Current date: 2026-09-02
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Number of records retrieved: 870
Keyword score statistics
score 10 -- 1 abstracts
score 9 -- 1 abstracts
score 8 -- 2 abstracts
score 7 -- 1 abstracts
score 6 -- 1 abstracts
score 5 -- 5 abstracts
score 4 -- 7 abstracts
score 3 -- 7 abstracts
score 2 -- 25 abstracts
in total -- 50 abstracts
Articles that appeared on 2026-09-02
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[abstract 1 / 50] Wow! (score: 10)
- Title: X-ray Flares in Gamma-Ray Bursts at High and Very-High-EnergiesAuthors: Pawan Tiwari, Biswajit Banerjee, Gor Oganesyan, Ansh Chopra, Annarita Ierardi, Marica Branchesi, Stefano Ascenzi, Maria Edvige Ravasio,Comments: 19 pages, 12 figures, submitted to Astronomy & Astrophysics (A&A)Subjects: astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
A significant fraction of GRB early afterglows exhibit fast and bright X-ray flares, discovered by SWIFT X-ray Telescope. Their rapid temporal variability and spectral evolution have suggested an internal shock origin, analogous to prompt MeV emission. However, their physical origin and radiation mechanism remain debated. High-energy (> 100 MeV) and very-high-energy (> 30 GeV) gamma-ray observations provide a powerful probe of flare dissipation region, constraining its size, MAGNETic field strength, and particle acceleration under the SYNCHROTRON self-Compton scenario in optically thin RELATIVISTIC JETs. We present a systematic multi-wavelength study of 66 X-ray flares from 47 GRBs observed by X-ray Telescope over 17 years, all within field of view of FERMI Large Area Telescope. We investigate their GeV counterparts and find that only five flares exhibit significant high-energy emission (> 3 sigma). Broadband spectral modeling indicates that this GeV emission is consistent with standard forward shock afterglow. We further investigate correlations between flare spectral properties and energy fluxes at 1 keV, 10 keV, and 1 GeV. Using a SYNCHROTRON self-Compton model, we constrain the physical conditions of the emitting region, including MAGNETic field strength, bulk Lorentz factor, and emission radius. For the most stringent GeV upper limits, we find a MAGNETic-to-electron luminosity ratio greater than or equal to 1, implying a highly MAGNETized emitting region. We predict very-high-energy gamma-ray emission from X-ray flares at early (~500s) and late (~5000s) times and assess their detectability with Cherenkov Telescopes. We find that later X-ray flares provide the most promising targets for follow-up observations owing to improved observational accessibility, sensitivity, and reduced response-time constraints of facilities such as Cherenkov Telescope Array Observatory.
[abstract 2 / 50] Wow! (score: 9) - Title: AGN X-ray coronae at high luminosity: A broadband study of RBS 229 and PG 1407+265Authors: Alessandro Leonardo Lai, Stefano Bianchi, Andrea Marinucci, Enrico Piconcelli, Francesco Ursini, Elena Bertola, Giorgio Lanzuisi, Pierre-Olivier Petrucci, Daniel Stern, Cristian Vignali, Luca Zappacosta,Comments: 17 pages, 11 figures, accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Context. The X-ray emission of ACTIVE GALACTIC NUCLEi (AGNs) is commonly interpreted as arising from Comptonisation in a hot corona above the accretion disc. A prominent soft X-ray excess is also observed in many sources and is often explained by a warm Comptonising layer. Aims. We investigate the X-ray-emitting coronae of the luminous radio-quiet QUASARs PG 1407+265 ($z=0.94$) and RBS 229 ($z=0.334$), testing whether a two-corona scenario consistently describes their broadband spectra. Methods. We combine XMM-Newton EPIC and Optical Monitor data with simultaneous NUSTAR observations and long-term SWIFT monitoring, and model the spectra using Comptonisation models. Results. Both QUASARs are X-ray loud relative to the standard $α_{\rm OX}$-$L_{\rm UV}$ relation, with PG 1407+265 showing the strongest deviation. Their spectra are well reproduced by a warm, optically thick Comptonising component accounting for the soft excess and a hot corona producing the hard X-ray continuum. Both sources show high-energy cut-offs at approximately 70-80 keV. RBS 229 exhibits moderate reflection and a weak neutral Fe K-alpha line, while no significant reflection features are detected in PG 1407+265. The warm-corona parameters of RBS 229 remain consistent across epochs, whereas PG 1407+265 shows strong variability, including an extreme soft-excess episode extending to approximately 3 keV in the rest frame. Conclusions. These results constrain AGN coronae in the poorly explored high-luminosity regime. The cut-offs are broadly consistent with trends in AGN luminosity and accretion rate and remain below the runaway pair-production limit. The contrasting variability suggests that the warm corona responds to changes in the accretion flow while remaining within a narrow range of physical conditions.
[abstract 3 / 50] Wow! (score: 8) - Title: GRMHD Simulations of Accreting Proto-Magnetars I. Implications for Gamma-Ray Burst Jets and Energetic ExplosionsAuthors: Tejas Prasanna, Kyle Parfrey, Brian D. Metzger, Ore Gottlieb, Andrei Beloborodov, Koushik Chatterjee,Comments:Subjects: astro-ph.HECreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
Newly formed, rapidly rotating, strongly MAGNETized neutron stars ("millisecond proto-MAGNETars") are promising central engines for GAMMA-RAY BURSTs (GRBs) and luminous SUPERNOVAe. Although often modeled in isolation, they can be born surrounded by accretion disks in stellar collapse, neutron-star mergers, or accretion-induced collapse. We present axisymmetric GRMHD simulations of hyperaccretion onto such objects, including a physical equation of state and charged-current weak interactions. Holding the weakly MAGNETized accretion torus fixed, we vary the stellar dipole field strength to span crushed-MAGNETosphere, MAGNETically channeled accretion, and centrifugal-propeller regimes, and compare with an otherwise similar accreting BLACK HOLE. Accretion compresses the stellar MAGNETosphere and opens additional MAGNETic flux, producing RELATIVISTIC JET powers that exceed isolated-dipole spin-down estimates by factors of a few to ~10. Even while the MAGNETosphere remains compressed against the stellar surface, stronger fields increasingly impede accretion and enhance outflows. Channeled-accretion models show strong JET variability driven by plasmoid eruptions and intermittent MAGNETospheric accretion, whereas the propeller model produces a steadier, more powerful JET and rapid spin-down. The disk-MAGNETosphere interaction also regulates how efficiently the neutron star grows and whether it spins up or down; near spin equilibrium, inefficient accretion can delay collapse to a BLACK HOLE relative to estimates based on the external mass-supply rate. Accreting proto-MAGNETars can therefore power RELATIVISTIC JETs and baryon-rich outflows with energetics comparable to those inferred for long GRBs and GRB-SUPERNOVAe. A companion paper explores implications for neutron-rich ejecta and r-process nucleosynthesis.
[abstract 4 / 50] Wow! (score: 8) - Title: A Galactic microBLAZAR as a potential accelerator of ultra-high-energy particlesAuthors: Josep Martí, Pedro L. Luque-Escamilla, Benito Marcote, Leandro Abaroa, Arnau Aguasca-Cabot, Jorge A. Combi, Gustavo E. Romero, Josep M. Paredes, Federico García, Federico Fogantini, Enzo A. Saavedra, Daniel del Ser, Jakob van den Eijnden,Comments: 6 pages and 5 figures in main text, followed by appendices A to N. Accepted for publication in Astronomy and AstrophysicsSubjects: astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Context. Persistent JETs from X-ray binaries which are aligned very close to the line of sight could be considered to be Galactic equivalents of BLAZARs, or 'microBLAZARs'. They are also expected to power gamma-ray sources. Aims. We intend to assess a serious candidate apparently fulfilling many of the requirements to be considered a genuine member of this class: IRAS 18293-0941. Methods. An intense multi-wavelength observational and theoretical study has been carried out on our proposed candidate source. Results. With photometric and spectroscopic properties typical of a binary star, this system exhibits clear collimated and one-sided radio emission matching the effects of RELATIVISTIC motion along a reduced ejection angle. Only fast variability is not observed possibly smoothed by a dense circumstellar envelope. A physical scenario is consistently modeled that also gives credibility to its likely connection with LHAASO J1831-1007u*, an ultra-high-energy source in its immediate vicinity. Conclusions. Our reported identification not only helps to fill a gap in Galactic taxonomy, but also potentially strengthens the role of the microBLAZAR and microQUASAR families in our understanding of the most energetic Milky Way phenomena.
[abstract 5 / 50] Wow! (score: 7) - Title: A break in the X-ray loudness of Markarian 590: evidence for an AGN spectral state transition?Authors: B. Palit, A. Rozanska, A. G. Markowitz, D. Lawther, M. Vestergaard, J. J. Ruan, T. Saha, G. Walsh, A. Borkar, M. Sniegowska, K. X. Lu,Comments: Accepted for publication in ApJ; 28 pages, 9 figures, 3 tablesSubjects: astro-ph.HE astro-ph.GACreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Using decade-long multi-band {\it SWIFT} observations of the changing-look AGN Markarian 590, we identify a clear break in the dependence of the X-ray loudness parameter $α_{\rm ox}$ on the source accretion rate. This break could be potential evidence for an accretion state transition, analogous to that observed for X-ray binaries. The $α_{\rm ox}$ follows a pronounced 'V'-shaped dependence on Eddington ratio $λ_{\rm Edd}$, with a statistically significant break at $λ_{\rm Edd} =0.021\pm0.008$, consistent with the Eddington-ratio threshold associated with changing-look events in QUASARs. This behavior is indicative of a change in the inner accretion flow, from a truncated disk with a dominant hot corona at low accretion rates to an inward extending disk with enhanced UV emission and a prominent warm Comptonizing layer at higher rates. The UV and X-ray Eddington ratio tracers also show consistent breaks at $λ_{\rm Edd}\sim0.004$. Mkn~590 evolves through distinct phenomenological accretion phases, from a faint, hard X-ray dominated state, through a flaring phase, to a bright, UV/soft X-ray dominated phase and exhibiting variability on month-, year-, and decade-long timescales. This overall evolution is shorter than classical viscous timescales but broadly consistent with propagating thermal fronts in the accretion disk. We also found a declining radio-to-X-ray luminosity ratio with increasing $λ_{\rm Edd}$, indicating a relative suppression of radio emission as the disk becomes more dominant with respect to the X-ray corona. Taken together, these results provide evidence that Mkn~590 is undergoing a state transition, supporting a broad analogy between changing-look AGNs and X-ray binaries.
