb Space Telescope (JWST) has unveiled a population of enigmatic, compact sources at high redshift known as ''Little Red Dots'' (LRDs), whose physical nature remains a subject of intense debate. Concurrently, the rapid assembly of the first supermassive BLACK HOLEs (SMBHs) requires the formation of heavy seeds, for which supermassive stars (SMSs) are leading theoretical progenitors. In this work, we perform the first quantitative test of the hypothesis that LRDs are the direct observational manifestation of these primordial SMSs. We present a novel, first-principles pipeline generating synthetic spectra for a non-rotating, metal-free $10^6 \, M_\odot$ SMS. We establish that its luminosity ($L_λ\approx 1.7 \times 10^{44} \, \text{erg} \, \text{s}^{-1} \, μ\text{m}^{-1}$ at 4050 Angstroms) provides a decisive constraint, matching prominent LRDs. Our model self-consistently reproduces their defining spectral features: the extreme, V-shaped Balmer break is an intrinsic photospheric effect, while the complex line phenomenology, strong H$β$ in emission with other Balmer lines in absorption arises from non-LTE effects in a single stellar atmosphere. Applying physically motivated broadening, our spectrum provides an excellent quantitative match to LRDs at both high ($z=7.76$) and low ($z=3.55$) redshift. Our model provides a simple, self-consistent physical picture for LRDs, offering a compelling alternative to multi-component obscured AGN scenarios and suggesting we may be directly witnessing the final, luminous moments of an SMBH progenitor before its ultimate collapse.
[abstract 25 / 50] (score: 3) - Title: Solar Spicules, Filigrees and Solar Wind SwitchbacksAuthors: Jeongwoo Lee, Haimin Wang, Jiasheng Wang, Meiqi Wang,Comments: 18 pages, 14 figuresSubjects: astro-ph.SRCreated: 2025-07-16; Updated: 2025-07-18; Datestamp: 2025-07-18
Spicules, the smallest observable JET-like dynamic features ubiquitous in the chromosphere, are supposedly an important potential source for small-scale solar wind transients, with supporting evidence yet needed. We studied the high-resolution H-alpha images (0.10'') and MAGNETograms (0.29'') from Big Bear Solar Observatory (BBSO) to find that spicules are an ideal candidate for the solar wind MAGNETic switchbacks detected by the Parker Solar Probe (PSP). It is not that spicules are a miniature of coronal JETs, but that they have unique properties not found in other solar candidates in explaining solar origin of switchbacks. (1) The spicules under this study originate from filigrees, all in a single MAGNETic polarity. Since filigrees are known as footpoints of open fields, the spicule guiding field lines can form a unipolar funnel, which is needed to create an SB patch, a group of fieldlines that switch from one common base polarity to the other polarity. (2) The spicules come in a cluster lined up along a supergranulation boundary, and the simulated waiting times from their spatial intervals exhibit a number distribution continuously decreasing from a few sec to ~30 min, similar to that of switchbacks. (3) From a time-distance map for spicules, we estimate their occurrence rate as 0.55 spicules per Mm^2 and second, sufficiently high for detection by PSP. In addition the dissimilarity of spicules with coronal JETs, including the absence of base brightening and low correlation with EUV emission is briefly discussed.
[abstract 26 / 50] (score: 3) - Title: Relativistic second gradient theory of continuous mediaAuthors: Mina Chapon, Lionel Darondeau, Rodrigue Desmorat, Clément Ecker, Boris Kolev,Comments:Subjects: gr-qcCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Variational Relativity is a framework developed by Souriau in the sixties to better formulate General Relativity and its classical limit\,: Classical Continuum Mechanics. It has been used, for instance, to formulate Hyperelasticity in General Relativity. In that case, two primary variables are involved, the universe (Lorentzian) metric $g$ and the matter field $Ψ$. A Lagrangian density depending on the 1-JET of these variables is then introduced which must satisfy the principle of General Covariance. Souriau proved in 1958 that under these hypotheses, the Lagrangian density depends only on the punctual value of the matter field $Ψ$ and of a secondary variable $\mathbf{K}$, the conformation, an invariant of the diffeomorphism group, which is the Relativistic analog of the inverse of the right Cauchy--Green tensor. In the present work, an extension of Souriau's results to a second order gradient theory in General Relativity is presented. Accordingly, new higher order diffeomorphisms invariants are found. Their classical limits are calculated, showing that the 3-dimensional Continuum Mechanics second gradient theory can be derived from such a RELATIVISTIC theory. Some of these invariants converge to objective quantities in the Galilean limit, others to non-objective quantities. The present work contributes thus to clarify the theoretical foundation of higher gradient Continuum Mechanics theory.
