Current date: 2026-07-14
Setting default datestamp limit: 0
Datestamp limit: 2026-07-14 (0 days ago)
Created/updated limit: 2026-07-07 (7 days ago)
Found keywords_cs.datFound keywords_cis.dat
Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics
Setting default set: physics
OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-07-14&until=2026-07-14&set=physics&metadataPrefix=arXiv
Scoring abstracts
Number of records retrieved: 1194
Keyword score statistics
score 11 -- 1 abstracts
score 10 -- 1 abstracts
score 7 -- 2 abstracts
score 6 -- 4 abstracts
score 5 -- 5 abstracts
score 4 -- 3 abstracts
score 3 -- 15 abstracts
score 2 -- 34 abstracts
in total -- 65 abstracts
Articles that appeared on 2026-07-14
-
[abstract 1 / 65] Wow! (score: 11)
- Title: FERMI-Large Area Telescope Detection of Very High Energy (>100 GeV) Emission from Compton-Dominated BlazarsAuthors: P N Naseef Mohammed, Vaidehi S. Paliya, C D Ravikumar,Comments:Subjects: astro-ph.HECreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
The observation of broad emission lines in the optical spectra of flat-spectrum radio QUASARs (FSRQs) suggests radiatively efficient accretion powering these objects. In such broad emission line BLAZARs, the intense broad-line region (BLR) radiation can provide seed photons for inverse Compton scattering, leading to a Compton-dominated spectral energy distribution. Interestingly, the same BLR photon field can also absorb very high-energy (VHE; E>100 GeV) $γ$-ray radiation, thus explaining the paucity of VHE-detected FSRQs. Here we report the results of a systematic search to identify VHE-emitting sources in a sample of 626 Compton-dominated BLAZARs (Compton dominance > 1), using $\sim$17.5 years of FERMI-Large Area Telescope observations. We identified 14 BLAZARs at greater than 4$σ$ confidence level, including 4 sources detected in the VHE band at high significance (> 5$σ$) for the first time. We also found 21 objects from which at least one VHE photon was detected, thus substantially expanding the known VHE FSRQ population. Investigating the temporal coincidence of the VHE photons with the $γ$-ray activity, we noticed the VHE emission to be detected during flaring as well as low JET activity epochs. By estimating the optical depth for the $γ$$γ$ absorption due to the BLR photon field, we constrained the VHE-emitting region to be located outside BLR (>1.1-1.4$\times$ BLR radius). We conclude that multi-wavelength followup observations of these enigmatic VHE-detected broad line BLAZARs will permit us to constrain the radiative processes responsible for the GeV-TeV emission, and will set the benchmark for their observations with the upcoming Cherenkov Telescope Array Observatory.
[abstract 2 / 65] Wow! (score: 10) - Title: Probing radiation micro-physics in M 87 I. Total intensity and broad-band spectraAuthors: Christian M. Fromm, Yosuke Mizuno, Ziri Younsi, Ainara Saiz-Perez, Hector Olivares, Antonios Nathanail, Alejandro Cruz-Osorio, Matthias Kadler, Karl Mannheim,Comments: 15 pages; 15 figures; submitted to A&ASubjects: astro-ph.HE astro-ph.GACreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Next generation Very Long Baseline Interferometers (VLBI) will provide dense sampling of the Fourier space together with high signal to noise ratios allowing to reliably observe and image faint JET structure in M 87 at mm-wavelength. The proposed next generation Event Horizon Telescope (ngEHT) and next generation Very Large Array (ngVLA) offers the unique capability to simultaneously resolve and image the accretion flow around the supermassive BLACK HOLE in M 87 together with the JET launching and acceleration zone. In order to explore these capabilities and to provide theoretical expectations we perform general RELATIVISTIC MAGNETohydrodynamic simulations of accretion on to BLACK HOLEs and JET launching. M 87 has been the target for multiple observations across the entire electroMAGNETic spectrum. Among these VLBI observations provide unique capability to resolve the JET structure down to several gravitational radii. In this work we provide possible observable signatures which will allow us to distinguish between different electron heating models and particle distributions. We use general RELATIVISTIC MAGNETohydrodynamics and simulate the accretion of the MAGNETised plasma onto Kerr-BLACK HOLEs in 3D. The multi-frequency radiative signatures of these simulations are computed taking different electron heating and distribution functions into account. The results of our simulations show that with a dynamical range of $1\times 10^4$ and a frequency range from 86 GHz to 345 GHz observations with future VLBI arrays have the potential to tell turbulent and MAGNETic RECONNECTion electron heating and the electron distribution function apart.
[abstract 3 / 65] Wow! (score: 7) - Title: Late-time X-ray afterglows of GRBs: Implications for particle acceleration at RELATIVISTIC shocksAuthors: Zhi-Qiu Huang, Om Sharan Salafia, Lara Nava, Annalisa Celotti, Giancarlo Ghirlanda,Comments: accepted by A&ASubjects: astro-ph.HECreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
Particle-in-cell (PIC) numerical simulations are currently among the most advanced tools to investigate particle acceleration at RELATIVISTIC shocks. Still, they come with limitations imposed by finite computing power, whose impact is not straightforward to evaluate a priori. Observational features are hence required as verification. energy electrons accelerated at external shocks, provides a testbed for such predictions. Current numerical studies suggest that in GRB afterglows the maximum SYNCHROTRON photon energy, which corresponds to the limit of electron acceleration, may fall within the $\sim$ 0.1--10 keV X-ray energy band at late times, $t\gtrsim 10^6 - 10^7$ s. To test this prediction, we analyzed the X-ray spectra of six GRBs with \emph{SWIFT}/XRT detections beyond $10^7$ s: our analysis reveals no clear evidence of a spectral cutoff. Using a model that accounts for the effect of the finite opening angle of the shock on the observed maximum SYNCHROTRON photon energy, we show that these observations are incompatible with PIC simulation predictions, unless one or more physical afterglow parameters attain values at odds with those typically inferred from afterglow modeling (small radiative efficiency, low ambient density, large equipartition fraction $ε_{\rm B}$ of the MAGNETic field). These findings challenge existing numerical simulation results and imply a more efficient acceleration of electrons to high-energies than seen in PIC simulations, with important implications for our understanding of particle acceleration in RELATIVISTIC shocks.
[abstract 4 / 65] Wow! (score: 7) - Title: Extending the infrastructure of the BAM code towards resistive general-RELATIVISTIC MAGNETohydrodynamics: tests and first applicationsAuthors: Matthew Beaudoin, Maximilano Ujevic, Ramon Jaeger, Anna Neuweiler, Henrique Gieg, Kenta Kiuchi, Tim Dietrich,Comments: 27 pages, 28 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Many astrophysical phenomena, including pulsars and short GAMMA-RAY BURSTs, are associated with the extremely strong MAGNETic fields present in neutron stars and neutron star mergers. While the ideal MAGNETohydrodynamic approximation, which assumes infinite conductivity, provides an excellent description of the neutron-star interior, it cannot capture non-ideal processes such as Ohmic dissipation and MAGNETic RECONNECTion. To overcome this limitation, we present an extension of the numerical-relativity code BAM incorporating a resistive general-RELATIVISTIC MAGNETohydrodynamic (GRMHD) description. We validate the new implementation through an extensive suite of special-RELATIVISTIC MAGNETohydrodynamic benchmark tests and by performing stable simulations of isolated and binary neutron star systems. For the latter, we investigate the impact of finite conductivity on MAGNETic-field amplification, mass ejection, and non-ideal GRMHD effects. In particular, we find that the component of the electric field parallel to the MAGNETic field, which is zero in the ideal case, can reach up to 10% of the total electric field strength. This highlights the potential importance of non-ideal effects for accurately modeling the long-term evolution of post-merger remnants, particularly in low-density regions. Although the present study is restricted to simplified piecewise-polytropic equations of state, it demonstrates the capabilities of the new resistive GRMHD framework and paves the way for future investigations employing more realistic microphysics.
[abstract 5 / 65] Yes (score: 6) - Title: SuperMIGHTEE : Spectral Ages of Remnant Radio Galaxy Candidates in the XMM-LSS FieldAuthors: Sushant Dutta, Veeresh Singh, C. H. Ishwara Chandra, Yogesh Wadadekar, Russ Taylor, Mattia Vaccari, Lucia Marchetti, Matt Jarvis, Catherine Hale, Solohery Randriamampandry, Zara Randriamanakoto,Comments: 17 pages, 8 figures, Accepted for publication in MNRASSubjects: astro-ph.GACreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
Remnant RADIO GALAXies, whose lobes are no longer replenished by JETs from the ACTIVE GALACTIC NUCLEus (AGN), offer key constraints on AGN duty cycles and the timescales of radio JETs. We present a spectral-ageing study of 14 candidate remnant RADIO GALAXies in the XMM-LSS field, combining new broad-band data from the MeerKAT MIGHTEE (L-band) and uGMRT superMIGHTEE (band-3 and band-4) surveys with complementary observations from LOFAR, GMRT, and JVLA, covering 144 MHz-1.5 GHz. Spectral modeling confirms 12 sources as genuine remnants, while two are reclassified as active, emphasising the importance of sensitive, multi-frequency coverage for robust remnant identification. Pixel-based spectral age maps yield results (~3-43 Myr) broadly consistent with integrated estimates, revealing relatively short spectral ages (~8-42 Myr). These ages likely reflect enhanced inverse-Compton losses at higher redshifts (0.35 < z < 2.85; median z = 1.25) and possible rapid lobe expansion in low-density environments. The ratios of remnant to total source ages (t_OFF}/t_s) span 0.04-0.83, indicating that the sample traces a broad range of evolutionary stages. Our findings reveal a previously underrepresented population of faint, rapidly fading remnants, suggesting that the remnant phase may be shorter and more dynamic than previously thought. This study highlights the crucial role of MIGHTEE and superMIGHTEE surveys in reliably classifying genuine remnants and provides a framework for constraining AGN life cycles in preparation for forthcoming SKA surveys.
[abstract 6 / 65] Yes (score: 6) - Title: Intrinsic Spectral Curvature from Finite-Cycle Transport at Relativistic ShocksAuthors: Ji-Hoon Ha,Comments: 16 pages, 5 figures, Accepted for publication in Physica ScriptaSubjects: astro-ph.HE physics.plasm-phCreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
Power-law spectra are a central prediction of shock acceleration and are commonly associated with asymptotic scale invariance under diffusive transport. In finite RELATIVISTIC shocks, strong anisotropy and limited residence times may restrict the number of effective shock crossings before the many-cycle diffusive limit is established. This work develops a reduced finite-cycle framework in which particle energization is described by discrete shock-crossing mappings, while downstream transport is encoded through an energy-dependent return probability. In this formulation, the local spectrum is controlled by the competition between the mean energy gain per cycle and the probability of surviving to the next cycle. A systematic decrease of the return probability with energy then produces intrinsic spectral curvature as a consequence of transport-limited cycle survival. The energy dependence of the return probability is estimated from the competition between MAGNETic deflection, downstream advection, and finite shock lifetime, yielding a characteristic steepening scale determined by macroscopic source parameters. For fiducial parameters relevant to compact BLAZAR emission regions, the steepening scale lies below the ultimate acceleration cutoff, so that curvature can appear before the terminal maximum energy is reached. These results point to a pre-asymptotic finite-cycle limit of RELATIVISTIC shock transport in which non-power-law spectra can arise from the limited survival of repeated shock-crossing cycles.
[abstract 7 / 65] Yes (score: 6) - Title: Gaussian-process evidence for a stochastic-variability transition in the recovering corona of 1ES 1927+654Authors: Lijuan Dong, Dahai Yan,Comments: 12 pages, 4 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
We investigate the stochastic X-ray variability of the changing-look ACTIVE GALACTIC NUCLEus 1ES 1927+654 during its 2018--2024 evolution, focusing on the recovery of the X-ray corona after its 2018 collapse. Using XMM-Newton EPIC-pn light curves in the 0.3--2.0 keV and 2.0--10.0 keV bands, we model the variability with Gaussian process (GP) covariance components including Matérn-3/2, damped-random-walk (DRW), stochastically driven damped simple-harmonic-oscillator (SHO), and white-noise terms. Bayesian model comparison reveals an X-ray stochastic-variability transition during the changing-look recovery phase. In the 2019 May 5 observation, the preferred covariance changes from a Matérn-3/2-like state to a DRW-like state within a single continuous exposure. A phenomenological gated-kernel estimate localizes this transition sharply in the hard band at $t_c\simeq23.5~{\rm ks}$, while the soft band shows the same qualitative change over a broader interval. This transition occurs after the X-ray corona had reappeared but before the later pronounced hardening and brightening of the coronal emission, suggesting an early timing-domain signature of disk--corona reconfiguration. Phenomenologically, the dominant variability evolves from a smoother, finite-memory correlated process to a rougher, shorter-memory red-noise process. In the later 2022--2024 observations, SHO-like components associated with the known millihertz QPO show increasing characteristic frequency and quality factor, indicating a faster and more coherent oscillatory component during the QPO-plus-JET phase. GP-based time-domain inference therefore provides a sensitive probe of stochastic-variability changes in recovering AGN coronae.
[abstract 8 / 65] Yes (score: 6) - Title: Magnetically Arrested Discs Powering Jets in a Large Sample of Low-Accretion FR I Radio GalaxiesAuthors: Huibo Fei, Han He, Bei You, MinFeng Gu, Liang Chen, Xuheng Ding, Leyi Wang,Comments:Subjects: astro-ph.GACreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
We study a sample of 289 Fanaroff-Riley type I (FR I) RADIO GALAXies selected from the LOFAR Two-Metre Sky Survey (LoTSS) DR1, identified by their edge-darkened radio morphologies. Using Sloan Digital Sky Survey (SDSS) DR17 optical photometry and spectroscopy, we derive Eddington-scaled accretion rates spanning -6.84 < log $\dot{m}$ < -0.87 (median $\approx$ -2.84). The vast majority of sources lie below $\dot{m}$ = 0.01, indicating that their central engines are well described by advection-dominated accretion flows (ADAFs). However, even for a rapidly spinning BLACK HOLE with a = 0.95, the maximum JET power predicted by the Blandford-Znajek mechanism in the standard ADAF regime is lower than the observed JET power (estimated from 151 MHz radio luminosity) for approximately 70% of the sample. We demonstrate that the MAGNETically arrested disc (MAD) scenario, in which large-scale poloidal MAGNETic flux accumulates near the event horizon, can fully account for the powerful JETs observed in these low-accretion systems. Within the MAD framework, the data are consistent with slow-spinning BLACK HOLEs with $a < 0.5$. This large, uniformly selected LoTSS sample extends the MAD requirement previously established for the bright 3CR FR I population, indicating that MAGNETically arrested discs are common in FR I RADIO GALAXies across a wide range of luminosities.
