Current date: 2026-10-19
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Created/updated limit: 2026-10-12 (7 days ago)
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Scoring abstracts
Number of records retrieved: 757
Keyword score statistics
score 10 -- 1 abstracts
score 9 -- 1 abstracts
score 8 -- 1 abstracts
score 7 -- 2 abstracts
score 6 -- 4 abstracts
score 5 -- 1 abstracts
score 4 -- 5 abstracts
score 3 -- 11 abstracts
score 2 -- 17 abstracts
in total -- 43 abstracts
Articles that appeared on 2026-10-19
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[abstract 1 / 43] Wow! (score: 10)
- Title: What can a uniform reflection pipeline establish about supermassive BLACK HOLE spin? An audit and a corrected analysis of 57 AGN with XMM and NUSTARAuthors: K. Balasubramaniam, H. -K. Chang, Ł. Stawarz,Comments:Subjects: astro-ph.HECreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
We audit an automated RELATIVISTIC-reflection pipeline that fitted one XMM-Newton EPIC-pn and NUSTAR epoch for each of 57 AGN with relxillCp+xillverCp, and repeat the analysis with its failures corrected. The pipeline's apparent constraints were not controlled: Small Window pn backgrounds were never subtracted, the nearest-in-time pairing selected mismatched or nearly empty spectra, single-start fits often stopped short of the minimum, and most fits were inadequate or at a parameter limit. The corrected analysis uses in-window backgrounds, 41 sources with eligible pn--NUSTAR pairs, multi-start fits, bidirectional profiles, criteria fixed in advance and eight model variations. 24 of the 41 reference fits have $p\ge0.01$ and 18 pass all quality checks. Their 90% spin sets comprise 1 two-sided interval (NGC 4051, $0.46\le a_*\le0.93$), 6 lower bounds, 4 upper bounds, 4 disconnected sets and 3 unconstrained profiles. For 10 of the 18 the best fit lies at $i\ge75^\circ$, implausible for type-1 AGN, and most of those constraints disappear when $i\le60^\circ$ is imposed. Only 2 of the 15 constrained sets keep their type both under that limit and with pn restricted to 3--10 keV (an upper bound for Mrk 1040 and a weak lower bound for 1H 0419-577). Simulations show that, with a correct model, the 90% sets contain the true spin in 82--92% of cases without drifting edge-on, but at high inclination one low-spin simulation in six yields a false lower bound. We make no statement about the spin distribution or a spin--JET relation.
[abstract 2 / 43] Wow! (score: 9) - Title: A BLAZAR is a BLAZAR is a BLAZAR ... Comparing long-term varaibility properties of PKS 1510-089 and PKS 2155-304Authors: M. Zacharias, A. Wierzcholska,Comments: 5 pages, 3 figures; Conference Proceedings Paper of the GAMMA 2026 conferenceSubjects: astro-ph.HE astro-ph.GACreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Blazars are typically divided by spectral appearance; may that be strength of optical emission lines or the frequency of the SYNCHROTRON peak. However, this may say nothing about the variability properties of the various types. Here, we study the long-term variability properties with nearly 20 years of multiwavelength data of one flat-spectrum radio QUASAR, PKS 1510-089, and one high-frequency-peaked BL Lac object, PKS 2155-304. Both exhibit strong variability with an energy-dependent variability amplitude. Using the total data sets, we do not find any correlation between the various bands. While the flux distributions of PKS 2155-304 are compatible with log-normal functions, this is not the case for PKS 1510-089. We conclude that the one-zone model is inadequate to describe the long-term evolution of BLAZARs, requiring multi-zone or stratified models. Nevertheless, the underlying JET physics appear similar between the two types and in both sources the variability is, in fact, variable.
[abstract 3 / 43] Wow! (score: 8) - Title: Gamma-ray calorimetry of Seyfert windsAuthors: Alberto Domínguez,Comments: Accepted for publication in A&A. 14 pages, 7 figures, 2 tablesSubjects: astro-ph.HE astro-ph.GACreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Two stacking analyses with the FERMI Large Area Telescope (LAT) detected GeV emission from radio-quiet Seyferts, one selected by an X-ray ultra-fast outflow (UFO) and one hard-X-ray-bright, with similar luminosities attributed to different mechanisms: wind shocks and the accretion-disk corona. We investigate how efficiently Seyfert outflows convert mechanical power into GeV photons, whether the two detections require distinct mechanisms, and how Seyferts compare with low-ionization nuclear emission-line regions (LINERs). Without new FERMI-LAT data reduction, we homogenize published measurements to 0.1-100 GeV, place local mechanical accelerators on one L_gamma-Edot diagram, and express eta = L_gamma/Edot as a fraction rho of the complete-calorimetry efficiency eta_max ~ 2.5%, inverting rho for the ambient density required by pp losses. Winds from Seyfert ACTIVE GALACTIC NUCLEi (AGN) have rho = 0.020 (+0.018/-0.011) for acceleration efficiency 0.1, a factor of ~13.5 below starburst superwinds (rho = 0.26 (+0.37/-0.16)). The difference exceeds a factor of three with probability 0.95 and is independent of acceleration parameters common to both classes; it is conditional on the wind kinetic powers, collapsing only if every wind sits at its minimum launch radius. The implied densities, ~10 and ~100 cm^-3, are consistency values: density, shock radius and speed are degenerate. The two stacking detections agree within a factor of 1.75 in gamma-ray output per unit Eddington luminosity, but the 95% interval, 0.26-24, is too wide to distinguish them. A third stack, of 186 low-luminosity AGN, extends the comparison 1.5 dex lower, ordered by AGN power. GeV detectability of non-JETted AGN is set by the product of mechanical power and calorimetric fraction. LINER outflows fail on power; for the adopted wind energetics, Seyfert UFO winds fail on calorimetry; starburst superwinds succeed on both.