[abstract 27 / 50] (score: 3) - Title: Multi-wavelength study of the high Galactic latitude SUPERNOVA remnant candidate \snr\ associated with the Calvera pulsarAuthors: Emanuele Greco, Michela Rigoselli, Sandro Mereghetti, Fabrizio Bocchino, Marco Miceli, Vincenzo Sapienza, Salvatore Orlando,Comments: Accepted for publication in A&ASubjects: astro-ph.HE astro-ph.GA astro-ph.SRCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
The candidate SUPERNOVA remnant (SNR) G118.4+37.0 (Calvera's SNR), discovered as a faint radio ring at high Galactic latitude and coincident with extended FERMI/LAT gamma-ray emission, is likely associated to the X-ray pulsar 1RXS J141256.0+792204 (Calvera). Previous XMM-Newton data hinted at soft diffuse X-ray emission inside the ring but lacked sufficient exposure for detailed characterisation. We obtained new XMM-Newton observations, and produced count-rate images, equivalent width and median photon energy maps to identify optimal regions for spectral analysis. We complemented these observations with a reanalysis of FERMI/LAT gamma-ray data and new Telescopio Nazionale Galileo observations aimed to search for Halpha emission. The X-ray diffuse emission is well described by a model of shock-heated plasma with temperature kT \sim 0.15 keV, mildly under-solar N and o abundances and densities ne=0.1-0.7 cm-3. According to our estimates, Calvera's SNR is 10-20 kya old and lies at a distance of 4-5 kpc. A distinti "Clump" region shows hared emission equally well described by a thermal (kT\sim 1.7 keV) or a non thermal model (Gamma \sim 2.7). The brightest X-ray area is close to the gamma-ray peak and to an isolated Alpha filament. G118.4+37.0 is a middle-aged remnant which expands in a tenuous medium and encountered a denser phase, likely the relic of the wind activity of the massive progenitor star. The estimated SNR distance is consistent within the uncertainties with that estimated for Calvera, confirming that this peculiar pulsar was born in the explosion of a massive star high above the Galactic disk. Our measured ambient density, together with the patchy morphology of the gamma-ray emission and the detection of Halpha filaments indicates that a hadronic origin is compatible with the gamma-ray flux, though a mixed leptonic-hadronic cannot be excluded
[abstract 28 / 50] (score: 2) - Title: Probing neutrino emission at GeV energies from compact binary mergers with the IceCube Neutrino ObservatoryAuthors: IceCube Collaboration, R. Abbasi, M. Ackermann, J. Adams, S. K. Agarwalla, J. A. Aguilar, M. Ahlers, J. M. Alameddine, N. M. Amin, K. Andeen, C. Argüelles, Y. Ashida, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, J. Baines-Holmes, A. Balagopal V., S. W. Barwick, S. Bash, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, B. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, I. Bodo, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, R. T. Burley, D. Butterfield, M. A. Campana, K. Carloni, J. Carpio, S. Chattopadhyay, N. Chau, Z. Chen, D. Chirkin, S. Choi, B. A. Clark, A. Coleman, P. Coleman, G. H. Collin, A. Connolly, J. M. Conrad, R. Corley, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, L. Fischer, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, G. Garg, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, S. Griswold, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, C. Haack, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Ha Minh, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häußler, K. Helbing, J. Hellrung, L. Hennig, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jeong, M. Jin, N. Kamp, D. Kang, W. Kang, X. Kang, A. Kappes, L. Kardum, T. Karg, M. Karl, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, H. Kimku, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, N. Krieger, J. Krishnamoorthi, T. Krishnan, K. Kruiswijk, E. Krupczak, A. Kumar, E. Kun, N. Kurahashi, N. Lad, C. Lagunas Gualda, L. Lallement Arnaud, M. Lamoureux, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, J. Liao, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, J. Madsen, E. Magnus, K. B. M. Mahn, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, F. Mayhew, F. McNally, J. V. Mead, K. Meagher, S. Mechbal, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, M. Moulai, D. Mousadi, T. Mukherjee, R. Naab, M. Nakos, U. Naumann, J. Necker, L. Neste, M. Neumann, H. Niederhausen, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke Pollmann, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, V. Palusova, H. Pandya, A. Parenti, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, J. Peterson, M. Plum, A. Pontén, V. Poojyam, Y. Popovych, M. Prado Rodriguez, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, S. Reusch, C. D. Rho, W. Rhode, B. Riedel, A. Rifaie, E. J. Roberts, S. Robertson, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, J. Savelberg, P. Schaile, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, F. G. Schröder, L. Schumacher, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shefali, N. Shimizu, B. Skrzypek, R. Snihur, J. Soedingrekso, A. Søgaard, D. Soldin, P. Soldin, G. Sommani, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, S. Tilav, K. Tollefson, S. Toscano, D. Tosi, A. Trettin, A. K. Upadhyay, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, D. Veske, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, M. Wolf, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, R. Young, F. Yu, S. Yu, T. Yuan, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman,Comments: 16 pages, 4 figuresSubjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
The advent of multi-messenger astronomy has allowed for new types of source searches by neutrino detectors. We present the results of the search for 0.5-100 GeV astrophysical neutrinos detected with IceCube and emitted from compact binary mergers detected by the LIGO, Virgo, and KAGRA interferometers from their first run of observation (O1) to the end of the first part of the fourth (O4a). An innovative approach is used to lower the energy threshold to 0.5 GeV and to search for an excess of GeV neutrinos in time coincidence with astrophysical transient events. Furthermore, we use a statistical combination of all observations, a binomial test, to search for a subpopulation of neutrino emitters. No significant excess was found from the studied mergers, with a best post-trial $p$-value of $40\%$, and there is currently no hint of a population of GeV neutrino emitters found in the IceCube data (post-trial $p$-value = $81\%$).
