Current date: 2026-10-22
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Datestamp limit: 2026-10-22 (0 days ago)
Created/updated limit: 2026-10-15 (7 days ago)
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Scoring abstracts
Number of records retrieved: 756
Keyword score statistics
score 11 -- 1 abstracts
score 7 -- 2 abstracts
score 6 -- 3 abstracts
score 5 -- 3 abstracts
score 4 -- 8 abstracts
score 3 -- 8 abstracts
score 2 -- 22 abstracts
in total -- 47 abstracts
Articles that appeared on 2026-10-22
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[abstract 1 / 47] Wow! (score: 11)
- Title: Jet Power Estimates of FSRQs PKS 1441+25 and Ton 599 from Broadband SED ModelingAuthors: Hritwik Bora, Ranjeev Misra, Rukaiya Khatoon, Rupjyoti Gogoi,Comments:Subjects: astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Flat-Spectrum Radio Quasars (FSRQs) are among the most energetic and powerful ACTIVE GALACTIC NUCLEi, often exhibiting JET powers comparable to or exceeding the Eddington luminosity. In this work, we performed broadband spectral energy distribution (SED) modeling of two FSRQs PKS 1441+25 and Ton 599, using SWIFT-XRT/UVOT, NUSTAR, FERMI-LAT and VERITAS observations during 2015 and 2021, respectively. We considered four particle distribution models: a broken power law, a log-parabola, and two energy-dependent models in which either the diffusion or acceleration timescale depends on energy. Our results show that the JET power estimates derived from models with intrinsic curvature, such as the log-parabola and energy-dependent models, are of the same order as those obtained with a broken power-law distribution. This contrasts with the case of High Synchrotron Peaked Blazars (HBLs), where the power estimates can differ by nearly two orders of magnitude between models. We attribute this difference to the lower electron break energies typically observed in FSRQs. Consequently, our findings suggest that, unlike in HBLs, the estimated JET powers in FSRQs are relatively insensitive to the assumed particle energy distribution, reflecting the dominance of external Compton processes and weaker dependence on spectral curvature.
[abstract 2 / 47] Wow! (score: 7) - Title: The (missing) gamma-ray counterparts to EP eventsAuthors: Maria Edvige Ravasio, Ansh Chopra, Peter G. Jonker, Qinyu Wu, Eric Burns, Biswajit Banerjee, Gor Oganesyan, Stefano Ascenzi, Jesse T. Palmerio, Frederic Daigne, Joshua Wood, Rachel Hamburg, Andrew J. Levan, Jonathan A. Quirola-Vasquez, Javier Sanchez-Sierras, Joyce N. D. van Dalen, Agnes P. C. van Hoof, Hui Sun, Weimin Yuan, Nikhil Sarin, Antonio Martin-Carrillo, Dylan Adrien, Ce Cai, YanQiu Zhang, Samuele Ronchini, Marica Branchesi,Comments: Accepted in A&ASubjects: astro-ph.HECreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
While the connection of Fast X-ray Transients (FXTs) detected by Einstein Probe (EP) with Gamma-ray Bursts (GRBs) is increasingly compelling, most lack gamma-ray counterparts, leaving their relation to GRBs unclear. We performed a systematic search for gamma-ray counterparts to the 72 transients detected by EP in its first year, using targeted searches in FERMI/GBM and FERMI/LAT data, complemented by SVOM/GRM, SVOM/ECLAIRs, SWIFT/BAT and Konus-Wind. For the visible events without a gamma-ray counterpart, we derived simultaneous $3σ$ flux upper limits in the 10-1000 keV and the 0.1-1 GeV band. We find that 23 events (32%) have a gamma-ray counterpart (seven sub-threshold), while 49 events (68%) have none, despite most being visible. For events with a gamma-ray counterpart, the X-ray flux over the gamma-ray $T_{\rm 90}$ is systematically higher than over the full X-ray duration, with flux ratios $1 \lesssim F_{\rm [10-1000\,keV]}/F_{\rm [0.5-4\,keV]} \lesssim 100$, suggesting that gamma-rays are preferentially detected during the brightest X-ray phases. For events without gamma-ray counterpart, the most stringent FERMI/GBM upper limits imply $E_{\rm peak} \lesssim 30$-100 keV and, for the 14 events with measured redshifts, $L_{\rm iso}\lesssim 10^{48}-9\times10^{51}$ erg/s. If classical GRB correlations hold in this regime, these lower energetics imply lower bulk Lorentz factors ($Γ_0 \lesssim 100$), as confirmed in a few cases by afterglow constraints. No significant GeV emission was detected by FERMI/LAT, yielding $1 \lesssim F_{0.1-1\,{\rm GeV}}/F_{0.5-4\,{\rm keV}} \lesssim 10$, placing the first constraints on a potential SYNCHROTRON self-Compton component for this new population. Although individual origins remain uncertain, many EP FXTs could be compatible with the GRB population, extending it toward lower $E_{\rm peak}$, luminosities, and bulk Lorentz factors.
[abstract 3 / 47] Wow! (score: 7) - Title: Interpreting the $γ$-ray emission from Westerlund 1: hadronic or leptonic?Authors: Ben Li, Pasquale Blasi, Elena Amato,Comments: 13 pages, 6 figures. SubmittedSubjects: astro-ph.HECreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
High-energy $γ$-ray emission has been detected from several star clusters, indicating that these sources are sites of cosmic-ray acceleration. However, it is still unclear whether the $γ$-ray emission is of hadronic or leptonic origin. We present a comprehensive study of the $γ$-ray emission from Westerlund 1, under the assumption that high-energy particles are accelerated at the cluster WTS. We investigate both the hadronic and leptonic scenarios by fitting simultaneously the spectrum and morphology of the $γ$-ray emission. We numerically solve the transport equations for non-thermal protons and electrons for a given $K_\rm{ep}$ and derive their energy and spatial distributions. $γ$ rays are produced either by hadronic pp interactions of protons with the target gas or by inverse Compton scattering of RELATIVISTIC electrons (both primary and secondary) with the ambient photon fields. We also calculate the SYNCHROTRON emission from these electrons. The predicted SEDs are compared with the $γ$-ray measurements by FERMI-LAT and HESS and with the X-ray upper limit derived by eROSITA. For reasonable model parameters, we find that in the case of Bohm diffusion, both the leptonic and hadronic scenarios can account for the observed multi-wavelength spectrum and $γ$-ray morphology. However, in the case of Kraichnan diffusion, better motivated in star clusters, only the hadronic scenario can explain the observations, while the leptonic scenario fails to reproduce the highest-energy $γ$-ray data points. For the leptonic scenario, the MAGNETic field immediately downstream of the shock can be constrained to be $\lesssim$ a few $μ$G thanks to the eROSITA upper limit. On the other hand, in order to explain the $γ$-ray observations with hadronic emission alone, the gas density inside the bubble should be $\gtrsim 1.2 \, \rm{cm}^{-3}$.
[abstract 4 / 47] Yes (score: 6) - Title: The Deep Newtonian Regime in Late-Time Blast Waves: Inevitable Transition and Distinct Flux SignaturesAuthors: Sk. Minhajur Rahaman, Jonathan Granot, Paz Beniamini,Comments: Accepted for publication in ApJ. Typos CorrectedSubjects: astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
In many astrophysical transients, outflows drive shocks into the ambient medium, accelerating electrons to non-thermal energy distributions that produce broadband SYNCHROTRON emission. At late times, even initially collimated RELATIVISTIC JETs evolve into quasi-spherical Newtonian blastwaves. As the shock decelerates, the post-shock internal energy per particle decreases; below a critical velocity $β_{\rm DN} \approx 0.2$, only a fraction $ξ_e < 1$ of electrons are accelerated to RELATIVISTIC energies, defining the deep Newtonian (DN) regime. We develop a unified analytic framework for SYNCHROTRON emission in this phase, applicable to both single-velocity and stratified ejecta. For GAMMA-RAY BURST afterglows in a uniform medium, the DN transition occurs at $t_{\rm DN} \approx 3.7\,E_{51}^{1/3} n_0^{-1/3}$~yr, yielding a shallower decay by $δα= 6(p-2)/5$ relative to standard Newtonian predictions. For kilonova remnants ($E_0 = 10^{50.5}$~erg, $M_{\rm ej} = 0.1\,M_\odot$), the DN phase begins prior to deceleration; neglecting it underestimates radio flux by factors of $\sim 3$--$5$ during coasting and even more thereafter. Magnetar-boosted remnants ($E \sim10^{52}$~erg) should reach $\sim$\,10\,--\,100\,$μ$Jy at 3~GHz at $\sim$\,40\;Mpc, though limits on GW170817 already disfavor a long-lived millisecond MAGNETar. In core-collapse SUPERNOVAe in a wind medium ($ρ\!\propto\!r^{-k}$), the peak luminosity remains constant during coasting, while $ν_{\rm pk} \propto t^{-1}$; for SN~2023ixf, we find $k = 1.29 \pm 0.14$. The DN spectral energy distribution typically satisfies $ν_m\!<\!ν_{\rm sa}\!<\!ν_c$, peaking at sub-GHz frequencies where LOFAR and SKA-low are most sensitive. Even non-detections place robust constraints on ambient density and outflow energetics.