[abstract 9 / 65] Yes (score: 5) - Title: Active Galactic Nuclei as high-energy neutrino sourcesAuthors: Filippo D'Ammando,Comments: Invited review article for The Astronomy and Astrophysics Review. Accepted for publication. 59 pages, 25 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-07-12; Updated: 2026-07-14; Datestamp: 2026-07-14
Identifying the sources of the high-energy astrophysical neutrinos has been one of the main topics in astrophysics since the first observation of high-energy neutrinos by the IceCube Neutrino Observatory. Active Galactic Nuclei (AGN) are sources of high-energy gamma-rays and are considered to be promising candidates to be sources of high-energy neutrinos and ultra-high energy COSMIC RAYs as well. However, several studies suggest that the neutrino emission from the $γ$-ray BLAZAR population only accounts for a small fraction of the total astrophysical neutrino flux. We present and discuss recent results on the search for correlations between astrophysical neutrinos and both gamma-ray and radio bright AGN. The IceCube Collaboration has reported high-energy neutrino events that may come from both the radio-loud AGN TXS 0506+056 and the radio-quiet AGN NGC 1068. Other cases of possible associations between high-energy neutrino events and individual BLAZARs were claimed with controversial results. We discuss the properties of these sources together with the different neutrino production mechanisms proposed for those sources. Finally, we outline future prospects in the field, focusing on remaining open questions, the development of upcoming neutrino facilities, and the evolving multi-frequency landscape within the multi-messenger era.
[abstract 10 / 65] Yes (score: 5) - Title: The Radio Properties of Extreme Coronal Line Emitters: Constraints on the Sub-parsec EnvironmentAuthors: Noah Franz, Kate D. Alexander, Collin T. Christy, Tanmoy Laskar, Stefanie Komossa, Enrico Ramirez-Ruiz, Jean Somalwar, Edo Berger, Ryan Chornock, Fabio De Colle, Gavin Farley, Megan Newsome, B. Ashley VanderLey,Comments: 24 pages, 5 figures. Submitted to ApJ. Comments welcomeSubjects: astro-ph.HE astro-ph.GACreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
A tiny fraction ($\ll1\%$) of galaxies display luminous, high-ionization metal emission lines, which may be persistent or variable. These extreme coronal lines (ECLs) are produced when soft X-ray photons intercept dense gas ($n\gtrsim10^{6-7}~{\rm cm^{-3}}$). The high X-ray flux required implicates intense nuclear activity, likely originating from tidal disruption events (TDEs) and ACTIVE GALACTIC NUCLEi (AGN). As ECLs are rarely seen even within these classes, their production may also require specific environmental conditions, but the details remain unclear (e.g., the geometry and volume filling factor of the ECL-producing gas). Here, we present the radio properties of a population of $27$ low-redshift ($z<0.3$) ECL emitting galaxies (ECLEs), providing a unique and previously unexplored probe of the properties of the circumnuclear medium (CNM; $\lesssim1$ pc from the BLACK HOLE) in these systems. We find that $\sim 50\%$ of ECLEs produce radio SYNCHROTRON emission with luminosity and evolution consistent with TDEs and/or AGN. Radio spectral modeling of four ECLEs reveals that the ECL-producing region is (1) clumpy with a low volume filling factor ($10^{-5}\lesssim f_{V}\lesssim10^{-2}$) and (2) likely distinct from the radio emitting region (implying, e.g., a clumpy toroidal geometry). For time-variable ECLEs, these are some of the first observational constraints on the CNM geometry in formerly quiescent galactic nuclei. The unique nature of ECLEs makes them an excellent high-energy laboratory to connect the physics of accretion, photoionization, and feedback in galactic nuclei, thus motivating continued multi-wavelength monitoring.
[abstract 11 / 65] Yes (score: 5) - Title: A spectacular multi-wavelength transient associated with an off-axis RELATIVISTIC JETAuthors: Delina Levine, Gregg Hallinan, Jean J. Somalwar, Dillon Z. Dong, Ehud Nakar, Kenta Hotokezaka, Vikram Ravi, Assaf Horesh, Jessie M. Miller, Casey Law, Steven T. Myers, Stella K. Ocker, Daniel D. Kelson,Comments: 57 pages, 10 figures, 3 tables. Submitted to Nature AstronomySubjects: astro-ph.HECreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
Many of the most luminous extragalactic transients originate from the accretion of material onto a BLACK HOLE (BH) via core-collapse, stellar mergers, or the tidal disruption of a star. Some produce energetic multi-wavelength emission, displaying short, blue optical flares and bright, long-lived radio afterglows. In rare cases, these have also launched powerful RELATIVISTIC JETs almost exclusively detected on-axis via high-energy emission. Here we report AT 2019ijn, a radio transient discovered in the Very Large Array Sky Survey, associated with a powerful RELATIVISTIC JET viewed off-axis and accompanied by a luminous ($νL_{ν, opt} \sim 10^{44}$ erg/s) optical transient. Originating from a star-forming dwarf galaxy at z = 0.273, AT 2019ijn's optical flare exhibited a fast rise ($t_{rise, rest} \sim 7$ d) and shallow decline ($t_{dec, rest} > 38$ d), followed a year later by an energetic ($E \sim 2\times10^{52}$ erg) radio counterpart persisting for $>6$ years. These combined properties are unprecedented and preclude known classes of stellar explosion powered by core-collapse. Instead, the implied accretion onto a BH and associated off-axis JET invokes an exotic BH-stellar merger or a JETted tidal disruption event (TDE) by a $10^4 - 10^6 M_\odot$ BLACK HOLE. Favoring a TDE, this work determines the JET-launching occurrence, with the low redshift allowing constraints on the late-time evolution in contrast to prior events. Upcoming radio sky surveys will offer an unprecedented new window for further discovery of AT 2019ijn-like off-axis RELATIVISTIC transients.
[abstract 12 / 65] Yes (score: 5) - Title: AT2019ijn: a fast-rising, slow-decaying blue optical transient with exceptionally bright radio emissionAuthors: Hucheng Ding, Xinwen Shu, Luming Sun, Liangduan Liu, Lei Yang, Yunwei Yu, Xueguang Zhang, Ying Gu, Fangkun Peng, Fabao Zhang, Zhumao Zhang, Ningyu Tang,Comments: Published in ApJ LettersSubjects: astro-ph.HE astro-ph.GACreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
We report the discovery of a peculiar optical transient, AT2019ijn, occurred in the nuclear region of a dwarf galaxy at z=0.273. It rises rapidly to peak at a luminosity of Mg=-21.1 in 5 days, followed by a slow decline over more than a month, during which the optical emission has a persistently high blackbody temperature of T_BB~1.5-1.6x10^4 K. The radio emission is exceptional which peaks at 640 days after optical discovery with a high luminosity of 2x10^31 erg/s/Hz. The peak radio luminosity is at least two orders of magnitude brighter than known radio-bright fast blue optical transients and SUPERNOVA explosions at similar epochs, but comparable to JETted tidal disruption events. The luminous and long-lasting radio emission with a late-time peak can be explained by an off-axis RELATIVISTIC JET with a viewing angle of ~40 deg. We discuss possible origins for AT2019ijn and favor a JETted tidal disruption event involving an intermediate-mass BLACK HOLE of ~10^5 Msun, although a JETted MAGNETar model cannot be fully ruled out. AT2019ijn represents a new class of RELATIVISTIC optical transients that highlights the importance of radio surveys for discovering off-axis JETted events.
[abstract 13 / 65] Yes (score: 5) - Title: HAMCOR: A physics-driven Hamiltonian framework for inferring AGN coronal geometry from X-ray reverberation lagsAuthors: Buffoli Fabio,Comments: 11 pages, 7 figures, 5 tablesSubjects: astro-ph.HECreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
We present HAMCOR (Hamiltonian-based AGN Multi-constraint CORonal inference framework), a geometry-agnostic method for inferring the X-ray coronal structure of accreting BLACK HOLEs using reverberation-lag measurements. Unlike conventional template-fitting approaches, HAMCOR reframes coronal geometry inference as the ground-state selection of a physical Hamiltonian. The corona is represented as a discrete emissivity distribution over a cylindrical grid, and its geometry emerges from five competing physical constraints: MAGNETic coherence, lag consistency, illumination consistency, pair-production stability, and energy budget feasibility. Minimisation is performed via projected gradient descent with Armijo backtracking line search on the probability simplex. We validate HAMCOR on three synthetic geometries (lamppost, column, ring) using the same grid as the real-data fits, recovering spatial correlations rho = 0.24, 0.50, 0.12 and fractional lag errors below 24 per cent. A hyperparameter sensitivity analysis confirms robustness over more than one order of magnitude in the coupling constants. We apply HAMCOR to five sources spanning seven orders of magnitude in BLACK HOLE mass: four AGN observed with XMM-Newton (Mrk 335, 1H 0707-495, IRAS 13224-3809, MCG-6-30-15) and the stellar-mass BLACK HOLE binary Cyg X-1 (M_bh = 14.8 M_sun), recovering consistent extended disc-corona geometries across the full mass range. We further present a multi-epoch analysis of Mrk 335 across five XMM-Newton observations (2006-2019), revealing that the coronal centroid remains stable at (R_c, z_c) ~ (6.3, 0.5) r_g across flux states spanning a factor of ~15 in reverberation lag amplitude, arguing against a collapsing or expanding lamppost. Schwarzschild-Shapiro delay corrections amount to ~79 per cent of the flat-spacetime lag on average; the recovered spatial morphology is robust to this correction.
[abstract 14 / 65] Yes (score: 4) - Title: GRACE: An Open-Source Framework for GPU-Accelerated Numerical RelativityAuthors: Carlo Musolino, Christian Ecker, Konrad Topolski, Marie Cassing, Keneth Miler, Harry Ho-Yin Ng, Khalil Pierre, Elias R. Most, Luciano Rezzolla,Comments:Subjects: gr-qc astro-ph.HECreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
We present GRACE, a new GPU-accelerated numerical-relativity framework designed to run efficiently on heterogeneous high-performance computing platforms. Developed from scratch and built exclusively on open-source libraries, GRACE employs Kokkos for performance portability across CPU and GPU architectures and p4est for adaptive mesh refinement. The code evolves the equations of ideal GRMHD -- with divergence-free MAGNETic fields maintained by constrained transport -- self-consistently coupled to the Einstein equations in the Z4c formulation, on fixed or adaptively refined grids. We validate the implementation against a suite of standard tests, ranging from MAGNETized shock tubes and the MAGNETic rotor in flat spacetime, through (MAGNETized) Bondi accretion onto a Schwarzschild BLACK HOLE and the ringdown of a perturbed spinning puncture, to neutron-star oscillation spectra in fixed and dynamical spacetimes and the merger of binary BLACK HOLEs. As more demanding applications, we evolve two binary neutron-star mergers -- an equal-mass, unMAGNETized system with an ideal-gas equation of state and an unequal-mass, MAGNETized system with a finite-temperature tabulated equation of state -- finding the inspiral dynamics to agree well with the FIL code. We also report single-device throughput together with strong- and weak-scaling results on multiple GPU and CPU architectures. GRACE is publicly released together with GRACEpy, a basic post-processing and data-analysis environment.
[abstract 15 / 65] Yes (score: 4) - Title: Search for GeV gamma-ray emission from PSZ G181.06+48.47 galaxy cluster using FERMI-LAT dataAuthors: Anuja Deshpande, Siddhant Manna, Shantanu Desai,Comments: 24 pages, 6 figures, 6 tablesSubjects: astro-ph.HECreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
We present a search for high energy gamma rays in the energy range from 1--300~GeV from the galaxy cluster PSZ2~G181.06+48.47 using 17.9~years of FERMI-LAT data. A binned likelihood analysis employing the 16-year source catalog reveals a significant $γ$-ray excess at the cluster position. Modelling the emission as a point source yields a detection with $\mathrm{TS}=19.0 (4.3 σ)$, a photon index of $Γ=3.20 \pm 0.62$, and an integrated photon flux of $(9.75\pm2.74)\times10^{-11}\,\mathrm{ph\,cm^{-2}\,s^{-1}}$, but leaves statistically significant residual emission at the cluster center. Replacing the point-source hypothesis with a RadialGaussian spatial template significantly improves the fit, with a preferred width of $σ=0.4^{\circ}$ and an extension significance of $\mathrm{TS}_{\rm ext}=36.8 (6.0σ)$. The adopted Gaussian model yields a source detection significance of $\mathrm{TS}=55.0 (7.4σ)$, a photon index of $Γ=2.62\pm0.26$, and an integrated photon flux of $(3.22\pm0.50)\times10^{-10}\,\mathrm{ph\,cm^{-2}\,s^{-1}}$, while reducing the residual emission at the cluster position to a level consistent with zero. The cluster spectral energy distribution shows significant emission only in the lowest energy interval (1.0--3.13~GeV), while all higher-energy bins are consistent with upper limits, indicating a soft $γ$-ray spectrum with no evidence for emission above $\sim5$~GeV. These results provide strong evidence that the $γ$-ray emission associated with PSZ2~G181.06+48.47 is spatially extended on a scale of $σ\approx0.4^{\circ}$ and is more consistent with diffuse intracluster emission than with a single unresolved point source.
[abstract 16 / 65] Yes (score: 4) - Title: Synchrotron radiation in nonuniform MAGNETic fieldAuthors: V. S. Beskin, A. Yu. Istomin, F. A. Kniazev, T. I. Khalilov,Comments: 5 figuresSubjects: astro-ph.HECreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
The distortion of the spectrum of SYNCHROTRON radiation received by a distant observer due to MAGNETic field inhomogeneity is discussed. It is shown that for single-particle radiation, a noticeable difference in the integrated spectrum from the case of a uniform MAGNETic field occurs only for observation times significantly exceeding the observer's departure from the beam pattern, and only for subRELATIVISTIC particles, when the radiation arrives from regions with significantly different MAGNETic fields during the observation time. For shorter observation times, field inhomogeneity leads only to small-scale distortions (smaller or comparable in frequency to the gyrofrequency) and does not manifest itself in the averaged spectrum. For the case of a particle ensemble, which is of interest for astrophysical applications, the difference in the integrated spectrum becomes negligible.