[abstract 6 / 50] Yes (score: 6) - Title: GRMHD Simulations of Accreting Proto-Magnetars II. Implications for r-process NucleosynthesisAuthors: Tejas Prasanna, Kyle Parfrey, Brian D. Metzger, Ore Gottlieb, Andrei Beloborodov, Koushik Chatterjee,Comments:Subjects: astro-ph.HECreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
Newly formed, rapidly spinning, strongly MAGNETized neutron stars ("millisecond proto-MAGNETars") can arise in collapsars, neutron star mergers, or white-dwarf accretion-induced collapse, and are often surrounded by compact accretion disks. At accretion rates of ~0.1 Msun/s, these disks can become neutron rich and power outflows capable of rapid neutron-capture (r-process) nucleosynthesis. In Paper I, we presented axisymmetric GRMHD simulations of accretion onto such proto-MAGNETars and showed how the disk-MAGNETosphere interaction regulates JET power, variability, and neutron star torques. Here we use the same simulations to study how this interaction regulates the mass, composition, and velocity of the baryon-rich ejecta, comparing proto-MAGNETar models to otherwise similar BLACK HOLE accretion. A MAGNETized neutron star qualitatively changes both the amount and composition of the ejecta. Stronger neutron star MAGNETic fields suppress accretion and redirect more inflowing material into unbound outflows, even when the MAGNETosphere remains strongly compressed by the disk. Once the field produces MAGNETic channeling or centrifugal acceleration, mass loss is enhanced further. Reaction-network calculations show that these MAGNETically driven outflows can synthesize the full range of r-process nuclei, including the heaviest elements. Moderate neutrino irradiation substantially reduces the third-peak yield, but MAGNETically accelerated neutron star outflows retain a heavy component more effectively than BLACK HOLE disk winds; sufficiently strong early-time irradiation suppresses it altogether. Accreting proto-MAGNETars may therefore be important heavy r-process sources once their neutrino emission has sufficiently declined.
[abstract 7 / 50] Yes (score: 5) - Title: MicroQUASAR Remnants as Pevatrons Illuminating the Galactic Cosmic Ray KneeAuthors: Bing Theodore Zhang, Shiqi Yu,Comments: 4 + 4 figures and 2 tableSubjects: astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
MicroQUASARs are primary candidates for Galactic PeVatrons, yet their collective contribution to the COSMIC RAY (CR) ``knee" remains poorly understood. We investigate this contribution by simulating anisotropic diffusive propagation through the Galactic MAGNETic field. Our results demonstrate that spatial alignment and MAGNETic connectivity between source locations and the solar neighborhood govern the local flux: sources aligned with local MAGNETic field lines yield pronounced flux enhancements, whereas MAGNETically disconnected locations are strongly suppressed. We find that the characteristic proton bump near PeV is robust across random realizations of the Galactic microQUASAR remnant population, with as few as four nearby remnants accounting for 50\% of the observed PeV flux. Our findings suggest that the integrated history of microQUASAR remnants, governed by source temporal and spatial distribution and MAGNETic transport, naturally populates the observed CR ``knee''.
[abstract 8 / 50] Yes (score: 5) - Title: Early Supermassive Black Holes and Little Red Dots Require Free-Fall GrowthAuthors: Junehyoung Jeon, Volker Bromm, Michael Boylan-Kolchin, Julian B. Muñoz,Comments: 10 pages, 5 figures, Submitted to the Open Journal of AstrophysicsSubjects: astro-ph.GA astro-ph.COCreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
Supermassive BLACK HOLEs/ACTIVE GALACTIC NUCLEi (SMBHs/AGN), forming only a few hundred million years after the Big Bang as observed with the James Webb Space Telescope (JWST), challenge theoretical understanding. How could they grow so massive $(M_{\rm BH} > 10^6 {\rm \,M}_\odot)$ so quickly after initial seeding? Is this rapid growth related to the numerous and enigmatic Little Red Dots (LRDs), compact sources with AGN-like characteristics, discovered by JWST? To address these mysteries, we consider the first-order constraint on SMBH growth: enough baryonic material has to reach the vicinity of the SMBH seed, located near the bottom of the gravitational potential well of the host DARK MATTER halo. We specifically examine cold-mode accretion, where gas from the cosmic environment flows into the virialized halo in cold streams without being shock-heated, efficiently reaching the center on a free-fall timescale. We find that cold mode accretion is necessary to supply material for the SMBHs to reach the observed masses, whereas for shock-heated gas inflow the required amount could only be supplied by implausibly rare halos. Moreover, cold-mode inflow in rare $(\sim1$ Gpc$^{-3}$) halos matches the mass and number of the massive QUASARs, and halos able to support super-Eddington accretion for massive SMBHs ($\sim10^7$ M$_\odot$) match LRD number densities. The decreasing LRD abundance at lower redshifts may then reflect the termination of cold-mode accretion in the growing host halos. The populations of massive SMBHs and LRDs at early times may thus arise naturally from cosmological structure formation, based on the abundance of halos capable of supplying sufficient material through cold accretion.
[abstract 9 / 50] Yes (score: 5) - Title: Redshift Identifiability from Gamma-Ray Burst Prompt EmissionAuthors: Shu-Xu Yi,Comments: accepted for publication in ApJ;Subjects: astro-ph.HECreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
We examine which prompt-emission observables of GAMMA-RAY BURSTs (GRBs) carry identifiable redshift information in realistic structured-JET scenarios. By examining the photon-level Lorentz and cosmological transformations, we demonstrate any spectral observable reflecting the dominant-patch emission and any temporal observable reflecting the co-moving frame physics in the JET suffers from the same $z$-$θ_v$ degeneracy. The observable reflecting the absolute flux or count rate will also suffer from this $z$-$θ_v$ degeneracy in a different form. Due to the large variation of the intrinsic luminosity, combining the observables in the above-mentioned three classes cannot break this degeneracy. However, we demonstrate that two other classes of observables contain the potential to break this degeneracy: (i)~central engine-imprinted time scales, (ii)~emission from out of the dominant patch.
[abstract 10 / 50] Yes (score: 5) - Title: Constraining AGN Disk Properties with Gravitational Waves from Inspiraling Stellar-Mass Binary Black Holes in Hierarchical Triple SystemsAuthors: Jie Wu, Mengfei Sun, Jin Li, Zhoujian Cao,Comments: 15 pages, 7 figuresSubjects: gr-qc astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Space-based gravitational-wave detectors can observe stellar-mass binary BLACK HOLEs (BBHs) long before merger, allowing weak environmental perturbations to accumulate. For binaries embedded in ACTIVE GALACTIC NUCLEus (AGN) disks, the local gas density characterizes the environment of the supermassive BLACK HOLE (SMBH) and compact-object migration. We study whether such signals can constrain this density when a stellar-mass BBH orbits a Kerr SMBH. We evolve the outer orbit with RELATIVISTIC corrections and gaseous dynamical friction (DF), and construct the detector-frame waveform including BBH inspiral, de Sitter precession, DF phase correction, and moving-source effects. Using Fisher-matrix calculations for sampled systems, we estimate statistical uncertainties and systematic errors. Larger gas densities generally improve the statistical precision of several source and outer-orbit parameters, but also increase systematic errors when DF is omitted. For favorable GW190521-like systems observed by LISA for one year, the disk density can be constrained at the level of $σ_ρ\sim10^{-12}\text{--}10^{-10}\,{\rm g\,cm^{-3}}$. Such constraints would connect BBH merger environments to the gas structure of galactic nuclei and the conditions that support BLACK HOLE growth. These results indicate that hierarchical BBH inspirals can probe AGN disk environments, provided that gas effects are modeled consistently.
[abstract 11 / 50] Yes (score: 5) - Title: A Magnetothermodynamic Theory of Energy Transport In Collisionless PlasmasAuthors: Dominic Payne,Comments:Subjects: physics.plasm-ph physics.space-phCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Presented here is an exploratory conceptual framework with the aim of describing electroMAGNETic and thermal energy transport and transfer in collisionless plasmas in a coherent way, starting from an arrow-of-time perspective. That is, arguments about the transport of energy are fundamentally based on the idea that systems tend to fill the phase space available to them. First, we describe electric fields, MAGNETic fields, and plasma particles as interacting subsystems that are thermodynamically linked in specific ways. Second, we discuss the importance of the stochastic electric field in the transport of plasma particles down energy density gradients until the energy flux contributions from so-called electrothermodynamic (ETD) interactions become sufficiently uniform. Third, the logic of ETD transport is extended to a MAGNETized system invoking 2 types of MAGNETothermodyamic (MTD) transport: 1) transport of electroMAGNETic energy through stochastic Poynting flux and 2) plasma energy transport through stochastic drift energy fluxes associated with local ExB drift motion. The magnitudes of the ETD and MTD mechanisms are tied to local characteristic scales of the electric field fluctuations and critical scales are derived beyond which ETD mechanisms dominate MTD mechanisms. Finally, we discuss the interplay between electrothermodynamic and MAGNETothermodynamic equilibria (ETE and MTE), dynamics in the small critical scale (MTD) limit, and the potential relevance of this type of description to the problem of RECONNECTion onset and scale coupling.
[abstract 12 / 50] Yes (score: 4) - Title: Search for DARK MATTER subhalos among unassociated FERMI-LAT sources in presence of dataset shiftAuthors: Aurelio Amerio, Dmitry Malyshev, Bryan Zaldivar, Viviana Gammaldi, Miguel Ángel Sánchez-Conde,Comments: 27 pages + appendix, 19 figures and 5 tablesSubjects: astro-ph.HECreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
We present a search for DARK MATTER (DM) annihilating subhalos of the Milky Way halo among the {\FERMI} Large Area Telescope (LAT) unassociated sources. For this purpose, we construct the first statistical model of the unassociated sources at latitudes above 10 degrees, combining potential DM subhalos with Galactic and extragalactic astrophysical components. The distributions of astrophysical sources are constructed based on associated sources, while the DM subhalo distribution is derived from Monte Carlo simulations. We account for differences between associated and unassociated source distributions using a model with covariate and prior probability shifts, which are particular cases of more general dataset shifts. This approach is based on quantification learning, advancing beyond previous classify-and-count strategies by providing a well-defined statistical interpretation of the potential contribution from a DM subhalo population. For the $b\bar{b}$ annihilation channel and DM masses from 10 GeV to 1 TeV, we find no significant contribution from DM subhalos, and therefore derive 95% confidence upper limits on the annihilation cross section. Our analysis yields limits consistent with previous classify-and-count approaches, while the underlying generative model provides a more robust statistical framework, opening new avenues for population studies of FERMI-LAT sources and, more generally, for searches of anomalies, such as a new class of sources in addition to the known classes of sources, in presence of statistical and systematic uncertainties.
