Current date: 2026-09-28
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Created/updated limit: 2026-09-21 (7 days ago)
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Scoring abstracts
Number of records retrieved: 672
Keyword score statistics
score 7 -- 1 abstracts
score 6 -- 2 abstracts
score 5 -- 3 abstracts
score 4 -- 2 abstracts
score 3 -- 8 abstracts
score 2 -- 18 abstracts
in total -- 34 abstracts
Articles that appeared on 2026-09-28
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[abstract 1 / 34] Wow! (score: 7)
- Title: Spectral and Polarization Properties of Coherent Radio Emission from Relativistic Magnetized Pair Plasma ShocksAuthors: Yuanhong Qu, Joonas Nättilä, Lorenzo Sironi,Comments: 17 pages, 8 figuresSubjects: astro-ph.HECreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
Fast radio bursts (FRBs) are millisecond-duration radio transients whose emission mechanism remains an open question. The so-called SYNCHROTRON maser instability in RELATIVISTIC MAGNETized shocks is a leading candidate for FRBs produced outside the compact object MAGNETosphere, yet its spectral and POLARIZATION predictions have not been systematically explored. We present three-dimensional particle-in-cell simulations of RELATIVISTIC MAGNETized pair plasma shocks with upstream MAGNETization $σ> 1$ and bulk Lorentz factor $γ_0 = 10$, assuming a plane-parallel shock geometry and neglecting radiative cooling, and compute the spectra and POLARIZATION of the precursor maser emission for an arbitrary line of sight. For on-axis observers aligned with the shock-propagation direction, the X-mode dominates the emission. The O-mode power increases at off-axis viewing angles and is primarily associated with currents parallel to the upstream background MAGNETic field. Assuming a spherical shock, we find full-width-at-half-maximum fractional bandwidths of $Δν/ν_0\simeq0.57$ and $0.82$ for $σ=3$ and $6$, respectively. For highly MAGNETized shocks, the intrinsic emission bandwidth accounts for most of the spectral width, while high-latitude contributions provide additional broadening. The integrated emission remains highly linearly polarized near the spectral peak, with a nearly constant POLARIZATION angle due to the dominance of the X-mode. Our results suggest that SYNCHROTRON maser emission can produce spectra with bandwidths and high linear POLARIZATION degrees compatible with observations of some non-repeating FRBs, and may provide testable signatures for distinguishing shock-powered FRBs from other emission mechanisms.
[abstract 2 / 34] Yes (score: 6) - Title: Interpreting the diversity of afterglow emission from radio-detected tidal disruption events with instantaneous and delayed outflowsAuthors: Yuri Sato, Mukul Bhattacharya, Jose Carpio, Jewel Capili, Kohta Murase,Comments: 19 pages, 9 figures, 3 tables, PRD, in pressSubjects: astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
Tidal disruption events (TDEs) occur when a star is gravitationally disrupted by the tidal field of a supermassive BLACK HOLE during a close encounter. Radio emission has recently been detected in TDEs and is commonly attributed to SYNCHROTRON radiation from both wind and JETted outflows. However, several TDEs exhibit bright radio flares at late times, which cannot be easily explained if the wind is launched promptly after the stellar disruption. The radio light curves of TDEs with delayed radio flares are modeled using three scenarios: an instantaneous wind, a delayed wind, and a delayed RELATIVISTIC JET. We show that the instantaneous wind model struggles to reproduce delayed radio flare events, indicating the necessity of an additional delayed outflow component. In contrast, the delayed wind model provides a consistent explanation for the observed radio phenomenology, successfully reproducing events both with and without delayed radio flares. For some delayed radio flare events (e.g., ASASSN-15oi and AT 2019dsg), both the delayed wind and delayed JET models can reproduce the observed radio light curves, making it challenging to distinguish between these scenarios based on radio data alone. To break this degeneracy, we present calculations of detailed multiwavelength spectra from radio to x-ray and very-high-energy gamma-ray bands, including both SYNCHROTRON and inverse-Compton processes. Within this framework, the delayed JET model produces x-ray and optical emission detectable at typical TDE distances, in contrast to wind-driven scenarios. Our results highlight how multiwavelength campaigns offer effective means to distinguish between possible outflow mechanisms. We apply our model to AT 2025aarm, which is one of the closest TDEs that has been observed, and show the importance of x-ray observations.
[abstract 3 / 34] Yes (score: 6) - Title: Energy extraction from a Kerr-Bardeen-Letelier BLACK HOLE by Comisso-Asenjo MechanismAuthors: Bijendra Kumar Vishvakarma, Dharm Veer Singh, Sanjay Siwach,Comments: 15 pages, 20 FiguresSubjects: gr-qcCreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We explore the energy extraction from a Kerr-like regular BLACK HOLE coupled with a cloud of strings (CoS) via the Comisso-Asenjo mechanism. We study the effects of the BLACK HOLE spin (a), BLACK HOLE charge (g) and CoS parameter (b) on the ergo-region of the BLACK HOLE and the MAGNETic RECONNECTion process, which is governed by the Comisso-Asenjo mechanism. We also analyze the phase space involving negative energy density of the RELATIVISTIC MAGNETized plasma at infinity. The rate of energy extraction in the MAGNETic RECONNECTion process is also computed and compared with that of the Blandford-Znajek mechanism.
[abstract 4 / 34] Yes (score: 5) - Title: Interaction of stellar dipole and disk MAGNETic fields in accretion-ejection systemsAuthors: Somayeh Sheikhnezami, Sarah Aslani,Comments: 23 pages, 20 figures, Accepted for publication in Astrophysical Journal, comments are welcomeSubjects: astro-ph.HECreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
We study JET formation from a MAGNETically diffusive, sub-Keplerian accretion disk threaded by different MAGNETic field configurations. We present two dimensional, axisymmetric MHD simulations in spherical coordinates employing the PLUTO code. Our results show that the reference simulation, in which the disk is threaded by an initial large scale poloidal MAGNETic field, reaches a quasi steady state and produces a well collimated JET.Both kinetic and MAGNETic torques are significant and evolve smoothly over time. The accretion process is established smoothly, with about 26\% of the accreting material being delivered into the outflow. Alternatively, applying a purely stellar dipolar MAGNETic field produces weak and unstable outflows, characterized by inefficient angular momentum transport and strongly suppressed accretion. Additionally, in simulations where the stellar dipolar MAGNETic field is present alongside the disk's initial poloidal MAGNETic field, the disk MAGNETic field predominantly stabilizes the system. It also facilitates angular momentum transport from the disk and sustains a significant outflow mass flux. Furthermore, we performed additional simulations that explicitly include an inner gap associated with the disk truncation region. These simulations were designed as a robustness test of the treatment of the innermost disk region and confirm that our main conclusions are not sensitive to the presence of this gap. Overall, our findings demonstrate that although the magnitude of stellar dipole plays an important role in the evolution of the accretion-ejection structure, the large scale poloidal MAGNETic field threading the disk is essential for launching and sustaining a stable and well collimated MAGNETized JET.