[abstract 29 / 50] (score: 2) - Title: Self-Similar Solutions for Geometrically Thin Accretion Disks with Magnetically Driven Winds: Application to Tidal Disruption EventsAuthors: Mageshwaran Tamilan, Kimitake Hayasaki, Takeru K. Suzuki,Comments: 36 pages, 10 figures, accepted for publication in Progress of Theoretical and Experimental Physics (PTEP)Subjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
We analytically derive self-similar solutions for a time-dependent, one-dimensional, MAGNETically driven accretion-disk-wind model based on the MAGNETohydrodynamic equations. The model assumes a geometrically thin, gas-pressure-dominated accretion disk and incorporates both MAGNETic braking and turbulent viscosity through an extended $α$-viscosity prescription in the vertical and radial directions, respectively. The $α$ parameter for the vertical stress is assumed to vary with the disk aspect ratio. We confirm that in the absence of a wind, our self-similar solutions agree with the classical solution of Cannizzo et al. (1990), in which the mass accretion rate follows a power-law decay with time as $t^{-19/16}$. This scaling has been widely used as a key indicator of the mass accretion rate in tidal disruption event (TDE) disks. In contrast, when a wind is present, both the mass accretion and mass loss rates decay more steeply than $t^{-19/16}$. Furthermore, we verify that the power-law indices of these rates are consistent with those obtained from the numerical simulations of Tamilan et al. (2024) at late times. In particular, our analytical solution demonstrates that MAGNETic braking leads to a more rapid decay of the mass accretion rate, mass loss rate, and bolometric luminosity. In the presence of a strong poloidal MAGNETic field, all three quantities asymptote to $t^{-5/2}$. This steep decay index can serve as a potential observational signature of MAGNETocentrifugally driven winds with strong poloidal MAGNETic fields in TDE disks.
[abstract 30 / 50] (score: 2) - Title: Bounds on neutrino-DM interactions from TXS 0506+056 neutrino outburstAuthors: G. D. Zapata, J. Jones-Pérez, A. M. Gago,Comments: 20 pages, 7 figures, 2 tables. Minor corrections, results unchanged, version accepted for publication in JCAPSubjects: hep-ph astro-ph.HECreated: 2025-07-16; Updated: 2025-07-18; Datestamp: 2025-07-18
We constrain the neutrino-DARK MATTER cross-section using the $13 \pm 5$ neutrino event excess observed by IceCube in 2014-2015 from the direction of the BLAZAR TXS 0506+056. Our analysis takes advantage of the DARK MATTER overdensity spike surrounding the supermassive BLACK HOLE at the center of the BLAZAR. In our results, we take into account uncertainties related to the different types of neutrino emission models and the features of the DARK MATTER spike, considering cross-sections that scale with energy as $σ\propto (E_ν /E_0)^n$, for values of $n = 1, 0, -1, -2$. In our best-case scenario, we obtain limits competitive with those derived from other active galaxies, tidal disruption events (TDEs), and the IC-170922A event.
[abstract 31 / 50] (score: 2) - Title: Multiple solutions to the static forward free-boundary Grad-Shafranov problem on MAST-UAuthors: K. Pentland, N. C. Amorisco, P. E. Farrell, C. J. Ham,Comments:Subjects: physics.plasm-ph cs.NA math.NACreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
The Grad-Shafranov (GS) equation is a nonlinear elliptic partial differential equation that governs the ideal MAGNETohydrodynamic equilibrium of a tokamak plasma. Previous studies have demonstrated the existence of multiple solutions to the GS equation when solved in idealistic geometries with simplified plasma current density profiles and boundary conditions. Until now, the question of whether multiple equilibria might exist in real-world tokamak geometries with more complex current density profiles and integral free-boundary conditions (commonly used in production-level equilibrium codes) has remained unanswered. In this work, we discover multiple solutions to the static forward free-boundary GS problem in the MAST-U tokamak geometry using the validated evolutive equilibrium solver FreeGSNKE and the deflated continuation algorithm. By varying the plasma current, current density profile coefficients, or coil currents in the GS equation, we identify and characterise distinct equilibrium solutions, including both deeply and more shallowly confined plasma states. We suggest that the existence of even more equilibria is likely prohibited by the restrictive nature of the integral free-boundary condition, which globally couples poloidal fluxes on the computational boundary with those on the interior. We conclude by discussing the implications of these findings for wider equilibrium modelling and emphasise the need to explore whether multiple solutions are present in other equilibrium codes and tokamaks, as well as their potential impact on downstream simulations that rely on GS equilibria.
[abstract 32 / 50] (score: 2) - Title: An Improved Boris Algorithm for Charge Particle Orbit in Tokamak PlasmasAuthors: Jian Wang, Xiaodong Zhang, Lei Ye, Xingyuan Xu,Comments:Subjects: physics.plasm-phCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
An improved Boris algorithm for simulating the motion of charged particles in electroMAGNETic fields has been developed. This enhancement addresses the issue of inaccurate fast-scale cyclotron phase calculations present in the original Boris algorithm, while preserving its advantage in simulating slow-scale guiding center motion. As a result, it strikes a balance between low and high-frequency dynamics, overcoming the limitations of traditional second-order volume-preserving algorithms (VPAs) which are constrained to a single characteristic frequency. Test particle simulations indicate that, in most cases, the improved Boris algorithm achieves significantly higher accuracy than conventional VPAs when simulating cases involving various frequencies of electric field within a typical Tokamak MAGNETic field, highlighting its superior efficacy in handling problems across a wide range of characteristic frequencies.
[abstract 33 / 50] (score: 2) - Title: Magnetorotational instability in a solar mean-field dynamoAuthors: Axel Brandenburg, Gustav Larsson, Fabio Del Sordo, Petri J. Käpylä,Comments: 15 pages, 10 figures, 2 tables, resubmitted to ApJSubjects: astro-ph.SR physics.plasm-phCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
We address the question whether the MAGNETo-rotational instability (MRI) can operate in the near-surface shear layer (NSSL) of the Sun and how it affects the interaction with the dynamo process. Using hydroMAGNETic mean-field simulations of $αΩ$-type dynamos in rotating shearing-periodic boxes, we show that for negative shear, the MRI can operate above a certain critical shear parameter. This parameter scales inversely with the equipartition MAGNETic field strength above which $α$ quenching set in. Like the usual $Ω$ effect, the MRI produces toroidal MAGNETic field, but in our Cartesian cases it is found to reduce the resulting MAGNETic field strength and thus to suppress the dynamo process. In view of the application to the solar NSSL, we conclude that the turbulent MAGNETic diffusivity may be too large for the MRI to be excited and that therefore only the standard $Ω$ effect is expected to operate.