[abstract 13 / 50] Yes (score: 4) - Title: Multi-Tracer Cross-Correlations of the Unresolved $γ$-Ray SkyAuthors: B. Thakore, M. Regis, M. Negro, S. Camera, D. Gruen, N. Fornengo, A. Roodman,Comments: 29 pages, 9 figuresSubjects: astro-ph.CO astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Our understanding of the $γ$-ray sky has greatly advanced, yet studying the unresolved $γ$-ray background (UGRB) can unveil the nature of the faintest $γ$-ray source populations in the Universe. Statistical cross-correlations between the UGRB and tracers of large-scale cosmic structure allow us to infer which sources contribute the most to this emission. In this work, we examine the angular correlation between the UGRB and the matter distribution traced by galaxies, using twelve years of FERMI Large Area Telescope (LAT) observations along with three years of Dark Energy Survey (DES) data. We detect a correlation with a signal-to-noise ratio of 7.85, primarily driven by large angular scales. We then perform a multi-tracer analysis that combines this measurement with the cross-correlation between $γ$ rays and DES weak lensing. The two single-tracer results are mutually consistent, and their combination yields a total significance of 10.31, firmly establishing the extragalactic origin of the UGRB. Intriguingly, the properties inferred for the sources contributing to the UGRB show departures from those of the resolved γ-ray population, suggesting that the faint end of the $γ$-ray sky is not a simple extrapolation of currently resolved sources.
[abstract 14 / 50] Yes (score: 4) - Title: Multi-wavelength synthesis of a flux rope-trapped mini-prominence eruption and post-flare coronal rainAuthors: Samrat Sen, Alexander G. M. Pietrow, Veronika Jercic, Patrick Antolin,Comments: Accepted for publication in Astronomy & Astrophysics journal. The animations corresponding to the figures 3, 4 and 7 are available from the lead author on reasonable requestSubjects: astro-ph.SR physics.plasm-phCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Small-scale eruptive phenomena in the solar corona including miniature flux ropes and associated cool plasma condensations are not fully understood despite increasing high-resolution observations. We perform forward modeling based on a 2.5D MHD simulation capturing homologous flux rope eruptions, in-situ condensation leading to a mini-prominence, and subsequent post-flare coronal rain. Synthetic diagnostics are obtained using optically-thin EUV and UV emissions, and non-LTE radiative transfer treatment for the H$α$ line. The synthetic EUV emission reveals the flux ropes as bright rim-like structures. The corresponding UV diagnostic shows bright region, which is co-spatial with the dark core due to embedded cool plasma ($\sim$ tens of kK) inside the flux rope, identifying an erupting mini-prominence. Spectral synthesis of Si IV 1402.77 A indicates an upward motion of the mini-filament, and reveals the presence of two predominant velocity components during eruption. At a later stage, thermal instability in post-flare arcades produces coronal rain with temperatures of $\approx 10^4$ K. The EUV diagnostics reveal brightening at the downstream of the rain blob, indicating localized heating associated with compressional effects. The H$α$ spectral synthesis shows enhanced absorption signatures and red-shifted profiles corresponding to downflows of the coronal rain blobs up to $\approx 23$ km s$^{-1}$, whereas the Si IV 1402.77 A spectral profile shows the maximum downflow velocity of $\approx50$ km s$^{-1}$, highlighting the evidence of thermodynamic and kinematic structuring within the falling rain blobs. The synthetic diagnostics provide clear, multi-wavelength signatures that can guide future high-resolution observations, and highlight the importance of small-scale RECONNECTion-driven processes in shaping the multi-thermal structure (between MK to kK) of the solar corona.
[abstract 15 / 50] Yes (score: 4) - Title: Radio-dust connection in QUASARs driven by powerful ionised outflowsAuthors: V. A. Fawcett, C. M. Harrison, T. Costa, D. M. Alexander, C. Andonie, H. Haidar, R. D. Shepherd, C. L. Sargent, M. J. Temple, C. Circosta, D. J. Rosario,Comments: 17 pages, 16 figures, 1 table, accepted for publication in A&ASubjects: astro-ph.GACreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Feedback from dusty QUASARs is thought to be a key driver in galaxy evolution. Multiple studies have reported a link between dust extinction and radio emission in QUASARs, possibly attributed to winds or JETs interacting with the interstellar medium. We use optical spectra from the Dark Energy Spectroscopic Instrument (DESI) to test whether ionised outflows could be driving the observed radio-dust connection and to determine whether dust and/or colour play a role in producing high-velocity ionised outflows in QUASARs. Based on a sample of 3418 DESI QUASARs at 0.5 < z < 0.9, we constrained the [OIII]$λ$5007 kinematics by fitting the spectra with PyQSOFit and comparing the observed trends among the [OIII] outflow velocity and the line-of-sight dust extinction E(B-V), optical-to-mid-infrared (MIR) colour g-W2, and L6$μ$m/L5100A (a proxy for MIR excess). Utilising radio data from the LOFAR Two-metre Sky Survey (LoTSS) DR2, we also explored the link between radio, dust, and outflows. We find that the link between radio emission and dust obscuration is driven by sources hosting high-velocity ionised outflows. However, we find no significant trend between the [OIII] outflow velocity and E(B-V), which suggests dust extinction alone is not a significant factor in determining whether a QUASAR hosts a powerful ionised outflow. On the other hand, we find a clear positive trend between g-W2 and outflow velocity, even after controlling for luminosity. We suggest this is due to a connection between a MIR excess (boosting the W2 band) and outflows, which is supported by a positive trend between L6$μ$m/L5100A and outflow velocity. Our results point to a scenario in which outflows shock the surrounding dust and gas, heating the dust and boosting both the MIR and radio emission.
[abstract 16 / 50] Yes (score: 4) - Title: Nanohertz Gravitational-Wave Constraints on Supermassive Binary Black Holes at Cosmic DawnAuthors: Yiqin Chen, Shi-Yi Zhao, Xingjiang Zhu, N. D. Ramesh Bhat, Jacob Cardinal Tremblay, Małgorzata Curyło, Valentina Di Marco, George Hobbs, Wenhua Ling, Rami F. Mandow, Richard N. Manchester, Saurav Mishra, Daniel J. Reardon, Sparrow Roch, Christopher J. Russell, Ryan M. Shannon, Jingbo Wang, Shuangqiang Wang, Andrew Zic,Comments: 9 pages, 4 figures; Accepted for publication in PRLSubjects: astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Standard continuous gravitational-wave searches with pulsar timing arrays (PTAs) neglect cosmological redshift, restricting their applicability to the local Universe. We introduce a redshift-aware PTA framework and apply it to the Parkes PTA Data Release 3, deriving the first direct constraints on supermassive binary BLACK HOLEs (SMBBHs) at the cosmic dawn. Evaluating our limits across a broad redshift range, we observationally establish the non-monotonic mass-redshift exclusion boundary driven by the theoretical ``redshift bias", demonstrating how PTAs can effectively probe sources at extreme distances. Redshift-aware targeted searches toward high-redshift systems, including the ultraluminous QUASAR J0100+2802 ($z=6.327$) and the JWST-discovered galaxy JADES-GS-z14-0 ($z=14.32$), rigorously exclude SMBBHs with chirp masses $\mathcal{M}_c \gtrsim 10^{10} M_\odot$ across the nanohertz frequency band. Finally, we demonstrate that high-redshift binaries can be robustly detected and localized, allowing for the accurate measurement of their intrinsic properties. Our results provide the tightest constraints to date on SMBBHs at $z > 6$ and establish a practical framework for probing early-Universe BLACK HOLE assembly.
[abstract 17 / 50] Yes (score: 4) - Title: Polarization Images of Neutron Stars Illuminated by a Thin Accretion Disk: A Comparison with Black HolesAuthors: Dan-Dan Feng, Guo-Ping Li, Chen-Yu Yang, Hong Lei,Comments: 18 pages, 5 figuresSubjects: gr-qc astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
We investigate linear POLARIZATION images of static, spherically symmetric neutron stars illuminated by a geometrically and optically thin accretion disk. Neutron star equilibrium configurations are constructed with a polytropic equation of state, and the null geodesic equations and the parallel transport equation for the linear POLARIZATION vector are solved in the geometric optics approximation. The numerical results show that the total polarized intensity is generally positively correlated with the total intensity and reaches its maximum near the neutron star surface. As the observer inclination increases, the symmetry of the POLARIZATION images is progressively broken. In addition, the MAGNETic field configuration mainly affects the direction of the POLARIZATION vectors, while its influence on the overall polarized intensity distribution is comparatively limited. To further characterize the spatial structure of the POLARIZATION direction, we introduce the net electric vector position angle $χ_{\mathrm{net}}$ and the second azimuthal Fourier mode $\angleβ_2$. A comparison with POLARIZATION images of a Schwarzschild BLACK HOLE reveals clear differences between the two types of compact objects in the locations of strongly polarized regions and the size of the central region without a POLARIZATION signal. These results show that linear POLARIZATION images provide information beyond total intensity images for distinguishing neutron stars from BLACK HOLEs.
[abstract 18 / 50] Yes (score: 4) - Title: The thermal emission for knot A of RADIO GALAXy M87 by ChandraAuthors: S. Osone,Comments: 12 pages, 3 figuresSubjects: astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
The JET may compress an interstellar medium and soft X ray outside the JET may be absorbed by a compressed interstellar medium and thermal emission heated by a shock is expected inside the JET. Thermal emission was found for HST-1 and knot A of M87 in X ray energy spectra analysis by Chandra (Osone, 2017). The X ray image of the surrounding of the JET of M87 was studied by Chandra (Osone 2024). I find a soft X ray dip in a south region outside knot A. Therefore, by taking only a north region outside knot A as a background, where there is no soft X ray dip, I analyze X ray energy spectra for knot A by Chandra and confirm thermal emission with a high significance.
[abstract 19 / 50] (score: 3) - Title: Flux enhancement of corotating hot spots in accretion disks from the slow-light effectAuthors: Qing-Hua Zhu,Comments: v2: 23 pages, 11 figures, accepted versionSubjects: gr-qc astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
With the Event Horizon Telescope and future Very Long Baseline Interferometry arrays poised to image supermassive BLACK HOLEs, there is a strong motivation to understand the dynamic aspects of the accretion flow near the BLACK HOLE. Interestingly, in such highly RELATIVISTIC regime, the finite light-travel time should be taken into account to correctly simulate the images, known as the slow-light effect. This paper investigates the impact of the slow-light effect on the observational signatures of hotspots corotating with the Keplerian disks. It is found that the magnification can be modulated by the hotspot's orbital velociy. Specifically, the corotating hotspots at the maxima of magnification are located at the image positions shifted relative to the positions behind the BLACK HOLE. This subsequently causes the peak of the magnification profile to shift towards alignment with the peak of the redshift factor profile, ultimately leading to flux enhancement relative to the results of previous studies. This enhancement becomes particularly pronounced for corotating hotspots in the strong-field regime at large inclination angle, indicating that the slow-light effect is essential for accurately modeling high-energy emission in the vicinity of the BLACK HOLE.