[abstract 5 / 34] Yes (score: 5) - Title: Deciphering the VHE gamma-rays spectra of Extreme High-Frequency peaked BL Lac Objects through a Photohadronic ModelAuthors: Sarira Sahu, D. I. Páez-Sánchez, A. U. Puga Oliveros, M. E. Iglesias Martínez, Jose Guerra Carmenate, R. de J. Pacheco-Aké, G. Sánchez-Colón, Subhash Rajpoot, P. Fernández de Córdoba, Gaetano Lambiase,Comments: 22 pages, 16 figures, 4 tablesSubjects: astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
Extreme high-frequency peaked BL Lac objects (EHBLs) have their SYNCHROTRON peak above $\sim 1$ keV and their inverse Compton peak extends up to several TeVs. Due to low luminosity of EHBLs, these objects are often undetected, and only a small number of them are thus known. As a result, they are poorly understood. Using a photohadronic model and including extragalactic background light correction we analyzed 22 very high-energy (VHE) gamma-ray spectra of 15 EHBL sources observed in different periods. We find that the photohadronic model used can adequately describe the observed VHE spectral energy distribution and furthermore, we classify them according to the value of the photon spectral index, $δ$. The redshift of the EHBL HESS J1943+213 is also tightly constrained using the same photohadronic model. Within the sample, a plurality of flaring epochs fall in the high-emission state which is followed by the low-emission state and the very-high-emission state respectively. These fractions of flaring epochs characterize only the present sample, not the EHBL population at large. Due to the anomalous behavior of the VHE gamma-ray spectra of the EHBL H 2356-309, we suggest it to be a new subclass of EHBL having hard and very soft intrinsic spectra during different flaring epochs.
[abstract 6 / 34] Yes (score: 5) - Title: 4FHL: The Fourth Catalog of Hard FERMI-LAT SourcesAuthors: LAT Collaboration,Comments: Accepted in ApJ. Contact authors: Alba Rico, Marco Ajello, Alberto Domínguez, Benoit Lott, Dario Gasparrini. The full catalog is available at the FSSC: https://fermi.gsfc.nasa.gov/ssc/data/access/lat/4FHL/Subjects: astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We present a catalog of sources detected above 50 GeV by the FERMI Large Area Telescope (LAT) on board the FERMI Gamma-ray Space Telescope using 16 years of observations. This is the Fourth Catalog of Hard FERMI-LAT Sources (4FHL), containing 673 objects detected in the 50 GeV-2 TeV energy range. The sensitivity and localization are improved by factors of $\sim$2 relative to the previous LAT catalog at the same energies (i.e. the 2FHL catalog). The increased photon statistics, nearly doubling the number of detections relative to 2FHL, enables more detailed population studies, including the identification of fainter sources detected above 50 GeV. The majority of the sources (84.7\%) are associated with extragalactic counterparts, primarily BL Lacertae objects, including 36 objects at redshift $z>1$. Galactic sources account for 10\% of the sample, mainly pulsar wind nebulae and SUPERNOVA remnants, while $\sim$5\% remain unassociated or of uncertain classification. Twenty sources are reported with no counterpart in previous LAT catalogs. The 4FHL catalog provides the deepest all-sky survey above 50 GeV to date. By focusing on this high-energy regime, it provides a fundamental link between space-based gamma-ray observations and the TeV range probed by current and future ground-based observatories. It serves as a useful reference for guiding future observations, including new potential targets for follow-up with Cherenkov telescopes.
[abstract 7 / 34] Yes (score: 4) - Title: Black hole-neutron star binaries with high spins and large mass asymmetries: III. Properties of the ejected material and its electroMAGNETic signaturesAuthors: Konrad Topolski, Samuel D. Tootle, Paramvir Singh, Mattia Bulla, Luciano Rezzolla,Comments: 29 pages, 18 figures, replaced outdated figure; matches the version accepted by PRDSubjects: gr-qc astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
Compact binary systems consisting of a BLACK HOLE (BH) and a neutron star (NS) are expected to provide detectable signals both in the gravitational wave and in the electroMAGNETic channels, thus representing excellent sources for multi-messenger astronomy. In this third paper in a series, we report on the geometric and thermodynamic properties of the purely dynamical ejecta component modeled in our general-RELATIVISTIC MAGNETohydrodynamical simulations of BHNS systems over a comprehensive binary parameter space consisting of large mass ratio and high BH spin. The tidal disruption and dynamical mass ejection is studied by monitoring the transfer of energy and angular momentum to matter for the particular case of a highly unequal-mass binary with large BH spin, extending known results for low-mass-ratio, irrotational BHNS binaries. By varying the binary parameters, we investigate their influence on the geometric, thermodynamic, and kinematic properties of the ejected matter. Furthermore, we employ the nuclear-reaction network SkyNet to obtain the elemental abundances resulting from the r-process active in the ejecta and study how they depend on the properties of the progenitor objects. Finally, using the radiative-transfer code POSSIS, we compute the kilonova light-curves from the results of our simulations, discuss their bolometric and optical/near-infrared evolution, and compare them with the AT2017gfo data and upper-limits for S190814bv, finding overall consistency.
[abstract 8 / 34] 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: Submitted to the Astrophysical JournalSubjects: astro-ph.GACreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
Since spectroscopic measurements provide only the line-of-sight velocity, transverse motions are difficult to constrain. As a result, transverse velocities have so far 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 seven 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 space 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 9 / 34] (score: 3) - Title: Theoretical and experimental assessment of Einstein-Cartan theory: A comparative analysis within the USMEG-EFT frameworkAuthors: Farrukh A. Chishtie,Comments: 14 pages, published at Canadian Journal of PhysicsSubjects: physics.gen-ph gr-qc hep-thCreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
The Unified Standard Model with Emergent Gravity (USMEG-EFT) framework achieves Standard Model-gravity unification by treating 4D General Relativity as an effective field theory. This work presents a comparative analysis of Einstein-Cartan (EC) theory and USMEG-EFT against experimental constraints and theoretical consistency requirements, distinguishing minimal EC with algebraically determined torsion from variants in which the spin connection is an independent quantum field. The latter class includes the Faddeev-Popov quantization framework of Brandt, Frenkel, Martins-Filho and McKeon adopted in their unification proposal, and for it gravitational wave POLARIZATION measurements directly test the additional propagating degrees of freedom. General relativity's spin-2 graviton produces exactly two tensor POLARIZATIONs, while EC theory with independent dynamical spin connection predicts up to six modes. LIGO-Virgo-KAGRA null tests for GW170817 favor pure tensor over pure vector and pure scalar hypotheses at Bayes factors exceeding $10^{20}{:}1$, improved to approximately $10^{26}{:}1$ with a gamma-ray-burst JET-orientation prior. Complementary matter-sector constraints from the Standard Model Extension yield $|\tilde{b}^n_\perp| < 8.4 \times 10^{-34}$ GeV, constraining background-torsion scenarios, while MICROSCOPE bounds equivalence principle violation at $η< 1.5 \times 10^{-15}$. For minimal EC theory, the four-fermion contact interaction generated upon coupling to fermions introduces non-renormalizable divergence structures at two-loop order, a case not addressed by the BRST framework established for the independent spin connection. We situate EC theory within the broader landscape of gauge gravity theories and acknowledge USMEG-EFT's limitations, including sub-Planckian validity and currently untestable distinctive predictions.