[abstract 17 / 65] (score: 3) - Title: On the construction of general large-amplitude spherically polarised Alfvén wavesAuthors: Jonathan Squire, Alfred Mallet,Comments: Accepted for publication in Journal of Plasma Physics LettersSubjects: astro-ph.SR astro-ph.HE physics.plasm-phCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
In a MAGNETised plasma on scales well above ion kinetic scales, any constant-magnitude MAGNETic field, accompanied by parallel Alfvénic flows, forms a nonlinear solution in an isobaric, constant-density background. These structures, which are also known as spherically polarised Alfvén waves, are observed ubiquitously in the solar wind, presumably created by the growth of small-amplitude fluctuations as they propagate outwards in the corona. Here, we present a computational method to construct such solutions of arbitrary amplitude with general multi-dimensional structure, and explore some of their properties. The difficulty lies in computing a zero-divergence, constant-magnitude MAGNETic field, which leaves a single, quasi-free function to define the solution, while requiring strong constraints on any individual component of the field. Motivated by the physical process of wave growth in the solar wind, our method circumvents this issue by starting from low-amplitude Alfvénic fluctuations dominated by a strong mean field, then "growing" MAGNETic perturbations into the large-amplitude regime. We present example solutions with nontrivial structure in one, two, and three dimensions, demonstrating a clear tendency to form very sharp gradients or discontinuities, unless the solution is one dimensional. As well as being useful as an input for other calculations, particularly the study of parametric decay, our results provide a natural explanation for the extremely sharp field discontinuities observed across MAGNETic-field switchbacks in the low solar wind.
[abstract 18 / 65] (score: 3) - Title: Spatial Variations of Polarized Synchrotron Emission in the QUIJOTE MFI Data using Neural NetworksAuthors: J. M. Casas, L. Bonavera, J. González-Nuevo, J. A. Rubiño-Martín, R. T. Génova-Santos, R. B. Barreiro, M. M. Cueli, D. Crespo, R. Fernández-Fernández, J. A. Cano,Comments: Accepted for publication in Astronomy & Astrophysics (11/07/26)Subjects: astro-ph.GA astro-ph.COCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Polarized SYNCHROTRON emission from ultra-RELATIVISTIC electrons spiraling the Galactic MAGNETic field has become one of the most relevant emissions in the Interstellar medium these last years due to the improvement in the quality of low-frequency observations. One of the recent experiments designed to explore this emission is the QUIJOTE experiment. We aim to study the spatial variations of the SYNCHROTRON emission in the QUIJOTE MFI data, by dividing the sky into physically separated regions. For such task, we firstly use a novel component separation method based on artificial neural networks to clean the SYNCHROTRON maps. After training the network with simulations, we fit both $EE$ and $BB$ spectra by assuming a power-law model. Then, we give estimations for the index $α_{S}$, the amplitude, and the ratio between $B$ and $E$ amplitudes. When analyzing the real data, we found a clear spatial variation of the SYNCHROTRON properties along the sky at 11 GHz, obtaining a steeper index in the Galactic plane of $α_{S}^{EE} = -3.1 \pm 0.3$ and $α_{S}^{BB} = -3.10 \pm 0.28$ and a flatter one at high Galactic latitudes of $α_{S}^{EE} = -3.05 \pm 0.16$ and $α_{S}^{B} = -2.98 \pm 0.23$. We found average values at all sky of $α_{S}^{EE} = -3.04 \pm 0.18$ and $α_{S}^{BB} = -3.00 \pm 0.26$. Furthermore, after obtaining an average value of $A_{S}^{EE} = 3.31 \pm 0.17$ $μK^{2}$ and $A_{S}^{BB} = 0.93 \pm 0.04$ $μK^{2}$, we estimate a ratio between $B$ and $E$ amplitudes of $A_{S}^{BB}/A_{S}^{EE} = 0.28 \pm 0.06$. Based on the results we conclude that, although neural networks seem to be valuable methods to apply on real ISM observations, combined analyses with Planck, WMAP and/or CBASS data are mandatory to reduce the contamination from QUIJOTE maps and then improve the accuracy of the estimations.
[abstract 19 / 65] (score: 3) - Title: Simulating AGN feedback in galaxy clusters with pre-existing turbulenceAuthors: Jia-Lun Li, H. -Y. Karen Yang,Comments: 17 pages, 12 figures, accepted by ApJSubjects: astro-ph.HECreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
Feedback from ACTIVE GALACTIC NUCLEi (AGN) is believed to play a significant role in suppressing cooling flows in cool-core (CC) clusters. Turbulence in the intracluster medium (ICM), which may be induced by AGN activity or pre-existing motions, has been proposed as a potential heating mechanism based on analysis of Chandra X-ray surface brightness fluctuations. However, subsequent simulation results have found the subdominant role of turbulence in heating the ICM. To investigate this discrepancy, we perform three-dimensional hydrodynamic simulations of a Perseus-like cluster including both AGN feedback and pre-existing turbulence, which is stirred to the observationally constrained level in the Perseus cluster. Our results indicate that, although the velocity field is dominated by the pre-existing turbulence, AGN heating through bubbles and shocks remains significant. More importantly, analysis of the velocity structure function and the energy power spectrum shows that the turbulent heating rate is smaller than the radiative cooling rate, especially in the cluster core. Our results offer insights relevant for recent XRISM observations and indicate that turbulent heating alone cannot offset radiative cooling in CC clusters.
[abstract 20 / 65] (score: 3) - Title: Reshaping the inner shadow of a Kerr BLACK HOLE by a torn accretion diskAuthors: Shiyang Hu, Dan Li, Chen Deng, Kejian He,Comments: 24 pages, 9 figures,accepted for publication in JCAPSubjects: gr-qc astro-ph.HECreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
When an accretion flow extends to the event horizon, their intersection defines the contour of the inner shadow. However, the morphological evolution of this critical feature remains largely unexplored within a torn accretion disk system, a configuration comprising distinct sub-disks formed when a tilted disk is disrupted by frame-dragging. To address this, we phenomenologically construct a torn accretion disk model and numerically simulate the inner shadow of a Kerr BLACK HOLE using RELATIVISTIC backward ray-tracing. We discover that the torn disk geometry profoundly alters the BLACK HOLE's observational signatures, inducing severe erosion of the inner shadow and generating novel features such as bifurcated shadows, crescent-like structures, and multiple orders of shadow rings. These exotic morphologies, which are predominantly governed by the spatial discontinuity between the sub-disks and the tilt angle of the outer sub-disk, are exceedingly difficult to replicate within standard equatorial accretion paradigms. Our findings demonstrate that these distinctive shadow structures hold significant potential to serve as robust diagnostic probes for torn accretion environments, simultaneously implying that relying solely on the inner shadow to test gravity theories is fundamentally insufficient.
[abstract 21 / 65] (score: 3) - Title: Extreme color-magnitude variability: connection to changing-look AGNsAuthors: Litao Zhu, Zhongxiang Wang, Alok C. Gupta, P. U. Devanand, Ruoheng Yang, Qiangmeng Huang, Man Lang, Jiawen Li,Comments: 15 pages, 17 figures, 3 tables, accepted for publication in A&ASubjects: astro-ph.GACreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
Context. Changing-look ACTIVE GALACTIC NUCLEi (CL-AGNs) challenge the unified model of AGNs and offer key insights into the physics of the accretion processes of super-massive BLACK HOLEs. While systematic spectroscopic comparisons have successfully identified large samples of CL-AGNs, photometric selection based on variability features provides an efficient alternative. Methods. We use the colour--magnitude (CM) variability method to continue our identification of the CL transition in AGNs, which utilizes the slope ($k$) of the CM variations to identify strong bluer-when-brighter behavior, while the variation amplitudes in optical and mid-infrared bands are also considered. The candidates thus selected from the Type-2 AGNs given in the Sloan Digital Sky Survey catalog are spectroscopically observed using the 3.6-m DOT and the 2-m HCT. Results. We confirm seven turn-on CL-AGNs among 12 candidates. Comparing them with both the general AGN populations and the spectroscopically identified CL-AGN sample, the CL-AGNs showed larger optical and MIR variations and $k$ values. The extreme CM variabilities of these sources (with optical magnitude changes $>$ 0.9) occurred recently. For four sources, flare-like brightening episodes were temporally associated with the turn-on transitions within 3--7 years, suggesting that these flares may trace short-timescale accretion enhancement, central brightening, and BLR re-illumination. Conclusions. The extreme CM variability serves as a highly efficient criterion for finding CL-AGNs. The properties of the CL-AGNs thus found suggest that they may represent AGNs at a pivotal state, which likely occur CL transitions due to enhanced accretion activity, while the cause of the accretion activity, determined to have a time scale of several years, remains to be investigated.
[abstract 22 / 65] (score: 3) - Title: The COSMIC RAY ionization rate from H3+ observations can be overestimated due to neglect of time-dependent chemistryAuthors: Ka Wai Ho, Munan Gong, Kedron Silsbee, Alexei Ivlev,Comments: 11 pages, 6 figures, Accepted for publication in ApJSubjects: astro-ph.GACreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
The COSMIC RAY ionization rate (CRIR) is a key parameter governing the physical, chemical and thermal evolution of the interstellar medium. The primary technique for measuring the CRIR in diffuse molecular clouds relies on observations of ${\rm H_3^+}$. Previous analyses of these observations have derived the CRIR under the assumption of steady-state chemistry. Here, we investigate the effect of time-dependent chemistry on the inferred CRIR from ${\rm H_3^+}$ observations. We perform 3D MHD simulations with coupled chemistry and driven turbulence. Following procedures similar to those used in the literature to analyze ${\rm H_3^+}$ observations, we conduct mock CRIR measurements by post-processing our simulations with different values of the CRIR to obtain steady-state abundances of ${\rm H_2}$ and ${\rm H_3^+}$. By comparing those with the abundances from time-dependent chemistry, we determine the best-fitting value of the CRIR. We find that the abundances of both ${\rm H_2}$ and ${\rm H_3^+}$ are higher in time-dependent chemistry simulations than in the steady-state case, especially in low-density regions. Furthermore, the inferred CRIR under the steady-state assumption is a factor of $\sim 2-5$ higher than the true CRIR, with a median value of $ζ_\mathrm{inferred}/ζ_\mathrm{true} \approx 3$. This bias increases with stronger MAGNETic fields, weaker FUV radiation fields, and stronger turbulence. Accounting for time-dependent chemistry, we report an average CRIR per ${\rm H_2}$ of $ζ_{H_2} = 2\times 10^{-17}~\mathrm{s^{-1}}$ from the ${\rm H_3^+}$ observations. The CRIR is consistent with a constant value over the column density range of $N=(2-6)\times10^{21}~\mathrm{cm^{-2}}$.
[abstract 23 / 65] (score: 3) - Title: Evading the CMB $μ$-distortion bound on Supermassive Primordial Black Hole seeds with Non-Gaussian tailsAuthors: Sanket Dave, Sheng-Feng Yan, Amara Ilyas, Yi-Fu Cai,Comments: 14 pages, 6 figures, revised version: additional text and referencesSubjects: astro-ph.CO gr-qc hep-ph hep-thCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Supermassive BLACK HOLEs (SMBHs) powering QUASARs at $z \gtrsim 6$ are difficult to grow from stellar mass remnants, motivating seeds from primordial BLACK HOLEs (PBHs) with masses $10^5-10^7 M_{\odot}$. This range is constrained by the COBE/FIRAS bound on the CMB $μ$-distortion, which limits the small-scale curvature variance to $σ_ζ^2 \lesssim 10^{-4}$. For Gaussian perturbations, the variance fixes the far tail of the one-point probability distribution function (PDF), making the PBH abundance negligible. We call this the Gaussian barrier. The barrier can be evaded only if the variance probed by the distortion is decoupled from the tail probability controlling collapse. We implement this idea in the non-perturbative $δN$ formalism and relate asymptotic PDF tails to the global shape of the $δN$ map. Four Gaussian-cored families are analyzed: generalized-normal, stretched-exponential, power-law, and log-normal tails. After standardizing each family to unit variance, we impose the FIRAS cap and compute the distortion-limited PBH abundance in the tail-shape parameter space. The ordinary exponential tail produced by standard single-field non-attractor dynamics is still too light to reopen the seed window. Algebraic tails from fractional-potential dynamics, and sufficiently heavy log-normal tails treated as a phenomenological proxy for multiplicative dynamics, can supply seed-relevant abundances while respecting the distortion bound.
[abstract 24 / 65] (score: 3) - Title: Relative dispersion and eddy diffusivity in laboratory experiments of $β$-plane turbulenceAuthors: Daphné Lemasquerier, Matthew Burke, Benjamin Favier, Joe H. LaCasce, Michael Le Bars,Comments: 24 pages, 9 figuresSubjects: physics.flu-dyn physics.ao-ph physics.geo-ph physics.plasm-phCreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
We present the first experimental measures of relative dispersion and turbulent diffusion in rapidly-rotating turbulence in the zonostrophic regime, i.e., in the presence of instantaneous and dominant zonal JETs. Synthetic Lagrangian trajectories are computed from time-resolved experimental velocity fields, from which we measure relative (two-particle) dispersion. Time-based and separation-based statistics are calculated, including the cumulative inverse separation time (CIST), for which analytical predictions exist in the inertial ranges (direct enstrophy cascade and inverse energy cascade) and in the diffusive regime. These statistics show evidence of a transition from a Richardson regime at scales larger than the energy-injection scale, to a diffusive regime, at scales larger than the transitional scale, the scale at which turbulence becomes anisotropic due to the interaction between turbulent eddies and Rossby waves. The analytical predictions for the CIST allow us to measure the turbulent energy dissipation rate in the Richardson regime, and the turbulent diffusivity in the diffusive regime. Our measurements of diffusivity are broadly consistent with predictions from mixing-length and zonostrophic theories but suggest a shallower dependence on the energy dissipation rate.