[abstract 34 / 50] (score: 2) - Title: New class of optimized stellarators with zero bootstrap currentAuthors: Ivan Calvo, Jose Luis Velasco, Per Helander, Felix I. Parra,Comments: 7 pagesSubjects: physics.plasm-phCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Until now, quasi-isodynamic MAGNETic fields have been the only known stellarator configurations that, at low collisionality, give small radial neoclassical transport and zero bootstrap current for arbitrary plasma profiles, the latter facilitating control of the MAGNETic configuration. The recently introduced notion of piecewise omnigenous fields has enormously broadened the space of stellarator configurations with small radial neoclassical transport. In this Letter, the existence of piecewise omnigenous fields that give zero bootstrap current is proven analytically and confirmed numerically. These results establish piecewise omnigenity as an alternative approach to stellarator reactor design.
[abstract 35 / 50] (score: 2) - Title: Disruptions of stars and binary systems on chaotic orbits in an axisymmetric Milky Way centerAuthors: Zephyr Penoyre, Elena Maria Rossi, Nicholas C. Stone,Comments: 27 pages, 20 figures, 1 appendixSubjects: astro-ph.GA astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Non-spherical potentials allow a wide range of trajectories, both regular and chaotic, whose periapse distances can vary orbit to orbit. In particular chaotic trajectories can bring a system arbitrarily close to the central massive BLACK HOLE leading to a disruption. In this paper, we work with an observationally benchmarked model of the innermost 200 pc of the Milky Way and show that low z-angular momentum trajectories are commonly chaotic. We compute the timescales and properties of close pericenter passages, and compare the implied collisionless disruption rate to the well-studied collisional rate from 2-body scatterings. We find that the relative collisionless rate can dominate by orders of magnitude. Our calculations are relevant for a wide range of disruption phenomena, including the production of hypervelocity stars (HVSs) and tidal disruption events (TDEs). Most of these disruptions involve stars come from the Nuclear Stellar Cluster, with a pericenter distribution that strongly favours shallow encounters, and a preference for high inclination interactions. The latter implies that unbound disrupted material - whether ejected stars or stellar debris - would be preferentially directed towards the galactic poles. Many of our conclusions apply generally to any galaxy with a non-spherical galactic centre potential and central massive BLACK HOLE.
[abstract 36 / 50] (score: 2) - Title: X-ray reflection spectroscopy with improved calculations of the emission angleAuthors: Yimin Huang, Honghui Liu, Temurbek Mirzaev, Ningyue Fan, Cosimo Bambi, Zuobin Zhang, Thomas Dauser, Javier A. Garcia, Adam Ingram, Jiachen Jiang, Guglielmo Mastroserio, Shafqat Riaz, Swarnim Shashank,Comments: 13 pages, 5 figures. v2: refereed version. Accepted for publication in ApJSubjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
The reflection spectrum produced by a cold medium illuminated by X-ray photons is not isotropic and its shape depends on the emission angle. In the reflection spectrum of an accretion disk of a BLACK HOLE, the value of the emission angle changes over the disk and, in general, is different from the value of the inclination angle of the disk because of the light bending in the strong gravitational field of the BLACK HOLE. Current reflection models make some approximations, as calculating a reflection spectrum taking the correct emission angle at every point of the disk into account would be too time-consuming and make the model too slow to analyze observations. In a recent paper, we showed that these approximations are unsuitable to fit high-quality BLACK HOLE spectra expected from the next generation of X-ray missions. Here, we present a reflection model with improved calculations of the emission angle that solves this problem.
[abstract 37 / 50] (score: 2) - Title: Magnetic fields in the intracluster medium with TNG-Cluster: properties, morphology, and tangential anisotropyAuthors: Katrin Lehle, Mateusz Ruszkowski, Dylan Nelson, Marine Prunier, Annalisa Pillepich,Comments: submitted to A&ASubjects: astro-ph.GA astro-ph.COCreated: 2025-07-16; Updated: 2025-07-18; Datestamp: 2025-07-18
We characterize the MAGNETic field properties of 352 massive galaxy clusters from the TNG-Cluster MAGNETohydrodynamical cosmological simulation with a focus on central MAGNETic field morphology in cool-core (CC) vs non-cool-core (NCC) clusters. We present the central values and radial profiles of MAGNETic field strength and plasma parameter as a function of mass, cooling status and redshift. Compared to low-redshift observations, TNG-Cluster produces reasonable MAGNETic field amplitudes in the central regions of clusters spanning a range of 1-200 muG. We then discuss the main finding of this work: z=0 cool-core clusters have preferentially tangential MAGNETic fields at a characteristic scale of ~ 0.1 r500c. These strongly tangential field orientations are specific to CCs. In contrast, across the full cluster population, MAGNETic fields show isotropic configurations at all radii and redshifts. As individual halos grow, the evolution of their MAGNETic field topologies is diverse: tangential features can be short-lived, persist over large cosmological time-scales, or periodically appear, vanish, and reappear towards z=0. We discuss the underlying physics and possible physical scenarios to explain the origin of these structures. We argue that both AGN feedback-driven outflows, and merger-driven sloshing motions, cannot explain the population-wide tangential bias in MAGNETic field orientation. Instead, we propose that the trapping of internal gravity waves is responsible for the tangentially biased MAGNETic field topologies that we find in cool-core TNG-Cluster halos, due to the strong entropy gradient in these clusters.