[abstract 10 / 34] (score: 3) - Title: Gravitational and kinematic redshifts of BLACK HOLEs in nonlinear electrodynamicsAuthors: Marco A. A. de Paula, Mustapha Azreg-Aïnou,Comments: 33 pages, 11 figuresSubjects: gr-qc astro-ph.GA astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
Spacetimes arising from nonlinear electrodynamics (NED) are a good laboratory for studying both the nature of regular BLACK HOLE (RBH) solutions and the imprints of nonlinear electroMAGNETic fields within this context. Over the past few decades, NED-sourced BLACK HOLE (BH) spacetimes have attracted considerable attention, but electrically charged RBHs obtained in the so-called $F$ framework have been less addressed in the literature. We consider two electrically charged, fully regular members of the h-family that are solutions to general relativity minimally coupled to NED. Because of their potential astrophysical and astronomical applications, we mainly focus our investigation on the motion of photons and its implications for the gravitational and kinematic redshifts, as well as for the shadow radius, considering the effective geometry followed by photons in NED. Moreover, we consider the observational data for Sagittarius A$^{\star}$ and Messier 87$^{\star}$ BHs to impose some constraints on the charge-to-mass ratio of the fully RBHs. We obtain the general equations that govern the gravitational and kinematic redshifts of NED-sourced BH spacetimes. In particular, for fully RBHs with BH charge-to-mass ratios above some moderate value, we observe discrepancies in their physical and geometrical properties compared to those of the Reissner--Nordström (RN) BH. Therefore, our results indicate that it is possible to distinguish NED-based RBH solutions from RN BHs, from the perspective of gravitational and kinematic redshifts, suggesting potential astrophysical relevance.
[abstract 11 / 34] (score: 3) - Title: ElectroMAGNETic Signatures of Kinetic Alfvén Wave Turbulence at Ion Inertial Scales in Earth's High-$β$ MagnetosheathAuthors: Mani K Chettri, Rupak Mukherjee, Hemam D. Singh,Comments: 21 pages, 8 figures, 3 tables. Revised versionSubjects: physics.plasm-phCreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We present a multi-diagnostic electroMAGNETic analysis of a dayside MAGNETosheath interval observed by the Magnetospheric Multiscale (MMS) mission on 2015 December 28 at high ion beta ($β_i = 14.4$), using burst-mode measurements. We combine the scale-dependent electric-to-MAGNETic field ratio, the parallel electric field, the MAGNETic compressibility, the wave-normal angle and circular-POLARIZATION measure, and the ion--electron frozen-in residuals. The electric-to-MAGNETic field ratio rises with wavenumber with a log--log slope of +0.92, whereas the ideal advection contribution remains flat, supporting dispersive fluctuations. A wave-normal angle of $75^\circ$ and a circular-POLARIZATION measure centred near zero support quasi-perpendicular propagation, while the compressibility and the ion temperature anisotropy do not support mirror-mode dominance. A continuous broken power-law fit gives $f_{\rm break} = 0.48 \pm 0.06$ Hz, corresponding to $k_\perp d_i = 0.85 \pm 0.11$ and $k_\perp ρ_i = 3.23 \pm 0.42$. Because $d_i$ and $ρ_i$ are well separated at this $β_i$, the break is more consistent with the ion inertial scale than with the ion gyroscale. Four-spacecraft phase differencing independently supports the Doppler conversion around the break. Above the break, the kinetic-range index is $-2.86 \pm 0.06$ (stat) $\pm 0.18$ (fit window), closer to the weakly damped dispersive limit than to the strongly damped limit, with a fluid-scale index of $-1.81 \pm 0.08$ below it. The observations are consistent with quasi-perpendicular KAW-like turbulence, but do not uniquely identify the mode; the spectral index constrains the cascade rather than the dissipation mechanism.
[abstract 12 / 34] (score: 3) - Title: J0011+3443: a GPS compact symmetric object, gravitational lens, or dual AGN?Authors: Efthalia Traianou, Tingting Liu, Roman Gold, Richard Mushotzky,Comments: 8 pages, 3 figures, 3 tables. Accepted for publication in A&ASubjects: astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We present new multi-frequency VLBA observations of J0011+3443 (TXS 0008+344, z = 0.89) at 2.3, 4.9, 8.5, and, for the first time, 23.6 GHz. The source consists of two compact components A and B at a projected separation of 314 +/- 2 pc, plus a third feature C detected at 23.6 GHz at 0.6 mas from A. Archival low-resolution radio measurements confirm an integrated gigahertz-peaked spectrum, with an observed-frame peak frequency of 0.73 +/- 0.08 GHz and a peak flux density of 879 +/- 125 mJy. Comparison with nearly frequency-matched low-resolution measurements shows that the VLBA recovers 0.85 +/- 0.11 of the 4.85 GHz flux density and 0.50 +/- 0.06 of the 8.46 GHz flux density. The lower recovered fraction at 8.5 GHz suggests that low-surface-brightness emission is resolved out or falls below the VLBA surface-brightness sensitivity. We therefore interpret the VLBA component spectra as spectra of the compact recovered emission only. The 23.6 GHz morphology, the absence of a detected flat-spectrum core, the similar compact spectra of A and B, and the steep integrated GHz spectrum favor an interpretation of J0011+3443 as a GPS-class compact symmetric object, possibly in a short-lived or relic phase, although a dual-AGN origin cannot be excluded without multi-epoch astrometry.
[abstract 13 / 34] (score: 3) - Title: First results on the search for the Galactic Center Excess in the sub-GeV band with the emulsion telescope in GRAINE 2023Authors: Yuya Nakamura, Shigeki Aoki, Takashi Azuma, Hirotaka Hayashi, Yudai Isayama, Atsushi Iyono, Takumi Kato, Tsuyoshi Kawahara, Kohichi Kodama, Ryosuke Komatani, Masahiro Komatsu, Masahiro Komiyama, Hideyuki Minami, Kunihiro Morishima, Fumiya Murakami, Shogo Nagahara, Naotaka Naganawa, Mitsuhiro Nakamura, Tomoaki Nakamura, Noboru Nakano, Toshiyuki Nakano, Kazuma Nakazawa, Miyuki Oda, Kazuhiro Okamoto, Hiroki Rokujo, Osamu Sato, Kai Shimizu, Amon Suganami, Yuki Sugi, Kou Sugimura, Satoru Takahashi, Ikuya Usuda, Saya Yamamoto, Jun Yamashita, Mayu Yamashita, Shoma Yoneno, Masahiro Yoshimoto,Comments:Subjects: astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
(Please check the paper for full abstract.) The Galactic Center Excess (GCE) is an unexplained excess of gamma-ray emission from the Galactic Center. The GRAINE experiment aims to reveal the origin of the GCE using an emulsion gamma-ray telescope with high angular resolutions of 1 deg at 100 MeV and 0.1 deg at 1 GeV. In this study, we search for the GCE in a small region near the Galactic Center using the GRAINE 2023 flight data. In particular, rather than focusing on the spectral peak of the GCE at 2 GeV, we focused on the energy range below 300 MeV, where the spectral differences between the DARK MATTER annihilation and millisecond pulsar scenarios are more pronounced. We searched for the GCE within 1 deg of the Galactic Center in the 75--300 MeV energy range. Although no significant excess was observed, we obtained an upper limit on the GCE flux of 1.70*10^-7 GeV cm^-2 s^-1 at the 2 sigma confidence level for the 1deg-radius ROI centered on the Galactic Center, based on a direct observation of the narrow region around the Galactic Center. This observation requires high angular resolution and represents a unique result from GRAINE. The obtained upper limit is consistent with the GCE flux near the Galactic Center, which was estimated from existing FERMI-LAT observations using a wide ROI and assuming an NFW profile. Although the current upper limit constrains some models, the available statistics are still insufficient to distinguish between the DARK MATTER annihilation and millisecond pulsar scenarios, and both remain consistent with the current results. We also estimated the projected sensitivity of future GRAINE experiments based on the present observation and demonstrated their potential to probe the origin of the GCE by comparing the projected sensitivity with the predicted GCE spectra.