[abstract 4 / 43] Wow! (score: 7) - Title: EMU detection of mysterious multiple component radio-continuum emission from nearby spiral Seyfert I type galaxy 'Sand-timer' (NGC 7213)Authors: M. D. Filipović, Z. J. Smeaton, B. S. Koribalski, R. Kothes, A. Ahmad, R. Z. E. Alsaberi, C. Bordiu, A. C. Bradley, E. J. Crawford, A. M. Hopkins, E. Järvelä, S. Lazarević, D. Leahy, J. L. Payne, S. F. ur Rahman, G. P. Rowell, H. Sano, M. Selby, S. S. Shabala, E. J. Stanton, S. Taziaux, K. Tsuge, D. Urosević, N. F. H. Tothill, J. Th. van Loon, V. Velović, G. L. White,Comments: Published in the Open Journal of AstrophysicsSubjects: astro-ph.GACreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
We present an Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) radio-continuum detection of the nearby spiral Seyfert I type galaxy NGC 7213 which we nickname `Sand-timer' due to its morphological appearance. We find intriguing, peculiar emission extending from the central supermassive BLACK HOLE (SMBH), which we refer to as galaxy hyperbubbles and/or ACTIVE GALACTIC NUCLEus (AGN) JETs. Finally, we find two previously undetected kiloparsec-scale features in the polarised intensity image, which appear most likely also related to the central SMBH, as restarted bipolar radio JETs, though somewhat obscured in the radio-continuum total intensity image. They resemble the bow shocks often seen in Fanaroff-Riley Class II (FR-II) RADIO GALAXies, and so we propose they most likely represent an early episode of the `Sand-timer's' AGN JET activity. An alternative scenario is that the core of NGC 7213 may be a supermassive binary BLACK HOLE (SMBBH) undergoing a tidal disruption event (TDE), potentially causing the peculiar radio-continuum emission.
[abstract 5 / 43] Wow! (score: 7) - Title: Sparking Dynamic, Relativistic Magnetic Reconnection in a Twisted Flux TubeAuthors: Michael P. Grehan, Christopher Thompson, Bart Ripperda, James R. Beattie,Comments: 31 pages, Figure 26, submitted to ApJSubjects: astro-ph.HE physics.plasm-phCreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
Magnetic RECONNECTion around neutron stars (NSs) forms small-scale currents while transferring energy to electron-positron pairs. These dissipating currents cover a wide range of scales, potentially leaving an imprint on time-variable X-ray bursts and pulsed radio emission. We present a reduced, planar model of internal RECONNECTion in a MAGNETic flux tube with RELATIVISTIC MAGNETization, finite resistivity, and strong guide field. Comparing with realistic NS parameters, this model represents the dynamics of a slender MAGNETic flux tube that is much thinner than the stellar radius. The seed current profile is smooth and does not spontaneously RECONNECT; instead, a discrete and localized current perturbation is introduced, representing e.g. localized energy release from a NS crust or MAGNETosphere. Three high-resolution RELATIVISTIC MAGNETohydrodynamics simulations are described: one has uniform resistivity and Lundquist number such that RECONNECTion proceeds in the plasmoid-mediated regime; the other two account for the feedback of charge starvation on the resistivity in current layers, where density is depleted; we provide a more general explanation for this depletion. All simulations produce a few dominant MAGNETic X-points and a secondary Kelvin-Helmholtz instability that excites high-wavenumber currents. We quantify the RECONNECTion rate, the intermittency of dissipation, and the time profile of current spikes. We further present three-dimensional simulations confirming a limited growth of the ideal kink mode in the strong guide field regime. Applications are discussed, including to radio pulse microstructure and current damping below the MAGNETar surface during an X-ray flare, leading to mass loss and X-ray afterglow.
[abstract 6 / 43] Yes (score: 6) - Title: Resistive alignment of a black-hole MAGNETosphereAuthors: Ruben Lier, Oliver Porth,Comments:Subjects: astro-ph.HE hep-th physics.plasm-phCreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
Recent numerical simulations have shown that black-hole MAGNETospheres evolve rapidly toward alignment between the MAGNETic axis and spin axis but the physical origin of this process has remained unclear. We develop an analytic theory of this alignment within resistive RELATIVISTIC MAGNETohydrodynamics. Taking the slow-spin Blandford-Znajek monopole solution as the exterior MAGNETic field, we reduce the induction equation to a relaxation equation for the current-sheet inclination angle. Our analysis shows that alignment results from second-order spin effects in the Blandford-Znajek solution combined with explicit resistive dissipation. We test this prediction using resistive-GRMHD simulations at several spins and resistivities and compare the measured late-time secular decay with the analytic prediction. This alignment timescale hence carries a unique signature which combines plasma dissipation with spacetime rotation.