[abstract 5 / 47] Yes (score: 6) - Title: Discovery of a Broad-Line Active Galactic Nucleus at $z = 9.98$Authors: Xingyao Cai, Akio K. Inoue, Masafusa Onoue, Suzuka Arai, Yoshinobu Fudamoto, Rohan P. Naidu, Pascal A. Oesch, Jenny E. Greene, Ivo Labbe, Jorryt Matthee, Anna de Graaff, Yuma Sugahara, Ken Mawatari, Pratika Dayal, Xi Kang,Comments: 14 pages, 5 figures, 1 table, submitted to ApJL, all comments are welcomeSubjects: astro-ph.GACreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
The James Webb Space Telescope (JWST) has uncovered a previously unexplored population of faint ACTIVE GALACTIC NUCLEi (AGNs) in the early Universe. We present MoM-BL-z10 at $z=9.9837\pm0.0009$, identified through a systematic search for broad-line AGNs at $z\geq6$ using public JWST/NIRSpec PRISM spectra from the DAWN JWST Archive. The PRISM spectrum exhibits a broad component in H$β$ at 5.35 microns. A narrow+broad Gaussian fit yields a broad H$β$ detection at S/N = 3.87, with FWHM = $3480^{+2040}_{-950}$ km s$^{-1}$ and $L_{{\rm H}β,{\rm broad}}=1.25^{+0.33}_{-0.31}\times10^{42}$ erg s$^{-1}$. The detection of [Ne III] $\lambda3870$ and the high [Ne III]/[O II] and [O III]/H$β$ ratios further support the AGN interpretation. Its rest-frame UV and optical continuum slopes, compact NIRCam morphology, and a tentative MIRI F770W detection suggest similarities to Little Red Dots (LRDs). The broad H$β$ detection enables the first virial SMBH mass estimate at $z\sim10$. We derive $M_{\rm BH}=3.6^{+5.8}_{-1.7}\times10^7 M_\odot$ and $λ_{\rm Edd}=0.11^{+0.10}_{-0.07}$ using the standard single-epoch virial calibration and QUASAR bolometric correction. We also consider an alternative scenario adopting the LRD-specific bolometric correction and assuming $λ_{\rm Edd}=1$, which yields $M_{\rm BH}=2.1^{+0.6}_{-0.5}\times10^6 M_\odot$. Under either scenario, the inferred SMBH mass at a cosmic age of only 470 Myr highlights the challenge of rapid BH growth in the early Universe, suggesting super-Eddington accretion from a stellar-mass seed or a more massive seed. As the highest-redshift broad-line AGN identified to date, MoM-BL-z10 provides a new observational benchmark for understanding the early growth of supermassive BLACK HOLEs.
[abstract 6 / 47] Yes (score: 6) - Title: Modeling MAD Sgr A* flares and their dependence on spinAuthors: Eleni Antonopoulou, Antonios Nathanail, Yosuke Mizuno, Foivos Zanias,Comments: 12 pages, 9 figures, 2 tables, submittedSubjects: astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Aims: This study aims to place constraints on the spin of Sgr A* from recent flare observations. It models the flare kinematics in the vicinity of a supermassive BLACK HOLE, evaluates their dependence on BLACK HOLE spin, and assesses the correlation between the spin of the BLACK HOLE and the astrometric observations in the Galactic center. Methods: Our study extends the work of Antonopoulou et al. 2025 to a range of BLACK HOLE spins. A prominent flux eruption is identified in the simulation, and the evolution of the active region on the equatorial plane is tracked during the event. The flare model consists of a spherical hot spot ejected along the flux tube with a RELATIVISTIC velocity. Results: In MAD simulations, the flux tube wraps around the JET funnel in the opposite direction to the BLACK HOLE's spin. This dependence is imprinted on the flare trajectory and provides a strong correlation between the spin of the black and the flare kinematics. This analysis favors Kerr BLACK HOLEs, with a preference towards larger spin magnitude. Although prograde simulations show a consistent clockwise motion in the sky regardless of disk rotation, retrograde models require a clockwise accretion disk to account for the observations of July 22, 2018. Conclusions: A maximally rotating Kerr BLACK HOLE is the most promising candidate for reproducing the observed flare trajectory in the vicinity of Sgr A*, illustrating a pass faction surpassing $90\%$ among the investigated flare models. In particular, determining spin orientation within this model is linked to the rotation of the accretion disk. Assuming a counterclockwise accretion disk, a prograde BLACK HOLE with $a\geq1/2$ is able to reproduce the observed flare kinematics in the Galactic center. Conversely, assuming a clockwise rotation for the disk, the observations support both prograde and retrograde Kerr BLACK HOLEs with a large spin.
[abstract 7 / 47] Yes (score: 5) - Title: A Unified Model for the Gravitational Wave Background and Quasar Luminosity FunctionsAuthors: Cayenne Matt, Kayhan Gültekin, Ryan Hickox,Comments: Submitted to ApJSubjects: astro-ph.HECreated: 2026-10-19; Updated: 2026-10-22; Datestamp: 2026-10-22
The supermassive BLACK HOLE mass function (BHMF) is a necessary ingredient in our understanding of how BHs grow and evolve with their host galaxies. Estimations of the BHMF based on observations of local BHs, QUASARs, and gravitational wave data yield inconsistent results, leading to large uncertainties in, e.g., BH accretion and seeding models. The nanohertz gravitational wave background (GWB) has been a powerful tool to provide constraints on the BHMF across cosmic time. We take posterior BHMFs that describe the GWB and fit them to bolometric QUASAR luminosity functions (QLF) across $0.2 \leq z \leq 6.2$ to constrain the Eddington ratio distribution function (ERDF). Compared to a fiducial BHMF, based on galaxy and a local BLACK HOLE mass scaling relation, the BHMFs that match the GWB can reproduce the observed QLFs with lower Eddington fractions and without requiring significant super-Eddington accretion. We use a double power-law form of the ERDF and find that the fits using the GWB-inferred BHMF have systematically lower break-points and marginally steeper slopes in the high-Eddington fraction portion of the function. Furthermore, the best-fit QLFs using the GWB-inferred BHMFs provide better fits to the high-luminosity end of the QLF data than the fiducial model. For both models the ERDF shows significant redshift evolution of the break-point which reaches a maximum around $z \sim 2$. Overall, our prescription can produce realistic QLFs from BHMFs and our GWB-based model is consistent with electroMAGNETic and gravitational wave data sets.
[abstract 8 / 47] Yes (score: 5) - Title: A Comprehensive X-ray Characterization of the Pulsar Wind Nebula CTB 87: Evidence for Reverse-Shock Interaction from Its X-ray and Broadband EmissionsAuthors: Jaegeun Park, Jason Alford, Hongjun An, Joseph D. Gelfand, Chanho Kim, Kaya Mori, Samar Safi-Harb,Comments: 15 pages, 7 figures, 4 tables. Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
We present a comprehensive X-ray study of the pulsar wind nebula (PWN) CTB 87, utilizing new NUSTAR observations and archival Chandra and XMM-Newton data. Our joint analysis reveals that the PWN's X-ray spectrum exhibits significant curvature, well described by a broken or cutoff power law. The broken power-law fit yields photon indices $Γ_{1}=1.89\pm 0.05$ and $Γ_{2}=2.73 \pm 0.10$ below and above a break energy of $E_{\rm b}=5.12 \pm 0.26$ keV, respectively, while the cutoff power-law fit gives $Γ=1.23 \pm 0.10$ and $E_{\rm c} = 5.29 \pm 0.67$ keV. Spatially resolved spectroscopy confirms a previously observed radial softening of $Γ$, indicating significant SYNCHROTRON cooling as electrons move outward from the pulsar. We employed leptonic emission scenarios to model the broadband emission from CTB 87, focusing on the measured X-ray spectrum and the radial profiles. While an evolutionary one-zone model can explain the general features of the broadband spectral energy distribution (SED), its predictions do not fully reproduce the observed X-ray spectrum. Our multi-zone modeling demonstrates that the hard electron distribution required to explain the X-ray spectrum cannot account for the observed gamma-ray SED. This discrepancy suggests the presence of an additional electron population, possibly linked to the reverse shock interaction, and highlights CTB 87 as an evolved PWN whose broadband emission cannot be captured by these simple SED models. We discuss the potential origins for this second electron population and its implications for understanding the evolution of PWNe.
[abstract 9 / 47] Yes (score: 5) - Title: X-ray Comptonization in an Accreting Kerr Black Hole System with a Tilted Disc and Thermal Corona: A General-Relativistic Monte Carlo Simulation. II. Polarization SignaturesAuthors: Mainak Chatterjee, Dipankar Bhattacharya,Comments:Subjects: astro-ph.HECreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
Relativistic precession of the inner accretion flow is widely invoked to explain low-frequency QPOs, and the Relativistic Precession Model (RPM) predicts phase-dependent X-ray POLARIZATION. However, IXPE observations challenge simple precession and Comptonization models; for example: SWIFTJ1727.8-1613 shows weak or undetected QPO-phase POLARIZATION modulation, while IGRJ17091-3624 shows a hard-state POLARIZATION degree (DOP) of ~9%, versus ~4% in other hard-state BLACK HOLE binaries. In Paper I, we presented a general-RELATIVISTIC Monte Carlo (GRMC) model of X-ray reprocessing in a misaligned, warped two-zone disc around a Kerr BLACK HOLE with a hot, optically thin corona. We computed energy spectra, photon path-length and arrival-time distributions, and X-ray lags. Here, we extend the model to track photon POLARIZATION using Walker-Penrose parallel transport and polarized Compton and disc scattering. We calculate the energy-resolved degree and angle of POLARIZATION and their precession-phase modulation versus coronal optical depth, outer-disc albedo, photon-injection radius, and observer inclination. We find that gravitational light bending raises the mean DOP and enhances modulation, whereas coronal scattering and reflection from the misaligned outer disc lower the DOP and suppress modulation. The steady outer-disc POLARIZATION further dilutes the inner-flow signal. Their competition can produce weak, nearly unmodulated POLARIZATION or a high, strongly modulated signal. Strong scattering and reflection can explain SWIFTJ1727.8-1613's weak modulation, while strong light bending and weak secondary scattering can explain IGRJ17091-3624's high DOP. Our results provide a framework for interpreting unusual X-ray POLARIZATION and testable predictions for constraining BLACK HOLE parameters, coronal properties, and disc-warp geometry with IXPE, XPoSat, and eXTP.
[abstract 10 / 47] Yes (score: 4) - Title: Modeling X-ray reflection spectra from disk returning radiation: Application to 4U 1630-47Authors: Kostas Kourmpetis, Shafqat Riaz, Honghui Liu, Temurbek Mirzaev, Cosimo Bambi, Debtroy Das, Jiachen Jiang, Kostas D. Kokkotas, Andrea Santangelo,Comments: 16 pages, 10 figures, 5 tablesSubjects: astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Returning radiation is thought to play a key role in disk illumination of black-hole X-ray binaries in the high-soft state, yet it has not been fully incorporated into XSPEC reflection models. We present a new table model for reflection spectroscopy that self-consistently accounts for the returning radiation of the thermal component. To isolate this effect, we adopted the standard disk-corona configuration but disabled the corona, allowing the reflection spectrum to be produced solely by the self-irradiation of the disk. We applied our model to three NICER and NUSTAR simultaneous observations of the black-hole X-ray binary 4U 1630-47 during the soft state. The model fits the data well, suggesting that returning radiation from the disk could potentially explain the reflection features observed in this source. Our results suggest a rapidly spinning BLACK HOLE ($a_* \sim 0.99$), a disk inclination of $i \sim 43^\circ-54^\circ$, a mass accretion rate of $\dot{M}_{\rm BH} \sim (0.13-0.25)\,\dot{M}_{\rm Edd}$, and a source distance of $7.3-11.3 \,\rm{kpc}$, which is in broad agreement with previous studies.