[abstract 38 / 50] (score: 2) - Title: MUSEing on the host galaxies of Tidal Disruption EventsAuthors: M. Pursiainen, G. Leloudas, J. Lyman, C. M. Byrne, P. Charalampopoulos, S. Kim, S. Schulze, J. P. Anderson, F. E. Bauer, L. Dai, L. Galbany, H. Kuncarayakti, M. Nicholl, T. Pessi, J. L. Prieto, S. F. Sanchez,Comments: Submitted to MNRAS on 16th of July 2025Subjects: astro-ph.HE astro-ph.GACreated: 2025-07-16; Updated: 2025-07-18; Datestamp: 2025-07-18
We present an analysis of twenty tidal disruption event (TDE) host galaxies observed with the MUSE integral-field spectrograph on ESO VLT. We investigate the presence of extended emission line regions (EELRs) and study stellar populations mostly at sub-kpc scale around the host nuclei. EELRs are detected in 5/20 hosts, including two unreported systems. All EELRs are found at z<0.045, suggesting a distance bias and faint EELRs may be missed at higher redshift. EELRs only appear in post-merger systems and all such hosts at z<0.045 show them. Thus, we conclude that TDEs and galaxy mergers have a strong relation, and >45% of post-merger hosts in the sample exhibit EELRs. Furthermore, we constrained the distributions of stellar masses near the central BLACK HOLEs (BHs), using the spectral synthesis code Starlight and BPASS stellar evolution models. The youngest nuclear populations have typical ages of 1 Gyr and stellar masses below 2.5MSun. The populations that can produce observable TDEs around non-rotating BHs are dominated by subsolar-mass stars. 3/4 TDEs requiring larger stellar masses exhibit multi-peaked light curves, possibly implying relation to repeated partial disruptions of high-mass stars. The found distributions are in tension with the masses of the stars derived using light curve models. Mass segregation of the disrupted stars can enhance the rate of TDEs from supersolar-mass stars but our study implies that low-mass TDEs should still be abundant and even dominate the distribution, unless there is a mechanism that prohibits low-mass TDEs or their detection.
[abstract 39 / 50] (score: 2) - Title: BASS LIII: The Eddington Ratio as the Primary Regulator of the Fraction of X-ray Emission in Active Galactic NucleiAuthors: Kriti Kamal Gupta, Claudio Ricci, Alessia Tortosa, Matthew J. Temple, Michael J. Koss, Benny Trakhtenbrot, Franz E. Bauer, Ezequiel Treister, Richard Mushotzky, Elias Kammoun, Iossif Papadakis, Kyuseok Oh, Alejandra Rojas, Chin-Shin Chang, Yaherlyn Diaz, Arghajit Jana, Darshan Kakkad, Ignacio del Moral-Castro, Alessandro Peca, Meredith C. Powell, Daniel Stern, C. Megan Urry, Fiona Harrison,Comments: 13 pages, 4 figures. Accepted for publication in ApJSubjects: astro-ph.GA astro-ph.HECreated: 2025-07-16; Updated: 2025-07-18; Datestamp: 2025-07-18
Active galactic nuclei (AGN) emit radiation via accretion across the entire energy spectrum. While the standard disk and corona model can somewhat describe this emission, it fails to predict specific features such as the soft X-ray excess, the short-term optical/UV variability, and the observed UV/X-ray correlation in AGN. In this context, the fraction of AGN emission in different bands (i.e., bolometric corrections) can be useful to better understand the accretion physics of AGN. Past studies have shown that the X-ray bolometric corrections are strongly dependent on the physical properties of AGN, such as their luminosities and Eddington ratios. However, since these two parameters depend on each other, it has been unclear which is the main driver of the X-ray bolometric corrections. We present here results from a large study of hard X-ray-selected (14-195 keV) nearby ($z<0.1$) AGN. Based on our systematic analysis of the simultaneous optical-to-X-ray spectral energy distributions of 236 unobscured AGN, we found that the primary parameter controlling the X-ray bolometric corrections is the Eddington ratio. Our results show that while the X-ray bolometric correction increases with the bolometric luminosity for sources with intermediate Eddington ratios ($0.01-1$), this dependence vanishes for sources with lower Eddington ratios ($<0.01$). This could be used as evidence for a change in the accretion physics of AGN at low Eddington ratios.
[abstract 40 / 50] (score: 2) - Title: MESA-QUEST: Modeling Quasi-Stars in MESAAuthors: Claire B. Campbell, Andrew D. Santarelli, Matthew E. Caplan,Comments: 2 pages, 1 figure, MESA template can be found in the ancillary files as well as the GitHub link within the paperSubjects: astro-ph.HECreated: 2025-07-16; Updated: 2025-07-18; Datestamp: 2025-07-18
Supermassive BLACK HOLE formation remains an unsolved problem. Quasi-stars have been suggested as a viable heavy-seeding mechanism. In this work, we implement methods for modeling quasi-stars previously used with the Cambridge STARS code into the 1D stellar evolution code MESA. The computational capabilities of MESA allow for more detailed simulations of quasi-star evolution due to its modularity and the ease of implementing of new physical processes and controls. Our implementation, the MESA Quasi-star Evolutionary Simulation Toolkit (MESA-QUEST), is available in a publicly accessible repository.