[abstract 7 / 43] Yes (score: 6) - Title: The transformative power of ALMA2040 for mm-VLBIAuthors: The Event Horizon Telescope Collaboration,Comments: 16 pages, 3 figures. Part of the ALMA2040 White Paper SeriesSubjects: astro-ph.IM astro-ph.HECreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
The Event Horizon Telescope (EHT) has resolved horizon-scale emission in M87* and Sgr A*. Extending these observations to fainter BLACK HOLEs, multiple frequencies, and evolving structures requires greater sensitivity and new observing capabilities. We investigate how ALMA2040 could expand the scientific reach of global millimeter very long baseline interferometry (mm-VLBI), compared with ALMA's Wideband Sensitivity Upgrade (WSU). Phasing a larger ALMA array and enabling simultaneous observations across multiple ALMA bands would improve sensitivity and frequency phase transfer, providing spectral and polarimetric diagnostics of gravity, accretion flows, MAGNETic fields, and RELATIVISTIC JETs. In the configurations studied, ALMA2040 achieves sub-mJy baseline sensitivity at 230 GHz and improves prospects for faint-source imaging at 345 GHz, opening a path from individual horizon-scale targets toward population studies. Simulated observations of M87* show improved multi-frequency recovery of emission from the compact ring-like region toward the JET base, enabling studies of the accretion-JET connection. For Sgr A*, simulations of interstellar scattering mitigation yield a 27% reduction in the error of the recovered intrinsic source structure relative to the WSU configuration. Beyond BLACK HOLEs, these capabilities benefit geometric-distance measurements, stellar masers, compact transients, and other applications of high-resolution astrophysics. Together with rapid-response capabilities across the VLBI network, ALMA2040 could support a transition from isolated snapshots toward multi-frequency, time-resolved studies of compact sources.
[abstract 8 / 43] Yes (score: 6) - Title: Exploring Cosmic Rays from Gravity-Limited Acceleration at Supermassive Black HolesAuthors: Elena Manao, Elisa Resconi, Frank M. Rieger, Paolo Padovani, Gia Dvali,Comments: Accepted for publication in PRLSubjects: astro-ph.HE astro-ph.GACreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
We show that horizon-scale MAGNETic fields around supermassive BLACK HOLEs (SMBHs), only limited by gravity, yield a universal, model-independent ceiling on electroMAGNETic energy density. For rotating SMBHs, this field enables particle acceleration up to $\sim\!10^{27}$\,eV set solely by fundamental constants. We identify a parameter space in accretion rate and MAGNETic field strength in which quiescent nuclei simultaneously satisfy the transparency conditions for Ultra-High-Energy Cosmic Rays (UHECR) escape and the field requirements for reaching Ultra-High Energies (UHE), naturally complementing photon-rich Active Galactic Nuclei (AGN), which favor neutrino production but suppress UHECR escape. We observe that, when including curvature energy losses, the energy of the primaries scales weakly as $E_{\rm curv}\!\propto\!M^{1/4}$ and allows to achieve UHE across different compositions and SMBHs masses ($10^6$--$10^{10}\,M_\odot$), without requiring extreme spins or super-Eddington accretion. A cross-correlation of the Pierre Auger Observatory (PAO) public data with galaxies hosting reliably measured SMBH masses, separating AGN from quiescent hosts, reveals marginal local excesses ($\lesssim\!2.8σ$) consistent with isotropy after correcting for the look-elsewhere effect. The framework provides a direct link between black-hole physics and the maximum energies of cosmic particles, and defines concrete observational tests for next-generation UHECR datasets.
[abstract 9 / 43] Yes (score: 6) - Title: ExHaLe-JET: Modeling BLAZAR JETs with an extended hadro-leptonic radiation codeAuthors: M. Zacharias, A. Zech, A. Reimer, C. Boisson,Comments: 6 pages, 3 figures; Conference Proceedings Paper of the GAMMA 2026 conferenceSubjects: astro-ph.HE astro-ph.GACreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Blazars - active galaxies with the JET pointing at Earth - emit across all electroMAGNETic wavelengths. As the one-zone model becomes increasingly inadequate to describe BLAZAR emission, more elaborate models are needed. In order to self-consistently describe the entire electroMAGNETic spectrum, extended JET models are necessary. Notably, kinetic descriptions of extended JETs can provide the temporal and spatial evolution of the particle species and the full electroMAGNETic output. ExHaLe-JET is a lepto-hadronic, extended-JET code allowing for in-depth studies of the particle and radiation evolution on all scales. Here, we present our ongoing study regarding acceleration scenarios of particles within the large-scale JET structure. A single acceleration of particles at the JET base (or elsewhere) is insufficient to produce sufficient photon flux. Thus, re-acceleration through, e.g., consecutive shocks along the JET is needed. We explore two possible scenarios for this.
[abstract 10 / 43] Yes (score: 5) - Title: A precessing AGN with S-shaped morphology discovered in MALSAuthors: J. D. Wagenveld, N. Gupta,Comments: 9 pages, 4 figures, 2 tables. Accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.GACreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
We present J1221$-$1354, a precessing AGN discovered in the MeerKAT Absorption Line Survey (MALS) using deep L-band (0.9--1.6\,GHz) radio data. Its `S'-shaped morphology, revealed by the excellent surface brightness sensitivity of MeerKAT, is consistent with JET precession. Ancillary optical and infrared data establish the source as a Type 2 AGN in a moderately overdense environment. The approaching (southern) JET is brighter but shorter than the receding JET, with the northern edge of the receding JET showing a significantly younger spectral age. These features are peculiar, but consistent with a JET reorientation event in an asymmetric ambient medium, in which the JET re-enters a cavity of previously deposited plasma. A simple ballistic model yields a precession period of $P=290\pm30$\,Myr, consistent with geodetic precession in a supermassive BLACK HOLE binary (SMBHB) with a binary separation of less than 1.1\,pc. We expect that deep radio continuum surveys in the near future will uncover many more such systems, helping to further strengthen the connection between JET precession and SMBHBs, and the latter's implications for the gravitational-wave background detected with pulsar timing arrays.