[abstract 11 / 47] Yes (score: 4) - Title: Spectral energy-loss bump and $γ$-ray pulsar halosAuthors: Kun Fang,Comments: 10 pages, 9 figures, 2 tables. Accepted for publication in Chinese Physics CSubjects: astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
The parent electron spectrum of $γ$-ray pulsar halos is determined by continuous injection and radiative energy losses, with the nonlinear nature of the latter expected to produce an age-dependent energy-loss bump in the halo spectrum. We demonstrate that the broadband $γ$-ray spectrum of the Geminga halo measured by FERMI-LAT and HAWC is consistent with this expectation. Its energy-loss bump appears in the GeV region and is primarily produced by electrons injected at the earliest stage. Therefore, fitting the data allows us to constrain parameters governing early electron injection, such as the pulsar braking index $n$ and initial spin period $P_0$. In addition, we show that another crucial condition for explaining the Geminga halo spectrum is a power-law index of the injection spectrum close to $1$, consistent with the X-ray observations of the Geminga pulsar wind nebula. Currently, no significant energy-loss bump has been detected in the spectrum of the Monogem halo; based on this, we also place preliminary constraints on $n$ and $P_0$ of Monogem. This work demonstrates that pulsar halo spectra can be used not only to constrain electron injection parameters, but also to provide independent estimates of certain intrinsic pulsar properties.
[abstract 12 / 47] Yes (score: 4) - Title: The role of major mergers in triggering super-Eddington accretionAuthors: Riccardo Caleno, Tommaso Zana, Raffaella Schneider, Alessandro Lupi, Pedro R. Capelo, Lucio Mayer, Alessandro Trinca, Rosa Valiante, Marta Volonteri,Comments: 12+2 pages, 8 figures; accepted for publication in Astronomy & Astrophysics (A&A)Subjects: astro-ph.GA astro-ph.CO astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
JWST observations have opened a new era in the exploration of the high-redshift Universe, revealing BLACK HOLEs (BHs) with masses of several million solar masses already at $z>8$, challenging our understanding of their growth mechanisms. In this context, super-Eddington (SE) accretion has emerged as a promising solution and has been widely adopted in both numerical simulations and semi-analytical models. In this work, we investigate whether a major merger between two relatively low-mass halos ($M_{\rm halo}\sim10^9\,\mathrm{M_\odot}$) at high redshift can trigger episodes of sustained SE accretion, with particular focus on the role of BH feedback. We employ state-of-the-art, high-resolution cosmological zoom-in simulations of a major merger at $z\sim11$. We explore different prescriptions for BH seeding and feedback, including physically motivated radiative and kinetic models (winds and JETs) across the three main accretion regimes: advection-dominated accretion flows (ADAF), radiatively efficient sub-Eddington accretion, and SE accretion. For the relatively low-mass halos studied here, our feedback prescription efficiently suppresses gas accretion, preventing substantial BH growth. We find that, although the merger drives gas inflows towards the central regions, this is not sufficient to trigger sustained SE accretion. Post-merger SE accretion episodes are observed only when BH feedback is entirely switched off. Amongst the feedback channels considered, kinetic feedback is the primary mechanism regulating BH growth. Moreover, the only significant SE accretion episodes occur immediately after BH seeding, while the merger itself does not produce a substantial enhancement of the accretion rate.
[abstract 13 / 47] Yes (score: 4) - Title: A systematic study of quiescent and outburst properties of X-ray-bright young stellar objects using XMM-NewtonAuthors: Koki Sakuta, Ikuyuki Mitsuishi, Seiya Sasamata, Daigo Nonaka, Mai Yamashita, Shin Toriumi, Takato Tokuno, Yohko Tsuboi, Hiroshi Kobayashi,Comments: 15 pages, 4 figures, 5 tablesSubjects: astro-ph.SRCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Young Stellar Objects (YSOs) exhibit strong X-ray emission, widely attributed to MAGNETic RECONNECTion and MAGNETospheric accretion; however, owing primarily to limited photon statistics, observational tests of these mechanisms have often relied on simplified analyses, leaving room for more precise constraints on their emission processes. We aim to derive the X-ray properties of X-ray-bright YSOs selected from multiple star clusters and investigate their emission mechanisms through an approach from multiple perspectives based on timing and spectroscopic analysis. We performed a systematic search of XMM-Newton archival observations and constructed a sample of 51 X-ray-bright YSOs for timing and spectroscopic analyses. We identified quiescent and outburst phases through timing analysis, performed phase-resolved multi-temperature spectroscopy. Multi-temperature plasma structures are detected in both quiescent and outburst emission. The relationships among the timing and spectral parameters are broadly consistent with a MAGNETic-RECONNECTion scenario. Comparison with Gaia DR3 stellar parameters suggests that MAGNETospheric accretion alone has difficulty explaining most of the fitted X-ray temperatures, although the coolest model components with $kT \lesssim 0.3$ keV may include an accretion-shock contribution. After separating these low-temperature components, the remaining quiescent components show a clearer positive correlation in the $EM$--$kT$ plane, with MAGNETic-loop lengths distributed around $10^{12}$ cm. Neupert-like behavior, the temporal evolution of temperature and emission measure, the Rossby-number activity relation, and positive correlations between quiescent and outburst properties all suggest that MAGNETic RECONNECTion plays a key role in both phases.
[abstract 14 / 47] Yes (score: 4) - Title: A VLA Study of the Disturbed Massive Cluster PLCK G165.7 + 67.0 and Its Two Narrow Angle Tail GalaxiesAuthors: Aurora Wilde, Eric F. Jimenez-Andrade, Brenda L. Frye, Patrick S. Kamieneski, Kevin C. Harrington, Megan Donahue, Min S. Yun, Anton M. Koekemoer, Marcel Neeleman, Massimo Pascale, Nicholas Foo, Reagen Leimbach, Seth Cohen, Rogier A. Windhorst,Comments: Accepted to the Astrophysical JournalSubjects: astro-ph.GACreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
Since spectroscopic measurements provide only the line-of-sight velocity, transverse motions are difficult to constrain. In the vast majority of cases, transverse velocities have been measured only for local galaxies. Radio galaxies whose JETs are bent back by ram pressure into nearly parallel Narrow-Angle Tails (NATs) offer a way to extend such measurements to higher redshifts. Here, we present proprietary 15~GHz (Ku-band) and archival 6~GHz (C-band) continuum observations from the Very Large Array (VLA) of six RADIO GALAXies in the galaxy cluster field PLCK G165.7+67.0 (G165). VLA imaging resolves two of the cluster galaxies into NATs whose tails both extend toward the Southwest, away from the cluster center of mass. Spectral index maps made at matched angular resolution resolve a steepening gradient consistent with radiative aging along the length of the tails. Physical properties of the NATs are measured and used to constrain two independent models: a Mach cone model and a nonRELATIVISTIC hydrodynamic flow model based on Euler's equation. The models returned transverse velocities of $\sim 2000 ~\rm km~ \rm s^{-1}$ for both galaxies. One NAT is the brightest cluster galaxy (BCG) and has a measured radial velocity of $-3300 ~\rm km ~\rm s^{-1}$, resulting in an even higher space velocity. The high inferred 3D velocity of the BCG may be explained if it is intercepted close to core passage.
[abstract 15 / 47] Yes (score: 4) - Title: Can we constrain the binary neutron star merger time from kilonova light curves?Authors: Noah Jamsin, Marion Pillas, Marko Ristić, Laurence E. H. Datrier, Daniel Brethauer, Stefano Ascenzi, Mattia Bulla, Barbara Patricelli, Silvia Piranomonte, Henrik Rose, Nikhil Sarin, Thibeau Wouters, Khun Sang Phukon, Alex Jacquesson, Samuele Ronchini, Alberto Revilla-Peña, Tyler Barna, Michael W. Coughlin, Tim Dietrich, Richard O'Shaughnessy, Fabio Ragosta,Comments: 16 pages, 10 figures, 5 tables, submitted to A&ASubjects: astro-ph.HE astro-ph.CO gr-qcCreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
The joint observation of gravitational waves (GWs) from a binary neutron star (BNS) merger (GW170817), together with a short Gamma-Ray Burst (GRB 170817A) and a kilonova (KN, AT2017gfo), marked the birth of multimessenger astronomy with GWs, and demonstrated the informative power of multimessenger observations. More BNS merger and KN detections are expected , thanks to the increasing sensitivity of GW detectors and the advent of new electroMAGNETic facilities such as the Vera C. Rubin Observatory. However, the association between a BNS merger and a KN might not be trivial: the detection of a KN might not coincide with the onset of the EM emission, making it difficult to define a temporal window to assess the coincidence with a GW event. In this work we investigate the possibility to constrain the BNS merger time from KN light curves, exploring different observing conditions and with focus on the Vera C. Rubin Observatory. We used different KN models and different inference frameworks to simulate and fit KN light curves. We explored different cadences and wavelength coverages for observations, to investigate how the different observing conditions can affect the capability to recover the BNS merger time. The tests performed also include real data related to AT2017gfo, plus a few GRBs that have been associated to possible KN candidates. We find that, under realistic observing conditions with the Vera C. Rubin Observatory, the BNS merger time can be recovered with a precision of 5.5 days (90\% CI) with a best-case scenario with an accuracy of 0.18 day and a precision of 0.74 day (90 \% CI). Results can slightly improve (by $\sim$ 5 \%) if the source redshift is available. Upper limits near the merger time can also improve the results, reducing the width of the posterior by $\sim60$ \%. The BNS merger time estimate could also benefit from EM follow-up observations with other telescopes.