[abstract 25 / 65] (score: 3) - Title: Effect of Neutron Star Jets on Common Envelope EvolutionAuthors: Deepanshu Gurjal, Luke Chamandy, Eric G. Blackman, Yangyuxin Zou, Baowei Liu, Jason Nordhaus,Comments: 11 pages, 8 figures, 1 table, submitted to ApJSubjects: astro-ph.SR astro-ph.HECreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
The common envelope (CE) phase is a key stage in binary star evolution that is still not very well understood. Once engulfed by the giant star, the binary companion may accrete envelope material. For neutron star (NS) companions, such accretion may in principle occur at mass rates several orders of magnitude above the Eddington limit and may result in outflows dominated by powerful bi-polar JETs with mass-loss rates similar to the accretion rates. Such JETs would impact the morphology of the system and the rate of envelope unbinding, which affect the duration and outcome of the CE event. Employing 3D global hydrodynamic simulations, we study the role of such NS JETs in a CE event involving a red giant branch star. The JETs eventually drill through and break out of the envelope, producing prominent low-density bi-polar lobes. The JETs cause about twice as much envelope mass to be unbound as compared to simulations of the same duration without NS JETs. However, the rate of mass unbinding due to the JETs decreases towards the ends of the simulations as the JETs break out and energetically decouple from the envelope. Moreover, JET activity leads to slightly reduced drag on the binary, decreasing the rate of orbital energy transfer to the envelope. Hence, while such powerful JETs can play an important role, negative feedback effects tend to prevent them from dominating envelope unbinding and dictating CE outcomes.
[abstract 26 / 65] (score: 3) - Title: Radio Halos in Galaxy Clusters as unveiled by the SKA telescopeAuthors: R. Cassano, G. Di Gennaro, V. Cuciti, A. Datta, M. Balboni, G. Bernardi, A. Bonafede, A. Botteon, M. Brüggen, G. Brunetti, S. Chatterjee, K. Dolag, S. Ettori, F. Gastaldello, S. Giacintucci, C. Giocoli, M. Gitti, R. Kale, M. Pandey-Pommier, G. W. Pratt, M. Rahaman, M. Rossetti, H. J. A. Röttgering, R. Santra, K. S. L. Srikanth, R. J. van Weeren, T. Venturi,Comments: Published in Advancing Astrophysics with the SKAII (AASKAII), 2026 (arXiv:2606.20366). Report-no: AASKAII/Cassano01Subjects: astro-ph.COCreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
Giant radio halos (RHs) are diffuse, Mpc-scale SYNCHROTRON sources observed in a growing fraction of galaxy clusters. They trace RELATIVISTIC particles and MAGNETic fields in the intracluster medium (ICM), providing a unique window into non-thermal processes and their role in cluster evolution. RHs are primarily found in merging systems, supporting models in which turbulence generated during cluster collisions re-accelerates pre-existing electrons to the energies required for the observed radio emission. In this scenario, the occurrence, power, and spectral properties of RHs depend on the energetics of cluster mergers, with the most massive and dynamically disturbed clusters hosting the most powerful halos. Low-frequency observations are crucial to uncover ultra-steep-spectrum RHs, a key prediction of turbulent re-acceleration models, and are expected to arise from less energetic merger events. LOFAR has enabled statistical studies of large cluster samples, placing robust constraints on RH occurrence and spectral trends. In this Chapter, we model RH formation and evolution using Monte Carlo simulations calibrated on LoTSS-DR2 findings, and we present predictions for SKA-Low in the AA4 configuration. Our results show that SKA will probe an unprecedented region of cluster mass and redshift space, detecting at least $\sim 2500$ RHs up to $z \approx 0.6$, including $\gtrsim 1000$ ultra-steep-spectrum systems, and revealing halos in clusters down to $\sim 10^{14}\, M_\odot$ and out to $z \approx 1$. These surveys will provide stringent tests of turbulent re-acceleration models and significantly advance our understanding of non-thermal processes in galaxy clusters.
[abstract 27 / 65] (score: 3) - Title: Magnetospheric flows in X-ray pulsars II: Heating, cooling and ionization degree at sub-critical accretionAuthors: Alexander A. Mushtukov, Alexander Y. Potekhin, Valery F. Suleimanov, Andrew Yu, Sergey S. Tsygankov,Comments: accepted for publication in MNRAS, 19 pages, 9 figuresSubjects: astro-ph.HE astro-ph.SRCreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
Magnetospheric accretion flows in X-ray pulsars shape their spectra, POLARIZATION, and variability. We model the thermal balance of the flow enveloping the neutron star MAGNETosphere in the sub-critical regime ($L \lesssim 10^{37}\,\mathrm{erg\,s^{-1}}$), where radiation forces do not control the dynamics and single Compton scatterings dominate. The energy budget includes Compton heating by surface X-rays, compressional (adiabatic) heating in the converging flow, and radiative cooling dominated by free-free emission and contributed also by cyclotron emission. We show that the interplay of these processes leads to efficient cooling of the flow in the inner MAGNETosphere. We compute the flow temperature profile as a function of luminosity and find that near the stellar surface the temperature can fall to a few tens of eV at $L < 10^{35}\,\mathrm{erg\,s^{-1}}$. Under such conditions, the accreting plasma, modelled here as pure hydrogen, is no longer fully ionized. In the strong MAGNETic fields typical for X-ray pulsars, such temperatures permit partial recombination of electrons and protons into neutral hydrogen. As a result, a significant fraction of the flow becomes weakly ionized, while external illumination ionizes this gas only partially within a geometrically thin layer immediately above the neutron star surface. This implies that MAGNETospheric accretion at low luminosities proceeds through a partially ionized medium, in contrast to the commonly assumed fully ionized flow.
[abstract 28 / 65] (score: 3) - Title: What Causes the Asymmetry of Conjugate Hard X-Ray Footpoints in Solar Flares?Authors: Mirabbos Mirkamalov, Rui Liu, Runbin Luo, Arun Kumar Awasthi,Comments: 20 pages, 7 figures, 1 tableSubjects: astro-ph.SRCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Hard X-ray (HXR) emission in solar flares critically diagnoses nonthermal electron acceleration, transport, and precipitation. Observations commonly show asymmetric HXR photon fluxes between paired footpoints, whose physical origin remains debated, as the conventional MAGNETic mirroring mechanism often fails to explain the observed asymmetry. Here we performed rigorous statistical tests on the association between photospheric MAGNETic parameters within the HXR footpoint regions and the asymmetry of HXR production. We analyzed 103 time intervals taken from around the peaks of HXR bursts in 67 M- and X-class flares with a clear double-ribbon morphology observed by both the Ramaty High Energy Solar Spectroscopic Imager and the Solar Dynamics Observatory. We found that conjugate HXR footpoint sources are asymmetric in photon fluxes, maximum intensities, and sizes, but rather symmetric in mean intensities. The photon flux ratio of the stronger over weaker footpoint source shows a strong linear correlation with the size ratio and a nonlinear correlation with the maximum intensity ratio. The asymmetry of MAGNETic field strength and flux at the conjugate footpoints shows a positive correlation with the HXR asymmetry, contrary to what MAGNETic mirroring effects predict. Importantly, the asymmetry of unsigned photospheric vertical electric current (PVEC) exhibits a strong positive correlation with the HXR footpoint asymmetry. PVEC at HXR footpoints most likely maps the footprints of coronal current layers where flaring RECONNECTions occur. This tight linkage suggests that the electric-current-associated physical processes, including RECONNECTion-induced electric fields and current-driven micro-turbulence, are at work to modulate the production and precipitation of nonthermal electrons.
[abstract 29 / 65] (score: 3) - Title: Pre-flare and active region plasma flows and structure seen by the short wavelength camera on SOLAR-C/EUVSTAuthors: James McKevitt, Sarah Matthews, David H. Brooks, Toshifumi Shimizu, Akiko Tei, Ignacio Ugarte-Urra, Shinsuke Imada, Shin Toriumi, Charles M. Brown, Ryohko Ishikawa, Yukio Katsukawa, Hirohisa Hara, Duncan Rust, David Walton, Berend Winter, Deborah Baker, Hamish Reid, Peter Young, Tiago M. D. Pereira, Louisa Bradley, Alexey Shitvov, Louise Harra, International SOLAR-C team,Comments: Published in PASJSubjects: astro-ph.SR astro-ph.IMCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
The mechanisms triggering solar flares and driving coronal heating occur across wide temperature ranges on small spatial scales and short timescales, making them difficult to observe with current instrumentation. The upcoming SOLAR-C mission, launching in the late 2020s, will provide unprecedented plasma diagnostic capability with its high-throughput extreme-ultraviolet (EUV) spectroscopic telescope (EUVST), capable of ~0.2 arcsec/pix spatial sampling (~0.4 arcsec resolution), continuous temperature coverage from 0.02-15 MK, and exposure times down to 0.5 seconds. We present forward modelling of the spectrograph's short wavelength camera (170-210 Å; SOLAR-C/EUVST-SW) and its response to log T~6.2 coronal plasma in a three-dimensional MHD-simulated pre-flare active region. We compare this performance to that of the previous-generation EUV Imaging Spectrometer (EIS) on Hinode (SOLAR-B). Our results demonstrate that SOLAR-C/EUVST can distinguish individual flux tubes in simulated active region loops which Hinode/EIS cannot resolve. In simulated pre-flare plasma, SOLAR-C/EUVST captures sharp velocity gradients between adjacent upflowing and downflowing plasma which Hinode/EIS is unable to resolve. Doppler velocity measurement accuracy will reach better than 1 km/s in active regions. We show that this next-generation spectrograph can be expected to directly observe processes potentially related to flare triggering, such as plasma flows from low-altitude RECONNECTion linked to emerging flux, and determine whether active region loops consist of a small number of strands or the hundreds predicted by MAGNETic RECONNECTion-induced nanoflare heating models.
[abstract 30 / 65] (score: 3) - Title: Radio and X-ray flux rebrightening six years after outburst in a partially-obscured extreme changing-look AGNAuthors: Tianyao Zhou, Xinwen Shu, Lei Yang, Tao Wu, Luming Sun, Yibo Wang, Guobin Mou, Ning Jiang, Wenjie Zhang, Hucheng Ding, Fabao Zhang, Yujun Yao, Liming Dou, Yogesh Chandola, Ningyu Tang, Jianguo Wang, Tinggui Wang,Comments: Published in ApJ, 24 pages, 6 main figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
SDSS J1548+2208 is a unique partially-obscured nuclear transient that exhibits multiwavelength outbursts in mid-infrared, X-ray and radio. We present the results from multiwavelength photometric and spectroscopic follow-up observations with a time span of ~2500 days since its discovery. We find that the mid-infrared and X-ray emission (with a hard X-ray spectrum) are still in a high flux level relative to the pre-flare state, suggesting a sudden increased, and possibly long-sustained accreting activity from central BLACK HOLE. This is supported by the slowly-evolving high-ionization coronal lines. The mid-infrared color turns blue slowly in the rising phase, which is distinct from stellar tidal disruption events (TDEs). All these properties point to the origin of outbursts from an extreme changing-look AGN and the scenario with a normal TDE seems disfavored. The radio spectral energy distribution (SED) in ~0.65-15 GHz is unusual, displaying a double-peak feature with distinct variability characteristics. In addition, we find evidence for the late-time radio rebrightening more than six years since the initial outburst, as well as a possibly new X-ray flare, though the significance for the latter is not high. The peculiar radio flux and SED evolution could be explained by a nascent outflow expanding into and shocking circumnuclear diffuse medium filled by denser clouds. In this case, SDSS J1548+2208 represents a rare changing-look AGN which can launch radio outflows. Continued multiwavelength observations are required to map the dust and gas distribution on pc-scales, providing new insights into the environmental properties that could regulate AGN changing-look phenomenon.
[abstract 31 / 65] (score: 3) - Title: Collisionless whistler heat-flux instability in ultra-high-$β$ plasmasAuthors: Rhisiart Davies, Prakriti Pal Choudhury, Archie F. A. Bott,Comments:Subjects: physics.plasm-ph astro-ph.GA astro-ph.HECreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Kinetic instabilities, notably the whistler heat-flux instability (WHFI), are known to suppress thermal transport significantly in the moderate- to high-$β$ plasmas relevant to many astrophysical systems. This paper explores WHFI-regulated heat transport in a new regime: ultra-high-$β$ plasmas with $β_{e} \gtrsim L_{\mathrm{T}}/ρ_e$. Extrapolating previous theories of the WHFI to ultra-high-$β$ plasmas, we propose that the MAGNETic energy in unstable whistler fluctuations becomes comparable to that of the background MAGNETic field at saturation. We corroborate this hypothesis using 1D3V and 2D3V kinetic simulations using the particle-in-cell code OSIRIS. We find that, in ultra-high-$β$ plasmas, the heat flux is localised and no longer regulated primarily by resonant pitch-angle scattering of electrons; instead, thermal energy is transported predominantly by advection at the whistler phase velocity. Heat-flux suppression is observed in 1D3V and 2D3V simulations; however, we show that the saturation of the WHFI and the regulation of heat flux are sensitive to dimensionality in the ultra-high-$β$ regime. The amplitude and phase velocity of the heat-flux-regulating whistler waves scale differently with $β_e$, yielding parallel heat fluxes, normalised to the free-streaming value, of $q_{e\parallel} / q_\mathrm{fs} \approx 4.7 β_{e}^{-1}$ and $q_{e\parallel} / q_\mathrm{fs} \approx 0.3 β_{e}^{-1/2}$ in 2D3V and 1D3V simulations, respectively. We perform 2D3V simulations with background MAGNETic fields inclined to the temperature gradient, showing cross-field heat transport remains negligible. We develop a heuristic theory from kinetic equations that explains these phenomena. Our work extends our understanding of how the WHFI modifies thermal transport to regimes applicable to high-energy-density physics and the reionised intergalactic medium.