[abstract 14 / 34] (score: 3) - Title: A tidal disruption event in a QUASAR at redshift 7.19Authors: S. Fujimoto, Q. Fei, G. B. Brammer, K. Inayoshi, V. Kokorev, L. C. Ho, R. Li, F. Walter, V. Bromm, L. Colina, P. Dayal, S. L. Finkelstein, M. Ginolfi, Z. Liu, G. C. K. Leung, G. E. Magdis, J. Matthee, R. P. Naidu, P. Oesch, M. Onoue, P. G. Pérez-González, D. Watson, J. Álvarez-Márquez, J. Antwi-Danso, Y. Asada, G. Barro, C. M. Casey, J. Chisholm, S. Gillman, R. Marques-Chaves, J. P. U. Fynbo, T. R. Greve, I. Labbe, R. A. Meyer, F. Rizzo, A. Robbins, R. Schneider, C. L. Steinhardt, S. Toft, A. Trinca, F. Valentino, R. Valiante, M. Vestergaard, M. Xiao,Comments: 18 pages, 8 (+2) figures, 1 table. Submitted to OJA. Comments are welcome!Subjects: astro-ph.GA astro-ph.HECreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
We report a long-lived nuclear transient in GNz7q, a red QUASAR at $z=7.19$ powered by a $\sim3\times10^{7}\,M_\odot$ BLACK HOLE and hosted by a compact, dusty starburst galaxy. The transient was identified in more than two decades of imaging with HST, Spitzer, and JWST. After a rapid rise, the source faded smoothly by $Δm\simeq1.1$ mag in the rest-frame ultraviolet over $\sim2$ rest-frame yr, with coherent, wavelength-dependent evolution across 1--5 $μ$m that places GNz7q above the 99.9th percentile of the SDSS QUASAR variability distribution and is absent at $z\gtrsim5$. The duration and energetics disfavor superluminous SUPERNOVAe, and stochastic QUASAR variability reproduces the multi-band evolution with a probability of $\lesssim10^{-5}$. A panchromatic model combining a thermal continuum with a $t^{-5/3}$ decline reproduces the light curves, yielding a peak bolometric luminosity of $\simeq3\times10^{45}$ erg s$^{-1}$ and a radiated energy of $\simeq1.5\times10^{53}$ erg, which imply the tidal disruption of a star of a few solar masses and place the event among the most energetic tidal disruption events (TDEs) known. A redshifted, extremely broad Balmer-line component in independent JWST/NIRSpec spectroscopy is consistent with a transient, non-virialized broad-line region. JWST/MIRI photometry further reveals delayed mid-infrared emission from $\simeq1500$ K dust at a sub-parsec radius, consistent with a dust echo of the flare. The relatively low black-hole mass and dense star-forming nucleus of GNz7q are conditions under which TDEs are expected to be most efficient. These observations provide a time-domain view of episodic black-hole fueling and its dusty nuclear environment 700 million years after the Big Bang. Wide-field surveys with Roman and Euclid in the near-infrared, complemented by LSST at lower redshifts, may uncover such transients in large numbers.
[abstract 15 / 34] (score: 3) - Title: Long-term X-ray variability of the NLS1 Ark 564Authors: Neha P R, Nikita S Arun, Savithri H. Ezhikode, Ranjeev Misra, Bari Maqbool, Jeena K, Joe Jacob,Comments:Subjects: astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We present a systematic spectral study of the X-ray emission from the Narrow- Line Seyfert 1 (NLS1) galaxy Ark 564 using SWIFT/XRT observations spanning sixteen years. The source exhibits significant variability in both the soft and hard X-ray bands, along with a strong positive correlation between them, indicating a closely coupled emission mechanism within the accretion flow-corona system. A simple absorbed power-law model is statistically insufficient to describe the spectra, confirming the presence of an additional soft component. To investigate the origin of the soft excess, we performed multi-model spectral fitting. Incor- porating a warm Comptonization component yields a statistically improved fit, supporting the scenario in which the soft excess arises from Comptonization in a warm, optically thick corona. We also applied a RELATIVISTIC reflection model to representative observations; however, given the moderate spectral resolution and limited high-energy coverage of SWIFT/XRT, the current data do not allow us to robustly determine whether reflection provides a superior or physically preferred description. Our results indicate that warm Comptonization offers a consistent explanation for the observed soft excess in Ark 564 within the limitations of the available data, while deeper broadband observations are required to defini- tively distinguish between competing models and comprehensively characterise the long-term X-ray spectral variability of the source
[abstract 16 / 34] (score: 3) - Title: Dilatonic Reissner--Nordström BLACK HOLEs in a Bertotti--Robinson MAGNETic backgroundAuthors: Kenneth Hong,Comments:Subjects: gr-qcCreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We construct an exact static, MAGNETically charged solution of four-dimensional Einstein--Maxwell--dilaton theory that generalizes the centered Reissner--Nordström BLACK HOLE in a Bertotti--Robinson MAGNETic background. Its pure-background limit is the MAGNETic EMD deformation of Bertotti--Robinson spacetime. Using the Emparan--Teo solution-generating technique, the charged construction reduces in canonical Weyl coordinates to replacing the Schwarzschild horizon rod by the Reissner--Nordström rod of half-length $σ=\sqrt{m^2-e^2}$ and integrating the resulting nonlinear background--rod interaction. This yields a completely explicit solution for arbitrary dilaton coupling $α$, with the expected special limits and numerical verification of the full field equations. The horizon exhibits a coupled mechanical, electroMAGNETic and intrinsic response to the monopole--background interaction. The residual conical stress is tied to north--south MAGNETic POLARIZATION; increasing the background field produces the ordered reversal scales $B_{\rm pole}
[abstract 17 / 34] (score: 2) - Title: Exact moment methods for conservation laws in phase spaceAuthors: Tileuzhan Mukhamet, Katharina Kormann,Comments:Subjects: physics.plasm-phCreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We construct exact moment models for a class of conservation laws based on a parametrization of the distribution functions by its moments as proposed in [Burby, Sci. Rep. 13 (2023)]. In particular, we derive moment models for the Vlasov--Maxwell and the RELATIVISTIC Vlasov--Maxwell systems. The new models can be viewed as a higher degree extension of the Direct Quadrature Method of Moments (DQMOM). We propose slicing moment method for the representation of the distribution function. For simulations with strong kinetic effects, we utilize a hybrid formulation that transforms adaptively a fraction of fluid nodes into particles in order to capture multi-streaming. We demonstrate convergence and performance of our strategies on the weak and strong Landau damping and two-stream instability experiments in non-RELATIVISTIC and RELATIVISTIC limits.
[abstract 18 / 34] (score: 2) - Title: TDCOSMO XXVI: Uniform lens modeling of eight doubly imaged QUASARsAuthors: Ryan Brady, Xiang-Yu Huang, Simon Birrer, Anowar J. Shajib, Nafis Sadik Nihal, Cameron Lemon, Martin Millon, Veronica Motta, Dominique Sluse, Frederic Courbin,Comments: Published in the Open Journal of Astrophysics. Version 3: Corrects an improper coordinate framing that introduced a reflection about the declination axis, which affected reported position angles and relative RA signs. Position angles and relative RAs have been corrected throughout the relevant tables and figures. These corrections do not affect the underlying lens modeling or conclusions thereofSubjects: astro-ph.CO astro-ph.GACreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
We present the first uniform gravitational lens modeling analysis of eight doubly imaged QUASARs from multi-band observations with the Hubble Space Telescope. Previous time-delay cosmography analyses by the TDCOSMO Collaboration have primarily relied on quadruply imaged QUASARs, while doubly imaged systems, despite being more abundant, remain underutilized due to their fewer geometric constraints. Using an open-source $\texttt{Lenstronomy}$ framework, we reconstruct the lensing systems with a pipeline tailored for doubles. Comparing our results to the literature, the modeled Einstein radii agree at an average of 1.5$σ$, which is expected given data and modeling heterogeneity, while modeled image separations differ from Gaia DR2 measurements with an r.m.s of only 3.6 mas. We find a strong correlation between Fermat potential precision and the surface brightness of the spatially extended host arcs, establishing that arc surface brightness is the primary driver of mass model precision in doubly imaged systems. To further quantify the information contributed by the lensed arcs, we performed a conjugate point analysis that uses only the QUASAR image positions to constrain the lens mass profiles. The resulting posteriors are substantially broader than those from full image modeling, and a strong anti-correlation between mass parameter hypervolume and arc magnitude additionally confirms that arc brightness determines the degree to which the lens mass profile can be constrained in doubles. A hierarchical cosmographic analysis incorporating time-delay measurements and stellar kinematics to infer $\text{H}_0$ will be presented in a subsequent publication. The uniform pipeline and arc surface brightness trends established here will significantly accelerate the construction of time-delay cosmography samples from the large lens populations expected from LSST, Roman, and Euclid.