[abstract 11 / 43] Yes (score: 4) - Title: Transition from Diffusion to Drift-Dominated Cosmic Ray Transport and the Origin of the KneeAuthors: Luis Enrique Espinosa Castro, Carmelo Evoli, Pasquale Blasi,Comments: 16 pages, 9 figuresSubjects: astro-ph.HECreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
In a MAGNETic field with a complex topology, as can be the Galactic MAGNETic field, COSMIC RAY transport cannot simply be described by diffusion parallel and perpendicular to MAGNETic field lines, because the gradients and curvature of the large-scale MAGNETic field induce drift motions. These effects become especially important at high energies. Here we revisit the possibility that the competition between diffusion and drifts may lead to a knee in the COSMIC RAY spectrum. We carry out test-particle simulations of COSMIC RAY transport in a mock Galactic MAGNETic field made of a regular large scale component, with a non-trivial topology and a homogeneous and isotropic turbulent MAGNETic field, with a spectrum that is assumed to be Kolmogorov-like in the basic setup. These simulations are used to infer the escape time and the grammage accumulated by COSMIC RAYs with energy in the TeV--10 PeV energy range. In the case of a large scale MAGNETic field with a purely azimuthal structure, the drift due to the curvature of MAGNETic field lines produces a knee in the PeV range, but the model fails to reproduce the grammage, due to the exceedingly low value of the perpendicular diffusion coefficient. If the large scale MAGNETic field acquires a component perpendicular to the Galactic disc, the parallel diffusion coefficient becomes quickly dominant in terms of particle escape, and drifts are unable to compete. A knee structure does not appear in such a scenario. However, if the parallel diffusion coefficient becomes energy independent at $E\gtrsim 1$ TeV, a knee may arise around PeV energies due to drift dominance. We discuss two cases in which this situation may occur.
[abstract 12 / 43] Yes (score: 4) - Title: Gas Motions in Hydra-A: XRISM Constraints on ICM Kinematics Across Jet-Inflated CavitiesAuthors: Anwesh Majumder, B. R. McNamara, P. E. J. Nulsen, H. Russell, T. Rose, T. Heckman, A. Simionescu, A. Fabian, M. W. Wise, N. Werner, M. McDonald,Comments: 17 pages, 6 figures; Accepted in ApJSubjects: astro-ph.HE astro-ph.COCreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
We report on two deep XRISM observations of the central and northern regions of Hydra-A's X-ray atmosphere, covering the bubbles inflated by JETs from the central galaxy's ACTIVE GALACTIC NUCLEus. We use spatial-spectral mixing, combining Chandra's high spatial resolution with XRISM's high spectral resolution, to investigate atmospheric kinematics. The velocity dispersion in the northern region, $σ_v = 140^{+30}_{-20}$ km s$^{-1}$, is comparable to that in the central region ($σ_v = 162 \pm 10$ km s$^{-1}$). We show that motion of the large-scale cocoon shock front could be responsible for the large dispersion toward the north. The dispersion in the northeast quarter of the central pointing, $σ_v = 260 \pm 50$ km s$^{-1}$, is among the highest measured. This region contains an X-ray-bright feature previously identified as metal-rich, possibly gas uplifted in the wake of previous-generation cavities. Dispersions in all other quarter regions are low ($σ_v \leq 180$ km s$^{-1}$) and consistent with previous XRISM results from other objects. The kinetic energy at the center is comparable to the enthalpies of the cavities, while in the north it is roughly an order of magnitude smaller. The JET thus drives gas motion efficiently at smaller scales ($r < 95$ kpc) and inefficiently at larger scales ($95-317$ kpc toward the north along the JET). A bulk flow toward our line of sight of $-100 \pm 30$ km s$^{-1}$ in the southwest quarter of the central pointing, measured with respect to the central galaxy, is also observed, possibly due to sloshing. No significant bulk motion was detected in any other region.
[abstract 13 / 43] Yes (score: 4) - Title: An "inside-out" approach to modeling supermassive BLACK HOLE binary inspiralAuthors: Laura Blecha,Comments: 31 pages, 13 figures, accepted to ApJSubjects: astro-ph.HECreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
The inspiral and merger of two supermassive BLACK HOLEs (SMBHs) releases immense energy in low-frequency gravitational waves (GWs). Recent pulsar timing array (PTA) observations of the stochastic nHz GW background (GWB) are consistent with a SMBH binary origin. GW data from PTAs and from the upcoming Laser Interferometer Space Antenna (LISA) can probe late-stage binary evolution where electroMAGNETic constraints are scarce. However, the complexity of the relevant astrophysics necessitates a well optimized approach. I argue that a key physical quantity to constrain with PTAs is the orbital semi-major axis at which binary inspiral transitions from the astrophysical to the GW-dominated regime ($a_{\rm GW}$). This quantity should be treated as a free parameter in analysis of the GWB. Using this premise, I present a simple analytic framework for modeling SMBH binary inspiral in an "inside-out" fashion. At orbital separations slightly larger than $a_{\rm GW}$, a power-law scaling for the astrophysical inspiral timescale is assumed, while the outermost phase (prior to the PTA regime) is simply modeled via a delay time. I show that the GWB spectral shape and amplitude are most sensitive to $a_{\rm GW}$ (normalized to $10^9 M_{\odot}$, equal-mass binaries and expressed in gravitational units), with weaker dependence on the inner power-law index and the outer delay time. The GWB is largely insensitive to the mass and mass-ratio scaling of $a_{\rm GW}$ and to the boundary between the inner and outer astrophysical inspiral regimes. I compare with models for gas- and stellar-driven binary inspiral and discuss implications for LISA and for GW source parameter inference.