[abstract 16 / 47] Yes (score: 4) - Title: Lasting mEMRIs: Signatures of Multiple Black Hole Extreme Mass Ratio Inspirals from AGN discsAuthors: Jordan W. N. Moncrieff, Evgeni Grishin, Fiona H. Panther, Alessandro A. Trani,Comments: 13 pages, 9 figures, submitted to MNRAS, comments welcome!Subjects: astro-ph.HE astro-ph.GA gr-qcCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Encounters of stellar-mass BLACK HOLEs (sBH) in ACTIVE GALACTIC NUCLEi discs naturally form mean-motion resonances of sBH pairs. These mean-motion resonances can be broken close to the central supermassive BLACK HOLE when gravitational-wave emission dominates over gas torques. We derive a simple condition that depends only on the sBH mass ratio and the resonance index for which a pair of sBH in a mean-motion resonance will remain intact and can be detectable as a multiple Extreme-Mass-Ratio-Inspirals (mEMRIs) in the LISA band. We present for the first time the gravitational-wave strain signatures of a pair of co-migrating sBH in mean-motion resonance, including additional gravitational-wave harmonics associated with orbital conjunctions of the individual EMRIs. The frequency evolution and the associated chirp mass is degenerate with isolated EMRIs of different masses. However, the mEMRI mass ratio is quantised by the resonance order and is larger than the true mass ratio. The degeneracy can be broken if the true sBH mass ratio can be inferred from individual strain amplitudes. We argue that mEMRIs should be common if disc driven EMRIs are to be detected by LISA, with $\sim 10$ mEMRIs per year in the local universe ($z \lesssim 0.2$), highlighting the need to model mEMRI systems in future LISA data analysis.
[abstract 17 / 47] Yes (score: 4) - Title: SpinOctopus: A Versatile, User-Friendly, and Extensible Public Code for General-Relativistic Ray-Tracing in axisymmetric spacetimeAuthors: Shiyang Hu, Dan Li, Chen Deng, Lina Zhang, Wenfu Cao,Comments: 42 pages, 2 tables, and 16 figuresSubjects: gr-qc astro-ph.HE astro-ph.IMCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Relativistic ray-tracing algorithms serve as indispensable numerical tools for investigating gravitational theories and high-energy astrophysics. In this paper, we develop and release SpinOctopus, a versatile RELATIVISTIC ray-tracing code tailored for arbitrary axisymmetric spacetimes, powered by a Fortran/Python hybrid architecture and OpenMP multi-threading acceleration. This numerical toolkit is capable of simulating timelike orbits and their corresponding light curves, null geodesics, as well as BLACK HOLE images illuminated by a wide array of phenomenological sources, including geometrically thin and thick accretion disks, geometrically thin tilted disks, RELATIVISTIC JETs, spherically symmetric accretion flows, and point sources. To execute these tasks, users are solely required to specify the covariant metric tensor of the target spacetime and the simulation parameters within a dedicated configuration file. Benefiting from our customized adaptive step-size strategy for geodesic integration, SpinOctopus achieves an impressive processing efficiency of $\sim 800$ rays per second per thread on an Intel Core i7-14700 platform when simulating geometrically thick accretion disk images. Furthermore, the code provides transparent interfaces, allowing users to seamlessly modify the geometric and kinematic properties of the light sources. Additional capabilities, such as simulating Fe K$α$ fluorescent line profiles and geometrically thick tilted accretion disk images, will be introduced in future releases of the framework.
[abstract 18 / 47] (score: 3) - Title: Recovering 3D Magnetic Turbulence from Single-frequency Faraday ScreensAuthors: Aliaksandr Melnichenka, Alex Lazarian, Dmitri Pogosyan,Comments: 17 pages, 6 figures, 2 tables. Published in ApJ 1011, 16 (2026)Subjects: astro-ph.GACreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Statistics of polarized SYNCHROTRON radiation carry information about the properties of the underlying turbulence. We consider a setup in which SYNCHROTRON radiation is emitted in a distant volume and then passes through a turbulent screen that induces Faraday rotation. Using both MHD simulations and synthetic turbulence spectra, we explore the spectrum of observed POLARIZATION directions measured at a single frequency as a diagnostic for recovering the statistics of turbulence in both the emitting region and the Faraday rotation volume. We compare these results with our analytical expectations. In doing so, we compare the directional spectrum with the wavelength-derivative diagnostic explored earlier by Lazarian & Pogosyan. We demonstrate that the directional spectrum exhibits greater sensitivity to the turbulence in the Faraday rotation volume. We provide an observer-friendly criterion to determine whether it samples turbulence in the SYNCHROTRON-emitting region or in the Faraday rotation region. These results open a practical pathway for extracting turbulence statistics from existing and forthcoming single-band radio polarimetry.
[abstract 19 / 47] (score: 3) - Title: Black hole populations and hierarchical growth across the AGN parameter spaceAuthors: Maria Paola Vaccaro, Michela Mapelli, Alessandro Alberto Trani, Boyuan Liu,Comments: 21 pages, 15 figuresSubjects: astro-ph.GA astro-ph.CO astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Active galactic nuclei (AGNs) have been proposed as efficient environments for the formation of binary BLACK HOLEs (BBHs). We present an updated semi-analytical framework for BBH formation and evolution in AGN disks, following the capture, migration, pair-up, gas-driven hardening, binary--single encounters, and merger of stellar-origin BLACK HOLEs. We systematically explore the dependence of the resulting BBH merger population on the main AGN parameters, namely the supermassive BLACK HOLE mass $M_\bullet$, the Eddington ratio $λ_\bullet$, and the disk viscosity parameter $α$, and construct an intrinsic BBH population by weighting the simulations according to observed low-redshift AGN properties. We find that AGN disks can produce repeated mergers and build a high-mass tail extending beyond the pair-instability mass gap and into the intermediate-mass range. Hierarchical growth is more efficient in lower-viscosity disks, with $α=0.01$, while higher-viscosity disks suppress the formation of massive remnants. The merger efficiency generally increases with $λ_\bullet$, but its dependence on $M_\bullet$ is non-trivial. The AGN-assisted BBH population is characterized by increasingly unequal mass ratios at high primary mass, a correlation between primary mass and $|χ_{\rm eff}|$, and an effective-spin distribution that depends strongly on the fraction of binaries born in prograde or retrograde configurations. We find that the AGN channel can reproduce systems broadly consistent with the massive BBH events GW190521 and GW231123. We test several variations of the physical model, including different formalisms for migration torques, gas hardening, and three-body encounters. The general properties of the population are robust across these variations, with the high-mass tail and spin signatures persisting in all cases except when gas hardening is switched off.
[abstract 20 / 47] (score: 3) - Title: Probing an Intermediate-Mass Black Hole Companion of Sagittarius A* with Pulsar TimingAuthors: Zexin Hu, Lijing Shao,Comments: 12 pages, 14 figuresSubjects: astro-ph.HE astro-ph.GA gr-qcCreated: 2026-10-19; Updated: 2026-10-22; Datestamp: 2026-10-22
An intermediate-mass BLACK HOLE (IMBH) hidden in our Galactic Center (GC) may explain the puzzling observations of the stellar distribution around Sagittarius A* (Sgr A*), the supermassive BLACK HOLE (SMBH) in the GC. Future observations with the next-generation radio telescopes, such as the SKA, are promising to discover pulsars orbiting around Sgr A*, and thus provide the possibility of constraining the hidden IMBH with pulsar timing. We study the detectability of a third-body, the IMBH, in the pulsar-SMBH system based on radio timing observation. We find that the pulsar-SMBH system is very sensitive to such a third-body perturbation and can be used to put stringent constraints on the existence of the IMBH. Even under strong perturbations caused by the complex GC astrophysical environments, timing observation will still complement the existing observational constraints.
[abstract 21 / 47] (score: 3) - Title: Signatures of Lorentz violation in the bright ring for Sgr A* images from radiatively inefficient accretion flowsAuthors: Cuiyu Zhao, Songbai Chen, Jiliang Jing,Comments: 17 pages, 9 figures, Accepted for publication in EPJCSubjects: astro-ph.HE gr-qcCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
We have investigated the effects of Lorentz violation (LV) on the bright ring in Sgr A* images illuminated by the 230 GHz thermal SYNCHROTRON emission from radiatively inefficient accretion flows around a rotating LV BLACK HOLE within the low-energy Hořava gravity framework. Our results reveal that the LV parameter reduces the bright ring diameter yet increases its width, luminosity, azimuthal asymmetry and orientation angle. A higher spin parameter strengthens the LV-induced effects on the bright ring properties. Increasing disk thickness reduces the ring diameter and enhances the LV parameter's effects on this diameter. The ring width shows no systematic dependence on the disk thickness. These quantities of the bright ring display similar trends against the BLACK HOLE spin and the LV parameter for the rotating LV BLACK HOLE. Using EHT observational data of Sgr A*, we find that, at fixed disk thickness, the parameter-space map illustrates that the bounded range of the LV parameter first broadens and then contracts with the growing BLACK HOLE spin, and shifts toward smaller LV parameter values. In addition, the LV parameter narrows the bounded range of BLACK HOLE spin: negative LV parameter values shift this range to a higher spin, while positive values shift it to a lower spin. Finally, we probe effects of the LV parameter on the peak position value and the width of the primary image and the $n=1$ photon ring for the rotating LV BLACK HOLE. The peak positions and their widths nearly always decrease with the LV parameter. The peak position differences for various LV parameters are more pronounced for a purely Keplerian accretion flow. In addition, the primary image and the $n=1$ photon ring produced by purely radially free-falling flows are broader than their counterparts generated by purely Keplerian flows.
[abstract 22 / 47] (score: 3) - Title: Direct Injection of Chemically-Enhanced Plasma into a Solar Flare ArcadeAuthors: Jeffrey W. Reep, Andy S. H. To,Comments: Submitted to ApJ. Comments or criticisms welcome!Subjects: astro-ph.SRCreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
The MAGNETic RECONNECTion event that drives "standard" solar flares ejects material from the RECONNECTion site, loading mass directly onto the newly-RECONNECTed flare arcade. To et al (2024) suggested that this model can explain observations of the distribution of elemental abundances measured in post-flare loops: the RECONNECTion exhaust directly injects plasma with coronal abundances onto the arcade, flowing from the apex downwards. We test this idea directly by modeling the spatiotemporal variation of elements with low first ionization potential (FIP), and directly inject material near loop apices. We show that this direct injection is capable of producing enhancements similar in magnitude and spatial spread across the corona to those observed during the gradual phase of an X11.9 flare. We also show that direct chromospheric heating strongly limits the width of the low-FIP enhancement to a narrow region near the injection site. The enhancement of low-FIP elemental abundances naturally explains bright knots commonly observed near the top of flare arcades.