[abstract 19 / 34] (score: 2) - Title: Isochrones in primordial MAGNETic field evolutionAuthors: Axel Brandenburg, Mattia Cielo, Oksana Iarygina, Franco Vazza,Comments: 13 pages, 14 figures, 2 tables, resubmitted to A&ASubjects: astro-ph.COCreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
In the early universe, a primordial MAGNETic field undergoes a turbulent decay while its length scale increases due to an inverse cascade. The size of the largest processed eddy scales with the Alfvén speed and grows with time. In a diagram of Alfvén speed vs.\ length scale, all possible solutions must lie on a line through the origin with a slope proportional to the inverse of the present time. In principle, however, such lines can also be defined for earlier times. The lines for earlier times form isochrones that may be observationally accessible, for example through the MAGNETically driven stochastic gravitational wave background. However, the position and slope of these isochrones is sensitive to the zero point of the time. Here, we show that for any initial MAGNETic field, a proper time can be determined such that the resulting isochrones at early times are nearly parallel to those at late times, i.e., they have the same slope. We use two-dimensional numerical simulations of decaying MHD turbulence and vary the initial position of the peak of the MAGNETic energy spectrum. In this case, the evolution is governed by the conservation of anastrophy. A fit to the Alfvén time yields an accurate estimate of the factor by which the decay time is longer than the Alfvén time, while the offset in the fit provides an estimate of the proper time that needs to be added to the nominal time since the beginning of each simulation. We also find that the presence of an initial velocity field of realistic strength helps producing a more straight track from the beginning. The MAGNETic field parameters lie on universal isochrones even for early times. They provide a testable framework for MAGNETic fields generated at times as early as the end of inflation, starting with the time of reheating.
[abstract 20 / 34] (score: 2) - Title: Quintic Modification to Lifshitz Quasi-topological Black HolesAuthors: A. Bazrafshan, A. R. Olamaei, M. Ghanaatian,Comments:Subjects: gr-qcCreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We extend the analysis of Lifshitz BLACK HOLEs to quintic order in five-dimensional quasi-topological gravity coupled to a massive Abelian vector field. Starting from a static ansatz with a constant-curvature horizon, we derive the reduced field equations and identify the radially conserved quantity of the one-dimensional effective system. We then analyze the algebraic conditions that permit Lifshitz backgrounds, both in the absence and in the presence of the massive vector field. Since closed-form black-hole solutions are not available for the generic quintic theory, we construct numerical solutions using regular near-horizon expansions together with a numerical shooting method. We present solutions for the RELATIVISTIC branch \(z=1\) and the Lifshitz branch \(z=2\), covering the three horizon topologies \(k=-1,0,+1\). The numerical profiles remain qualitatively consistent with those found previously in cubic and quartic quasi-topological Lifshitz gravity. A controlled planar comparison through the genuine quartic point \(\hatμ_5=0\) further shows that the very small quintic couplings used in the representative examples produce nearly quartic profiles, whereas larger admissible values of \(\hatμ_5\) lead to clearly resolved changes in both the normalized radial profiles and the Hawking temperature. We also compute the Wald entropy and Hawking temperature and examine the thermal behavior through dimensionless logarithmic temperature--entropy plots. For the representative branches considered here, the heat capacity is positive. For a fixed-theory planar \(z=2\) family, the conserved radial charge is further used to determine the energy density; the differential and integrated first laws are verified numerically to the precision of the computation, and the corresponding Helmholtz free-energy density is found to be negative relative to the Lifshitz vacuum normalization adopted here.
[abstract 21 / 34] (score: 2) - Title: Structural quasi-universality in highly MAGNETized differentially rotating neutron starsAuthors: Pratul Manna, Surajit Kalita,Comments: 10 pages with 6 figures and 3 tables; accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.HE astro-ph.SR gr-qcCreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
Universal relations among macroscopic properties of neutron stars provide a powerful framework to probe their internal structures while minimizing uncertainties associated with the equation of state (EoS). Although such relations have been extensively studied for uniformly rotating stars, their extension to differentially rotating and strongly MAGNETized configurations is relatively less explored. We systematically investigate equilibrium configurations for a wide range of EoSs, rotation profiles, and MAGNETic field strengths with XNS numerical simulation code. For sequences with fixed angular momentum, we analyze the dependence of normalized moment of inertia on compactness. We establish a generalized quasi-universal relation between the moment of inertia and compactness that remains remarkably insensitive to the underlying EoS across uniformly rotating, differentially rotating, and strongly MAGNETized toroidal configurations. For sequences with fixed angular momentum, the normalized moment of inertia exhibits a quasi-universal dependence on compactness, with deviations primarily due to MAGNETic field strength and degree of differential rotation. We derive analytic expressions for these dependencies, enabling a unified phenomenological model applicable over a wide range of stellar configurations. As astrophysical applications, we quantify the systematic bias in MAGNETar luminosity estimates and the rotational kinetic energy of post-merger remnant of GW170817. These results extend quasi-universal relations beyond the standard assumptions of uniform rotation and weak MAGNETization, providing a robust framework for interpreting observations of highly MAGNETized and differentially rotating neutron stars, and enabling more reliable constraints on their astrophysical properties.
[abstract 22 / 34] (score: 2) - Title: Non-linear dynamo waves in MAGNETized shear flows: a candidate mechanism for the solar cycleAuthors: Uddipan Banik,Comments: 20 pages, 3 figures, 1 table; comments welcomeSubjects: astro-ph.SR astro-ph.EP astro-ph.HE physics.plasm-phCreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
Large-scale MAGNETic reversals in planets, stars, and accretion disks require a non-linear theory coupling the MAGNETic field to its sustaining flow. We derive exact non-linear solutions to incompressible MAGNETohydrodynamics in background rotational shear, with large-scale velocity and MAGNETic fields linear in position (affine form). They reveal a cyclic feedback between meridional circulation, shear, MAGNETic tension, induction, and the Coriolis force. The steady-circulation reversal orbit, or dynamo wave, periodically reverses all MAGNETic components and supports slower modulations. In the solar near-surface shear layer (NSSL), moderate shear permits stable 11-year reversals with poleward speeds of 8-12 m/s and poloidal and toroidal amplitudes of 4-11 G and 2.2-3.8 kG near 1 Mm depth, in reasonable agreement with regional observations. At stronger shear, an 88-year reversal exhibits a 203-207-year modulation, reproducing the Gleissberg and Suess-de Vries activity timescales but requiring weaker poloidal fields. Such reversals, however, remain observationally unestablished. At tachocline density, an 11-year reversal and the inferred return flow require toroidal fields of hundreds of kilogauss over a broad shear range, exceeding large-scale-field reconstructions but partly permitted by seismic upper limits. This favors a shallow NSSL origin for a local cycle, while leaving open the issue of a global dynamo. Toroidal dominance prolongs the cycle because shear acting on a weak poloidal field changes only a small fraction of the stronger toroidal field per rotation. Balancing the weak MAGNETic torque against advection and the Coriolis force also requires slow circulation, which gradually turns the poloidal field and reverses toroidal induction. Efficient poloidal regeneration would shorten this delay. A long solar cycle therefore favors a primarily shear-driven dynamo.