[abstract 14 / 43] Yes (score: 4) - Title: Multiple Instance Learning for Interpretable Plasmoid Detection in the FLARE DeviceAuthors: Charles Marsden, Adam Robbins, Hantao Ji,Comments: 8 pages, 2 figures. Submitted to Physics of PlasmasSubjects: physics.plasm-phCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Multiple instance learning (MIL) is a form of weakly supervised learning widely used in healthcare and biomedical imaging, where labels may be available for groups of observations ("bags") but not individual observations ("instances"). This setup is well-suited to plasmoid detection in MAGNETic RECONNECTion experiments, since identifying dynamic MAGNETic structures is best accomplished taking in data from many time steps as a whole, as opposed to viewing frames in isolation. Instance-level consideration enables researchers to determine the range of times most affecting model output, thus serving as a tool for the temporal localization of plasmoids. Despite its success in the life sciences, to the best of our knowledge, MIL is yet to be reported in peer-reviewed plasma physics literature. We evaluate a MIL model against a convolutional recurrent neural network (CRNN), an architecture commonly found in plasma physics literature, on a plasmoid detection task, using a highly imbalanced dataset of 1152 MAGNETic RECONNECTion shots from the FLARE device at PPPL. We demonstrate significant improvements in test performance (PR AUC: $Δ$=+0.0932, p=0.0039; F1: $Δ$=+0.0259, p=0.0488; Wilcoxon signed-rank test) against the CRNN model on full-channel input. We investigate the interpretability advantage provided by our MIL model for the temporal localization of plasmoids. Through its attention mechanism, we can discern relevant frames and even the number of plasmoids present in a shot. Overall, we show that MIL is a promising framework for similar event classification tasks in plasma physics.
[abstract 15 / 43] Yes (score: 4) - Title: Ranking Prompt--Plateau Correlations in Gamma-Ray Bursts with Symbolic RegressionAuthors: Fatemeh Rastegarnia, Rahim Moradi, Brwa Shukur Ismael, Mohsen Asaadi, Yu Wang,Comments:Subjects: astro-ph.HECreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Gamma-ray burst (GRB) correlations probe central engines, RELATIVISTIC outflows, and radiation processes. The Dainotti relation is an anticorrelation between the X-ray plateau luminosity $L_a$ and rest-frame plateau duration $T_a^{\rm rest}$. We use symbolic regression to compare it with other low-dimensional correlations in 251 GRBs with SWIFT-XRT plateau properties and SWIFT-BAT prompt-emission parameters. We perform a Dainotti-guided search, in which $\log T_a^{\rm rest}$ is always present, and an unrestricted search over subsets of at most three variables. The guided search recovers the Dainotti dependence; a D'Agostini fit gives $\log L_a=(51.92\pm0.30)-(1.31\pm0.09)\log T_a^{\rm rest}$, with intrinsic scatter $σ_{\rm int}=0.82\pm0.05$ dex. In the unrestricted ranking of 377 feature subsets, the classical Dainotti relation remains competitive, within the top $\sim25\%$ of the tested search spaces. The highest-ranked screened expression is $\log L_a\approx0.855\log L_{\rm peak}-0.782\log T_a^{\rm rest}$, with RMSE $\approx0.46$ and $R^2\approx0.88$. The highest-ranked runs repeatedly reduce to this prompt--plateau structure, without retaining additional spectral, absorption, or afterglow-shape variables. A direct regression gives $\log L_a=4.718+0.776\log L_{\rm peak}-0.805\log T_a^{\rm rest}$, with $R_{\rm P}=0.91$ for 246 bursts. An errors-in-variables refit gives consistent coefficients. After removing shared luminosity-distance dependence, the relation retains non-negligible explanatory power ($R^2\approx0.62$), consistent with a possible intrinsic component. Restricted Monte Carlo null tests give $p\approx0.01$. Plateau luminosity therefore shows a coupled dependence on prompt luminosity and plateau duration.
[abstract 16 / 43] (score: 3) - Title: Macroscopic Stability of a Rapidly Rotating Isothermal Magnetic MirrorAuthors: Richard Fitzpatrick,Comments: Extended and corrected version of previous submissionSubjects: physics.plasm-phCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
The macroscopic ideal-MHD stability of an axisymmetric mirror device with sonic levels of plasma rotation is analyzed by approximating the plasma equilibrium as a rotating isothermal theta pinch possessing an artificial gravity. Starting from a set of single-fluid, ideal-MHD, isothermal fluid equations, a linear, second-order, eigenmode equation for the radial component of the Lagrangian fluid displacement is derived which governs the stability of the equilibrium to small perturbations in the case of an arbitrary plasma angular velocity profile. The stability of the m=1 and m=2 modes is investigated. For the case of rigid plasma rotation, the plasma is found to be stable to these two modes provided that it is sufficiently short in the axial direction. For the case of sheared plasma rotation, the $m=2$ mode is found to be difficult to stabilize. This is the case for both monotonically decreasing rotation profiles, and profiles that peak off the MAGNETic axis.