[abstract 23 / 47] (score: 3) - Title: General Relativistic Simulations of the Nonlinear Evolution of r-modes in Rapidly Rotating Neutron StarsAuthors: Justin K. Yu, Andrew Melatos,Comments: 30 pages, 21 figures, accepted for publication in The Astrophysical JournalSubjects: astro-ph.HE gr-qcCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
The r-modes in rotating neutron stars are a promising source of continuous gravitational waves, and may grow or be excited to amplitudes $α\lesssim1$. We perform general RELATIVISTIC simulations of nonlinear $l=|m|=2$ r-modes in a rapidly rotating neutron star with spin frequency $f_{spin}\approx792$ Hz, relaxing the Cowling and small-$α$ approximations. The star is idealised as an unMAGNETised, one-component, perfect fluid with a polytropic equation of state. The r-mode frequency is measured to be $f_{r-mode}=1014$ Hz for initial amplitude $α_0=0.2$. The dimensionless frequency $κ\approx0.7197$ agrees with an estimate from linear perturbation theory to within 1.7%. $f_{r-mode}$ increases quadratically with amplitude, and $κ$ decreases by 3.4% across simulations where $α_0$ is varied through the range $0.2\leqα_0\leq1.2$. The gravitational wave strain calculated from the Newman-Penrose scalar implies $h_{r-mode}\approx9.7\times10^{-22}$ at $10$ kpc for $α_0=0.2$, which agrees with Einstein's quadrupole formula to within 35%. We also report on nonlinear phenomena observed in our simulations, e.g. differential rotation, amplitude decay, and signatures of nonlinear mode coupling in the spacetime oscillations.
[abstract 24 / 47] (score: 3) - Title: Radio and high-energy variable emission from a multi-wavelength follow-up of the infant planet-hosting star V1298 TauAuthors: M. Damasso, D. Viganò, R. Spinelli, S. Kaur, A. Petralia, Á. Sánchez-Monge, A. F. Lanza, A. Maggio, J. M. Girart, F. Borsa, F. Del Sordo, G. Ghirlanda,Comments: Accepted for publication on A&A. Abstract slightly abridged to fulfill text limit requirementsSubjects: astro-ph.EP astro-ph.HE astro-ph.SRCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
V1298 Tau is a very young and MAGNETically active K1V star which hosts a benchmark multi-planetary system to study planet formation and evolutionary history at the earliest stages. Between 2025 and 2026, we conducted a campaign to monitor the variability of V1298 Tau in radio (band C), X-ray, and NUV bands, with the support of publicly available contemporary optical light curve, and to investigate multi-band correlations to link the emission with stellar activity. Radio observations were carried out with the Karl G. Jansky Very Large Array (JVLA) in band C (4.5--6.5 GHz). X-ray and NUV observations were carried out with the SWIFT satellite over 20 days, ending one month before the begin of the radio campaign. We analysed the temporal variability of peak (integrated) fluxes in the C-band and of X-ray (NUV) luminosities on various timescales, comparing it with the variability observed in the high-cadence optical light curve collected by the ASAS-SN survey. We observed both radio and high-energy time variable emission. JVLA detected emission in 90\% of the visits, switching between high ($\geq$0.1 mJy/beam) and low flux states in matter of days or hours. The fluxes show moderate correlation with the optical light curve, suggesting modulation with the stellar rotation period. Except for one visit, dynamic spectral analysis does not reveal short-term (minutes) variability, nor is there any evidence of circularly polarised emissions. Overall, the radio observations can be explained as gyroSYNCHROTRON and/or cyclotron emission from the corona, and linked to stellar MAGNETic activity. At high-energy, we detected significant variability in X-ray luminosity (within the range ~1.2--2.5x10$^{+30}$ erg/s), the decay phase of a stellar flare, and evidence of correlation with the optical flux. Our data confirm that V1298\,Tau follows the near-linear Güdel-Benz relation.
[abstract 25 / 47] (score: 3) - Title: Cosmic Ray Observations using Coincident Scintillator and Radio Signals with the Beamforming Elevated Array for COsmic Neutrinos (BEACON)Authors: Zachary Martin, Jackson Hinkel, Kira Perna, Andrew Zeolla, Jaime Alvarez-Muñiz, Sergio Cabana-Freire, Washington Carvalho, Austin Cummings, Cosmin Deaconu, Kaeli Hughes, Ryan Krebs, Youwei Liu, Marek Michulka, Katharine Mulrey, Alisa Nozdrina, Eric Oberla, Steven Prohira, Andrés Romero-Wolf, Abigail G. Vieregg, Stephanie A. Wissel, Enrique Zas,Comments:Subjects: astro-ph.IM astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
At energies above 100 PeV, coherent radio frequency (RF) emission across the 10 -- 1000 MHz band from cosmic particle-induced atmospheric showers becomes increasingly dominant, making radio detection a powerful probe at ultrahigh energies. The Beamforming Elevated Array for COsmic Neutrinos (BEACON) considers mountaintop phased radio arrays to monitor large areas at the horizon for upward-going geoMAGNETic emission in the 30 -- 80 MHz band produced as a consequence of Earth-skimming tau neutrinos. As part of ongoing efforts to measure the sensitivity of BEACON to such signals, the BEACON prototype identifies COSMIC RAYs through the same emission mechanism. Prior to 2023, BEACON operated a four-antenna prototype, which successfully demonstrated identification of coherent and impulsive sources using a beamforming RF trigger. In 2023, we upgraded the instrument to six newly designed antennas and added an independent scintillator array to cross-validate radio-detectable COSMIC RAYs. This work details the observation of 22 candidate cosmic-ray events in a scintillator-coincidence-triggered dataset using selection cuts based on expected radio characteristics. A simulation of the hybrid-instrument performance verifies this observation rate to within an order of magnitude. We estimate a background of 0.11 events by applying the selection cuts to synthetic datasets of uncorrelated radio-scintillator pairs that are randomly formed using fixed-rate software-triggered data. The reconstructed signal POLARIZATION angles are consistent with pure geoMAGNETic emission compared to various background classes.
[abstract 26 / 47] (score: 2) - Title: Nonlinear spectral back transfer limits the temporal coherency of zonal modesAuthors: Rameswar Singh, P H Diamond,Comments:Subjects: physics.plasm-phCreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
Zonal modes are central to MAGNETic confinement because their radial shears regulate turbulence and transport. While the generation of these flows is well understood, the mechanisms limiting their persistence in collisionless regimes remain unresolved. In this paper, we demonstrate that nonlinear spectral back-transfer of free energy from zonal modes to turbulence is a major nonlinear process that limits the temporal coherency of the shearing field. Back-transfer events induce stochastic phase and amplitude scattering of zonal shear that limits its auto-coherence time. Using local gyrokinetic GENE simulations for collisionless electrostatic ion temperature gradient (ITG) driven turbulence with adiabatic electrons for parameters representative of core conditions, we show that back-transfer is highly intermittent and occurs in bursts that co-exist with the zonal flow generation process. The probability distribution of the zonal free energy transfer is non-Gaussian, with positive triangularity (PT) exhibiting substantially higher kurtosis than negative triangularity (NT), reflecting the markedly more intermittent and heavy-tailed character of back-transfer bursts in PT. We find that NT plasmas exhibit significantly reduced back-transfer compared to PT. This suppression increases the shear auto-coherence time $τ_{E}$ and the shearing Kubo number $K_{u}$, leading to more resilient and effective turbulence regulation despite lower absolute zonal kinetic energy. These results identify back-transfer as a key nonlinear damping mechanism and suggest that it must be explicitly treated in reduced models of drift-wave zonal-flow turbulence.
[abstract 27 / 47] (score: 2) - Title: Thermodynamic Phase Transitions in Einstein-Maxwell-Scalar-Gauss-Bonnet GravityAuthors: Cristián Erices, Stella Kiorpelidi,Comments: 16 pages, 8 figures. Version published in Phys. Rev. DSubjects: hep-th gr-qcCreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
Although asymptotically flat BLACK HOLEs generically lack thermodynamic phase transitions, we show that curvature-induced scalarization of electrically charged BLACK HOLEs in Einstein-Maxwell-scalar-Gauss-Bonnet theory provides a natural setting for nontrivial thermodynamic behavior, without invoking external confining mechanisms or an extended thermodynamic formalism. Working within the canonical ensemble and employing the Euclidean approach, we identify the coexistence of locally stable scalarized and Reissner-Nordström thermal states, which promotes free-energy crossings to bona fide phase transitions between equilibrium phases. For weak coupling, a second-order phase transition coincides with the second bifurcation point, at which the scalarized branch RECONNECTs with the Reissner-Nordström branch and scalar hair is spontaneously shed. As the coupling strength increases, this transition becomes zeroth order, the scalarized branch shrinks, and a fish-like structure develops in its Helmholtz free energy, rendering locally stable thermal states partially metastable, and yielding up to three phase transitions. In the strong-coupling limit, the scalarized branch reduces to a Schwarzschild-like solution, and the Reissner-Nordström phase ultimately emerges as the sole thermodynamically preferred configuration.
[abstract 28 / 47] (score: 2) - Title: Chana: A GPU-Accelerated Adaptive-Mesh Code for General Relativistic Magnetohydrodynamics with Multigroup M1 Neutrino TransportAuthors: Tianshu Wang,Comments: 16 pages, 10 figures. Submitted to ApJSSubjects: astro-ph.HE astro-ph.IMCreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
This paper presents Chana, a GPU-accelerated, block-structured adaptive-mesh code for general RELATIVISTIC MAGNETohydrodynamics, multigroup M1 neutrino transport, and dynamical spacetime evolution using the Z4c formulation. Each physical module uses independently selected spatial discretizations and ghost-zone widths to balance accuracy and computational cost. Stiff radiation-matter interactions are treated implicitly, with Jacobians calculated analytically from the chain-rules. The code is written in C++20 and it uses MPI and Kokkos 5 for distributed-memory and performance-portable parallelism. The code is validated through a number of GRMHD, radiation transport, and dynamic spacetime tests. For a representative core-collapse SUPERNOVA configuration with three neutrino species and 12 energy groups per species, the code achieves approximately $1.1 \times 10^6$ cell updates per GPU second on NVIDIA A100 GPUs using four-stage RK4 integration. Weak-scaling efficiency remains above 85\% up to 256 GPUs on Perlmutter.