[abstract 23 / 34] (score: 2) - Title: Saturation Mechanism of Cosmic Ray Streaming Instabilities with a Shell DistributionAuthors: Mohamad Shalaby, Rouven Lemmerz, Christoph Pfrommer,Comments: 12 pages, 7 figures, submitted to ApJ, comments welcome!Subjects: astro-ph.GA astro-ph.HE astro-ph.SR physics.plasm-phCreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
Cosmic rays (CRs) drive galactic winds and regulate galaxy growth while contributing to heating the central cooling plasma in dense galaxy clusters, making the nonlinear saturation of the instabilities that govern their transport a problem of central importance in astrophysics. Using fully kinetic particle-in-cell (PIC) simulations, we find that the streaming instability driven by CRs with a shell momentum distribution saturates through gyro-phase bunching around driven Alfvén waves. Fluid-PIC (FPIC) simulations with both ideal and Landau closures reproduce the PIC saturation amplitude, and the same gyro-phase bunching mechanism, indicating that nonlinear Landau damping (NLLD) does not determine the saturation level at our simulation parameters ($v_{\rm A} = 0.01c$, $n_{\rm CR}/n_i = 0.01$). Notably, the CR ions fully isotropize in the Alfvén-wave frame in all simulations, including the FPIC run with an ideal closure in which NLLD is entirely absent, showing that this isotropization does not require NLLD. We additionally confirm, using the FPIC ideal closure, that this saturation amplitude is unchanged across a tenfold increase in domain size, indicating that the mechanism is local rather than dependent on domain-scale processes. Together, these results indicate that, at least in this regime, NLLD is not the dominant saturation mechanism for the CR streaming instability, in tension with common assumptions built into CR transport models used in galaxy formation and interstellar medium simulations. Whether this conclusion extends to the lower CR densities and Alfvén speeds characteristic of the interstellar medium remains an open question that we address in an upcoming work.
[abstract 24 / 34] (score: 2) - Title: Mass and spin properties of black-hole mergers reveal formation in triplesAuthors: Jakob Stegmann, Aleksandra Olejak,Comments: 26 pages, 5 figures, comments welcomeSubjects: astro-ph.HE astro-ph.SR gr-qcCreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
Deciphering the formation channels of the observed binary BLACK HOLE mergers remains a central open problem in gravitational-wave astronomy. With hundreds of detections, the inferred distribution of masses and spins reveals a rich diversity which is difficult to reconcile with traditional formation scenarios from isolated binary stars or dense stellar environments. Here, we consider the large fraction of massive progenitor stars found in hierarchical triples and investigate BLACK HOLE mergers driven by gravitational perturbations from tertiary companions. Simulations of their dynamics and stellar evolution reproduce key features of the merger population, including: i) a sharp primary mass peak at $m_1\sim10\,\rm M_\odot$ dominating the population; ii) substantial fractions of systems with large spin-orbit angles within and beyond the peak, matching the skewed distributions of the spin parameters $χ_{\rm eff}$ and $χ_p$; iii) a mass-ratio distribution favouring equal masses with matching slopes. We further predict a sharp decline of mergers near $m_1\sim30\,\rm M_\odot$, coincident with the location of inferred features that may signal another channel dominating the high-mass tail. Our models of hierarchical triples demonstrate, for the first time, a formation scenario which simultaneously reproduces the principal properties inferred for the low-mass bulk of binary BLACK HOLE mergers.
[abstract 25 / 34] (score: 2) - Title: Demonstration of H-mode Error Field Identification in a Single Discharge via Island HealingAuthors: E. M. Bursch, A. Xie, J. L. Barr, S. K. Kim, N. C. Logan, S. M. Yang, J. G. Bak, W. Choi, Q. Hu, J. W. Juhn, J. Kim, J. Lee, N. Leuthold, J. K. Park, C. Paz-Soldan, L. Piron, G. Seo, J. Seo,Comments:Subjects: physics.plasm-phCreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
Non-disruptive compass scan error field identification via island healing is demonstrated on KSTAR in a single H-mode discharge. This method can allow for up to a 75% reduction in the operational time necessary for a complete compass scan by reducing the required discharges from four to one. Previous experiments on DIII-D, JET, and MAST-U have demonstrated the technique in Ohmic and L-mode but required multiple discharges and strong real-time n=1 MAGNETics diagnostics close to the plasma that are unlikely to be viable for future devices. The results presented here were made possible by implementing a new set of triggering algorithms relevant to fusion pilot plant operation into the KSTAR plasma control system, along with KSTAR's strong RMPs and long pulse lengths. This represents a significant step towards the disruption-free error field identification method being demonstrated for deployment on future disruption-averse tokamaks, including ITER and fusion pilot plants. Steps needed to close remaining gaps to viability are addressed.
[abstract 26 / 34] (score: 2) - Title: Toward Actionable Predictability of Tropical Mesoscale Convective Systems through Large-scale Recurrent Environments in Northern South AmericaAuthors: Vanessa Robledo, John F. Mejía, Jhayron S. Pérez-Carrasquilla, Mohamed Abdelkader, Humberto Vergara,Comments: 36 pages, 17 FiguresSubjects: physics.ao-phCreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
Mesoscale convective systems (MCSs) produce much of the extreme precipitation, floods, and landslides that affect northern South America (NOSA), yet remain difficult to anticipate because they are strongly governed by local processes. On the night of 31 March 2017, an MCS triggered a catastrophic flash flood in Mocoa, Colombia ---an event whose severity was not foreseen with sufficient lead time for emergency action, which typically requires several hours to a couple of days. Motivated by this disaster, this study investigates whether such events emerge within recurrent environments that provide a source of large-scale predictability, rather than as isolated and inherently unpredictable occurrences. We combine a 21-year (2001--2021) MCS tracking dataset, ERA5 reanalysis, equatorial Rossby (ER) wave diagnostics, and a Self-Organizing Map (SOM) to identify recurrent environments associated with MCS occurrence in the Orinoco--Amazon basin. The Mocoa environment maps onto one of nine recurrent configurations characterized by enhanced low-level moisture, neutral Orinoco low-level JET conditions, favorable upper-level circulation, and strong ER-wave activity. We further trace convective precursors to an upstream source region over the Guiana Highlands up to 24~h before arrival in the Mocoa region. Together, these results show that the Mocoa event was not climatologically exceptional but a high-impact expression of a recurrent, partly predictable large-scale regime, demonstrating that portion of MCS predictability arise from recurring large-scale conditions that can be monitored hours to days in advance, and support hazardous weather forecasting in NOSA and other tropical regions.