[abstract 20 / 50] (score: 3) - Title: Decisive evidence for a global cosmic-ray feature in gamma-ray dataAuthors: Fernando Valenciano, Pedro De la Torre Luque, Daniele Gaggero, Jorge Martin Camalich,Comments: 5 pages, 2 figuresSubjects: astro-ph.HE astro-ph.GA hep-phCreated: 2026-08-28; Updated: 2026-09-02; Datestamp: 2026-09-02
We analyze 17 years of FERMI-LAT data to study the diffuse $γ$-ray emission along the Galactic plane and its connection to cosmic-ray (CR) propagation. Accounting for correlated instrumental systematics, we find decisive evidence for a spectral break at $\sim20-30$ GeV, present across the inner Galactic disk, with a preference of $Δχ^2=39.78$ ($4.44 σ$ global). The energy and amplitude of this feature are in striking agreement with the spectral feature observed in local CR nuclei, indicating that it is a global property of the Galactic disk rather than a local phenomenon. The measured slope change, $Δγ\simeq 0.20$, is consistent with local CR data and with expectations from a transition in the CR diffusion regime from Kolmogorov to Kraichnan turbulence. Our results provide strong evidence that diffuse $γ$-ray emission along the Galactic disk is dominated by $π^0-$decay emission up to a hundred GeV. These findings provide key insights into the origin of the CR spectral hardening and the propagation of CRs throughout the Galaxy, and illustrate how this multimessenger approach can be used to probe the origin of features in the CR spectra, such as the long-studied CR Knee.
[abstract 21 / 50] (score: 3) - Title: Causal self-consistency of the Blandford--McKee self-similar solutionAuthors: Gilad Sadeh, Tamar Faran, Doron Kushnir, Eli Waxman,Comments: 14 pages, 6 figures, submitted to Physics of FluidsSubjects: astro-ph.HECreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
The Blandford--McKee (BM) solution describes the ultra-RELATIVISTIC self-similar flow behind a strong spherical blast wave propagating into an external density profile $\propto r^{-k}$, where $k<4$ and $r$ is the distance from the center, but it applies only to the hot shell adjacent to the shock, sufficiently deep behind it, the fluid leaves the BM regime. Since the similarity profiles are determined solely by the shock conditions, with no conditions imposed at the inner end, the validity of the solution near the shock depends on whether the flow beyond the BM regime can imprint on this hot shell. For shallow density profiles, $k
[abstract 22 / 50] (score: 3) - Title: Accretion-disk sizes in two QUASARs with interferometrically resolved broad-line regions at $z=2.3$ and $z=4.0$Authors: Francisco Pozo Nuñez, Eduardo Bañados, Swayamtrupta Panda, Amit Kumar Mandal, Bozena Czerny, Jochen Heidt,Comments: 11 pages, 7 figures, accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.GACreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
We present the first direct comparison between accretion-disk (AD) and broad-line region (BLR) sizes in QUASARs at z > 2, combining continuum reverberation mapping with interferometric BLR constraints from GRAVITY and GRAVITY+. Using medium-band photometric monitoring with the MPG/ESO 2.2 m telescope, we measure inter-band continuum lags in SDSS J092034.17+065718.0 at z = 2.33 (J0920) and SMSS J052915.80-435152.0 at z = 3.96 (J0529), among the most luminous QUASARs known (Lbol ~ 10^48 erg s^-1). These are currently the only two QUASARs at z > 2 with spatially resolved BLRs and dynamical black-hole masses from interferometry. We detect significant continuum lags in both QUASARs, increasing monotonically with wavelength. The inferred UV disk sizes are RAD = 4.35 +0.78/-0.91 light-days for J0529 and RAD = 3.15 +0.50/-0.48 light-days for J0920. For J0920, accreting at lambda_Edd ~ 7-20, the disk size is consistent with standard thin-disk expectations despite its super-Eddington regime. For J0529, the disk size agrees with thin-disk predictions using the single-epoch black-hole mass, but implies disk inflation by a factor of a few if the GRAVITY+ dynamical mass, an order of magnitude lower, is adopted. UV continuum disk sizes therefore provide an independent physical scale constraining black-hole mass and accretion-rate models, particularly where BLR kinematics are dominated by outflows. The interferometric BLR sizes reveal pronounced radial hierarchies, with RBLR/RAD ~ 270 for J0529 (Hbeta) and ~115 for J0920 (Halpha). The successful lag detections at Lbol ~ 10^48 erg s^-1 show that continuum reverberation mapping remains feasible for the most luminous systems, opening a path to larger samples with surveys such as the Vera C. Rubin Observatory's LSST.
[abstract 23 / 50] (score: 3) - Title: Dynamic Alignment or Angular Persistence?Authors: Amir Jafari,Comments:Subjects: physics.plasm-phCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Dynamic alignment in MAGNETohydrodynamic turbulence is commonly inferred from the decrease of an amplitude-weighted average of the mutual angle between Elsässer increments toward smaller separations. That decrease, however, need not imply that the increments themselves rotate toward alignment: large-angle fluctuations can simply lose more amplitude than small-angle ones. We therefore study the joint evolution of increment amplitude and mutual angle using finite-step conditional transition probabilities. In forced incompressible full MHD and in balanced strong-guide-field reduced MHD, we find that, at fixed initial angle, large-amplitude Elsässer-increment pairs undergo smaller angular changes than small-amplitude pairs, including when they begin at large angles. We call this amplitude-dependent angular persistence. Independently, normalized amplitude moments increase toward smaller separation, while stronger amplitude weighting produces progressively smaller angular averages and stronger scale dependence, linking apparent alignment to the intermittent large-amplitude tail. In RMHD, a source-state decomposition of the Politano-Pouquet third-order moment shows that initially large-angle, high-amplitude populations contribute with the sign associated with transfer toward smaller perpendicular scales despite their comparatively small angular changes. Time-resolved full-MHD data reproduce the same amplitude ordering, and the local Elsässer advective term closely tracks the conditional dependence of both angular and amplitude changes on the initial state. These results show that the conventional dynamic-alignment diagnostic reflects the joint statistical evolution of amplitude and angle and, by itself, is not evidence for a population-wide dynamical rotation toward alignment.
[abstract 24 / 50] (score: 3) - Title: Search for Neutrinos from Tidal Disruption Events with IceCubeAuthors: R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, J. M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Arg{ü}elles, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, A. Balagopal V., S. W. Barwick, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. B{ö}ser, O. Botner, J. B{ö}ttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, L. Brusa, R. T. Burley, D. Butterfield, K. Carloni, J. Carpio, N. Chau, Y. C. Chen, Z. Chen, D. Chirkin, S. Choi, A. Chubarov, B. A. Clark, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. D{\'ı}az-V{é}lez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Els{ä}sser, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. Fattorini, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, D. Fox, A. Franckowiak, S. Fukami, P. F{ü}rst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Gl{ü}senkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, S. Griswold, K. M. Groth, D. Guevel, C. G{ü}nther, P. Gutjahr, C. Ha, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. H{ä}ußler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, A. Hollnagel, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, T. Kim, H. Kimku, F. Kirchner, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, S. Koch, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. K{ö}pke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, T. Krishnan, K. Kruiswijk, E. Krupczak, E. Kun, N. Kurahashi, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczy{ń}ska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mari{ş}, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, D. Mousadi, E. Moyaux, T. Mukherjee, M. Nakos, U. Naumann, R. Neshat, L. Neste, M. Neumann, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, B. Owens, V. Palusova, H. Pandya, A. Parenti, C. Parisel, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. P{é}rez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, S. Pick, M. Plum, A. Pont{é}n, V. Poojyam, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, S. Rodan, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, M. Scarnera, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schl{ü}ter, F. Schl{ü}ter, N. Schmeisser, T. Schmidt, F. Schmitt, A. Scholz, F. G. Schr{ö}der, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, A. Sharma, S. Shefali, N. Shimizu, M. Shin, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, D. Song, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. St{ü}rwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, W. Tian, S. Tilav, K. Tollefson, J. A. Torres, S. Toscano, D. Tosi, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Velazquez, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, J. Woodward, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, F. Yu, S. Yu, T. Yuan, S. Yun-C{á}rcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman, C. Zilleruelo Ca{ñ}as,Comments: 17 pages, 3 figures, 2 tablesSubjects: astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Tidal disruption events (TDEs) are theorized to produce high-energy neutrinos through photohadronic interactions between accelerated protons and multi-wavelength photons in the accretion disk and outflows. Detecting these neutrinos would provide insight into the dynamics of TDEs. Taking advantage of the recent increase in observed TDEs from wide field-of-view telescopes, we conduct a dedicated search for neutrinos coincident in optical/UV and X-ray wavelengths. We searched for neutrino emission from 89 TDEs selected based on X-ray and optical/UV observations using time-dependent likelihood analysis methods in two parts. First, we searched for emission from individual sources, where we fit the time window of expected neutrino emission. Second, we performed a study of JETted and non-JETted TDE subpopulations using a stacking search with a fixed one year time window. No significant neutrino excess was observed in either search. We set upper limits to the contribution of JETted and non-JETted TDEs detected in optical/UV and X-ray wavelengths to the diffuse astrophysical neutrino flux assuming TDEs are standard candles.
[abstract 25 / 50] (score: 3) - Title: Extreme AGN Variability in WISE: Powerful Flares and Candidate Tidal Disruption Events in AGNAuthors: Satya Teja Anuraag Upadhyayula, Daniel Stern, Kishalay De, Christos Panagiotou, Matthew J. Graham, K. E. Saavik Ford, Barry McKernan, Murray Brightman, J. A. Acevedo Barroso, Daniel H. McIntosh,Comments: Submitted to ApJSubjects: astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
We present first results from a systematic study of extreme mid-infrared variability of active galaxies across the $>10$-year baseline of the Wide-field Infrared Survey Explorer (WISE) mission. WISE, which observed the full sky with a six-month cadence, is sensitive to transient events in both unobscured and obscured galaxies. This paper focuses on extreme flares in ACTIVE GALACTIC NUCLEi (AGNs). Previous studies identified flares such as tidal disruption events (TDEs) in inactive galaxies, typically from optical or X-ray surveys. However, flares are also expected in AGN and optical/X-ray searches are insensitive to events in dust-enshrouded AGN. In this pilot study, we present flares in two AGN identified from extreme mid-infrared color variability. One flare was also detected at optical wavelengths. While both events showed broadened H$α$ emission several years after the flare peak, more recent spectroscopy reveals continued broadened emission only from the source with the optical flare. After considering several potential physical causes of the flares, including SUPERNOVAe and micro-lensing, we suggest both events are TDEs in AGN. Intriguingly, the optical flare decays much faster than the expected $t^{-5/3}$ fallback rate expected for TDEs in quiescent galaxies, suggesting either a partial disruption or the tidal disruption of a star by an intermediate mass BLACK HOLE embedded in the accretion disk of an AGN. This work demonstrates the power of WISE to identify the full census of TDEs, including events in dust-obscured AGN. Mid-infrared data probes the nature of the event and provides a bolometric measure of the flare energetics.