[abstract 17 / 43] (score: 3) - Title: IXPE observation of the new MAGNETar source EP J223759.5+531421Authors: Roberto Taverna, Lorenzo Marra, Roberto Turolla, Ruth M. E. Kelly, Silvia Zane, Alice Borghese, Francesco Coti Zelati, Paolo Esposito, Gian Luca Israel, Nanda Rea, Haonan Yang, Yilong Wang,Comments: 14 pages, 9 figures, accepted for publication in ApJLSubjects: astro-ph.HECreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
We report on the detection of polarized X-ray emission from the new Galactic MAGNETar EP J223759.5+531421, discovered by the Einstein Probe Wide-field X-ray Telescope on 2026 June 28. The Imaging X-ray Polarimetry Explorer (IXPE) follow-up observation started on 2026 July 6 and detected the source at a (absorbed) flux of $\approx 4.5\times 10^{-11} \, \mathrm{ erg\,cm^2\,s}^{-1}$ ($2$--$7.5\, \mathrm{keV}$ range), confirming the presence of two thermally emitting regions on the star surface, with temperatures $\approx 0.5$ and $\approx 1\, \mathrm{keV}$. A significant (at $> 4σ$ confidence level) phase- and energy-integrated POLARIZATION degree of $\approx 7\%$ was detected with the POLARIZATION angle $\approx -2^\circ$ East of the celestial North. The two thermal components exhibit quite different POLARIZATION properties, with the hotter one being more polarized. The difference is larger in the phase-folded data, with the POLARIZATION degree reaching $\sim 63\%$ in the range $4$--$7.5\,\mathrm{keV}$, in correspondence with the secondary peak of the pulse profile, and never exceeding $\sim 30\%$ at lower energies. The POLARIZATION angle continuously oscillates from $-90^\circ$ to $+90^\circ$ over one rotational cycle and is well fit by the rotating vector model, with an inclination of the line of sight and of the MAGNETic dipole axis relative to the star spin axis of $\approx 28^\circ$ and $\approx 109^\circ$, respectively. The data point to an emission geometry in which the cold thermal component likely originates from two antipodal caps, possibly in a MAGNETically condensed state, while the hotter one comes from a smaller region covered by an atmosphere.
[abstract 18 / 43] (score: 3) - Title: Charge-activated birefringence of an Einstein-tensor-coupled vector field on Reissner--Nordström BLACK HOLEsAuthors: Mao-Yuan Wan, Chen Wu,Comments:Subjects: gr-qcCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
We study the propagation of a neutral vector test field non-minimally coupled to the Einstein tensor on a Reissner--Nordström BLACK HOLE. The interaction vanishes on a vacuum background, so electric charge is required to activate the curvature-induced response. The parity potentials have one symmetry: reversing the sign of the coupling exchanges the electric and MAGNETic susceptibilities. Because of this symmetry, the two POLARIZATIONs respond identically at first order in the coupling. The dominant propagation-level effect is therefore a common shift of the effective photon sphere and of the shadow radius, not a birefringent splitting. The variation of shadow size can mimic the charge variation of a BLACK HOLE. When the coupling is weak, POLARIZATION splitting appears only in the second-order term, distinguishing this interaction from corrections involving only charge. We follow this ordering through full-frequency absorption and scattering, the semiclassical glory, and ray-traced double shadows. The absorption parity asymmetry and the shadow rim splitting probe the difference between the effective potentials. The POLARIZATION-summed backward scattering isolates the helicity-reversing response, which is zero without the coupling. At the positive-coupling boundary the splitting grows but stays finite. Beyond it the even-parity potential has a pole outside the horizon. In the high-multipole limit, the two boundaries of the stability window both correspond to the thresholds of bound-state instability, but their physical properties differ: the negatively coupled boundary forms a regular potential well, while the positively coupled boundary marks the breaking of regularity. A Frobenius analysis shows a forced logarithmic branch at that pole. Without an additional physical connection condition, the continuation across the pole is not unique.
[abstract 19 / 43] (score: 3) - Title: Constrain the Size of Broad Line Region in NGC 1068 Using Sub-millimeter ExcessAuthors: Qi Guo, Junzhi Wang, Lingrui Lin, Yuqiang Li, Zhi-yu Zhang, Fengyao Zhu,Comments: 4 pages, 2 figures, Accepted for publication in MNRASSubjects: astro-ph.GACreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Constraining the size of broad-line region (BLR) close to the accretion disk in ACTIVE GALACTIC NUCLEi (AGNs) is key to understand the central engine and evolution of AGN. We propose a new method to constrain the BLR size, based on millimeter to sub-millimeter spectral energy distribution (SED), from which a sub-millimeter excess may be found. Such excess can be used to determine the solid angle of the free-free emission region from BLR, as a region with high electron density and optically thick at sub-millimeter wavelength for free-free continuum. Millimeter to sub-millimeter SED analysis toward the central source S1 in a nearby type II AGN NGC 1068 was done, which gave an upper limit on the solid angle of BLR region as(4.94 +/- 0.61) *10^-6 arcsec^2, corresponding to a radius no more than 0.085 pc. Such a constraint on the BLR size is important for estimating the masses of central supermassive BLACK HOLEs in AGNs.