[abstract 41 / 50] (score: 2) - Title: Chaos of charged particles in quadrupole MAGNETic fields under Schwarzschild backgroundsAuthors: Qihan Zhang, Xin Wu,Comments:Subjects: gr-qc astro-ph.GACreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
A four-vector potential of an external test electroMAGNETic field in a Schwarzschild background is described in terms of a combination of dipole and quadrupole MAGNETic fields. This combination is an interior solution of the source-free Maxwell equations. Such external test MAGNETic fields cause the dynamics of charged particles around the BLACK HOLE to be nonintegrable, and are mainly responsible for chaotic dynamics of charged particles. In addition to the external MAGNETic fields, some circumstances should be required for the onset of chaos. The effect of the MAGNETic fields on chaos is shown clearly through an explicit symplectic integrator and a fast Lyapunov indicator. The inclusion of the quadrupole MAGNETic fields easily induces chaos, compared with that of the dipole MAGNETic fields. This result is because the Lorentz forces from the quadrupole MAGNETic fields are larger than those from the dipole MAGNETic fields. In addition, the Lorentz forces act as attractive forces, which are helpful to bring the occurrence of chaos in the nonintegrable case.
[abstract 42 / 50] (score: 2) - Title: Einstein Probe Discovery of EP J182730.0-095633: A New Black Hole X-ray Binary Candidate in Faint Outburst?Authors: Huaqing Cheng, Qingchang Zhao, L. Tao, H. Feng, F. Coti Zelati, H. W. Pan, A. L. Wang, Y. N. Wang, M. Y. Ge, A. Rau, A. Marino, L. Zhang, W. J. Zhang, F. Carotenuto, L. Ji, C. C. Jin, D. Y. Li, B. F. Liu, Y. Liu, E. L. Qiao, N. Rea, R. Soria, S. Wang, Z. Yan, W. Yuan, B. Zhang, G. B. Zhang, S. N. Zhang, W. D. Zhang, A. Beardmore, J. S. Bright, X. L. Chen, Z. Fan, S. Y. Fu, J. P. U. Fynbo, J. W. Hu, J. J. Jin, P. G. Jonker, A. K. H. Kong, E. Kuulkers, C. K. Li, H. L. Li, Z. K. Lin, C. X. Liu, H. -Y. Liu, J. Z. Liu, X. W. Liu, Z. Lu, C. Maitra, H. Y. Mu, C. -Y. Ng, Y. L. Qiu, S. Tinyanont, Y. Wang, S. X. Wen, S. S. Weng, Jianfeng Wu, D. Xu, Y. K. Yan, Z. Yan, Y. -P. Yang, P. Zhang, S. Zhang, Q. Zhao, Z. M. Cai, Y. Chen, Y. F. Chen, C. Z. Cui, W. W. Cui, H. B. Hu, M. H. Huang, S. M. Jia, G. Jin, Z. X. Ling, H. Q. Liu, S. L. Sun, X. J. Sun, Y. F. Xu, C. Zhang, M. Zhang, Y. H. Zhang,Comments: 22 pages, 5 figures (plus 3 in appendix), 3 tables in appendix. Accepted for publication in ApJ LettersSubjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Black hole X-ray binaries (candidates) currently identified in our galaxy are mainly transient sources, with the majority discovered through the detection of their X-ray outbursts. Among these, only four were found during faint outbursts exhibiting peak X-ray luminosities $L_{\rm X}\lesssim10^{36}~{\rm erg~s^{-1}}$, likely due to the previous lack of sensitive, wide-field monitoring instruments in the X-ray band. In this Letter, we present the discovery of an intriguing X-ray transient, EP J182730.0-095633, via the Einstein Probe (EP) and subsequent multi-wavelength follow-up studies. This transient, located on the Galactic plane, experienced a faint and brief X-ray outburst lasting about 20 days. Its X-ray spectrum is non-thermal and consistent with a power-law model with a nearly constant photon index of $Γ\sim2$ throughout the outburst. A long-lasting millihertz quasi-periodic oscillation (QPO) signal was detected in its X-ray light curve, centered around a frequency of $\sim0.04$ Hz. A transient near-infrared source was identified as its counterpart, although no optical emission was detectable, likely due to significant extinction. A radio counterpart was also observed, displaying an inverted radio spectrum with $α\sim0.45$. The X-ray spectral and temporal characteristics, along with the multi-wavelength properties, indicate that the source is a faint low-mass X-ray binary, with the compact object likely being a BLACK HOLE. This work demonstrates the potential of the EP in discovering new X-ray binaries by capturing faint-level X-ray outbursts.
[abstract 43 / 50] (score: 2) - Title: ALMA discovery of Punctum -- a highly polarized mm source in nuclear starburst galaxy NGC 4945Authors: E. Shablovinskaia, C. Ricci, C-S. Chang, R. Paladino, Y. Diaz, D. Belfiori, S. Aalto, M. Koss, T. Kawamuro, E. Lopez-Rodriguez, R. Mushotzky, G. C. Privon,Comments: Accepted to A&ASubjects: astro-ph.HE astro-ph.GACreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
We report the discovery of a highly polarized millimeter (mm) continuum source in the central region of NGC 4945, identified through ALMA Band 3 observations. This starburst Seyfert 2 galaxy contains numerous compact mm sources, yet only one - located approximately 3.4" (~60 pc) from the galactic center and unresolved with ~0.1" resolution - exhibits an unusually high POLARIZATION degree of 50% $\pm$ 14%, likely originating from non-thermal SYNCHROTRON radiation. The source is faint, yet clearly detected in two separate epochs of observation taken 14 days apart, with flux of 0.104 $\pm$ 0.018 and 0.125 $\pm$ 0.016 mJy, as well as in earlier ALMA observations, showing no variability at any timescale. The spectral index remains stable within large uncertainties, -1.8 $\pm$ 2.5 and -1.3 $\pm$ 2.5. The source, which we further refer to as Punctum due to its compactness, revealed no clear counterparts in existing X-ray or radio observations. Assuming association with the central region of NGC 4945, we estimate upper limits for its luminosity of ~1 $\times$ 10$^{37}$ erg s$^{-1}$ in the 3-6 keV X-ray band (from archival Chandra data) and ~5 $\times$ 10$^{35}$ erg s$^{-1}$ at 23 GHz (from archival ATCA data). A comparison of the radio, mm (including POLARIZATION), and X-ray properties with known astrophysical sources emitting SYNCHROTRON radiation, such as accreting neutron stars, SUPERNOVA remnants, and non-thermal galactic filaments, revealed no clear match in any of these scenarios. The exact nature of this highly polarized source remains undetermined.