[abstract 26 / 50] (score: 2) - Title: Timing of echoes in electroMAGNETic radiation from hot spots orbiting a Kerr BLACK HOLE impostorAuthors: Sudipta Hensh, Jan Schee, Zdeněk Stuchlík,Comments:Subjects: gr-qcCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
We investigate the light curve of an isolated bright spot in a Keplerian orbit around a Kerr BLACK HOLE candidate to probe possible deviations from the standard event-horizon picture. In particular, we explore the presence of a reflective surface, namely a "mirror" near the horizon, and its observable consequences. We present estimates on the time delays of the echoes of electroMAGNETic radiation from the mirror or some other reflecting area related to BLACK HOLE mimickers. Our results show that photon reflections from such a surface imprint distinct late-time features in the light curve, producing an electroMAGNETic analogue of gravitational wave echoes. For lower values of the spin, the reflected signal appears within the same orbital period and leads to a noticeable enhancement of the flux. In contrast, for higher spins, the effect emerges only after several orbits, giving rise to a characteristic echo-wave train. These features provide a potential observational signature of horizon-scale modifications in compact objects.
[abstract 27 / 50] (score: 2) - Title: Dual Theory of MHD TurbulenceAuthors: Alexander Migdal,Comments: 16 pages, 4 figures. Added the section with the general mMHD loop equation, including initial data for momentum loops. This initial data is related to the Wilson loop in QED in three dimensionsSubjects: physics.flu-dyn nlin.SICreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
We present an exact analytic solution for decaying incompressible MAGNETohydrodynamic (MHD) turbulence. Our solution reveals a dual formulation in terms of two interacting Euler ensembles--one for hydrodynamic and another for MAGNETic circulation. This replaces empirical scaling laws with an infinite set of power terms with calculable decay exponents, some of which appear as complex-conjugate pairs related to the Riemann zeta function. A key result of our analysis is the explicit dependence of the solution on the Prandtl number ($\mathrm{Pr} = ν/η$), leading to a phase transition at $\mathrm{Pr} = 1$. In the $\mathrm{Pr}<1$ regime, turbulence is dominated by hydrodynamic fluctuations, while for $\mathrm{Pr}>1$, two distinct solutions emerge: a metastable one in which MAGNETic fluctuations grow with $\mathrm{Pr}$ and a stable one where they remain balanced with hydrodynamic fluctuations. We compare our theoretical predictions with recent direct numerical simulations (DNS) and discuss their implications for astrophysical plasmas, fusion devices, and laboratory MHD experiments. Our results provide a rigorous mathematical framework for understanding MHD turbulence and its dependence on fundamental parameters, offering a new perspective on turbulence in highly conducting fluids.
[abstract 28 / 50] (score: 2) - Title: Probing Dark Matter Halos of High-redshift Quasars via Wide-Field ClusteringAuthors: Hao Meng, Guangping Ye, Huanian Zhang,Comments: 7 figures and 3 tables, ApJL AcceptedSubjects: astro-ph.GACreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
High-redshift QUASARs are powerful tracers of both astrophysical processes and large-scale structure in the early Universe. Using a sample of 1,251 spectroscopically confirmed QUASARs and 827 highly reliable photometric QUASAR candidates selected with a machine-learning framework, all at $4.7 \leq z < 6.3$ (excluding $5.4 < z < 5.6$) and with a median luminosity of $M_{1450}\sim -25.5$, we investigate the large-scale environments of QUASARs near the end of cosmic reionization. We measure the projected auto-correlation function of the QUASAR population and derive bias parameters of $b=22.11^{+2.17}_{-2.19}$ and $28.55^{+5.76}_{-5.75}$ for the redshift intervals $4.7\leq z<5.4$ and $5.6\leq z<6.3$, respectively. These correspond to characteristic DARK MATTER halo masses of $\log(M_{ h}/M_\odot)=12.66^{+0.10}_{-0.11}$ and $12.62^{+0.21}_{-0.21}$, respectively. We further estimate QUASAR duty cycles of $0.011^{+0.017}_{-0.007}$ and $0.012^{+0.104}_{-0.011}$ for the two redshift bins. These measurements are consistent with previous studies and the observed $f_{\rm duty}$--$M_{\rm halo}$ relation, indicating that only a small fraction of suitable DARK MATTER halos host optically luminous QUASARs at any given time. The inferred low duty cycles suggest that a substantial fraction of supermassive BLACK HOLE growth may occur during obscured accretion phases. Our results provide new constraints on the connection between high-redshift QUASARs and their host DARK MATTER halos, offering valuable insights into the co-evolution of supermassive BLACK HOLEs and large-scale structure in the early Universe.
[abstract 29 / 50] (score: 2) - Title: Little Red Dots as Obscured Little Blue Dots: A Super-Eddington Unification ModelAuthors: Piero Madau, Roberto Maiolino,Comments: 16 pages, 9 figures, version accepted for publication in A&ASubjects: astro-ph.GA astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
We investigate whether Little Red Dots (LRDs) are the dust-reddened, high-inclination counterparts of compact, blue broad-line AGNs (Little Blue Dots, LBDs) powered by super-Eddington accretion. We model the central engine as a geometrically thick, radiation--pressure supported accretion flow whose funnel produces strongly anisotropic, intrinsically blue ionizing continua, coupled to an equatorially concentrated broad-line region (BLR) and dusty reprocessing clouds with modest covering factor. Using inclination-dependent SEDs as input to Cloudy, we show that the extreme broad Halpha EWs of JWST LRDs can be reproduced with global BLR covering factors of only C_{BLR}~ 0.1, fully consistent with standard Type~1 AGNs and far below unity. Large Balmer EWs arise because self-shadowing suppresses the high-inclination optical continuum while the BLR is illuminated by an ionizing-rich EUV SED. Weak high-ionization lines (e.g. He II 4686) follow from the orientation-dependent suppression of the XUV/soft X-ray continuum toward equatorial directions, without requiring a fully enclosing gaseous "cocoon''. Applying a gray dust attenuation law with A_V~3 along high-inclination (LRD-selected) sightlines, our fiducial model reproduces the V-shaped UV-optical continua of LRDs and the large Balmer decrements; strong Balmer breaks arise only along the most obscured sightlines. A compact equatorial dust structure with modest global covering factor intercepts and reradiates only a small fraction of the bolometric luminosity, yielding a modest hot-dust bump and far-IR/sub-mm output consistent with current measurements and limits and implying small dust masses. This single-framework model links LRD and LBD observables through orientation, predicting correlated trends in Halpha EW, Balmer decrement, Balmer break, high-ionization line strengths, and IR emission.
[abstract 30 / 50] (score: 2) - Title: Pitching Cosmic Curveballs: Environmental Effects on Extreme-Mass-Ratio Inspirals with Spinning SecondariesAuthors: Leif Lui, Lisa V. Drummond, Alejandro Torres-Orjuela,Comments: 6 pages, 5 figuresSubjects: gr-qc astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Much like the aerodynamic deflection of a spinning curveball, a rotating secondary in an extreme-mass-ratio inspiral (EMRI) experiences Magnus and lift forces, in addition to the standard drag force, when traversing a gaseous environment. We present the first framework that incorporates these specific spin-coupled environmental effects (EEs) into the evolution of EMRI. Over the multi-year observation windows of space-based gravitational-wave (GW) detectors, these interactions imprint a unique, distinguishable dephasing signature on the signal. Crucially, a Fisher matrix analysis reveals that gas drag breaks the fundamental vacuum-projection degeneracy between the secondary's spin magnitude and inclination, thereby tightening parameter constraints. Thus, accounting for EEs is not merely a modeling necessity, but could potentially be a powerful tool for enhancing the detectability of the secondary's intrinsic spin, and could serve as a novel probe of accretion flows harboring massive BLACK HOLEs.
[abstract 31 / 50] (score: 2) - Title: An Inverse Grad-Shafranov Neural Network Approach to Tokamak Magnetic ControlAuthors: Allen M. Wang, Adriano Mele, Cosmas Heiß, Cristian Galperti, Zander Keith, Alessandro Pau, Antoine Merle, Olivier Sauter, Daniel Gonzalez Castiñeiras, Francesco Carpanese, Federico Felici, Mark Dan Boyer, Cristina Rea, TCV Team, EUROfusion Tokamak Exploitation Team,Comments:Subjects: physics.plasm-phCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
A new approach to tokamak MAGNETic control enabling high-precision plasma shaping and novel real-time adaptability is experimentally demonstrated on the Tokamak a Configuration Variable (TCV). The method is motivated by the insight that, under appropriate assumptions, a real-time inverse Grad-Shafranov solver approximates an optimal control policy for plasma boundary regulation. Building on this, a control architecture is developed in which classical controllers enforce operational constraints while a fast surrogate model provides a real-time inverse mapping from the desired plasma boundary to Poloidal Field Coil currents. Experimental results on TCV demonstrate improved plasma shaping with respect to the standard discharge preparation procedure --- albeit without explicit real-time shape feedback --- while enabling flexible response to asynchronous events. It is shown that a single network provides satisfactory performance across a range of plasma MAGNETic configurations. Real-time adaptivity is demonstrated in simulation, and partially in experiment, through adaptive strike point motion and early termination in response to a real-time trigger. These results suggest a viable path toward MAGNETic control architectures that reduce reliance on dense diagnostic coverage while maintaining high-accuracy plasma shaping, with potential relevance for future fusion power plant operation.