[abstract 32 / 65] (score: 2) - Title: Clapping propulsion and thin vortex rings: a computational study of vortex dynamics, energy equivalence, and core potential energyAuthors: Suyog V. Mahulkar, Jaywant H. Arakeri,Comments: 38 pages, 23 figures. Substantially revised version with expanded analysis of three-dimensional vortex dynamics and energetics, including vortex ring simulations and core potential energy analysisSubjects: physics.flu-dynCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
We report a computational study of clapping propulsion using two thin rigid plates forming a 60-degree interplate cavity that generates a thrust-producing JET during closure. Plate kinematics are prescribed from experiments for two cases: dynamic and stationary, with forward motion constrained in the latter. The computations show that interplate pressure is higher in the stationary case compared to that in the dynamic case, resulting in differences in the thrust produced and in the evolution of wake vortices, with the stationary case forming triangular and Omega-shaped loops, while the dynamic case forms an elliptical loop for each plate. We examine the energy budget in the post-clapping phase, when the vortices are fully formed. The energy consists of kinetic energy and a component associated with vortex formation, whose sum approximately matches the work done on the fluid. This extra term, which we call the core potential energy, is found to be equal to the integral of pressure over the core volume of the vortex. This component is also checked using separate axisymmetric vortex ring simulations, where the kinetic energy is about 60% of the injected slug energy, and the remaining part is the core potential energy. Sullivan et al.(2008) had commented on this deficit for vortex rings and hypothesized the existence of a potential energy associated with the vortex structure.
[abstract 33 / 65] (score: 2) - Title: Probing missing physics from inspiralling compact binaries via time-frequency tracksAuthors: Debtroy Das, Soumen Roy, Anand S. Sengupta, Cosimo Bambi,Comments: 15 pages, 9 figures. v2: minor stylistic modificationsSubjects: gr-qc astro-ph.HECreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
The orbital evolution of binary BLACK HOLE (BBH) systems is determined by the component masses and spins of the BLACK HOLEs and the governing gravity theory. Gravitational wave (GW) signals from the evolution of BBH orbits offer an unparalleled opportunity for examining the predictions of General Relativity (GR) and for searching for missing physics in the current waveform models. We present a method of stacking up the time-frequency pixel energies through the orbital frequency evolution with the flexibility of gradually shifting the orbital frequency curve along the frequency axis. We observe a distinct energy peak corresponding to the GW signal's quadrupole mode. If an alternative theory of gravity is considered and the analysis of the BBH orbital evolution is executed following GR, the energy distribution on the time-frequency plane will be significantly different. We propose a new consistency test to check whether our theoretical waveform explains the BBH orbital evolution. Through the numerical simulation of beyond-GR theory of gravity and utilizing the framework of second-generation interferometers, we demonstrate the efficiency of this new method in detecting any possible departure from GR. Finally, when applied to an eccentric BBH system and GW190814, which shows the signatures of higher-order multipoles, our method provides an exquisite probe of missing physics in the GR waveform models.
[abstract 34 / 65] (score: 2) - Title: Population of Binary Black Holes Inferred from One Hundred and Fifty Gravitational Wave SignalsAuthors: Vaibhav Tiwari,Comments:Subjects: astro-ph.HECreated: 2026-07-12; Updated: 2026-07-14; Datestamp: 2026-07-14
The LIGO-Virgo-KAGRA collaborations have reported gravitational wave signals from more than 150 binary BLACK HOLEs in the fourth catalog (GWTC-4). Here, we investigate the population properties of these binary BLACK HOLEs using the mixture-model framework Vamana. We present one-dimensional distributions of masses and spins, explore their correlations, and examine their evolution with redshift. These features may reflect astrophysical processes associated with binary BLACK HOLE formation channels, although most remain poorly constrained. A notable feature is a peak near $10M_\odot$ in the primary mass and $8M_\odot$ in the chirp mass. Additionally, the primary and secondary masses correlate uniquely, producing pronounced peaks in the chirp mass around $14M_\odot$ and $27M_\odot$. The three peaks are roughly separated by a factor of two. A simple explanation for such well-placed peaks is a hierarchical merger scenario, in which the first peak arises from mergers of BLACK HOLEs of stellar origin, and higher-mass peaks arise from repeated mergers of BLACK HOLEs from lower-mass peaks. Although most binaries do not exhibit the high spins and characteristic mass ratios expected from hierarchical mergers, those that do are associated with the peaks observed in the chirp mass distribution.
[abstract 35 / 65] (score: 2) - Title: Axion-photon conversion in stochastic MAGNETic fieldsAuthors: Wataru Chiba, Ryusuke Jinno, Kimihiro Nomura,Comments: 31 pages, 8 figuresSubjects: hep-ph astro-ph.CO astro-ph.HE gr-qcCreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
We investigate axion-photon conversion in stochastic MAGNETic fields, focusing on the evolution of the photon intensity and POLARIZATIONs induced by conversion into axions. Assuming Gaussian MAGNETic fields characterized by the power spectra of their helical/non-helical components, we express the expectation values and variances of the photon intensity and linear/circular POLARIZATIONs after conversion in terms of these spectra. We find nontrivial dependencies of these statistical quantities on the characteristic MAGNETic field correlation length, the propagation distance, and the axion mass. Moreover, we find that nontrivial POLARIZATIONs emerge even if the photons are initially unpolarized, that the variances of these observables become suppressed in specific frequency regions, and that a peak structure arises in the expectation value of the circular POLARIZATION in the presence of statistically helical MAGNETic fields. We also point out consistency relations among these statistical quantities that hold independently of the specific forms of the MAGNETic field power spectra.
[abstract 36 / 65] (score: 2) - Title: Integrated full pulse modeling for pellet injection in tokamaks: HPI2 model improvement and validation in WESTAuthors: A. Panera Alvarez, F. Koechl, J. Artaud, E. Geulin, B. Pégourié, E. Vergnaud, C. Bourdelle, S. Wiesen, the WEST Team,Comments:Subjects: physics.plasm-ph physics.comp-phCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Reliable modeling and control of core density is essential for reactor-relevant MAGNETic confinement fusion operation, motivating cryogenic pellet injection as a primary fueling actuator and the need for predictive pellet source models in integrated modeling. Here we present an upgrade of the physics-based pellet code HPI2 in which the plasmoid release spatial step is determined self-consistently from ablation physics, $dx_{var}=v_{\mathrm{pel}}\,t_{\mathrm{exit}}$ (optionally rescaled to trade accuracy for computational cost), removing an ad-hoc discretization parameter and improving numerical robustness across injection conditions. The upgraded model is first validated in stand-alone against a high-field-side pellet-fueled, ohmic, WEST discharge (#58656) by comparing synthetic and measured interferometry line-integrated density increments, obtaining a mean error of $\sim 10\%$. We then perform full-radius, time-dependent integrated modeling validation by coupling the new HPI2 within the High Fidelity Pulse Simulator (HFPS) workflow (JINTRAC/IMAS), combining JETTO with SANCO for the impurity/radiation evolution and TGLF-SAT2 for the turbulent transport. The coupled simulations reproduce the main density rise and relaxation after pellet injection and the associated electron-temperature transient, while taking into account the strong influence of tungsten radiation in WEST, supporting the consistency of HPI2 as a predictive pellet particle source in integrated modeling frameworks. Ultimately, this validation study supports the use of pellet modeling tools in integrated modeling studies for larger devices such as ITER.
[abstract 37 / 65] (score: 2) - Title: Computing statistical solutions of a Mach 2000 astrophysical JETAuthors: Stephan Simonis, Gauthier Wissocq,Comments:Subjects: math.NA cs.MS cs.NA physics.comp-ph physics.flu-dynCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
The multi-dimensional compressible Euler equations admit non-unique entropy solutions in turbulent regimes, and extreme-Mach astrophysical flows are a natural setting in which this breakdown of deterministic well-posedness becomes computationally visible. We compute statistical solutions of a Mach~2000 astrophysical JET, defined as the pushforward of an initial probability measure through a vectorial lattice Boltzmann method, by Monte Carlo sampling with $M=1000$ realizations on grids of up to $12.8$ million cells. Under mesh refinement the individual realizations diverge pathwise, while the statistical solution converges: Wasserstein distances of the one- and two-point marginals, the ensemble mean, and the ensemble standard deviation all exhibit stable positive convergence rates. A spatially resolved analysis along the JET axis traces this dichotomy to the structure of the one-point laws, which are numerically Dirac in the undisturbed core, skewed in the sheared turbulent regions, and intermittent two-state mixtures at the random leading front. We conclude that the computed statistical solution is non-Dirac and remains stable in the extreme compressible regime, in which no strong solution is expected to exist.
[abstract 38 / 65] (score: 2) - Title: Geodesic completeness of singularity free gravityAuthors: Vasil Todorinov,Comments:Subjects: gr-qcCreated: 2026-07-12; Updated: 2026-07-14; Datestamp: 2026-07-14
Generalizing the gravitational potential first proposed in [1] we derive a large class of RELATIVISTIC singularity free theories of gravity, which reduce to flat spacetime at large distances. We verify that for the chosen gravitational potential the force and the space-time curvature resolve the singularity and vanish at large distances. We show that those singularity free BLACK HOLE solutions generically have a two horizon structure. Furthermore, we show that there is a subclass of potentials which produce a geometries geodesically complete through the origin. We discuss the implications of the effects resulting from such theories and show that BLACK HOLEs solutions are predicted to have minimum allowed mass.
[abstract 39 / 65] (score: 2) - Title: Optical Emission Spectroscopy Measurements of keV Apparent Ion Temperatures in Avalanche Energy's Centrifugal Mirror MachineAuthors: M. Affolter, E. C. Hayes, A. Helson, E. McKee, A. Gargone, S. Hepner, R. Langtry,Comments: Technical ReportSubjects: physics.plasm-phCreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
Newly formed ions in $E \times B$ devices are rapidly accelerated by strong radial electric fields and execute large cycloidal orbits in the presence of an axial MAGNETic field. At locations where these orbits intersect, ions originating from different birth radii arrive with substantially different velocities, producing a non-Maxwellian velocity distribution with a large velocity variance. Through Coulomb collisions and collective interactions, this distribution relaxes toward a drifting Maxwellian in the rotating frame. Here, we present the first optical emission spectroscopy (OES) measurements of the line-of-sight-convolved ion-velocity distribution, from which an apparent ion temperature is determined, in Avalanche Energy's centrifugal mirror machine. High-resolution $H_α$ spectra obtained along five chordal lines-of-sight spanning the plasma radius are analyzed using two complementary models representing limiting cases of the ion dynamics: a collisionless cycloidal model based on the ion-velocity distribution arising from deterministic single-particle orbits, and a rotating Gaussian model based on collisions and collective processes that fully randomize the cycloidal motion into a drifting Maxwellian in the rotating frame. Combined, these approaches bracket the possible degree of velocity-space relaxation and provide a stringent test of the inferred ion energies. Both models reproduce the measured spectra relatively well and yield density-weighted apparent ion temperatures of $1.40\pm0.43$ keV for the rotating Gaussian model and $1.55\pm0.24$ keV for the cycloidal model. These results provide direct spectroscopic evidence that strong $E \times B$ rotation in a device only a few centimeters in size can generate ion populations with keV energy spreads.
[abstract 40 / 65] (score: 2) - Title: The Chirp-Mass Ladder: A New Rung EmergesAuthors: Vaibhav Tiwari,Comments:Subjects: astro-ph.HECreated: 2026-07-12; Updated: 2026-07-14; Datestamp: 2026-07-14
The population of binary BLACK HOLEs (BBHs) observed through gravitational waves (GWs) now includes around 250 events with the release of GWTC-5.0, enabling more detailed studies. The inferred chirp-mass distribution shows prominent peaks at approximately $7.5M_{\odot}$, $14M_{\odot}$, and $27M_{\odot}$, with subsequent peaks spaced by approximately a factor of two. A parsimonious explanation for this structured distribution is a hierarchical merger scenario, in which the first peak arises from mergers of BLACK HOLEs of stellar origin, and higher-mass peaks arise from repeated mergers. Notably, with the addition of new observations, an intermediate peak near $19M_{\odot}$ emerges. This feature had been anticipated in earlier work as a consequence of intergenerational mergers involving second- and third-generation (G) BLACK HOLEs, thereby highlighting the predictive power of the hierarchical-merger interpretation. Furthermore, two groups of $1G+2G$ mergers recently reported in separate studies can be understood as distinct rungs -- $1G+2G$ and $3G+4G$ -- within this hierarchical chirp-mass ladder, a unification that describes both spin transitions with a single mechanism. Although expected correlations between mass ratios and spins are observed in multiple events across the mass range, the lack of clear signatures across all rungs invites investigation into the role of hierarchical mergers in shaping the BBH population.
[abstract 41 / 65] (score: 2) - Title: Exploring the Galactic plasma with pulsars in the SKA EraAuthors: Caterina Tiburzi, M. T. Lam, D. J. Reardon, N. K. Porayko, M. Mevius, S. K. Ocker, S. C. Susarla, J. R. Dawson, J. P. W. Verbiest, A. Deller, G. M. Shaifullah, N. D. R. Bhat, J. -M. Grießmeier, M. Walker, W. Jing, F. A. Iraci, M. Geyer, L. Levin, M. J. Keith, The SKA Pulsar Science Working Group,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Tiburzi01. arXiv admin note: substantial text overlap with arXiv:2512.16158Subjects: astro-ph.HECreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
The ionised media that permeate the Milky Way have been active topics of research since the discovery of pulsars in 1967. In fact, pulsars allow one to study several aspects of said plasma, such as their column density, turbulence, scattering measures, and discrete, intervening structures between the neutron star and the observer, and aspects of the MAGNETic field throughout. Such sources of information allow us to characterise the electron distribution in the terrestrial ionosphere, the Solar Wind, and our Galaxy and have an important impact on other experiments involving pulsars such as Pulsar Timing Arrays. In this article, we review the state-of-the-art of plasma research using pulsars, the aspects that should be taken into consideration for optimal plasma studies, and we provide future perspectives on improvements to those enabled by the SKA.