[abstract 20 / 43] (score: 3) - Title: Resolving the AGN Feeding and Feedback Cycle with ALMA2040Authors: Ilaria Ruffa, Francesco Salvestrini, Almudena Alonso Herrero, Anelise Audibert, Elena Bertola, Viviana Casasola, Roberto Decarli, Daniel Espada, Umberto Maio, Dieu D. Nguyen, Mamta Pandey-Pommier, Miguel Pereira-Santaella, Francesca Pozzi, Jahang Prathap, Sabine Thater, Maria Vittoria Zanchettin,Comments: Part of the ALMA2040 White Paper Series. 10 pages, 4 FiguresSubjects: astro-ph.IM astro-ph.GACreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
Understanding how supermassive BLACK HOLEs (SMBHs) grow and regulate the growth of their host galaxies requires tracing the cold molecular interstellar medium (ISM) throughout the full AGN feeding-feedback cycle. Molecular gas constitutes both the primary fuel for STAR FORMATION and black-hole accretion and one of the ISM phases most directly affected by AGN-driven radiation, winds, and radio JETs. Over the past decade, ALMA has resolved circumnuclear molecular discs, rings, spirals, tori, and JET-driven outflows on scales of tens of parsecs in nearby AGN. These studies have demonstrated that combining spatially resolved gas kinematics with multi-line diagnostics is essential for disentangling the physical processes underlying the observed gas conditions. However, our current picture remains largely based on a limited number of exceptionally nearby systems. Most local AGN have instead been observed with ALMA in a single transition at moderate or low angular resolution, preventing a systematic characterisation of both the dynamics and physical state of the gas. Moreover, existing studies have largely overlooked kinetic-mode AGN hosted by massive early-type galaxies, despite their central importance for understanding maintenance-mode feedback. In this White Paper, we argue that ALMA2040 should transform these detailed case studies into a statistical framework. A $\sim10\times$ improvement in line sensitivity relative to the current ALMA, together with fast mosaicking, ultra-wide instantaneous bandwidth, and longer baselines (resolving up to $\sim9$ mas at 230 GHz), will enable homogeneous, multi-line mapping of the molecular ISM on giant molecular clouds scales across statistically significant samples of both radiative- and kinetic-mode AGN out to $z\lesssim0.1$.
[abstract 21 / 43] (score: 3) - Title: Modeling extreme mass-ratio inspirals in astrophysical and dark-matter environmentsAuthors: Dongjun Li, Hao-Jui Kuan, Colin Weller, Chaoyi Yang, Kelvin Ka-Ho Lam, Patrick Bourg, Adrian Ka-Wai Chung, Yanbei Chen, Nicolás Yunes, Huan Yang,Comments: 28 pages, 8 figuresSubjects: gr-qc astro-ph.HECreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
Extreme mass-ratio inspirals offer a powerful probe of massive BLACK HOLEs and their environments, but interpreting their signals requires accurate models of orbital dynamics and radiation. Here we bring together advances in black-hole perturbation theory to establish a unified RELATIVISTIC framework for adiabatic inspirals in perturbative astrophysical environments. Built on the modified Teukolsky formalism, the framework requires neither post-Newtonian nor slow-rotation approximations. As a first application, we calculate the leading cloud-induced corrections to gravitational-wave fluxes and conservative orbital dynamics for circular, equatorial inspirals around a rotating BLACK HOLE surrounded by a synchronized ultralight scalar cloud, combining these corrections with the previously calculated scalar response. In our fiducial system, a cloud containing $10^{-4}$ of the black-hole mass produces about $-57.3$ radians of orbital dephasing over two years. The phase contributions from gravitational-wave flux corrections and background-induced orbital shifts each exceed the scalar contribution in magnitude and partially cancel, highlighting the need for coupled matter-gravity modeling. Extensible to other environments and modified gravity theories, our framework provides the RELATIVISTIC inputs needed to assess detection losses and parameter biases, and to probe the nature of black-hole environments with future space-based gravitational-wave observations.
[abstract 22 / 43] (score: 3) - Title: Maximal efficiency of geometric beaming and POLARIZATION of highly super-Eddington X-ray sourcesAuthors: Varpu Ahlberg, Alexandra Veledina, Eugene Churazov, Ildar Khabibullin,Comments: 12 pages, 7 figures, submitted to A&ASubjects: astro-ph.HECreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Geometric beaming is an often invoked explanation for the apparent super-Eddington luminosities of ultraluminous X-ray sources. It is a natural consequence of the geometrically thick envelope that is expected to surround the inner accretion disk in the super-Eddington accretion regime; as the radiation can only freely escape through a narrow funnel-shaped cavity, the flux along the funnel axis is enhanced. A fraction of the photons will nevertheless escape the funnel cavity at larger angles, reducing the effectiveness of the beaming. To explore the limits of geometric beaming, we performed Monte Carlo simulations of conservative radiative transfer in an infinitely optically thick funnel while accounting for POLARIZATION. We discovered that the beaming becomes inefficient when the funnel opening angle is small $(\lesssim15^\circ$) because the photons tend to remain trapped within the cavity until they reach the upper edge of the funnel where they can escape at larger angles. For most of the photons to escape a narrow funnel through a small solid angle, the funnel has to be unrealistically long. Consequently, geometric beaming could at most boost the apparent luminosity by a factor of a few dozen in our idealized simulations. While larger boost factors on the order of $\sim$100 are possible for funnels with a length of $\gtrsim10^5$ Schwarzschild radii, this requires very narrow opening angles of $\lesssim3^\circ$. Additionally, we found that aberration due to mildly RELATIVISTIC velocities does not significantly change this result. The maximal POLARIZATION degree of light reflected by the funnel remained on the order of a few percent for face-on sources and $\lesssim10\%$ for edge-on sources.