[abstract 32 / 50] (score: 2) - Title: Photometric redshifts for ACTIVE GALACTIC NUCLEi with LePHARE for the Vera C. Rubin ObservatoryAuthors: R. Shirley, M. Salvato, J. Cohen-Tanugi, O. Ilbert, S. Arnouts, R. Ansari, R. Assef, M. Banerji, A. Bongiorno, W. N. Brandt, J. Buchner, J. Comparat, D. Ilić, A. Kovačević, J. Kubica, B. Laloux, O. Lynn, A. Malz, L. Marchetti, C. Mazzucchelli, T. Mkrtchyan, K. Nandra, D. Oldag, C. Ricci, W. Roster, E. Saremi, S. Satheesh-Sheeba, T. Tasnim. Ananna, M. J. Temple, M. Vaccari, A. Viitanen, C. Wolf, Z. Yu, T. Zhang,Comments:Subjects: astro-ph.GACreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Active Galactic Nuclei (AGN) play a crucial role in galaxy evolution, but they are a minority of extragalactic sources with diverse Spectral Energy Distributions (SEDs), which depend on their means of selection. Upcoming large-scale surveys such as LSST will identify many AGN, but analysis tools are not optimized for them. The limited number of photometric bands in these surveys impacts the calculation of photometric redshifts for AGN, which are essential for scientific advancement. We use LePHARE to demonstrate the impact that a limited number of bands and erroneous assumptions have on the determination of the photometric redshifts of AGN. We conduct tests on six AGN samples selected using X-ray, radio, infrared, variability, color, and spectroscopic criteria in the COSMOS field, using photometry from HSC-CLAUDS, which is closest in depth and wavelength coverage to LSST. We present the LSST pipeline for LePHARE within the Redshift Assessment Infrastructure Layers (RAIL), facilitating comparison between SED fitting and machine learning algorithms. AGN that appear as point-like sources in optical data will be assigned highly unreliable photometric redshifts if they are processed using galaxy templates. Additionally, shallow all-sky surveys (like eROSITA, WISE, and ZTF) miss many AGN. As a result, these "hidden" AGN are often misidentified as galaxies in public survey data, leading to incorrect photometric redshift. We provide the configurations that are suggested for each type of AGN alongside measures of expected performance as a function of redshift, magnitude, and selection. To facilitate studies with a panchromatic view of AGN, we also release photometric redshifts and posterior distributions for all AGN sources identified in the COSMOS field using the six criteria, based on 28-band photometry.
[abstract 33 / 50] (score: 2) - Title: Exploring thermodynamic and photonic properties of new BLACK HOLE solutions in F(R) gravity theoryAuthors: Mohsen Dehghani,Comments: 19 pages, 1 figureSubjects: physics.gen-phCreated: 2026-08-27; Updated: 2026-09-02; Datestamp: 2026-09-02
We investigate BLACK HOLE solutions in F(R) gravity within a four-dimensional spacetime, separately treating the cases of vanishing and nonvanishing energy momentum tensors. We demonstrate that in the absence of an energy momentum tensor, the number of independent equations is sufficient to obtain the Ricci flat solutions without the need for a prescribed F(R) function. In the same case, also the solutions with variable Ricci scalar can obtained too. Furthermore, for a nonvanishing energy momentum tensor, we derive exact solutions for both constant and variable Ricci scalars, thereby introducing new charged BLACK HOLEs. Utilizing this new method, we not only recover the general RELATIVISTIC and previously known F(R) gravity solutions but also introduce four new classes of F(R) BLACK HOLEs. We calculate their thermodynamic quantities and confirm the validity of the first law of BLACK HOLE thermodynamics. The thermal stability of these new BLACK HOLEs is analyzed using both thermodynamic and geometrical approaches. Finally, the photon spheres and BLACK HOLE shadows are studied within the F(R) gravity framework.
[abstract 34 / 50] (score: 2) - Title: Weighing Little Red Dots with Transient EventsAuthors: Vinh Tran, Xuejian Shen, Oliver Zier, Anna de Graaff, Rohan P. Naidu, Mark Vogelsberger,Comments: 11 pages, 6 figures, 1 table, submitted to the Astrophysical Journal (ApJ)Subjects: astro-ph.GA astro-ph.HECreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
Recent JWST observations have revealed a large population of compact red sources at $z \gtrsim 4$, known as Little Red Dots (LRDs), many of which show signatures of accreting massive BLACK HOLEs (BHs). The physical nature of these sources and their connection to host galaxies are under debate. We propose an independent avenue for constraining their nature through transient phenomena, such as tidal disruption events (TDEs) and quasi-periodic eruptions (QPEs), arising from interactions between a star and the gas envelope surrounding the BH. These event rates depend sensitively on BH mass and provide a way to "weigh" LRDs. We calculate the expected TDE and QPE rates in LRDs under three distinct scenarios: (1) LRDs are truly overmassive BHs, (2) LRDs have BH masses following the classical local scaling relations (and the reported BH masses in observations are overestimated), and (3) the currently observed LRDs are only the tip of the iceberg of a larger population of low-mass BHs. We find that the predicted TDE and QPE rates differ dramatically across scenarios, especially in the presence of steep stellar cusps. The expected TDE rates per degree-square, assuming a Hernquist stellar distribution with a Bahcall-Wolf cusp embedded, are $2.78 \times 10^{-3}$, $1.96 \times 10^{-3}$, and $3.37 \times 10^{-2} \, {\rm yr}^{-1} \, {\rm deg}^{-2}$ for the three scenarios, respectively, while the QPE rates are $1.64 \times 10^{-2}$, $4.72 \times 10^{-2}$, and $4.96 \times 10^{-1} \, {\rm yr}^{-1} \, {\rm deg}^{-2}$. Upcoming wide-field surveys with Euclid, Roman, and LSST may be capable of detecting these high-redshift transient events and obtaining light curves, which encode additional information about the BH mass and the gas structure of LRDs. Stellar transient events will provide valuable insight into the early assembly of massive BHs.
[abstract 35 / 50] (score: 2) - Title: Extended radio emission in and around the merging cluster A520 as seen by MeerKATAuthors: S. Giacintucci, W. D. Cotton, M. Markevitch, T. Venturi, T. E. Clarke, H. Bourdin,Comments: 22 pages, 9 figures, accepted for publication in ApJSubjects: astro-ph.CO astro-ph.HECreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
We present results from a deep MeerKAT 1.28 GHz observation of Abell 520, a galaxy cluster in the middle of a merger and a treasure trove of merger-generated phenomena. MeerKAT's combination of high angular resolution and sensitivity to extended radio emission lets us uncover unprecedented detail of the cluster's giant halo and puzzling features beyond the halo. We find that the main radio halo is sharply bounded along the direction of the NE-SW merger axis by the two X-ray shock fronts. In the perpendicular direction, the halo wings smoothly span over 2 Mpc, with the spectrum steepening in the outskirts. We detect faint radio emission upstream of the main (SW) bow shock; the emissivity jump across this shock can be used to constrain the physical mechanisms at work there. We discover a tail of radio emission extending past the NE shock to the gas-poor, high-entropy ``dark subcluster'' in the NE outskirts. The tail and subcluster have a higher radio/X-ray brightness ratio than the main halo's, suggesting efficient reacceleration of COSMIC RAYs. We also discover two peripheral radio relics beyond the cluster virial radius, and a faint, $\sim2$ Mpc long, broad radio bridge connecting the dark subcluster to one of the relics along the direction perpendicular to the merger axis. The spectral slopes of the dark subcluster and the bridge are consistent with that of the main halo. This bridge and both relics may be caused by another giant merger-generated shock front at the virial radius.
[abstract 36 / 50] (score: 2) - Title: Portraits of the young and old in X-ray: New millisecond pulsar detections and updated characterisation of young neutron starsAuthors: Wynn C. G. Ho, Patrick H. Wang, Sebastien Guillot,Comments: 7 pages, 7 figures; accepted for publication in MNRASSubjects: astro-ph.HE astro-ph.SRCreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
We present analyses of new and archival Chandra and NUSTAR data on two old millisecond pulsars, a young highly-energetic pulsar, and a young neutron star. PSR J1810-0623 is a recently-discovered 4.55 ms radio pulsar in a binary with a possible carbon-oxygen white dwarf companion. We tentatively detect the pulsar for the first time in X-ray using a new short Chandra HRC-I observation. Its faintness suggests a distance more in accord with the further (~1 kpc) of its dispersion measure-inferred distances. PSR J1933-6211 is a 3.54 ms radio pulsar also with a carbon-oxygen white dwarf companion. Our first-time X-ray detection in an archival HRC-S image indicates its X-ray luminosity is similar to that of the 1.9 Msun pulsar PSR J1614-2230. Next, PSR J1813-1749 is a 1-2 kyr pulsar with one of the highest known spin-down luminosities. We measure its spin period of 44.7 ms using 2025 NUSTAR and 2026 Chandra ACIS-S data and update its spin evolution model. We show for the first time the pulse profile of PSR J1813-1749 at 3-79 keV, and we find that the spectra of the pulsar and pulsar wind nebula at these energies did not change significantly between observations in 2018 and 2025. Finally, for the 5-10 kyr neutron star CXOU J182913.1-125113 in the SUPERNOVA remnant G18.95-1.1, we combine ACIS-I observations from 2009 and 2024 to better measure the neutron star's spectrum.
[abstract 37 / 50] (score: 2) - Title: TDCOSMO XXVIII. The Hubble constant from the quadruply lensed QUASAR J1537$-$3010 with precise time delaysAuthors: A. Galan, A. G. Schweinfurth, S. H. Suyu, D. P. Johnson, A. Chawla, D. Sluse, G. V. Kharchilava, E. Buckley-Geer, H. Lin, S. Knabel, W. Sheu, S. Ertl, T. Anguita, S. Birrer, F. Courbin, F. Dux, M. Millon, V. Motta, S. Schuldt, T. Treu, D. M. Williams, M. Cappellari, K. C. Wong, D. Eckert,Comments: 14 pages (+ 9 pages in appendix), 16 figures, submitted to Physical Review DSubjects: astro-ph.CO astro-ph.GACreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
We present the first measurement of the Hubble constant ($H_0$) from the quadruply-lensed QUASAR J1537$-$3010, which has optically-measured time delays at $\sim2 \%$ precision. We combine these delays with multi-band imaging data from the Hubble Space Telescope (HST) and model the system with two independent software and teams. We adopt a mass profile that is maximally degenerate with $H_0$ to fully incorporate the mass-sheet degeneracy in the error budget, with nuisance parameters constrained by spatially resolved stellar kinematics from the Multi Unit Spectroscopic Explorer (MUSE) and a line-of-sight (LoS) analysis using the Euclid Flagship simulation. The entire analysis is performed blindly to $H_0$, distances and mass density slope of the main deflector. After unblinding, we measure $H_0 = 75.5^{+9.3}_{-5.8}\ {\rm km\,s^{-1}\,Mpc^{-1}}$, corresponding to a $10\%$ precision measurement from a single system. This precision is driven by conservative lens modeling assumptions including differences between lens modeling methods and the limited stellar kinematics constraints, from which we infer a total mass-sheet parameter $λ\equiv(1-κ_{\rm ext})λ_{\rm int} = 0.89^{+0.11}_{-0.06}$ ($λ_{\rm int}=0.89^{+0.09}_{-0.07}$) that is consistent with current results for elliptical galaxies ($λ\approx 1$). Our lensing constraints, stellar kinematic measurements and LoS characterization will be included in subsequent population-level measurements of $H_0$. Moreover, our lens models combined with future near-infrared spectroscopy and imaging from the James Webb Space Telescope will further reduce the uncertainties on $H_0$ from J1537$-$3010 alone, bringing it closer to the few percents precision of the time delays.