[abstract 42 / 65] (score: 2) - Title: Scalar and ElectroMAGNETic Perturbations around a Black Hole with a Topological Defect: Quasinormal Modes and Quasi-bound States in a Plasma MediumAuthors: Dilmurod Umarov, Farruh Atamurotov, Ahmadjon Abdujabbarov, Chengxun Yuan, G. Mustafa,Comments: 16 pages, 8 figures, 4 tablesSubjects: gr-qcCreated: 2026-07-12; Updated: 2026-07-14; Datestamp: 2026-07-14
We investigated the influence of a plasma environment on the optical and perturbative properties of a BLACK HOLE with a topological defect, characterized by the parameter \(k\). We first established a straightforward correspondence between the real part of the quasinormal-mode (QNM) frequencies in the eikonal limit and the black-hole shadow radius. We then demonstrated that the Lyapunov exponent associated with the photon sphere exhibits only a weak dependence on the plasma frequency, while it monotonically decreases as the topological-defect parameter \(k\) increases. Subsequently, we analyzed massive scalar-field perturbations by deriving the associated effective potential and computing the QNM spectrum using the third- and sixth-order WKB approximations for both homogeneous and radially inhomogeneous plasma configurations, including the singular isothermal sphere (SIS) and non-singular isothermal sphere (NSIS) density profiles. Our results show that the presence of plasma induces shifts in both the oscillation frequencies and the damping rates of the modes, and that larger values of \(k\) systematically suppress the real part of the QNM frequencies. Among the plasma models considered, the NSIS profile generally yields slightly higher oscillation frequencies than both the SIS and homogeneous cases. Finally, we derived the dynamical equations governing electroMAGNETic perturbations in a cold, unMAGNETized plasma and demonstrated that the axial and polar sectors decouple. In the axial sector, the plasma frequency enters as an effective mass term, thereby permitting the existence of quasi-bound states only in the case of a homogeneous plasma and only when the plasma frequency lies below a critical threshold that depends on the topological-defect parameter \(k\) and the multipole index \(l\).
[abstract 43 / 65] (score: 2) - Title: Low-hard to high-soft spectral state transitions in the faintest early-X-ray-detected optical tidal disruption event TDE 2025aarmAuthors: Pietro Baldini, Arne Rau, Andrea Merloni, Jean Somalwar, Seán J. Brennan, Elias Kyritsis, Hannah C. I. Wichern, Peter Boorman, Panos Charalampopoulos, Lixin Dai, Gaurava K. Jaisawal, Chichuan Jin, Tianying Lian, Kirpal Nandra,Comments: 12 pages, 6 figures (+ appendices). Submitted to A&ASubjects: astro-ph.HE astro-ph.GACreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
We report the X-ray and optical spectroscopic properties of TDE 2025aarm, the second closest tidal disruption event (TDE) discovered to date. The proximity of this source, combined with a deep and intense X-ray monitoring campaign spanning six months, allowed us to probe the source down to an unprecedented 0.2-10 keV luminosity of $\sim7\times10^{39}$ erg s$^{-1}$ close to the optical peak. This renders TDE 2025aarm the faintest early-X-ray-detected TDE to date. After the first X-ray detection, the source brightened by nearly two orders of magnitude, reaching a peak luminosity of $\sim5\times10^{41}$ erg s$^{-1}$ about four months after the optical peak. Through time-resolved X-ray spectral analysis, we find that TDE 2025aarm evolved from an initially hard, power-law-dominated X-ray state into a softer, disk-dominated state as the luminosity increased, before hardening again at later times. Such low-hard-to-high-soft state transitions are commonly observed in BLACK HOLE X-ray binaries (XRBs) but have not previously been reported in thermal TDEs. We show that the spectral evolution can be described by variations in the relative contributions of an accretion disk and a Comptonizing component, qualitatively resembling the disk--corona evolution observed in XRBs. We also present the results of our optical spectroscopic follow-up campaign with HET/LRS2, confirming the TDE classification and revealing NIII Bowen fluorescence features. The extremely faint early-time X-ray emission of TDE 2025aarm further supports the idea that the historical dichotomy between X-ray-bright and X-ray-undetected TDEs is largely driven by selection effects related to the depth, cadence, and duration of X-ray follow-up observations. TDE 2025aarm therefore provides new insight into both the accretion physics of TDEs and the possible universality of accretion across several orders of magnitude in BLACK HOLE mass.
[abstract 44 / 65] (score: 2) - Title: The Black Hole Occupation Fraction as a Fossil Record of Seeding, Dynamics, and Galaxy AssemblyAuthors: Emma Jane Weller, Priyamvada Natarajan, Colin J. Burke,Comments: 10 pages, 5 figures. Submitted for reviewSubjects: astro-ph.GACreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
The BLACK HOLE occupation fraction (BHOF) is a powerful but intrinsically layered diagnostic of massive BLACK HOLE (BH) seeding and subsequent galaxy assembly. We measure the total, central, and wandering BHOF in the ASTRID cosmological hydrodynamical simulation from $z=5$ to $z=0$ in galaxies with stellar masses ranging from $10^7$-$10^{12}$ $\mathrm{M}_\odot$. For the full population, the total BHOF remains close to unity across most stellar masses and redshifts, reflecting efficient seeding in eligible halos. At low stellar masses, the central BHOF declines toward the present day, while the wandering BHOF rises, indicating that mergers dynamically redistribute BHs away from galaxy centers. We further show that selecting only heavy-seed descendants substantially decreases the low-mass BHOF; meanwhile, selecting only active BHs yields a much smaller late-time BHOF at all stellar masses, demonstrating that AGN-selected samples trace duty cycles rather than intrinsic BH occupation. At $z=0$, primary (central) galaxies have higher BHOFs than satellites, and star-forming low-mass galaxies preferentially host wandering rather than central BHs. Our results show that the BHOF, when decomposed by BH location, seeding history, accretion state, and larger-scale galactic environment, encodes a rich fossil record of BH origins and dynamics.
[abstract 45 / 65] (score: 2) - Title: Counting b-JETs at the FCC-ee as a probe of top-QUARK flavor physicsAuthors: Shaouly Bar-Shalom, Jose Wudka,Comments: 18 pages, 6 figures, 5 tablesSubjects: hep-ph hep-exCreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
We explore the sensitivity of a future FCC-ee to multi-TeV new physics (NP) that can generate vector, scalar and tensor flavor-changing (FC) $eetu_k$ contact interactions ($u_k=u,c$ for $k=1,2$), probed via single top-QUARK production, $e^+ e^- \to t \bar{u}_k, t \bar{u}_k γ$ (+ c.c.) and leading (following the top-QUARK decay) to two- and four-JET signals, $e^+ e^- \to 2j + X, 4j + X$, where $X$ denotes any non-JET final-state particles. Our analysis exploits an approximately conserved Standard Model (SM) quantum number introduced in [1] and termed "$b$-Parity" ($b_P$), which is applicable to scattering processes of the type $e^+ e^- \to n \cdot j_b + m \cdot j_\ell + X$, where $n$ and $m$ are the number of produced $b$-JETs and light-JETs ($u,d,c,s,$ and/or gluons) and $b_P=(-1)^n$. The FC $eetu_k$ four-fermion interactions can generate distinct $b_P$-odd ($b_P = -1$) signals in these multi-JET events, for which the only significant SM background stems from $b$-JET misidentification. We demonstrate that the FCC-ee, operating at a $\sqrt{s} = 240$ GeV (the $ZH$ run phase) with high luminosity and excellent flavor-tagging performance, is an ideal platform to search for these $b_P$-odd signatures. Indeed, by simply counting the number of final-state $b$-JETs, the FCC-ee can probe NP scales of $Λ\sim 10$ TeV for the new heavy states that generate the vector, scalar and tensor $eetu$ and/or $eetc$ interactions. This reach, remarkably about 40 times the assumed FCC-ee center-of-mass energy, improves upon current bounds on some of these four-fermion operators by an order of magnitude and it critically relies on high-purity b-JET tagging.
[abstract 46 / 65] (score: 2) - Title: Six-Class BPT Galaxy Classification for Survey-Scale AGN Candidate Prioritization: Deep Tabular Model and Informative Missingness SignalsAuthors: Shanquan Gui,Comments: 12 pages,16 figures, submitted to A&ASubjects: astro-ph.GACreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
The Baldwin--Phillips--Terlevich (BPT) diagram is widely used to classify galaxies into star-forming systems, composite galaxies, and ACTIVE GALACTIC NUCLEi (AGNs), but its survey-scale application is limited by the requirement for high signal-to-noise emission-line measurements. We test whether machine-learning models can reproduce six-class BPT labels while using measured quantities, derived line ratios, and potentially informative missing-data patterns as inputs. We analyze 1.47 million galaxies with a 27-dimensional feature set that combines raw survey measurements, derived quantities, and missingness indicators. Five deep tabular architectures are benchmarked against gradient-boosted trees and classical machine-learning baselines, and the resulting probabilities are evaluated through hard-classification metrics, precision--recall curves, top-$k$ retrieval, ablation tests, and feature-interpretation diagnostics. {CNN--Transformer gives the strongest overall classification performance (accuracy = 0.8266), while boosted trees remain highly competitive for this low-dimensional tabular problem. In the binary star-forming-versus-AGN comparison, CNN--Transformer achieves a Class~1 versus Class~4 ROC AUC of 0.9998. Missingness indicators provide substantial predictive information, especially the OH\_P50N\_missing feature. Feature interpretation further shows that $\log([\mathrm{Ne\,III}]/[\mathrm{O\,II}])$, combined with stellar mass or specific star-formation rate, separates star-forming galaxies from AGN hosts. The models are most useful as AGN candidate-ranking tools that complement, rather than replace, traditional BPT diagnostics. High-ranked samples can reach high purity, while broader candidate lists recover most AGNs, but transferability to other surveys requires further validation.
[abstract 47 / 65] (score: 2) - Title: Assessing the large-scale angular clustering of UNIONS Lyman Break Galaxies via cross-correlationsAuthors: Constantin Payerne, Christophe Yèche, William d'Assignies Doumerg, Hendrik Hildebrandt, Martin Kilbinger, Calum Murray, Thomas de Boer, Kenneth C. Chambers, Scott Chapman, Alan W. McConnachie,Comments: 20 pages, 19 figures, to be submitted to The Open Journal of AstrophysicsSubjects: astro-ph.COCreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
Lyman-break galaxies (LBGs), selected via the strong spectral break blueward of the Lyman limit, are powerful tracers of large-scale structure at redshifts $z>2$. In this work, we assess the feasibility of using LBGs selected from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) multi-band photometric catalog as cosmological probes of the high-redshift Universe using two-point statistics. We demonstrate that spatially varying imaging systematics, driven by variations in PSF depth, seeing across the UNIONS footprint, limit robust measurements of the LBG auto-angular power spectrum on large scales, even after correcting the LBG field with linear or non-linear mitigation techniques. This study shows that clustering analyses of faint galaxy samples close to survey depth are challenging. We therefore turn to cross-correlation measurements with external tracers, in particular the \textit{Planck} CMB lensing convergence and QUASARs from DESI DR1 and \textit{Quaia}, which are less sensitive to the angular imaging systematics. Using both data and mock catalogues, we demonstrate that the LBG--CMB lensing cross-power spectrum can be measured more robustly than the auto-spectrum, with an amplitude consistent with theoretical predictions. Residual systematics primarily manifest as excess variance at large angular scales, without introducing a significant bias in the recovered signal. Taken together, these results establish UNIONS-selected LBGs as reliable tracers for cross-correlation cosmology at $z\sim 2.5$, and highlight cross-correlation techniques as a powerful and robust avenue for extracting cosmological information from photometric high-redshift galaxy samples in the presence of complex imaging systematics.
[abstract 48 / 65] (score: 2) - Title: Faraday depth similarities across scales with LoTSS & DRAGONSAuthors: Anna Ordog, Rebecca A. Booth, Ana Erceg, Vibor Jelić, Jo-Anne C. Brown, Marijke Haverkorn, Alex S. Hill, T. L. Landecker,Comments:Subjects: astro-ph.GACreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
Faraday rotation of diffuse Galactic SYNCHROTRON emission is a powerful tracer of the complex, MAGNETised interstellar medium (ISM), whose structures span a wide range of spatial scales, requiring both interferometric and single-antenna broadband radio polarisation observations for full characterisation. We compare Faraday rotation in the interferometric LOw-Frequency ARray Two-Metre Sky Survey (LoTSS; 120-168 MHz) and the single-antenna Dominion Radio Astrophysical Observatory Global Magneto-Ionic Medium Survey of the Northern Sky (DRAGONS; 350-1030 MHz), which are complementary in their sensitivity to spatial and Faraday-depth scales. We calculate first moments (M1) of polarised intensity versus Faraday depth, producing polarised-intensity-weighted mean Faraday depth maps of the regions common to both surveys. These maps show remarkable agreement between the surveys despite the lack of overlap in frequency or spatial-scale coverage. In the northern Galactic region, the M1 maps are morphologically similar with only small spatial shifts in the boundaries between positive and negative M1, and strong pixel-by-pixel correlation. In the southern Galactic region, both surveys trace the Faraday-depth gradient with Galactic longitude previously identified in LoTSS. Faraday depth spectra show consistent numbers and locations of peaks for more than half of the pixels. The strong structural similarity between the surveys, demonstrated by computing structure functions, suggests coupling across spatial scales in the MAGNETised ISM, enabling both interferometric and single-antenna observations to trace the same features. Instances of differences point to ISM configurations where observational effects such as depolarisation dominate or where this coupling breaks down due to local physical conditions.
[abstract 49 / 65] (score: 2) - Title: Challenges in probing turbulent and MAGNETic support in cores: the W43-MM1 protocluster case studyAuthors: M. Valeille-Manet, F. Louvet, F. Motte, A. M. Stutz, C. Arce-Tord, P. C. Cortés, M. Fernandez-Lopez, N. A. Sandoval-Garrido, P. Sanhueza, R. H. Álvarez-Gutiérrez, S. Chevalier, A. Ginsburg, A. Koley, P. Saha, S. Savorgnano, R. Veyry,Comments:Subjects: astro-ph.GACreated: 2026-07-10; Updated: 2026-07-14; Datestamp: 2026-07-14
Estimating the level of non-thermal support in cores is both challenging and crucial for constraining the earliest stages of STAR FORMATION. We quantify the kinetic and MAGNETic support operating within the cores of the high-mass protocluster W43-MM1, and test the assumptions behind the virial theorem used to interpret observations. We used ALMA 12m molecular line observations of DCN (3-2), 13CS (5-4), and CH3CN (5_3-4_3) to estimate kinetic support. The plane-of-sky MAGNETic field strength (B_POS) was derived from dust-POLARIZATION observations using the Davis-Chandrasekhar-FERMI method, obtained at the three-beam scale (~12500 au) and extrapolated to core scales (~2500 au) using the density-field strength relation. We derive kinetic support estimates for 45 cores (21 prestellar and 24 protostellar), of which 21 also have MAGNETic field estimates. Velocity dispersions range from 0.34 to 4.48 km/s, and B_POS values span 1.1-49.3 mG at core scales. Using the virial theorem, ~70% of cores appear stable against collapse when considering turbulence alone, and ~85% when combining both kinetic and MAGNETic support (alpha_vir,B > 1). These are unexpectedly high values, particularly for protostellar cores expected to be undergoing collapse. We conclude that contamination of linewidths by organized motions (1-3 km/s, consistent with previous observational studies), together with the omission of surface terms in the observational virial theorem, prevents accurate measurement of non-thermal support in cores. This highlights that simplified virial analyses can introduce significant biases when assessing physical support mechanisms within cores.