[abstract 44 / 50] (score: 2) - Title: Rare events algorithm study of extreme double JET summers and their connection to heatwaves over EurasiaAuthors: Valeria Mascolo, Francesco Ragone, Nili Harnik, Freddy Bouchet,Comments:Subjects: physics.ao-phCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Several large scale circulation patterns have been identified in relation to extreme Northern Hemisphere summer heatwaves. Three main ones are a double JET over Eurasia, a positive phase of the summer northern annular mode, and a quasi-wave-3 geopotential height anomaly. While there is some evidence suggesting these patterns are related to each other, the explicit nature of their relation, as well as the explicit mechanisms by which they are related to extreme heatwaves is still not known. The double JET structure has gained attention recently due to evidence that its persistence has been increasing, possibly explaining the rise in the number of extreme heatwaves over Europe. In this paper we study the occurrence and persistence of double JET states in ERA5 and in stationary simulations with the CESM1.2 model, using an index which measures the degree of JET separation. Additionally, we perform simulations with CESM1.2 coupled to a rare event algorithm in order to improve the statistics of rare summer-long double JET states. We find that extreme double JET states are characterised by three centers of extreme high surface temperature and 500hPa geopotential height anomalies, alongside a strong low pressure over the Arctic. The geopotential height anomaly pattern is consistent with both a positive Northern Annular Mode (NAM) and quasi-wave-3 patterns found in the literature. Moreover, we find a large percentage of co-occurrence of heatwaves at these centers, and a double JET state, with the percentage increasing with the duration of the double JET state.
[abstract 45 / 50] (score: 2) - Title: Introduction to Stability and Turbulent Transport in Magnetic Confinement Fusion PlasmasAuthors: J. F. Parisi,Comments: 93 pages, 18 figuresSubjects: physics.plasm-phCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
This tutorial provides an accessible introduction to the principles of stability and turbulent transport in MAGNETic confinement fusion plasmas. Key concepts, models, and practical implications are discussed to guide researchers new to the field. Some challenges and opportunities are discussed.
[abstract 46 / 50] (score: 2) - Title: Probing the Schwarzschild BLACK HOLE immersed in a DARK MATTER halo through astrophysical testsAuthors: Tursunali Xamidov, Sanjar Shaymatov, Qiang Wu, Tao Zhu,Comments: 10 pages, 4 captioned figures, 3 captioned tablesSubjects: gr-qcCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
We investigate a recently derived Schwarzschild-like BLACK HOLE (BH) immersed in a Dehnen-type $(α,β,γ)=(1,4,5/2)$ DARK MATTER (DM) halo. We obtain constraints on the two model parameters, i.e., the halo core radius $r_s$ and the DM density parameter $ρ_s$ in both the weak and the strong field regimes. In the weak field, we model test particle geodesics and match the predicted perihelion shift to Mercury (Solar System) and the orbit of the S2 star data, obtaining upper limits on $r_s$ and $ρ_s$. In the strong field, we analyse twin high frequency quasiperiodic oscillations (QPOs) from four microQUASARs (e.g., GRO J1655-40, GRS 1915+105, XTE J1859+226, and XTE J1550-564). Because QPO frequencies depend only on the local spacetime curvature, they can serve as a probe of halo-induced deviations from general relativity. Our MCMC analysis produces posterior distributions for model parameters, revealing close agreement between the theoretical QPO frequencies and the observations for GRS 1915+105 and GRO J1655-40. The same analysis also yielded best-fit values and upper bounds for each parameter. Our combined geodesic and QPO analysis demonstrates that timelike orbits and epicyclic oscillations can act as sensitive probes of DM halos around BHs, offering a pathway to distinguish Dehnen-type profiles from alternative DM distributions in future analysis and observations.
[abstract 47 / 50] (score: 2) - Title: Reconstructing Air-Shower Observables using a Universality-Based Model at the Pierre Auger ObservatoryAuthors: Maximilian Stadelmaier,Comments: Presented at the 39th International Cosmic Ray Conference (ICRC 2025), 8 pages, 6 figuresSubjects: astro-ph.HE hep-phCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Based on solutions of the cascade equations, the air-shower universality is a framework that for all air showers with the same energy, zenith angle, depth of shower maximum, and muon number predicts the same longitudinal, lateral, and energy distributions of electroMAGNETic shower particles. We employ a universality-based model of shower development that incorporates hadronic particle components to reconstruct observables from extensive air showers produced by ultra-high-energy COSMIC RAYs. The model can estimate key parameters, such as the depth of the shower maximum and the number of muons at the event level. We discuss the performance of the reconstruction algorithm using both air-shower simulations, and preliminary results obtained from the Phase-I data of the Pierre Auger Observatory.