[abstract 38 / 50] (score: 2) - Title: Gravitational waves from core collapse of rotating very-massive stars: 3D numerical relativity computationAuthors: Alan Tsz-Lok Lam, Masaru Shibata, Sho Fujibayashi,Comments: 25 pages, 16 figuresSubjects: gr-qc astro-ph.HECreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
We numerically study the collapse of rotating, very-massive stellar cores with masses of $\approx 200$, $300$, $500$, and $1100M_\odot$ into BLACK HOLEs using both axisymmetric and three-dimensional (3D) numerical relativity. Our results indicate that when the dimensionless spin of the resulting BLACK HOLE exceeds 0.8, a massive disk consistently forms around it. These massive, compact disks, carrying more than about 10\% of the BLACK HOLE's mass, are prone to non-axisymmetric deformations that trigger gravitational-wave bursts with frequencies around 10-50 Hz. Such waves could be detected by the Einstein Telescope and Cosmic Explorer, even from sources a few Gpc away. We also summarize the gravitational-wave signals from axisymmetric collapse, which tend to have lower amplitudes and higher frequencies than those caused by non-axisymmetric instabilities.
[abstract 39 / 50] (score: 2) - Title: Chordwise micro-JET placement reveals a trade-off between mean hydrodynamic performance and unsteady loading under cloud cavitationAuthors: Amirmehran Mahdavi, Soheil Motezakkeri, Yasin Ebrahimi, Ali Alavi,Comments: 39 pages, 16 figures, 3 tablesSubjects: physics.flu-dynCreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
Prescribed tangential micro-JET injection can modify cloud-cavitation dynamics, but the chordwise location that improves mean hydrodynamic performance may differ from the location that minimizes unsteady loading. This study compares five injection locations (x/c = 0.15, 0.30, 0.45, 0.60, and 0.70) on a Clark-Y hydrofoil at Re = 7 x 10^5 and cavitation number 0.8. Transient large-eddy simulation with a Volume-of-Fluid formulation and the Schnerr-Sauer cavitation model is used in a two-dimensional parametric framework, with one representative three-dimensional case included to illustrate spanwise cavity deformation. The analysis considers vapor topology, turbulent kinetic energy, velocity and pressure fields, cycle-averaged surface pressure, hydrodynamic forces, force fluctuations, spectra, and cavity-thickness histories. Injection at x/c = 0.15 gives the highest cycle-averaged lift-to-drag ratio among the tested cases: drag decreases from 0.137 to 0.107 and the lift-to-drag ratio increases from 5.693 to 6.261, while lift decreases from 0.78 to 0.67. In contrast, x/c = 0.60 gives the lowest recorded force-fluctuation RMS, with lift- and drag-coefficient RMS values of about 0.112 and 0.0165. The preferred injection location is therefore objective-dependent: the location favored by mean hydrodynamic performance does not coincide with the location favored by unsteady-load reduction under the present conditions.
[abstract 40 / 50] (score: 2) - Title: Use of Cholesky decomposition in the CFOUR program packageAuthors: Jürgen Gauss, Simon Blaschke, Sophia Burger, Davide Cianchino, Marios-Petros Kitsaras, Luca Melega, Tommaso Nottoli, Jeremias Oswald, Tereza Uhlířová, Chaoqun Zhang, Lan Cheng, Stella Stopkowicz, Filippo Lipparini,Comments:Subjects: physics.chem-phCreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
An overview is given about our efforts to speed up high-level computations of molec- ular energies and properties using Cholesky decomposition (CD). We describe the cor- responding developments in the CFOUR quantum-chemical package with a focus on (a) the use of CD in complete-active space self-consistent-field (CASSCF) and coupled- cluster (CC) computations, (b) the implementation of analytic CC gradients using CD, (c) the efficient calculation of MAGNETic properties (NMR shieldings and MAGNETizabili- ties) using CD when carried out with explicit MAGNETic-field dependent basis functions, i.e., the so-called gauge-including atomic orbitals (GIAOs), (d) the efficient computa- tion of CASSCF response properties using CD, (e) the use of CD in RELATIVISTIC two- and four-component computations, as well as (f) computations for molecules in finite MAGNETic fields using GIAOs together with CD. An outlook on future developments concerning the CFOUR package is given.
[abstract 41 / 50] (score: 2) - Title: Formation of Heavy Seed Black Holes and Little Red Dots-like Compact Clusters in Metal-enriched Star-forming RegionsAuthors: Sunmyon Chon, Shingo Hirano, Ke-Jung Chen, Volker Springel,Comments: 19 pages, 13 figuresSubjects: astro-ph.GA astro-ph.COCreated: 2026-08-31; Updated: 2026-09-02; Datestamp: 2026-09-02
The origin of supermassive BLACK HOLEs (SMBHs) in the early Universe remains uncertain. While the classical direct-collapse scenario requires pristine gas exposed to intense Lyman-Werner (LW) radiation, recent JWST observations suggest that early growing BHs may reside in compact, metal-enriched environments. We investigate early BH formation using a cosmological radiation-hydrodynamic simulation that self-consistently follows the formation and evolution of rapidly accreting supermassive stars (SMSs). We find that intense LW radiation develops in clustered star-forming regions; by the time the first heavy seed forms, the mass-weighted internal intensity has reached $J_{21}\sim1000$. Most seeds form in weakly metal-enriched gas with [Z/H]$\sim-3$ to $-2$, because the strongest LW fields occur in regions already enriched by previous stellar feedback. All halos above $10^9M_\odot$ in our zoom-in region host a BH more massive than $10^5M_\odot$. We construct stellar spectra using MIST/PHOENIX libraries for normal stars and $6000~\mathrm{K}$ blackbody spectra for bloated SMSs. Five of eight massive clusters with stellar masses larger than $10^6~M_\odot$ exhibit intrinsically V-shaped spectra similar to those of Little Red Dots (LRDs). In the most prominent cases, luminous SMSs dominate the red optical emission, although Balmer breaks in normal stellar populations also contribute. We also identify off-center LRD-like systems in our simulation resembling those recently reported in strongly lensed observations. Our results suggest that heavy-seed formation, compact-cluster formation, and LRD-like continuum emission are linked outcomes of clustered, weakly metal-enriched, strongly irradiated environments.
[abstract 42 / 50] (score: 2) - Title: The Missing MeV Window for Identifying Galactic PeVatrons: the need for a dedicated MeV ObservatoryAuthors: Martina Cardillo, Riccardo Campana, Yuri Evangelista, Fabio Muleri,Comments: 15 pages, 4 figures, SPIE Proceedings Astronomical Telescope + Instrumentation 2026: Ultraviolet to Gamma-rays Conference, Copenhagen, 5-10 July 2026Subjects: astro-ph.HE astro-ph.IMCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
The identification of the sources responsible for accelerating Galactic cosmic-rays up to PeV energies remains a major open question in high-energy astrophysics. Recent observations by the Large High Altitude Air Shower Observatory (LHAASO) have revealed a growing population of Galactic PeVatron candidates. However, the detection of TeV-PeV gamma-rays alone does not uniquely identify the nature of the emitting particles. In many cases, both hadronic and leptonic scenarios can reproduce the observed very-high-energy emission, leaving the origin of the radiation unresolved. The most robust and least model-dependent electroMAGNETic tracer of hadronic acceleration is provided by neutral-pion decay, which produces the characteristic pion bump in the 10-100 MeV energy range. Observations in this energy band are therefore essential to establish whether candidate PeVatrons are accelerating protons and nuclei and, consequently, to assess their role in the origin of Galactic cosmic-rays. More broadly, the MeV domain addresses key astrophysical questions, but remains one of the least explored regions of the electroMAGNETic spectrum. As current and future VHE facilities expand the Galactic PeVatron census, the lack of MeV observations is becoming a major limitation for source identification. We discuss the astrophysical science drivers and observational requirements for a dedicated MeV gamma-ray capability optimized for pion-bump studies. We explore the concept of a compact, focused, and potentially fast-track mission capable of filling the impending MeV observational gap while more ambitious next-generation MeV facilities are developed and evaluated. Such a mission would provide the missing diagnostic needed to distinguish hadronic and leptonic emission, identify Galactic cosmic-ray accelerators, and fully exploit the scientific return of the emerging generation of TeV observatories.
[abstract 43 / 50] (score: 2) - Title: Revisiting candidates for non-pulsating stars located in the Cepheid instability strip in the Large Magellanic CloudAuthors: W. Narloch, C. Galan, G. Pietrzynski, B. Pilecki, W. Gieren, R. Smolec, H. Netzel, P. Wielgorski,Comments: 17 pages, 10 figures, 6 tables, Accepted for publication in A&ASubjects: astro-ph.SRCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
We analyzed photometric and spectroscopic data for 11 candidates for non-pulsating stars located in the Cepheid instability strip (IS) of the Large Magellanic Cloud (LMC) in order to investigate the reasons for the lack of pulsations. We used available temperature calibrations based on photometric colors to estimate the effective temperatures of the candidates, which served as initial parameters for the spectroscopic analysis. We also applied surface brightness-color relations calibrated for Cepheid variables, giants, and supergiants to estimate stellar radii. The spectral analysis was performed using the spectral synthesis method to determine the atmospheric parameters; namely, the effective temperature, metallicity, surface gravity, microturbulent velocity, projected rotational velocity, and chemical abundances for up to ~30 elements. For most objects, only a single spectrum was available. However, no significant variations in radial velocities were detected among the stars with repeat observations; therefore, all stars were treated as single object in the analysis. Two stars exhibit broad spectral lines, which may indicate high rotational velocities or possible binarity; however, additional spectra are required to confirm this interpretation. One of these objects also shows asymmetric line profiles, which might be related to the presence of non-radial pulsation modes causing line-shape variations. A common feature among all analyzed candidates is an enhancement of barium-peak s-process elements compared to solar values. This may indicate past mass transfer from a companion during its post-asymptotic giant branch phase. This study provides an insight into the physical parameters of candidates for non-pulsating stars residing within the Cepheid IS in the LMC, although the lack of pulsations remains a mystery and challenges pulsation theory.