[abstract 50 / 65] (score: 2) - Title: Electron Acceleration and Plasma Heating in an Impulsive Confined C-class Solar FlareAuthors: I. N. Sharykin, I. V. Zimovets, G. V. Koynash, E. F. Ivanov, V. V. Fedenev, S. A. Anfinogentov,Comments:Subjects: astro-ph.SR astro-ph.IMCreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
A detailed analysis of the impulsive C2.8 solar flare SOL2023-03-19T02:12 is presented, focusing on the microwave (MW) and X-ray domains. The flare was selected because of its impulsive nature, the relatively simple MAGNETic morphology of its parent active region (AR) NOAA 13256, its confined evolution, its moderate intensity, pronounced non-stationary temporal behaviour, and the availability of a unique multi-wavelength dataset. This dataset includes MW spectral observations in the frequency range 2.8-12 GHz obtained with the new Solar Radio Spectropolarimeter (SOLARSPEL), together with MW images from the Siberian Radioheliograph (SRH). The flare was also observed by two imaging X-ray telescopes, Solar Orbiter/STIX and ASO-S/HXI. Nonlinear force-free field extrapolations are used to reconstruct the three-dimensional MAGNETic configuration of the AR. We present evidence for a direct coupling between the thermal plasma and the non-thermal electron population in the frame of collisionless plasma during the initial flare stage. Some simple relationships about electron acceleration process are presented and discussed. Analysis of the extrapolated MAGNETic field indicates that the flare onset was associated with a system of low-lying sheared MAGNETic loops located along the polarity inversion line (PIL). Given the confined nature of the event and the reconstructed MAGNETic configuration, we infer that MAGNETic RECONNECTion most likely occurred within current sheets possessing a substantial guide-field component. The observed non-stationary QPPs in the non-thermal emission, with periods decreasing from approximately 15 to 9 s, are interpreted as signatures of a sequence of MAGNETic RECONNECTion episodes occurring in different MAGNETic structures and triggered quasi-periodically by a process that remains uncertain, but which may involve propagating slow MAGNEToacoustic waves.
[abstract 51 / 65] (score: 2) - Title: Anisotropy and intermittency in drift-wave turbulence with zonal flows: a two-dimensional continuous wavelet analysisAuthors: Katsunori Yoshimatsu, Zetao Lin, Hideaki Miura, Kai Schneider,Comments: 21 pages, 10 figuresSubjects: physics.plasm-ph physics.flu-dynCreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
We examine anisotropy and spatial intermittency at small scales in drift-wave turbulence with zonal flows. We use a two-dimensional directional continuous wavelet transform, which allows simultaneous localization in scale, position, and direction. This wavelet analysis is applied to vorticity fields obtained from numerical simulations of the modified Hasegawa--Wakatani model, a reduced model of resistive drift-wave turbulence in MAGNETized plasmas with zonal flows. Directional wavelet statistics characterize the anisotropy of the turbulence. The second-order moment is enhanced around directions perpendicular to the zonal flow. Spatial intermittency, characterized by scale-dependent flatness, is more pronounced around directions along the zonal flow.
[abstract 52 / 65] (score: 2) - Title: Quasinormal modes of Bonanno-Reuter BLACK HOLEs via the Spectral MethodAuthors: Davide Batic, Denys Dutykh, Fabio Scardigli,Comments: 42 pages, 1 figure, XXIX TablesSubjects: gr-qcCreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
In this work, we explore the quasinormal modes (QNMs) of the Bonanno-Reuter BLACK HOLE, one of the first regular BLACK HOLE metric suggested by the Asymptotically Safe Gravity (ASG) program. The running parameter $α$ is set to a positive value, the related running Newton coupling vanishes at high energies, fully achieving an ultraviolet fixed point and eliminating non-physical UV divergences. This yields a singularity-free geometry. Hence, we focus on the resulting renormalisation-group-improved Schwarzschild metric, which naturally produces an (Anti)deSitter non-singular core. On the basis of this background, we compute the QNM spectrum for scalar, electroMAGNETic, and gravitational perturbations by employing the Spectral Method (SM). This method, recognised for its enhanced precision compared to high-order WKB methods, allows the identification of fundamental modes, extensive collections of overtones, and purely imaginary overdamped modes that were entirely missed in previous analyses. These characteristics, resolved here for the first time in the Bonanno-Reuter BLACK HOLE, underscore the crucial importance of high-precision spectral methods in investigating delicate signatures of BLACK HOLE models inspired by quantum gravity.
[abstract 53 / 65] (score: 2) - Title: Lorentz-Violating Photon Decay into Neutrinos and Constraints from PeV Photon StabilityAuthors: Zurab Kepuladze,Comments: 10 pagesSubjects: hep-ph astro-ph.HECreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
We study the vacuum decay of a Lorentz-violating photon into a neutrino-antineutrino pair. Lorentz-violating corrections to the photon dispersion relation are parametrized through an effective invariant mass $m_{\mathrm{eff}}^{2}=k_αk^α$. This makes the otherwise forbidden decay $γ\toν\barν$ kinematically allowed. The process proceeds through the Standard Model one-loop neutrino electroMAGNETic vertex and is therefore strongly suppressed. Using the low-$q^{2}$ anapole form factor, we derive the decay rate and apply it to TeV and PeV photons. We find that below the electron-positron threshold the neutrino channel is open but generally too slow to provide stronger constraints than existing bounds. Above the threshold, $γ\to e^{+}e^{-}$ dominates unless the relative photon-electron LIV parameter closes this channel. In that case, the neutrino decay gives an independent constraint on photon-neutrino relative LIV parameters.
[abstract 54 / 65] (score: 2) - Title: Divergence Without Transition in Adiabatic Theory: Exact Cancellation in Reflectionless PotentialsAuthors: Amitava Bhattacharjee,Comments:Subjects: physics.plasm-phCreated: 2026-07-11; Updated: 2026-07-14; Datestamp: 2026-07-14
Adiabatic invariants play a central role in plasma physics, from MAGNETic moment and bounce action to wave action in slowly varying media. Their perturbative constructions are often asymptotic, and exhibit factorial growth. We show that such divergence does not by itself imply non-adiabatic transitions. For the reflectionless potential hierarchy associated with Korteweg--de Vries solitons, the exact backward-wave coefficient vanishes, although Berry's phase-integral iteration and the corresponding Lie-transform construction are divergent. Darboux factorisation gives the transmitted wave explicitly. Its modulus and phase define a normal form in which the moving canonical frame is distorted inside the interaction region but returns to its original asymptotic form, leaving only a phase shift and no action change. The exact phase integral is nevertheless an unstable fixed point of the derivative iteration. For the one-soliton symmetry point, an explicit Borel calculation exhibits nonzero singularities in an individual Lie-transform family even though the exact off-diagonal connection coefficient vanishes. Analyticity of the exact connection data then requires these representation-dependent ambiguities to cancel in the completed connection matrix. Thus divergence diagnoses failure of local diagonalisation, whereas the global symplectic connection determines whether reflection survives.
[abstract 55 / 65] (score: 2) - Title: Scalarization of Einstein-Euler-Heisenberg BLACK HOLE with multiple horizonsAuthors: Hong Guo, Yun Soo Myung,Comments: 28 pages, 15 figuresSubjects: gr-qcCreated: 2026-07-12; Updated: 2026-07-14; Datestamp: 2026-07-14
Scalarizations of the Einstein-Euler-Heisenberg (EEH) BLACK HOLE (EEHBH) with multiple horizons are investigated in the EEH-scalar theory by introducing a quadratic scalar coupling to the Maxwell term. For mass $M=1$ and Euler-Heisenberg parameter $μ=0.03$, the MAGNETically charged EEHBH admits four horizon families (low, cold, negative, and hot), with triple horizons appearing in the narrow band of MAGNETic charge $q\in[0.95,1.0065]$. The onset scalarization around the low, cold, and high horizons is then analyzed for the MAGNETic charge $q=0.5,\,1,\,2$, implying infinite branches of scalarized BLACK HOLEs for each case. We construct the three fundamental branches of scalarized BLACK HOLEs. From the positivity condition of their mass, we find the upper bounds on primary scalar charges $q_{s}$ for scalarized low and cold horizons. These bounds determine the allowable regions for the Hawking temperature and entropy. Furthermore, we perform a time-domain stability analysis and find that the instabilities arise only at small scalar charge regime. Therefore, stable and physically viable scalarized BLACK HOLEs exist in an intermediate window of the primary scalar charge for low and cold horizon solutions and a lower bound for hot horizon solution.
[abstract 56 / 65] (score: 2) - Title: Post-Newtonian N-Body Dynamics in Extended Theories of GravityAuthors: Antonio Tedesco,Comments: 19 pages; accepted for publication in The European Physical Journal CSubjects: gr-qcCreated: 2026-07-12; Updated: 2026-07-14; Datestamp: 2026-07-14
We derive the complete first post-Newtonian (1PN) Lagrangian and corresponding equations of motion for the RELATIVISTIC $N$-body system in Scalar-Tensor-Fourth-Order Gravity (STFOG), including the Non-Commutative Spectral Geometry (NCSG) sector as a special case. In the regime $Φ\sim Ψ$ ($γ\sim 1$), the linearized fourth-order field equations are solved in the Standard Post-Newtonian gauge, and the variational Lagrangian is built directly from the point-particle action. The resulting dynamics is governed by three Yukawa functions $ζ$, $\mathcal{W}$ and $Ξ$, which encode the scalar, gravitoMAGNETic and three-body sectors and depend on the effective masses $(m_R,m_Y,m_ϕ)$ of the additional propagating modes. In this context, we show that the nonlinear metric component ${}^{(4)}\!g_{00}$ plays no role at 1PN level. The 1PN orbital motion of the above extended theories is thus obtained in closed form, and the Einstein--Infeld--Hoffmann equations are recovered in the corresponding general-RELATIVISTIC limit. The formalism provides a common framework for the RELATIVISTIC celestial mechanics of the Solar System, binary pulsars such as PSR J0737-3039, Galactic-center stellar orbits and triple systems.
[abstract 57 / 65] (score: 2) - Title: Constraints on Annihilating Dark Matter from Gamma-Ray Background-Galaxy Shape Correlations: Model-independent Null Results and Moderate Template-based SignalsAuthors: Masato Shirasaki, Deheng Song, Oscar Macias, Shunsaku Horiuchi, Naoki Yoshida,Comments: 15 pages, 9 figures, 1 table. To be submitted to Physical Review DSubjects: astro-ph.CO hep-phCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
We revisit the cross-correlation between the unresolved $γ$-ray background and galaxy shapes to constrain the annihilation cross section of particle DARK MATTER. Our analysis uses $γ$-ray photons from 14 years of observations with the FERMI Large Area Telescope (LAT), together with galaxy shape catalogs from the Dark Energy Survey Year 3 (DES Y3) and the Dark Energy Camera All Data Everywhere (DECADE) project, enabling us to probe cosmological large-scale signals over a common sky area of $\sim 12{,}000\,\mathrm{deg}^2$ shared by the $γ$-ray and galaxy data sets. In order to better access signals from large-scale structure, we employ a Fourier-space estimator for the cross-correlation in contrast to the previous DES Y3 analysis. We find that our measurements are consistent with a null detection in a model-independent $χ^2$ test, while template-based analyses yield signals at the $\sim 3σ$ level. Our null results exclude an enhanced annihilation cross section for wino-like DARK MATTER with a mass of $2-3$ TeV under a modest substructure boost factor of $\sim 30$ in Milky Way-sized halos. For larger boost factors of $\sim 100$, the constraints become significantly stronger and exclude the canonical thermal annihilation cross section $\langle σv \rangle = 3 \times 10^{-26}\,\mathrm{cm}^3/\mathrm{s}$ for a $7-40$ GeV DARK MATTER particle annihilating into $b\bar{b}$ or $τ^{+}τ^{-}$. The template-based analysis favors a power-law $γ$-ray energy dependence of the cross-correlation, but also indicates deviations from that expected based on the mean intensity of the unresolved $γ$-ray background around 100 GeV. We further consider decaying DARK MATTER scenarios and derive $2σ$ lower limits on the particle lifetime of $\sim 10^{26}-10^{27}\,\mathrm{s}$, depending on the decay channel.
[abstract 58 / 65] (score: 2) - Title: A Space Mission to Earth's Nearest Black Hole: Reality or Science Fiction?Authors: Cosimo Bambi,Comments: 12 pages, 3 figures. Talk given at the workshop "Frontier Research in Astrophysics - V" (Palermo, Italy, 15-20 June 2026)Subjects: gr-qc astro-ph.HECreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Black holes are the sources of the strongest gravitational fields in the present-day Universe, offering unparalleled opportunities to test Einstein's theory of General Relativity in the strong-field regime. In this talk, I will examine the prospect of sending small spacecraft on an interstellar mission to the nearest BLACK HOLE. While highly speculative and fraught with technical challenges, such an endeavor is not entirely beyond the realm of possibility. Although the necessary technology does not yet exist, it may become available within the next 20 to 30 years. The mission itself could span 80 to 100 years, yet the scientific return would be profound and potentially unattainable through other means.