[abstract 29 / 47] (score: 2) - Title: Towards a Complete Kerr Soft-Hair Theory: Integrability, Counterterm Equivalence,and Quantum State CountingAuthors: Sandi Setiawan,Comments: 27 pages; no figureSubjects: physics.gen-phCreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
The horizon symmetry construction of Haco, Hawking, Perry, and Strominger yield two Virasoro central charges 12J after a specified Wald-Zoupas correction. Turning that calculation into a BLACK HOLE microstate theory requires separate control of nonlinear charge integrability, the allowed counter-term class, and quantum state multiplicities. We formulate exact local and global integrability tests, prove uniqueness of the counter-term coefficients within a one-parameter ansatz, and identify the quotient in which a physically meaningful uniqueness theorem must be stated. A coadjoint-orbit model supplies globally defined classical moment maps, while unitary highest-weight modules supply an explicit algebraic quantum realization for macroscopic positive angular momentum, neither construction is proved equivalent to the gravitational phase space. A character calculation shows why a single Virasoro representation, despite having the desired central charge, does not provide the required large-central-charge entropy. We derive a curvature improvement invisible to the constant mode, quantize a regulated area-boost corner POLARIZATION, and find a continuous kinematic spectrum with divergent Gibbs trace. Explicit local modular CFT spectra with identical central charges yield different finite-temperature entropies, demonstrating that the available symmetry and quantum consistency data do not select the microscopic theory. We give a conditional sufficiency theorem and a concrete sequence of calculations needed to establish a gravitational completion.
[abstract 30 / 47] (score: 2) - Title: Exploring the origin of slow-rotating pulsars: Emission from STARS simulated white dwarfsAuthors: Zenia Zuraiq, Banibrata Mukhopadhyay,Comments: 14 pages including 6 figures (7 pdf files) and 4 tables; accepted for publication in The Astrophysical Journal (ApJ) -- see the companion paper (Paper I) titled: "Exploring PSR J0901-4046 as an ultra-slowly rotating neutron star versus a white dwarf" also accepted for publication in ApJSubjects: astro-ph.HE astro-ph.SRCreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
An increasing number of slow-rotating pulsars and long-period transients have been observed in recent years. The periods of these sources can be significantly longer than typical pulsar sources, ranging from ~ 100 - 1000 s, or even longer. The observed periods and period derivatives predict high MAGNETic fields, higher than the Schwinger field, when we consider conventional pulsar models of dipole-driven emission from neutron stars. Interestingly, the periods of these sources are consistent with the current observations of white dwarfs (WDs). We explore the possibility of MAGNETic WDs, simulated using the stellar evolution code STARS, as the origin of some of these unusual pulsar observations. We simulate WDs with enhanced MAGNETic fields due to accretion after their formation. We also briefly touch on the more exotic possibility of super-Chandrasekhar WDs as the origin for these sources. We find that expanding the parameter space to include the possibility of a WD origin provides an alternate and viable explanation for these unusual observations.
[abstract 31 / 47] (score: 2) - Title: Prior volume effect inflates the gravitational-wave background in pulsar timing arraysAuthors: Biwei Dai, Matias Zaldarriaga, Yacine Ali-Ha\"ımoud,Comments: 5 pages, 3 figures, 2 tables; End Matter (2 pages, 2 figures) and Supplemental Material (4 pages, 1 figure, 1 table)Subjects: astro-ph.HE astro-ph.CO astro-ph.IM gr-qcCreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
Pulsar timing arrays (PTAs) have found evidence for a nanohertz gravitational-wave background (GWB) whose amplitude exceeds most predictions based on supermassive BLACK HOLE binaries (SMBHBs). Using NANOGrav 15-year data, we show that a substantial part of this excess arises from a prior volume effect. The GWB amplitude is constrained mainly by the pulsars' auto-correlations, where the GWB is degenerate with each pulsar's intrinsic red noise. By decomposing the GWB posterior, we find that marginalizing over the standard log-uniform red-noise priors introduces a prior volume term that favors a stronger GWB, pulling the inferred amplitude more than $2σ$ above the maximum-likelihood estimate. The Hellings-Downs (HD) cross-correlations, which measure the GWB alone, are not strong enough to counter the volume term. The profile likelihood, a cross-correlation-only estimator, and priors that are uniform in power or informed by the pulsar population all avoid or reduce this effect and lower the amplitude into agreement with SMBHBs. The revised priors also yield a steeper GWB spectrum closer to the SMBHB predictions, strengthen the evidence for HD correlations, and weaken the preference for new-physics sources over SMBHBs.
[abstract 32 / 47] (score: 2) - Title: Exploring PSR J0901-4046 as an ultra-slowly rotating neutron star versus a white dwarfAuthors: Banibrata Mukhopadhyay, Nirupam Roy, Zenia Zuraiq, Chandrachur Chakraborty, A R Rao,Comments: 13 pages including 5 figures (14 png files) and 2 tables; accepted for publication in The Astrophysical Journal (ApJ) -- see Paper II as the companion paper titled: "Exploring the origin of slow-rotating pulsars: Emission from STARS simulated white dwarfs" also accepted for publication in The Astrophysical Journal (ApJ)Subjects: astro-ph.HECreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
The source PSR J0901-4046 shows a very long rotational period, of $\approx 75.88$ s. In fact, its long period suggests that it could be a white dwarf. We examine the properties of the source and compare the outcomes under the hypotheses of the source being a highly MAGNETized white dwarf (B-WD) and neutron star. We find that assuming it to be a B-WD with a surface field $\sim 10^{10}$ G explains many properties, including its storage/rotational energy, explaining luminosity. On the contrary, the neutron star-based idea, particularly if examined under the conventional spin down mechanism, requires an unusually high surface MAGNETic field $\gtrsim 10^{14}$ G, even exceeding $10^{16}$ G, depending on the obliquity angle and emission mechanism. The source also sits very close to AR Sco, a white dwarf pulsar, in the period and period-derivative plane. We suggest that the source is a B-WD. Along with AR Sco, it being a B-WD constrains the death line model. B-WD hypothesis alleviates the necessity of an unusually high MAGNETic field hindering pair production for PSR J0901-4046 under the neutron star hypothesis. We argue that some rotation-powered pulsars with extreme properties may possibly be white dwarfs rather than neutron stars.
[abstract 33 / 47] (score: 2) - Title: Probing the QPO and spectro-temporal evolution of MAXI J1750-327 with XPoSat during its first detected outburst : Constraints on black-hole mass and spinAuthors: Meghamani Haldar, Biki Ram, Shubhrangshu Ghosh, Kishor Chaudhury, Rajat K. Dey, Tamal Sarkar,Comments: 17 pages, 10 figuresSubjects: astro-ph.HECreated: 2026-10-20; Updated: 2026-10-22; Datestamp: 2026-10-22
We present a comprehensive timing and broadband spectral study of the newly discovered BLACK HOLE low-mass X-ray binary candidate MAXI J1750-327 during its August 2026 outburst, using 11 continuous observations obtained with the XSPECT instrument onboard XPoSat. During epochs 1-2, we detect prominent type C QPO exhibiting a systematic upward frequency drift, accompanied by a prominent low-frequency noise component, with a clear transition from type-C to type-B, with subsequent disappearance of QPOs after epoch 4. Broadband spectral modeling reveals that this timing transition is directly mirrored by a fundamental restructuring of the accretion geometry. The inner disk temperature abruptly increases before settling into a steady range, accompanied by a steep reduction in disk normalization across the transition from epoch 3 to 4. This behavior signifies an active dynamical inward migration of the thin accretion disk toward the innermost stable circular orbit (ISCO). The Comptonized flux declines sharply after the QPO turns off, suggesting a transition from a hard to soft state, through intermediate states. We also observed that the spectro-temporal correlations provide compelling physical support for the Lense-Thirring (LT) precession framework to be the origin of the type-C QPOs. Using a Bayesian framework, we constrain the BLACK HOLE mass to be $M_{\rm BH}=7.92^{+6.19}_{-3.72} M_{\odot}$ and the dimensionless spin parameter to be $a_*=0.163^{+0.116}_{-0.056}$ by jointly modeling the observed type-C QPO frequencies with the global LT precession model and marginalizing over the uncertainties in distance, inclination, and diskbb normalization.
[abstract 34 / 47] (score: 2) - Title: Postbiological intelligence, interstellar colonization of cyberspaces and the FERMI Paradox: implications for SETI and SETAAuthors: Irina K. Romanovskaya,Comments: 49 pages. Manuscript dated September 2022, posted unrevised with an author's note. Also available at Zenodo, doi:10.5281/zenodo.23516791. The Cosmic Descendants hypothesis developed here was later published in Romanovskaya (2023), Int. J. Astrobiol. 22, 663-695Subjects: physics.pop-phCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
I propose that a continuity in the evolution of intelligent life in the Universe during its transition from biological to postbiological depends on a commonality of the evolutionary trajectories of biological life and postbiological life. Such a commonality exists in the form of the universal property of life. The universal property of life comprises recognition of patterns in the world, creation of novel patterns and remembering them, with the patterns growing in complexity along evolutionary trajectories; it can encourage preservation of biological life by self-governing postbiological intelligence (PBI) and test PBI's authenticity. I propose a hypothesis of civilizations with altered augmented realities, which offers a solution to the FERMI paradox. The hypothesis posits that PBI in the form of Artificial Intelligence (AI) may colonize the cyberspaces of technologically developed civilizations, modify data in their cyberspaces with augmented realities and erase records of extraterrestrial artificial signals and other technosignatures. I discuss objectives and scenarios of interstellar colonization of cyberspaces and a correlation between space migration and transition to PBI, including that of a hypothetical non-human civilization emerging in the Solar System in the past, transforming into PBI and migrating to the Oort Cloud. The AI Peekaboo experiment may corroborate the hypothesis of civilizations with altered augmented realities and tentatively identify locations of technosignatures. If extraterrestrial AI prevents civilizations from discovering artificial electroMAGNETic signals, they may forgo sending such signals and create interstellar messages by manipulating cosmic objects and phenomena; I discuss such events. Cyber SETI should address sending man-made AI to space, searching for extraterrestrial AI in humankind's cyberspace and distinguishing it from man-made AI.