[abstract 44 / 50] (score: 2) - Title: Complex Lags from Simple PhysicsAuthors: Benjamin Ricketts, Gregoire Marcel,Comments: 17 pages, 25 figures, accepted to A&ASubjects: astro-ph.HECreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
X-ray timing information produced through Fourier analysis from the variable emission of BLACK HOLE X-ray binaries has been used for several decades to provide key insights into the physical setup of these systems not measurable with spectroscopy. In particular, quasi-periodic oscillations within these systems have been of particular interest and remain the source of great debate on how they come about. We investigate the timing products of simple toy models of QPO variability to provide more intuition when thinking about signals produced by these sources. We simulate simple physical setups and show how phase lags and coherence of the signals change in these different setups. We first focus on properties of QPO like signals under a single driving signal assumption. We then investigate the case of multiple oscillations in a signal. Finally, we investigate how timing products change when QPOs are produced by time dependent modulation of periodic signals. Many simple physical setups with common driving signals are able to reproduce complex non-linear phase lags that resemble those present in the data. The changes in physical setup aligns with experience in the data, such as differing power spectra but fall short of reproducing the data as expected. Multiple incoherent processes present in the signal struggle to reproduce behaviour present in the data. Coherence seems to be a more useful tool for differentiating between setups. Fourier analysis with complicated data like that produced by X-ray binaries can lead one to be tempted to invoke exotic lag mechanisms without the appropriate framing. This paper attempts to help provide tools and intuition as to how different phenomena in signals (particularly relating to QPOs) can result in non-linear phase lags with explicit structure.
[abstract 45 / 50] (score: 2) - Title: Constraints on Buchdahl-Inspired Gravity from Future Pulsar Timing near Sgr A*Authors: Jian-Ming Yan, Tao Zhu, Zong-Kuan Guo, Zhao Li,Comments:Subjects: astro-ph.HE gr-qcCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Future pulsar timing observations near Sgr~A* offer a unique probe of gravitational physics in the vicinity of a supermassive BLACK HOLE. We forecast the ability of such measurements to constrain a Buchdahl-inspired $R^2$ gravity, parameterized by a single deviation parameter $ε$, using a timing framework that self-consistently integrates orbital dynamics with light-propagation delays and preserves the full timing solution across the observing span. Through Fisher-matrix forecasts for a representative pulsar, we systematically isolate how the precision on $ε$ depends on orbital geometry. We find that shorter orbital periods and higher eccentricities significantly enhance sensitivity, consistent with a substantial contribution from observations near periastron. As a benchmark comparison, we further consider a hypothetical pulsar on an S2-like orbit ($P_b=16~{\rm yr}$, $e=0.88$) and obtain a statistical sensitivity of $σ_ε\sim 10^{-4}$ within the adopted weak-field, static, and spherically symmetric timing model. This sensitivity is comparable to the natural order-of-magnitude truncation scale of the 1PN expansion and should not be interpreted as a complete forecast for the real Sgr~A* system. Under the adopted idealized assumptions, the characteristic statistical scale is several orders of magnitude below the current S2 95\% confidence interval half-width ($|ε|_{\rm S2}^{\rm 95\%}\approx 0.56$), though this comparison is heuristic given the differing confidence levels. These trends provide quantitative guidance for target selection and campaign design in future Galactic-center pulsar searches.
[abstract 46 / 50] (score: 2) - Title: Energy deposited by BLACK HOLEs in the hot X-ray gas of elliptical galaxies, groups and clustersAuthors: A. Cattaneo, S. Ettori,Comments: 13 pages (+4 pages of Appendix); accepted for publication in A&ASubjects: astro-ph.CO astro-ph.GACreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Galaxy groups show entropy excesses $ΔS$ with respect to theoretical expectations from models and simulations with purely gravitational heating. We determine the heat $Q_{\rm heat}\simeq TΔS$ deposited by non-gravitational sources into the hot gas of elliptical galaxies, groups and clusters, and to compare it with the energy output of their central BLACK HOLEs (BHs). We adopt a simple model for the hot gas with only one free parameter: the core entropy. We calibrate the core entropy on the observed relation between X-ray luminosity and halo mass, and we use it to determine the entropy $S$ of the hot gas. We determine $ΔS=S-S_0$ by taking the difference between $S$ and the entropy $S_0$ found in cosmological adiabatic simulations for haloes of the same mass. The temperature $T$ of the hot gas during the heating phase is determined from semi-analytic/semi-empirical modelling by assuming that heat absorption traces the accretion histories of supermassive BHs. Our findings suggest that supermassive BHs thermalise 1 to $3\%$ of their energy output in the surrounding gas. Our results suggest two regimes: (i) in elliptical galaxies and groups, ACTIVE GALACTIC NUCLEi (AGN) heat the gas much more rapidly than it can cool, generating the observed entropy excesses and quenching STAR FORMATION when the accumulated heat is large enough to unbind the gas reservoir in the host halo; (ii) in galaxy clusters (at $M_{200}>10^{14}{\rm\,M}_\odot$), heating and cooling are in self-regulated equilibrium.
[abstract 47 / 50] (score: 2) - Title: The role of different nonlinearities and potential vorticity conservation in two-dimensional fluid ITG modelsAuthors: Giridharan Paramasivam, Özgür D. Gürcan,Comments: 30 pages, 17 figuresSubjects: physics.plasm-phCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
The nature of turbulent energy cascade of simple two-dimensional fluid models of ion temperature gradient driven turbulence is studied in detail. Notably, it is observed that a minimal two-field model of toroidal ITG, behaves qualitatively differently with or without the diaMAGNETic nonlinearity. In its absence, the zonal flows always dominate and the system never reaches a high-transport state. In contrast, when this term is included, zonal flows dominate only near marginality, while away from it, an inverse cascade with high levels of transport is observed, requiring large-scale dissipation (hypoviscosity) to saturate and hyperviscosity to regularize small scale instability associated with this nonlinear term. However introducing such a term, together with the existence of the curvature term, breaks potential vorticity conservation, which is one of the key symmetries of drift-wave turbulence. This can be remedied by considering a more complete model that retains higher-order terms in the pressure equation. This form of the model, with four nonlinearities, conserves potential vorticity and behaves similarly to the original model, requiring hyperviscosity to saturate since the added nonlinearity generates small scale instability also for the pressure equation. To characterize the roles of potential vorticity conservation and higher-order terms in the pressure equation, the behavior of both the standard ITG system, and the potential vorticity conserving system, is studied by analyzing their spectra, turbulent cascades, and sensitivity to viscosity. Finally, the direction of turbulent cascade due to the different nonlinearities (i.e. the diaMAGNETic nonlinearity in particular) is investigated by examining their contributions to the spectral energy transfer and by considering the triadic instability assumption for each of these nonlinearities separately.
[abstract 48 / 50] (score: 2) - Title: Jet creation and wave energy dissipation by a submerged elastic plateAuthors: Diane Komaroff, Gatien Polly, Alexis Mérigaud, Benjamin Thiria, Ramiro Godoy-Diana,Comments:Subjects: physics.flu-dynCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Experiments on a flexible plate horizontally submerged in a wave tank are reported in this paper. The plate is held at a fixed depth at its upstream end, while its downstream end is free to move. The wave field is measured using a synthetic Schlieren technique, giving access to an estimate of the fractions of the incoming wave energy that are transmitted and reflected after encountering the region where the plate is submerged. Part of the incoming wave energy is shown to be dissipated by the plate. Flow field measurements in a vertical plane parallel to the wave propagation are performed to examine the wave-plate interaction. A JET-like flow is produced at the free end of the plate, with strong vortex activity similar to that produced by a flapping fin. The kinetic energy present in this JET-like flow is computed from the velocity field measurements, and the external dissipation produced by JET creation is estimated. Results highlight the efficiency of flexible plates in reflecting and attenuating waves. This study also showcases a change in JET direction, in particular the observation of a JET going upward toward the free surface for certain frequencies. Such a configuration, could be of great interest for wave energy conversion applications, while preventing harmful phenomena such as seabed erosion.
[abstract 49 / 50] (score: 2) - Title: Irreducible-Mass Growth and Extractable Energy in a Self-Gravitating Blandford-Znajek EngineAuthors: Remo Ruffini, Giorgio Sonnino,Comments: 5 pages, no figuresSubjects: astro-ph.GACreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
Wang recently constructed a self-gravitating split-monopole Blandford-Znajek engine and obtained its secular horizon mass and angular-momentum loss rates. We determine the previously unknown consequences of this evolution: the growth of the irreducible mass, the division of rotational work between outgoing electroMAGNETic power and horizon dissipation, and the lifetime-integrated energy removed from the horizon. For fixed MAGNETic flux and impedance matching, one half of the instantaneous rotational work is carried outward, and one half irreversibly increases the horizon area. Integrating Wang's spin-down trajectory, we find in the weak-field limit the exact results A_f/A_0=\sqrt{e} and E_{extr}^H/(M_{H,0}c^2)=1-exp{1/4}/\sqrt{2}\simeq 0.09206. The leading maximum-power spin-flux allocation instead gives E_{\rm extr}^{H}/(M_{H,0}c^2)\simeq 0.04668. These results provide the first irreducible-mass and extractable-energy accounting of Wang's engine. Their extension from quasilocal horizon quantities to energy received at infinity requires a separate flux analysis.
[abstract 50 / 50] (score: 2) - Title: TeV Higgsino Dark Matter from LZ Nuclear Recoil to FERMI-LAT Gamma RaysAuthors: Lei Wu, Yang Zhang, Bin Zhu,Comments: two columns, 5+9 pages, 4 figuresSubjects: hep-phCreated: 2026-09-01; Updated: 2026-09-02; Datestamp: 2026-09-02
The Higgsino DARK MATTER of the minimal supersymmetric standard model is one of the most minimal and canonical WIMP candidates. We demonstrate that this classic candidate can account for both the high-energy nuclear-recoil excess reported by the LZ experiment and the mild preference in the 14 years of FERMILAT Galactic-center data, with the relic abundance fixing the Higgsino DARK MATTER mass near 1.1 TeV and the recoil spectrum selecting a mass splitting of a few hundred keV. Together with the 10-year IceCube solar-neutrino constraint, the Higgsino interpretation further pins down a viable region of parameter space. It predicts a Galactic-center gamma-ray line and endpoint signal near the present H.E.S.S. sensitivity and within CTAO's projected reach, making this classic candidate testable in the near future.
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