[abstract 27 / 34] (score: 2) - Title: Tracing the Host-Galaxy Environments of FRBs with a New Sample of Localized Sources Detected with the DSA-110Authors: Frank M. Verdi, Vikram Ravi, Myles B. Sherman, Jakob T. Faber, Stella Koch Ocker, Kritti Sharma, Casey J. Law, Gregg Hallinan, Kaitlyn Shin, Liam Connor,Comments: 26 pages, 18 figures, 3 tables. Submitted to ApJSubjects: astro-ph.HECreated: 2026-09-24; Updated: 2026-09-28; Datestamp: 2026-09-28
We characterize the source environments of a sample of fast radio bursts (FRBs) detected with the Deep Synoptic Array (DSA-110). We present new analyses of a sample of 24 FRBs which have been localized to host galaxies with spectroscopic redshifts. Four of these bursts have been confidently associated with galaxies near or beyond redshift 1, and several are published here for the first time. Combining these new bursts with previously analyzed DSA-110 sources, we use a sample of 43 DSA-110 FRBs with known redshifts to measure host-galaxy contributions to dispersion measure (DM) and Faraday rotation measure (RM). We find characteristically large and significantly correlated host-galaxy contributions to DM and RM, suggesting that most FRBs reside in overdense, MAGNETized regions within their host ISM. Additionally, we identify a subset of FRBs with detectable scattering, and show that their scattering timescales and inferred host DM values are broadly consistent with an empirical relation established for Galactic pulsars. Combined with two-screen modeling of some bursts, our results indicate that density fluctuations within the host-galaxy ISM are the dominant source of extragalactic scattering. Comparisons of FRB host-galaxy properties with pulsars and simulations of young and old progenitor populations support a scenario in which FRBs preferentially form and remain associated with HII regions throughout their emission lifetime, favoring MAGNETars formed in core-collapse SUPERNOVAe as the sources of FRBs.
[abstract 28 / 34] (score: 2) - Title: Bayesian inference of non-Maxwellian distribution functions from collective Thomson scattering spectraAuthors: Kentaro Sakai, ByungJun Kang, Akito Nakano, Takeo Hoshi,Comments: 11 pages, 9 figuresSubjects: physics.plasm-ph astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We investigate Bayesian inference of non-Maxwellian electron distribution functions from collective Thomson scattering (CTS) spectra. We represent distribution functions using multiple candidate models of different complexity and perform inference on synthetic spectra generated from known non-Maxwellian distribution functions. Our analysis demonstrates that a sufficiently flexible model can approximate the overall shape of the ground-truth distribution function. The most plausible model is identified based on model evidence, a statistical measure representing the probability to obtain the observed data given the model. When the candidates include the ground-truth model, the model evidence favors the ground-truth model. Without the ground-truth model as a candidate, the model evidence favors the candidate model with the fewest parameters that adequately approximates the data. The posterior probability density function of the most plausible model reveals the characteristic features and associated uncertainties of the underlying distribution function. The origin of the additional spectral peaks is attributed to a combination of modifications to the dispersion relation and reduced Landau damping. This enables the objective and data-driven identification of distribution functions directly from observed CTS spectra.
[abstract 29 / 34] (score: 2) - Title: Goal-Oriented Weighting of Reynolds-Stress Data for Learning Turbulence Models in Complex FlowsAuthors: Zhuolin Zhao, Haochen Wang, Youngwoo Kim, Solkeun Jee, Heng Xiao,Comments:Subjects: physics.flu-dynCreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
Data-driven turbulence models for the Reynolds-averaged Navier-Stokes (RANS) equations offer a promising route to improving predictions of complex flows. Such models, specifically the turbulence constitutive relations, can be learned efficiently from high-fidelity Reynolds-stress data without evaluating the RANS equations during training. However, conventional losses weight all tensor-component and spatial errors equally, although their influence on a quantity of interest (QoI) can differ significantly; reducing the aggregate stress error therefore does not necessarily lead to an improved QoI prediction. Training against flow-level observations accounts for this dependence but requires repeated, potentially expensive RANS solutions. In canonical shear flows, physical reasoning can identify the shear component as the only one relevant for the mean-flow prediction. Motivated by this example, we propose a goal-oriented method to select and weight Reynolds-stress training data for complex flows. For a specified QoI, a single offline adjoint evaluation quantifies its sensitivity to local perturbations of each Reynolds-stress component. These sensitivities are converted into fixed weights in the supervised loss, enabling training without further RANS solutions. We validate the weighting in square-duct and periodic-hill flows, then apply it to a film-cooling JET in crossflow, where it improves velocity and cooling-effectiveness predictions over uniformly weighted training despite using a velocity-only QoI. Beyond turbulence modelling, this work suggests a broader strategy for aligning supervised learning with downstream prediction goals while preserving training efficiency.
[abstract 30 / 34] (score: 2) - Title: Simulating tidal disruption events in nuclear star clustersAuthors: Philip Cho, Kai Wu, Francesco Flammini Dotti, Taras Panamarev, Shuo Li, Shiyan Zhong, Klaus Reuter, Rainer Spurzem,Comments: 14 pages, 14 figures, 2 tables. Submitted to Astronomy & AstrophysicsSubjects: astro-ph.GA astro-ph.SRCreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
Context. Nuclear star clusters (NSCs) and supermassive BLACK HOLEs (SMBHs) often coexist at the centers of galaxies, engaging in complex dynamical interactions that influence SMBH growth. Stars that approach the SMBH too closely are tidally disrupted, and a fraction of their debris is accreted onto the BLACK HOLE. Such events may contribute to SMBH growth in gas-deficient galaxies. Aims. Our work aims to improve the theoretical framework for understanding the mass accretion of stellar debris following tidal disruption events (TDEs) through numerical simulations. We perform direct N-body simulations of an NSC with a central SMBH embedded in a fully self-consistent dynamical model to test a new TDE accretion prescription in a set of pilot simulations. Methods. The previous TDE prescription used a fixed accretion radius and assumed that the entire stellar mass was accreted after disruption. In the new partial-mass accretion model, the mass added to the SMBH depends on the orbital eccentricity and penetration factor of the disrupted star. Results. We find that most TDEs involving main-sequence stars are marginally eccentric or marginally hyperbolic and contribute approximately half of the stellar mass to SMBH growth, consistent with recent hydrodynamical simulations. In all simulated models, the TDE-driven mass accretion rate exhibits an early peak followed by a rapid decline. Models with higher initial SMBH masses exhibit a faster decline in the accretion rate, consistent with more rapid loss-cone depletion and inefficient replenishment
[abstract 31 / 34] (score: 2) - Title: Probing the cosmic web with fast radio bursts: II. ScintillationAuthors: Sharon Lapiner, Nir Mandelker, Paz Beniamini, S. Peng Oh,Comments: 19 page + 6 in appendixSubjects: astro-ph.CO astro-ph.GA astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We consider the formation of multiphase gas in cosmic web objects (CWOs) through cooling and fragmentation within the shock-heated medium of cosmic sheets and filaments, and the circumgalactic medium (CGM) of haloes. This leads to dense, cool ($\sim10^{4}\,\mathrm{K}$), small-scale cloudlets in pressure equilibrium with their surroundings. Such ionized overdensities can affect the propagation of radio waves emitted by fast radio bursts (FRBs), allowing us to probe the small-scale structure in CWOs by examining their impact on the scintillation pattern of the observed FRB flux. While we find that the probability of encountering a high-temperature filament or sheet with cold cloudlets is rather small and usually confined to high redshifts, the expected high rates of FRBs may still permit detection through scintillation along rare sightlines. We suggest scintillation from the Milky Way (MW) interstellar medium as a promising probe: CWO plasma screens can suppress it, placing constraints on their cold-gas properties. Filaments and sheets can suppress MW scintillation from sources at $z_\mathrm{S}\gtrsim2$ and $3$, respectively, while cold and turbulent cloudlets in the CGM can be probed by sources at redshifts as low as $z_\mathrm{S}\sim0.5$, constraining remarkably low volume-filling fractions, $f_\mathrm{v}$ (e.g. $f_\mathrm{v}\gtrsim10^{-5}$ for $z_\mathrm{S}\gtrsim2$). To provide testable predictions, we estimate the fraction of FRBs expected to encounter CWOs that may suppress MW scintillation below a given frequency, and express this as a function of the average extragalactic dispersion measure. Future FRB samples could map these constraints onto bounds on the existence and properties of cloudlets in CWOs, such as their density, size, $f_\mathrm{v}$, and turbulence.