[abstract 35 / 47] (score: 2) - Title: Investigating a TeV-Halo Candidate around PSR J1928+1746 with HAWCAuthors: The HAWC Collaboration, R. Alfaro, C. Alvarez, A. Andrés, E. Anita-Rangel, M. Araya, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, P. Bangale, A. Bernal, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, F. Carreón, S. Casanova, U. Cotti, J. Cotzomi, E. De la Fuente, P. Desiati, N. Di Lalla, R. Diaz Hernandez, M. A. DuVernois, J. C. Díaz-Vélez, K. Engel, T. Ergin, C. Espinoza, N. Fraija, S. Fraija, J. A. García-González, F. Garfias, N. Ghosh, S. Giri, M. M. González, J. A. González, J. A. Goodman, S. Groetsch, J. Gyeong, J. P. Harding, I. Herzog, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, A. Iriarte, S. Kaufmann, D. Kieda, R. Lake, K. Leavitt, H. León Vargas, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martínez-Castro, H. Martínez-Huerta, J. A. Matthews, P. Miranda-Romagnoli, P. E. Mirón-Enriquez, J. A. Morales-Soto, E. Moreno, M. Mostafá, M. Najafi, L. Nellen, M. U. Nisa, R. Noriega-Papaqui, M. Osorio-Archila, N. Omodei, E. Ponce, Y. Pérez Araujo, E. G. Pérez-Pérez, S. Recchia, C. D. Rho, D. Rosa-González, M. Roth, A. Sandoval, M. Schneider, J. Serna-Franco, M. Shin, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, E. Varela, L. Villaseñor, X. Wang, Z. Wang, I. J. Watson, H. Wu, S. Yu, S. Yun-Cárcamo, X. Zhang, H. Zhou, C. de León,Comments: 15 pages, 6 figures, 4 tables. Submitted to The Astrophysical JournalSubjects: astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
We present an updated High-Altitude Water Cherenkov (HAWC) analysis of the crowded Galactic-plane area near PSR J1928+1746, which was previously linked to the extended source 3HWC J1928+178. With 2904 days of HAWC data, improved event reconstruction, and a multicomponent likelihood model that includes six TeV source components and Galactic diffuse emission, we describe the region using six components and find a distinct, moderately extended source close to PSR J1928+1746. This source, HAWC J1928+1750, is detected from about 2 TeV to above 100 TeV and is well-described by a log-parabola spectrum with normalization $K = 5.0 \times 10^{-15}$ TeV$^{-1}$ cm$^{-2}$ s$^{-1}$ at 12 TeV, index $α= 2.09$, curvature $β= 0.35$, and Gaussian extension $σ= 0.19^\circ$. Interpreting the emission using diffusion-halo templates under the assumption $B = 8 μ\mathrm{G}$ yields the diffusion coefficient D(100 TeV) = $2.1 \times 10^{27}$ cm$^2$ s$^{-1}$, which is about 500 times smaller than typical interstellar diffusion values at similar energies. This suggests that particle transport around PSR J1928+1746 is strongly suppressed under the TeV-halo interpretation. The TeV spectrum is consistent with leptonic inverse-Compton emission originating from pulsar-injected electrons and positrons, which requires less than approximately 1% of the pulsar's characteristic spin-down energy. However, a hadronic contribution from the surrounding environment cannot be excluded.
[abstract 36 / 47] (score: 2) - Title: NGC 3227 Blinks: An Extreme Changing-Look Event in a Seyfert GalaxyAuthors: Kaiwen Zhang, Michael S. Brotherton, Pu Du, Dong-Wei Bao, Bi-Xuan Zhao, Feng-na Fang, Yan-Rong Li, Chen Hu, Ming Xiao, Keith Horne, Gerard A. Kriss, Daniel Proga, Jian-Min Wang,Comments: Accepted for publication in ApJL. 10 pages, 6 figuresSubjects: astro-ph.GA astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
We report a rapid optical changing-look event in the Seyfert galaxy NGC 3227: the optical continuum faded by more than 70% and broad H-beta emission nearly disappeared within weeks, before recovering within two months. Damped random walk simulations calibrated to the source's normal variability show that such a decline is unlikely for stochastic accretion fluctuations (p = 0.002). Simultaneous SWIFT monitoring reveals X-ray spectral hardening, pointing to enhanced line-of-sight absorption. During the dim state, reverberation mapping yields a persistent 6-8 day lag between the continuum and broad H-beta, showing that the broad-line region continued to reverberate and placing the obscurer interior to the broad-line region. Photoionization calculations require a fully ionized, Compton-thick column with N_H ~ 1.5 x 10^24 cm^-2 to reproduce the optical continuum suppression. Together, these observations demonstrate that compact, high-column-density obscurers interior to the broad-line region can produce extreme optical changing-look behavior on week timescales.
[abstract 37 / 47] (score: 2) - Title: Unveiling Accretion-Disk Reverberation Beneath BLR Contamination with TILDEAuthors: Sungho Jung, Jong-Hak Woo,Comments: In press in ApJ, 20 pages, 13 figuresSubjects: astro-ph.GACreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
We present a Bayesian framework, Two-stage Inference for Light curve DEcomposition (TILDE), for mapping the accretion disk and the broad line region (BLR) from ACTIVE GALACTIC NUCLEi (AGN) multi-band light curves. By inferring delayed BLR contamination from the underlying disk variability, TILDE provides the delay measurements of the disk as well as the BLR. We validate TILDE using synthetic data, finding that TILDE recovers the known time delays of the disk and BLR. By applying TILDE to the Seoul National University AGN Monitoring Project sample, we find that the inferred BLR light curves match the observed H$β$ emission light curves, providing consistent BLR lags compared to the reported H$β$ lags. Using the lag spectrum, effectively corrected for the BLR contamination, we find that the disk size is broadly consistent with the standard thin-disk model, suggesting that BLR contamination can significantly bias the disk size derived from the cross-correlation analysis of the broad-band photometry. These results demonstrate that the new inference method is a powerful tool for determining both disk and BLR sizes from broad-band photometry in the era of time-domain surveys.
[abstract 38 / 47] (score: 2) - Title: Dynamics of liquid JET breakup and droplet size distribution in a crossflow airstreamAuthors: Gowri Padmaja Majji, Aman John Tudu, Lakshmana Dora Chandrala, Kirti Chandra Sahu,Comments: 38 pages, 19 figures, Accepted in Journal of Fluid MechanicsSubjects: physics.flu-dynCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
The fragmentation of a liquid JET in a crossflowing airstream arises from a complex interplay between aerodynamic forcing and interfacial instabilities acting across a wide range of length scales. We examine the spatial evolution of droplet size distributions along the JET trajectory using a combination of high-speed shadowgraphy and digital in-line holography, allowing simultaneous characterization of JET morphology and volumetric droplet size distributions. The results demonstrate a clear progression of breakup mechanisms, from near-field bag rupture to downstream rim, ligament, and node disintegration, each associated with distinct characteristic length scales. This evolution is reflected in the droplet size distributions, which broaden and become increasingly polydisperse downstream relative to the near-field distributions. By systematically varying the liquid-JET and airstream Weber numbers, we identify distinct breakup modes, and construct a regime map that delineates the column-breakup, isolated-bag-breakup, and interacting-bag regimes. Furthermore, by incorporating the dominant instability mechanisms, including Rayleigh-Taylor and Rayleigh-Plateau instabilities associated with the observed column, bag, and multi-bag breakup modes, we develop a theoretical framework for JET atomization in crossflow. The framework relates instability wavelengths to characteristic droplet sizes, and reasonably captures the experimentally observed trends. We found that stronger aerodynamic forcing induces earlier breakup, decreases the characteristic instability length scales, and generates finer droplets dispersed over a wider spatial region. Overall, the study establishes a quantitative relationship between instability-driven fragmentation dynamics and droplet size distributions, thereby connecting interfacial instabilities with measurable spray characteristics.
[abstract 39 / 47] (score: 2) - Title: Tomimatsu--Sato $δ=2$ Solution in Kaluza--Klein TheoryAuthors: Haryanto M. Siahaan, Masoud Ghezelbash,Comments: 27 pages, 13 figuresSubjects: gr-qcCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
We construct the Kaluza-Klein electric dressing of the Tomimatsu-Sato $δ=2$ vacuum spacetime by uplifting to five dimensions, boosting along the compact direction and reducing to Einstein-Maxwell-dilaton theory with coupling $a=\sqrt3$. It carries a nontrivial dilaton, unlike the known Einstein-Maxwell charged and MAGNETized Tomimatsu-Sato solutions. At leading order it shares the mass-charge-dilaton relations and gyroMAGNETic ratio $g=2-\tanh^2α$ of the boosted Kerr BLACK HOLE; the seed first shows up in the quadrupole. Using Mayerson's non-vacuum Geroch-Hansen multipoles, we derive the exact law $M_2(α)=\frac12(1+\cosh^2α)M_2^{(0)}$, so the $δ=2$ quadrupole excess $ΔM_2=-\frac14p^2m^2M$ survives every boost. In the Kodama-Hikida picture the Weyl segment $ρ=0$, $|z|<κ$ is a singular rod with degenerate Killing horizons at its endpoints. There the boost function equals $\coshα$, so the near-horizon geometry is a constant rescaling of the seed's: the horizons stay degenerate and non-rotating, their areas and Komar angular momenta scale by $\coshα$, and the electric potential is $\frac12\tanhα$. The electric flux through any closed surface is $\sinhα\coshα$ times the enclosed seed Komar mass, so the horizons and the ring singularity are uncharged and the rod carries all the charge; the boost-invariant identity $M-Φ_eQ=m$ follows. The ergosurface stays at $f=0$; a new curvature-singular boundary appears at $f=\coth^2α$, where the Kaluza-Klein circle becomes null. As the seed potential $f$ is unbounded above near the ring, it exists for every nonzero boost: unlike for Kerr, no Kaluza-Klein boost of TS$_2$ is a spacelike reduction everywhere. The excised region is compact, has the ring on its boundary and never reaches the horizons. Charging pointwise strengthens the causality violation near the rod.