[abstract 48 / 50] (score: 2) - Title: Evidence for an Inverse Cascade of Magnetic Helicity in the Inner HeliosphereAuthors: Masatomi Iizawa, Yasuhito Narita, Tommaso Alberti, Stuart D. Bale, Axel Brandenburg, Abraham C. -L. Chian, Horia Comişel, Shuichi Matsukiyo, Nobumitsu Yokoi,Comments: 6 pages, 3 figuresSubjects: astro-ph.SR physics.plasm-ph physics.space-phCreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
To elucidate the cascade direction of the solar wind turbulence, we analyzed MAGNETic helicity density spectra from the Parker Solar Probe data across more than 500 heliocentric distances. For the first time, we confirmed a persistent inverse cascade extending from the Sun to Mercury's orbital vicinity. This finding challenges the conventional hypothesis that the MAGNETic helicity density within the inner heliosphere is random. Furthermore, our analysis revealed a radial sign change of the spectral MAGNETic helicity density at a frequency whose value decreases logarithmically with distance. These results provide new insights into the evolution of solar wind turbulence in the inner heliosphere.
[abstract 49 / 50] (score: 2) - Title: Detection of low-luminosity X-ray pulsations from the accreting millisecond pulsar IGR J17511-3057: an ever-thinning thread between bright accretion and sub-luminous statesAuthors: Giulia Illiano, Alessandro Papitto, Sergio Campana, Alessio Marino, Arianna Miraval Zanon, Francesco Carotenuto, Francesco Coti Zelati, Maria Cristina Baglio, Filippo Ambrosino, Christian Malacaria, Caterina Ballocco, Gaurava K. Jaisawal, Marco M. Messa, Emilie Parent, Thomas D. Russell, Andrea Sanna, Anastasios Tzioumis,Comments: 11 pages, 5 figures. Submitted to A&ASubjects: astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
After nearly a decade in quiescence, the accreting millisecond pulsar IGR J17511$-$3057 displayed a new outburst on 2025 February 11, its third since discovery, following previous activity in 2009 and 2015. We report on an XMM-Newton Target of Opportunity observation performed on 2025 March 4, more than twenty days after the outburst onset. From the X-ray spectrum - well described by an absorbed Comptonization model - we estimated an unabsorbed 0.5$-$10 keV luminosity of $L_X \sim 7 \times 10^{33} \, \mathrm{erg \, s^{-1}}$ (assuming a source distance equal to the upper limit of $6.9$ kpc). To place this in context, we analyzed an archival Chandra observation performed in 2019, which yielded a quiescent luminosity of $L_\mathrm{X,q} \sim 2 \times 10^{32} \, \mathrm{erg \, s^{-1}}$ in the same energy band. Although this comparison indicates that the source was still well above its quiescent level during the XMM-Newton observation, the estimated low luminosity during the late stage of the 2025 outburst would typically place the source in the propeller regime. Nevertheless, we unexpectedly detected coherent X-ray pulsations with an amplitude peaking at $\sim$42% in the 0.3$-$3 keV band. We also observed a spectral softening compared to the early stages of the outburst. Finally, we report a 3$σ$ upper limit of 60 $μ$Jy beam$^{-1}$ on the source flux density at 5.5 GHz from ATCA observations acquired on 2025 April 12, following a decline of the accretion activity, as indicated by our analysis of NICER data from 2025 March 15, which revealed no significant X-ray pulsations at a luminosity level of $L_X \sim 1 \times 10^{34} \, \mathrm{erg \, s^{-1}}$. We discuss our findings in the context of other accreting millisecond pulsars and draw comparisons with transitional systems in the sub-luminous disk state.
[abstract 50 / 50] (score: 2) - Title: Where is the Supervirial Gas? III. Insights from X-ray Shadow Observations and a revised Model for the Soft Diffuse X-ray BackgroundAuthors: Anjali Gupta, Smita Mathur, Joshua Kingsbury, Esma Korkmaz, Sanskriti Das, Yair Krongold, Manami Roy, Armando Lara-DI,Comments: Accepted for Publication in ApJSubjects: astro-ph.GA astro-ph.HECreated: 2025-07-17; Updated: 2025-07-18; Datestamp: 2025-07-18
Shadow observations provide a powerful tool to separate foreground components of the soft diffuse X-ray background (SDXB) from the background components. Such observations have now established that the ``local'' foreground is made of the solar wind charge exchange and the local bubble, and the background emission is from the extended circumgalactic medium (CGM) of the Milky Way and from the unresolved extragalactic sources. New data and careful analyses of the SDXB led to two new discoveries in recent years: (1) excess emission near 0.5 keV that is identified as the NVII emission line, and (2) excess emission near 0.8-1.0 keV that is identified with an additional, super-virial temperature hot thermal component of the CGM. The goal of this paper is to use SUZAKU shadow observations along six sightlines to determine whether either of these components is from the ``local'' sources. We eliminate the ambiguity regarding the origin of NVII emission, ruling out the local origin. We confirm that the Milky Way CGM contains nitrogen-rich plasma, with a super-solar average (N/O) of 2.6+-0.5, and suggest that nitrogen-enhanced plasma is widespread throughout the CGM. We find super-solar Ne abundance in two sighlines, also from the CGM. Similarly, we rule out the local origin of the hot thermal component and confirm that it is present beyond the shadowing clouds. Furthermore, we provide a revised model of the soft diffuse X-ray background, which is crucial for extragalactic astronomy.
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