[abstract 32 / 34] (score: 2) - Title: A solution to the paradox of youth in the Galactic centreAuthors: Rodrigo P. Silva, Alexandre C. M. Correia, Tjarda C. N. Boekholt, Paulo J. V. Garcia,Comments: 7 pages; Published in A&A; added ZenodoSubjects: astro-ph.GA astro-ph.SRCreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
The supermassive BLACK HOLE at the Galactic centre, Sgr A*, is surrounded by an S cluster of young stars. These stars are predominantly B-type stars, but their origin remains uncertain. Unlike massive stars in the Galactic field, which exhibit a binary fraction of about $70\%$, those in the S cluster show a significantly lower fraction. It is key to understand this discrepancy for constraining their formation. We show that the binary deficit arises naturally from dynamical interactions between stellar binaries and Sgr A* in an in situ formation scenario. Using K-amplitude data, we derived an observational binary fraction of $f_{\mathrm{obs}} = 0.43 \pm 0.09$ for the S-cluster stars. Our dynamical modelling predicts that interactions with Sgr A* cause $18\%$ of the binaries to merge, $20\%$ to be disrupted, and $62\%$ to survive, yielding a theoretical binary fraction of $f_{\mathrm{theo}} = 0.38 \pm 0.10$. The predicted binary fraction with distance from Sgr A* is also consistent with independent observational constraints. These results show that the decline in binarity towards the Galactic centre is driven by stronger tidal forces, and they support an in situ origin of the S cluster in the same event that produced the FERMI bubbles.
[abstract 33 / 34] (score: 2) - Title: A statistical hardness classification of ultraluminous X-ray sources using long-term SWIFT/XRT monitoringAuthors: Sinan Allak, Wei Yu, Menglei Zhou, Honghui Liu, Andrea Santangelo,Comments: Accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.HECreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
We characterize long-term hardness behavior in 29 ultraluminous X-ray sources (ULXs) using over 3500 archival SWIFT/XRT observations. We classify observations as soft-band dominated, hard-band dominated, or uncertain from the hardness ratio (HR; 1.5--10/0.3--1.5 keV count rates) and its confidence bounds. We derive $f_{\rm soft}$ and $f_{\rm hard}$ and define the Crossing Index (CI) as the fraction of consecutive confidently classified observations on opposite sides of $HR=1$. We analyze these descriptors with rule-based classification and unsupervised hierarchical clustering. The rule-based analysis identifies eight soft-band-dominated, five hard-band-dominated, and 16 mixed-band systems; clustering yields a similar three-group structure. Known or candidate accretor types tend to occupy band-dominated groups, whereas unknown accretors are more common in the mixed-band group. All four sources with reported long-term X-ray modulation discussed in an orbital or super-orbital context are classified as mixed-band. The three-cluster solution is preferred in 25 of 29 leave-one-out trials, while bootstrap tests find the band-dominated groups more stable than the mixed-band group. As the classification uses observed count rates, the groups represent SWIFT/XRT signatures rather than intrinsic spectral states. Response-folding tests show that modeled HR depends on absorption column density and photon index. Bayesian reanalysis of a representative low-count source reduces CI from 56.3\% to 38.5\% while preserving its mixed-band classification. Random downsampling produces no systematic shift in CI; halving the observations changes median CI by at most $\sim10\%$ across four sources. Larger samples with independent absorption constraints can test links among these observational classes, accretor type, long-term periodic modulation, and other X-ray properties.
[abstract 34 / 34] (score: 2) - Title: Impact of MAGNETic drift configuration on the edge radial electric field in the TCV tokamakAuthors: S. Rienäcker, L. Vermare, P. Hennequin, C. Honoré, B. Labit, S. Coda, L. Frassinetti, B. Vincent, O. Panico, Y. Wang, K. Singh,Comments:Subjects: physics.plasm-phCreated: 2026-09-25; Updated: 2026-09-28; Datestamp: 2026-09-28
The edge radial electric ($E_r$) in the Tokamak à Configuration Variable (TCV) is compared in matched L-mode discharges with opposite ion MAGNETic drift directions (favorable versus unfavorable $B \! \times \! \nabla B$ configurations). As previously reported on the WEST and AUG tokamaks, the $E_r$ profile---measured by Doppler backscattering (DBS)---exhibits a "well" just inside the separatrix in the favorable drift case, which is absent or less pronounced in the unfavorable counterpart. This observation holds over a broad range of plasma conditions, notably also in Ohmic discharges with nearly identical edge density and temperature profiles. Density fluctuation characteristics inferred from DBS are not drastically different: Under Ohmic heating, edge fluctuation levels tend to be higher in the favorable configuration, while radial correlation lengths are similar. The edge $E_r$ difference appears uncorrelated with carbon toroidal rotation behavior. Reducing density, or increasing auxiliary heating power tends to accentuate the edge $E_r$ disparity. Plasma current has little impact on both favorable and unfavorable $E_r$ profiles---in contrast to results from WEST. Approaching the L-H transition via auxiliary heating, edge $E_r \times B$ shear and pressure grow more readily in the favorable configuration, and DBS fluctuation levels are reduced relative to the unfavorable case. Overall, our results confirm that the edge $E_r$ sensitivity to MAGNETic drift configuration is a robust, multi-machine phenomenon, with a plausible connection to confinement level and H-mode access.
arXiv:2609.30494 [pdf, ps, other]
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arXiv:2609.30641 [pdf, ps, other]
arXiv:2609.31457 [pdf, ps, other]
arXiv:2607.20609 [pdf, ps, other]
arXiv:2609.30649 [pdf, ps, other]
arXiv:2509.08848 [pdf, ps, other]
arXiv:2510.21555 [pdf, ps, other]
arXiv:2605.25199 [pdf, ps, other]
arXiv:2608.19928 [pdf, ps, other]
arXiv:2609.14551 [pdf, ps, other]
arXiv:2609.30441 [pdf, ps, other]
arXiv:2609.30793 [pdf, ps, other]
arXiv:2609.31408 [pdf, ps, other]
arXiv:2602.13180 [pdf, ps, other]
arXiv:2604.24908 [pdf, ps, other]
arXiv:2606.10863 [pdf, ps, other]
arXiv:2606.24835 [pdf, ps, other]
arXiv:2608.02824 [pdf, ps, other]
arXiv:2609.30367 [pdf, ps, other]
arXiv:2609.30376 [pdf, ps, other]
arXiv:2609.30378 [pdf, ps, other]
arXiv:2609.30452 [pdf, ps, other]
arXiv:2609.30485 [pdf, ps, other]
arXiv:2609.30616 [pdf, ps, other]
arXiv:2609.31020 [pdf, ps, other]
arXiv:2609.31037 [pdf, ps, other]
arXiv:2609.31083 [pdf, ps, other]
arXiv:2609.31106 [pdf, ps, other]
arXiv:2609.31305 [pdf, ps, other]
arXiv:2609.31324 [pdf, ps, other]
arXiv:2609.31424 [pdf, ps, other]