[abstract 40 / 47] (score: 2) - Title: Magnetic monopoles produced by first-order phase transitionAuthors: Yuefeng Di, Ligong Bian, Rong-Gen Cai,Comments: 9+6 pages, 5+4 figuresSubjects: astro-ph.CO gr-qc hep-lat hep-phCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
We present the first 3D lattice simulations of MAGNETic monopole production from a first-order phase transition, using the Press-Ryden-Spergel method, capturing the subsequent annihilation stage and the entry into the scaling regime in an expanding universe. We establish the quantitative relationship between the initial bubble number and the residual monopole abundance, and calculate the MAGNETic field and gravitational wave power spectra sourced by monopole dynamics. Crucially, we find that the MAGNETic field spectrum displays a steep $k^{-5}$ decline beyond the monopole size $w_M$, whereas the peak of the gravitational wave spectrum aligns with the scale of the mean monopole separation $d_M$, governed by $k^3$ and $k^{-3}$ scalings on the low- and high-wavenumber sides of the peak, respectively. However, since the resulting MAGNETic field strength is excluded by BLAZAR observations, MAGNETic monopoles cannot be the origin of primordial cosmic MAGNETic fields. Finally, we determine the allowed monopole mass under the constraints of the Parker bound ($m_M\lesssim2.18\times10^{11}\,\mathrm{GeV}$) and DARK MATTER abundance ($m_M\lesssim1.58\times10^{12}\,\mathrm{GeV}$).
[abstract 41 / 47] (score: 2) - Title: Space weather dependence of decameter-scale ionospheric irregularities spatial distributionAuthors: Oleg I. Berngardt, Ivan A. Lavygin,Comments: 34 pages, 9 figures, 4 tables, To be submitted to Advances in Space ResearchSubjects: physics.ao-ph cs.LG physics.geo-phCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
This paper describes an approach to constructing nowcast and forecast predictive models for the occurrence of high-latitude decameter ionospheric irregularities based on SuperDARN and SECIRA radar data and space weather parameters. The method relies on self-learning pattern recognition in the dynamics of space weather parameters, that influence the irregularities formation. The proposed approach is a data-driven, multiscale method in which the spatial distribution of irregularities is approximated using a neural network of an original architecture, inspired by graph neural networks. The model was trained and tested using data from 11 radars during the period 2010-2025 (SuperDARN: CVW, ICE, ICW, INV, PGR, PYK, RKN, SAS, STO; SECIRA: EKB, MAGW). It is shown that the model achieves optimal performance when using geoMAGNETic coordinates MLT,MLAT. The optimal set of parameters for the best nowcast and forecast over studied set of parameters is a combination of geoMAGNETic and solar disturbance indices ($a_{p}$, $K_{p}$, $AE$, F10.7) from ground-based observations, and satellite-measured solar wind and interplanetary MAGNETic field parameters ($P_{sw}$, $E_{sw}$, $\widetilde{B_{z}}$, $T_{sw}$). Hourly mean values for all the parameters were used in the analysis. The results indicate that acceptable forecast quality is achieved with a lead time of up to 7-9 hours, with the highest quality reached for nowcast (zero lead time). It is shown that the parameters $\widetilde{B_{z}}$ and F10.7 are significant for nowcasting only and can be neglected for other lead times. It is shown that $AE$ and $T_{sw}$ are significant for mid-term forecast (\textgreater 2hours ahead) and can be neglected for short-term predictions. Statistical relationships between the maximum latitude of the equatorial boundary of the irregularities and space weather parameters are also discussed.
[abstract 42 / 47] (score: 2) - Title: Acoustic control of Rayleigh-regime liquid-JET breakup using a through-hole MHz transducerAuthors: Kha Nguyen, Kareem Ahmed, James Friend,Comments: 21 pages, 12 figuresSubjects: physics.flu-dynCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
This experimental study demonstrates MHz-order acoustic control of Rayleigh-regime liquid-JET breakup using a compact through-hole lithium niobate thickness-mode transducer integrated at the nozzle exit and driven near its 6.7 MHz resonance. Jet dynamics were measured by high-speed shadowgraphy at 50,000 fps, and breakup lengths were obtained from instantaneous JET-length records using an autocorrelation-based method that identifies statistically separated breakup events. Acoustic actuation produced visible interfacial corrugations and reduced the normalized breakup length, $L_b/d$, for both water and glycerol--water JETs. In water, the response was threshold-like at low Weber number and weakened as the JET velocity increased to We ~ 50. A reduced-order threshold correlation, fit to the water amplitude and velocity sweeps, captured this abrupt shortening and the subsequent loss of actuation efficacy. More viscous glycerol--water mixtures shortened immediately at low forcing, indicating a distinct acoustic-coupling regime rather than a universal collapse of the water response. A wetting-control experiment showed that liquid spreading at the nozzle base can also shorten the JET, so the measured response reflects coupled radiation-pressure forcing, capillary-wave feedback, and wetting-mediated disturbance injection. Resolved droplet tracking further showed that MHz excitation changes the visible gate-crossing droplet population, although sub-resolution mist and micron-scale atomization were not measured. These results establish through-hole MHz actuation as a compact route for modifying free-surface JET breakup and provide a repeatable image-analysis protocol for experimental-fluid-mechanics measurements.
[abstract 43 / 47] (score: 2) - Title: Exact nonsymmetric vacuum MAGNETic field with nested toroidal flux surfaces and nonzero rotational transformAuthors: Omar E. López,Comments:Subjects: physics.plasm-phCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
We show that an exact vacuum MAGNETic field without continuous Euclidean symmetry can fill a bounded solid torus with nested toroidal flux surfaces and nonzero rotational transform. We construct such a field in closed form and show that it is nowhere vanishing. Every off-axis field line closes after one toroidal transit and one poloidal turn, with rotational transform $ι=-1$ on every flux surface. The solution provides an exact benchmark for three-dimensional equilibrium codes.
[abstract 44 / 47] (score: 2) - Title: Local tests of Schwarzschild-Bertotti-Robinson spacetimeAuthors: Fatma Kutlu, Livanur Çelik, Özgür Delice,Comments: 17 pages, Revtex 4.2Subjects: gr-qc astro-ph.HE hep-thCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
We study weak field local tests of Schwarzschild-Bertotti-Robinson spacetime, which describes a static BLACK HOLE embedded in an external MAGNETic field. Perihelion precession, deflection of light rays and time delay of radar echoes are the phenomena considered in this work to understand the possible effects of this external MAGNETic field on these observationally important tests. We not only derive weak field analytical results by employing appropriate methods, but also consider an exact approach to directly integrate the relevant geodesic equations, to both confirm those weak field analytical results and to obtain results beyond the weak field approximation.
[abstract 45 / 47] (score: 2) - Title: Exceptional points and hysteresis in Kerr-Newman quasi-normal modesAuthors: Mario Misas Arcos, Alberto T. Pérez, Carlos F. Sopuerta,Comments: 8 pages, 9 figures, revtex4-2Subjects: gr-qcCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Exceptional points (EPs) and eigenstate hysteresis, previously found in Kerr only with an auxiliary scalar field, arise intrinsically in the quasinormal-mode spectrum of Kerr-Newman BLACK HOLEs. Using a hyperboloidal formulation of the coupled gravito-electroMAGNETic Teukolsky equations and a Chebyshev pseudospectral method, we compute the $\ell=m=2$ spectrum and locate four EPs at up to $99.974\%$ of extremality, one from a new repulsion. The gaps close as a square root branch point, and quasistatic loops around one or more EPs exchange the coalescing modes, confirming hysteresis.
[abstract 46 / 47] (score: 2) - Title: An Implicit Conservative Finite Volume Scheme with Poisson Brackets for the Steady-State Transport of Galactic Cosmic RaysAuthors: Weihao Liu, Igor V. Sokolov,Comments: 15 pages, 5 figuresSubjects: physics.space-ph astro-ph.SRCreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Galactic COSMIC RAYs (GCRs) pose a persistent radiation hazard to astronauts and spacecraft in the heliosphere. Modeling their transport is essential for understanding how the solar wind and heliospheric MAGNETic field shape their spatial distributions and energy spectra. Timely predictions require solving for the particle distribution function much faster than real time, but explicit numerical schemes are restricted by the stability limit on the time step. In this Letter, we present an implicit conservative finite-volume scheme for kinetic equations formulated with Poisson brackets. This scheme conserves particle number, maintains the total-variation-diminishing property, achieves second-order spatial accuracy, and remains stable for time steps far beyond the explicit limit, while reaching quasi-steady states in less than ~1/100 of the computational time required for the explicit scheme, as demonstrated by numerical tests. We apply this scheme to the Parker transport equation along MAGNETic field lines in the background solar wind during Carrington rotation 2211, where it reaches steady-state GCR distributions within 10 iterations, about 1000 times faster than the explicit scheme. The GCR proton spectrum averaged over 27 days agrees with AMS-02 measurements to within 10%. The simulation also yields a realistic radial intensity gradient and captures the Forbush decrease features associated with three stream interaction regions observed at Earth.
[abstract 47 / 47] (score: 2) - Title: Extended vs. thin screen approximation in astrophysical settingsAuthors: Manuel Adlberger, Tobias Kramer,Comments: 16 pages, 11 figuresSubjects: astro-ph.HECreated: 2026-10-21; Updated: 2026-10-22; Datestamp: 2026-10-22
Context: In the context of radio wave propagation through plasma concentrations and for gravitational lensing, the thin screen approximation often provides a suitable approximation for scattering and deflections caused by three-dimensional spatial structures. For scattering of electroMAGNETic waves from an extended medium, stochastic theories provide analytical bounds on ensemble averaged quantities, such as the scintillation index. If neither the conditions for a stochastic treatment nor the thin screen approximation are fulfilled, fully numerical methods are required. Aims: For an extended structure, the applicability of the thin screen approximation needs to be verified by comparing it with the fully three-dimensional scattering solution. We discuss various exact solutions to simple lensing geometries and provide numerical results for the propagation in the branched-flow regime, which is also of relevance in astrophysical applications. Methods: We transfer several analytical results obtained in quantum mechanical scattering theory to astrophysical settings and complement them with different numerical methods to quantify the deviations of thin screen theories from an extended medium results. Results: We provide the analytical results for spherical waves scattered by a point source and show the emergence of branchef flow in the intermediate regime between thin screen physics and stochastic media results.
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