[abstract 59 / 65] (score: 2) - Title: O5 dark-siren forecasts for modified GW propagation: background robustness of the $Ξ$ posteriorAuthors: Zhaorui Zhang, Hong-Bo Jin,Comments: 10 pages, 4 figuresSubjects: astro-ph.COCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Binary BLACK HOLE mergers without electroMAGNETic counterparts are expected to dominate O5 gravitational-wave catalogs. Recent CHIMERA~2.0 forecasts typically fix $Ω_m$ to a CMB-informed value and use spectroscopic hosts when available, but the corresponding sensitivity of the $Ξ$ posterior has not been assessed for pure dark sirens on the public O5 mock catalog. We analyze 300 O5-sensitivity mock events without galaxy catalogs, varying $Ω_m$ over $[0.20,\,0.35]$ (including Planck $0.315$), and compare fixed-background inference with joint $(H_0,\,Ω_m,\,Ξ)$ inference. The marginalized $Ξ$ posterior is $0.9783 \pm 0.3548$ and shows no change across this interval. Only GW luminosity distances enter the analysis, so the likelihood constrains $Ξ\, D_L^{\rm EM}(H_0,\,Ω_m)$; when $Ω_m$ is changed, $H_0$ shifts to compensate and the $Ξ$ marginal remains unchanged. Joint inference gives $Ξ^{\rm joint} = 0.9550 \pm 0.3710$, with $|ρ| \lesssim 0.05$ for the $Ω_m$--$Ξ$ and $H_0$--$Ξ$ pairs, whereas $ρ_{H_0 Ω_m} \simeq -0.4$ and the $H_0$ median moves by $\simeq 4.2\,{\rm km\,s^{-1}\,Mpc^{-1}}$ over the adopted $Ω_m$ range. Galaxy-catalog analyses on the same events at fixed $Ω_m = 0.3$ reach $\sim 7.5\%$ precision on $Ξ$, compared with $\pm 36.3\%$ here; the larger uncertainty is driven mainly by missing host redshifts. Sub-percent $Ξ$ tests will therefore still require measured redshifts even if dark sirens dominate the detection rate.
[abstract 60 / 65] (score: 2) - Title: VSC: A Zero-Dimensional Fusion Design Platform for Multiple Magnetic ConfigurationsAuthors: Zekun Wang, Huasheng Xie, Feng Zhang, Jian Bao, Ming Yang,Comments: 33 pages, 11 figuresSubjects: physics.plasm-phCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
The VeloAlpha System Code (VSC) is a computational framework for zero-dimensional fusion power-balance studies across five MAGNETic-confinement configurations: tokamaks, MAGNETic mirrors, field-reversed configurations (FRCs), dipoles, and stellarators. A common power-balance formulation connects fusion production, charged-particle deposition, radiation, transport loss, external heating, and fusion gain, while each configuration retains its own geometry, profile weights, confinement model, and operating constraints. The same solver interface supports both single-point calculations and two-dimensional plasma operating contour (POPCON) scans, producing fusion and heating powers, gain, radiation and transport losses, geometry quantities, and configuration-specific validity indicators. VSC therefore makes it possible to study how assumptions about density, temperature, MAGNETic field, confinement, and geometry shape the accessible operating space of different fusion concepts within one traceable framework. By combining reduced-order physics models with a unified computational platform, VSC enables rapid assessment and comparative analysis of candidate fusion reactor concepts during the early design stage.
[abstract 61 / 65] (score: 2) - Title: Cosmic-ray anisotropy: sensitivity of methods and implications for KASCADE dataAuthors: M. Yu. Kuznetsov, N. A. Petrov, E. M. Shinkevich,Comments: 22 pages, 17 figuresSubjects: astro-ph.HECreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
We study the problem of measuring the anisotropy of high-energy COSMIC RAYs across all angular scales. The limited field of view and non-uniform exposure of ground-based cosmic-ray experiments reduce their sensitivity to real anisotropy of cosmic-ray arrival directions. A widely used signature of anisotropy -- a dipole of the flux expansion over the right ascension -- provides very limited understanding of the underlying physics of cosmic-ray origin and propagation. In this study we test two other methods: the angular power spectrum and the autocorrelation function for sensitivity to possible medium- and small-scale anisotropies of cosmic-ray flux. We find that the autocorrelation function is the most sensitive estimator for an underlying physical anisotropy in most of the models tested, while the angular power spectrum can provide additional knowledge about cosmic-ray flux properties, when the anisotropy is strong enough. As a test of our findings, we apply these methods to $10\%$ sample of the KASCADE experiment public data. Namely, we consider all-particle set of events and sets of individual mass groups classified by a convolutional neural network. We find an indication of anisotropy at $> 2.5 σ$ level at $\sim 10^\circ$ angular scale for the iron nuclei mass group at $E \gtrsim 20$ PeV with both the angular power spectrum and the autocorrelation methods.
[abstract 62 / 65] (score: 2) - Title: Superdiffusion of COSMIC RAYs in the vicinity of their accelerators and the resulting $γ$-ray emissionAuthors: Zhaodong Shi, Guangwei Wang, Rui-zhi Yang,Comments: Accepted for publication in MNRAS. 18 pages, 16 figures, 1 tableSubjects: astro-ph.HECreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
We study the distribution of COSMIC RAYs (CRs) in the vicinity of their accelerators, assuming that the transport of CRs in the interstellar medium surrounding the accelerators is described by the superdiffusion, beyond the normal diffusion. We find that the superdiffusivity, which is characterized by the superdiffusion parameter $α$, impacts significantly the distribution of CRs. For impulsive injection, the CR distribution behaves a constant radial profile, except with a power-law tail for $α< 2$ or a Gaussian tail for $α=2$ at large distance, $r$, from the accelerators. For stationary injection, the radial profile of CR protons tends to being proportional to $r^{α- 3}$, while that of CR electrons can deviate from the $r^{α- 3}$ profile, due to their severe energy losses. We also compute the $γ$-ray emission, produced by the interactions of CRs with ambient gas and radiation fields, within 100 pc regions around the accelerators. We find that by investigating the $γ$-ray morphology, we can distinguish the superdiffusion from the normal diffusion with present and next-generation imaging air Cherenkov telescopes.
[abstract 63 / 65] (score: 2) - Title: Can third- and fourth-order multipoles plus radial variation of iso-density ellipses explain the observed flux ratios in B1422$+$231? YES, and a lesson learned from a TNG100 lensing galaxy sampleAuthors: Ruizhe Feng, Dandan Xu, Dominique Sluse, Giulia Despali, Anowar Shajib, Cai-Na Hao,Comments: 18 pages, 10 figures, 4 tables, submitted to ApJ. Comments are welcome!Subjects: astro-ph.GA astro-ph.COCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Flux ratio anomalies in multiply-imaged QUASAR lenses are a long-standing issue. Using a classical system B1422+231 as a case study, we investigate how typical non-clumpy perturbations beyond elliptical shapes -- multipoles $m_3, m_4$ and radial variations in $q, ϕ_q$ -- can account for the observed image positions and flux ratios under different observational precisions. We extract these perturbations from a pre-selected strong-lensing galaxy sample from the TNG100 simulation. Smooth macroscopic models (SIE+$γ$, EPL+$γ$) are then fitted to the observed image positions alone and to both positions and flux ratios, with and without including the extracted perturbations. With astrometric uncertainty of $σ_{p}=10$ mas, both macro-models alone can already successfully fit image positions within $3σ_{p}$. At $σ_{p}=2$ mas, however, 'astrometric anomalies' appear if smooth macro-models alone are adopted. In this case, adding the extracted perturbations can explain the anomalous image positions. When both positions and flux ratios are adopted, the SIE+$γ$ model family already shows 'flux ratio anomalies' at photometric uncertainty $σ_{f} \le 10\%$ (keeping $σ_{p}=10$ mas). When EPL+$γ$ is used, the smooth model alone can simultaneously fit both positions and flux ratios with $σ_{f}=10\%, 5\%$, but not with $σ_{f}=2\%$, where 'flux ratio anomalies' appear. Adding all four types of extracted perturbations can rescue the macro-models and explain the observed anomalous flux ratios. We present important lessons learned regarding model flexibility and degeneracy.
[abstract 64 / 65] (score: 2) - Title: Zonal-flow generation and saturation of electroMAGNETic ion-scale turbulence in tokamaksAuthors: Y. Zhang, T. Adkins, M. Barnes, A. V. Dudkovskaia, M. R. Hardman, P. G. Ivanov, D. Kennedy, A. A. Schekochihin,Comments:Subjects: physics.plasm-phCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Local flux-tube gyrokinetic simulations of ion-scale turbulence in tokamak plasmas at finite plasma beta are conducted to investigate the generation of zonal flows via turbulent stresses. A parameter scan in the safety factor $q$ and electron beta $β_e$ reveals a transition from low- to high-transport states when $β_{\mathrm{eff}} \equiv q^2β_e$ exceeds a certain critical value $C_{\mathrm{nl}}$. While the linear stability limits for kinetic and ideal ballooning modes also scale as $β_e \propto 1/q^2$, they lie above the observed transition, indicating that the effect is not due to linear instabilities but to nonlinear dynamics. At low $β_{\mathrm{eff}}$, Reynolds stress dominates and drives zonal flows. At higher values, Maxwell stress becomes comparable, suppressing zonal-flow formation and leading to divergent transport. This nonlinear-transition boundary is determined for both the Cyclone Base Case and a spherical tokamak (ST40) configuration, suggesting that the relation $β_{\mathrm{eff}} = C_{\mathrm{nl}}$ may have broader applicability, though $C_{\mathrm{nl}}$ appears to be configuration-dependent. For the Cyclone Base Case, the ratio of energy transfer rates into zonal flows due to Maxwell and Reynolds stresses is observed empirically to scale as $β_e$ for $β_e$ below a critical value $β_{e,\mathrm{sb}}$ (scaling breakdown). The value of $β_{e,\mathrm{sb}}$ is found to increase with decreasing aspect ratio, suggesting that the linear scaling remains valid over a wider range of $β_e$ for more compact MAGNETic equilibria. This low-$β_e$ scaling provides the basis for a practical method to predict the nonlinear-transition threshold with minimal reliance on highly electroMAGNETic nonlinear simulations.
[abstract 65 / 65] (score: 2) - Title: Why gas-focused microJETs are so fast: kinetically resolved, shear-driven flow focusing in vacuumAuthors: Alfonso M. Ganan-Calvo,Comments: 6 pages, 5 figures (15 plots)Subjects: physics.flu-dynCreated: 2026-07-13; Updated: 2026-07-14; Datestamp: 2026-07-14
Gas-focused liquid microJETs -- the flow-focusing sample delivery on which serial femtosecond crystallography depends -- reach speeds several times the pressure-driven (Bernoulli) bound, unexplained by continuum, local-equilibrium models that do not resolve the rarefied, hypersonic expansion of the focusing gas. We resolve that expansion with a deterministic kinetic (Shakhov--BGK) solver and couple it to the slender liquid JET. The JET is \emph{shear-driven}, not pressure-driven: the tangential stress of the hypersonic gas supplies nearly all of the axial momentum, accounting for the anomalous speed. The gas does not become ballistic behind the near field -- its stress decays as a power law and it stays coupled -- and its constitutive regime is set by a single rarefaction parameter $δ=D/\ell_0$, the orifice diameter over the source mean free path, through the thermodynamic Deborah number $De_θ\simeq K\!n\,M$ (Knudsen times Mach), whose $De_θ=1$ surface maps where the Newtonian-gas closure fails: the small-$δ$ vacuum corner where crystallography JETs operate. The kinetically computed surface stress is the input for the fully non-Newtonian (viscoelastic-liquid) sequel.
arXiv:2607.10407 [pdf, ps, other]
arXiv:2607.11439 [pdf, ps, other]
arXiv:2601.21827 [pdf, ps, other]
arXiv:2607.11670 [pdf, ps, other]
arXiv:2607.09920 [pdf, ps, other]
arXiv:2607.10060 [pdf, ps, other]
arXiv:2607.10167 [pdf, ps, other]
arXiv:2607.10359 [pdf, ps, other]
arXiv:2606.30764 [pdf, ps, other]
arXiv:2607.09871 [pdf, ps, other]
arXiv:2607.10047 [pdf, ps, other]
arXiv:2607.11545 [pdf, ps, other]
arXiv:2607.11805 [pdf, ps, other]
arXiv:2607.09854 [pdf, ps, other]
arXiv:2607.11316 [pdf, ps, other]
arXiv:2607.11402 [pdf, ps, other]
arXiv:2206.07447 [pdf, ps, other]
arXiv:2510.12860 [pdf, ps, other]
arXiv:2511.23267 [pdf, ps, other]
arXiv:2604.20499 [pdf, ps, other]
arXiv:2605.25689 [pdf, ps, other]
arXiv:2606.00901 [pdf, ps, other]
arXiv:2607.03138 [pdf, ps, other]
arXiv:2607.10225 [pdf, ps, other]
arXiv:2607.10267 [pdf, ps, other]
arXiv:2607.10304 [pdf, ps, other]
arXiv:2607.10342 [pdf, ps, other]
arXiv:2607.10977 [pdf, ps, other]
arXiv:2607.11447 [pdf, ps, other]
arXiv:2607.11546 [pdf, ps, other]
arXiv:2607.11761 [pdf, ps, other]
arXiv:2507.11491 [pdf, ps, other]
arXiv:2507.21566 [pdf, ps, other]
arXiv:2510.25579 [pdf, ps, other]
arXiv:2512.21108 [pdf, ps, other]
arXiv:2605.10465 [pdf, ps, other]
arXiv:2605.25282 [pdf, ps, other]
arXiv:2606.03944 [pdf, ps, other]
arXiv:2606.17195 [pdf, ps, other]
arXiv:2606.18081 [pdf, ps, other]
arXiv:2607.06096 [pdf, ps, other]
arXiv:2607.07487 [pdf, ps, other]
arXiv:2607.09850 [pdf, ps, other]
arXiv:2607.09853 [pdf, ps, other]
arXiv:2607.09856 [pdf, ps, other]
arXiv:2607.09865 [pdf, ps, other]
arXiv:2607.09943 [pdf, ps, other]
arXiv:2607.09964 [pdf, ps, other]
arXiv:2607.10029 [pdf, ps, other]
arXiv:2607.10048 [pdf, ps, other]
arXiv:2607.10136 [pdf, ps, other]
arXiv:2607.10199 [pdf, ps, other]
arXiv:2607.10404 [pdf, ps, other]
arXiv:2607.10475 [pdf, ps, other]
arXiv:2607.10614 [pdf, ps, other]
arXiv:2607.10889 [pdf, ps, other]
arXiv:2607.10974 [pdf, ps, other]
arXiv:2607.10982 [pdf, ps, other]
arXiv:2607.11144 [pdf, ps, other]
arXiv:2607.11208 [pdf, ps, other]
arXiv:2607.11405 [pdf, ps, other]
arXiv:2607.11485 [pdf, ps, other]
arXiv:2607.11559 [pdf, ps, other]
arXiv:2607.11789 [pdf, ps, other]
arXiv:2607.11802 [pdf, ps, other]