[abstract 23 / 43] (score: 3) - Title: Relations between optical spectral parameters and the (far-)infrared continuum in Type~1 ACTIVE GALACTIC NUCLEiAuthors: Maša Lakićević, Luka Č. Popović, Sladjana Marčeta-Mandić, Oliver Vince, Paola Marziani,Comments: Accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.GACreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
This study combines multi-wavelength continuum data with optical spectral properties for a far-infrared (FIR)-selected sample of Type 1 ACTIVE GALACTIC NUCLEi (AGNs) from AKARI data. We explore the relation between AGN physics and concomitant STAR FORMATION processes using empirical correlations of optical and multiwavelength data. We measured spectral parameters including full widths at half maximum (FWHMs) and velocity shifts of broad and narrow optical emission lines, as well as continuum luminosities from GALEX FUV to AKARI 160 microns. The sample contains 88 AGNs observed at both optical and FIR wavelengths. About 50% are Seyfert 1s with both broad H$β$ and H$α$ lines; almost all remaining objects are S1.9s with only broad H$α$. The FWHMs of broad H$β$ and H$α$ are anti-correlated with luminosity in most bands. Shifts of narrow H$β$, H$α$, and [O III] 5007 lines and FWHM of [O III] 5007 correlate with optical and IR luminosities. Luminosities at 65 and 90 microns are more strongly connected with optical and other spectral properties than those at 140 and 160 microns. These trends extend the well-known Eigenvector 1 (EV1) correlations into the MIR and FIR domain. The anti-correlation between broad-line FWHMs and NIR and MIR luminosities is probably caused by the inclination of the torus and accretion disc: higher inclinations see less AGN radiation. However, most objects fall into Population A along the QUASAR EV1 main sequence, where narrower broad H$β$ profiles and FIR excess emission are commonly linked to higher Eddington ratios.
[abstract 24 / 43] (score: 3) - Title: Survey of Orion Disks with ALMA (SODA) IV: Millimeter variability of protoplanetary disksAuthors: D. Krebs, A. Hacar, J. Forbrich, S. E. van Terwisga,Comments: Accepted by A&A on 12/10/2026Subjects: astro-ph.SR astro-ph.EP astro-ph.GACreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Context. Short-term millimeter-wavelength variability in Class II young stellar objects (YSOs) has been considered minimal, often dismissed as very rare in ALMA-based studies on short timescales. However, recent findings suggest that variability on sub-day timescales is significant. Aims. This study aims to quantify short timescale (~1 hour to ~3 days) millimeter flux variability in unresolved Class II YSO disks observed as part of the SODA survey, leveraging its large dataset to assess the statistical significance of such variability across the LDN 1641 and LDN 1647 regions in Orion. Methods. We analyze ALMA Band 6 observations of 873 YSOs obtained over multiple epochs using a custom flux extraction pipeline to separate individual execution blocks. By computing variability factors and statistical deviations from the mean flux, we identify sources exhibiting significant variability, accounting for noise and calibrator stability. Results. Even with conservative selection criteria, we identify 20 variable sources within the sample (~5.3% of all detections). The maximum of the measured variability factor is >=7 over about one hour. More liberal selection criteria yield up to 60 sources that could be called potentially variable (~15.9%). Conclusions. The number of variable sources detected in our sample indicates physical processes operating on time scales of hours, likely associated with MAGNETic RECONNECTion and/or SYNCHROTRON radiation or strong cases of MAGNETic accretion changes. These detections show the need to reconsider typical stability assumptions in single-epoch observations and calls for follow-up studies in star-forming regions with ALMA. Masses derived from unresolved measurements could potentially be biased by this sort of variability.
[abstract 25 / 43] (score: 3) - Title: Characterizing the Martin Luther King Event: Sun to Earth Evolution of the January 19, 2026 GeoMAGNETic StormAuthors: Abril Sahade, Cecilia Mac Cormack, Andreas J. Weiss, Antonio Niemela, Diego G. Lloveras, Erika Palmerio, Teresa Nieves-Chinchilla,Comments:Subjects: astro-ph.SRCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
We present a comprehensive Sun-to-Earth analysis of the extreme space weather event of 18 -19 January 2026, hereafter the Martin Luther King (MLK) storm, which produced a severe (G4) geoMAGNETic storm and one of the most intense solar radiation storms of Solar Cycle 25. The geoMAGNETic disturbance was driven by a fast Earth-directed coronal mass ejection (CME) associated with an X1.9-class flare from NOAA Active Region 14341. We combine multi-viewpoint remote-sensing observations, in situ measurements from Solar Orbiter and Wind, and physics-based MAGNETohydrodynamic simulations using the CORHEL-CME framework to reconstruct the eruption from the low corona to 1 au and identify the mechanisms governing its geoeffectiveness. Observations and simulations indicate that the eruption originated from a right-handed MAGNETic flux rope embedded in a complex MAGNETic environment dominated by a neighboring positive-polarity coronal hole. The simulations reproduce the observed CME morphology, asymmetric expansion, MAGNETic fields measured at both spacecraft, and Dst index evolution. The main discrepancy is attributed to filament material not included in the model. Favorable MAGNETic polarity alignment between the CME and coronal-hole field minimized MAGNETic erosion through interchange RECONNECTion, enabling rapid escape and preservation of the strong southward MAGNETic field that drove the geoMAGNETic storm. The prolonged recovery phase resulted from interaction between the trailing CME and a following high-speed stream from the same coronal hole. These results demonstrate that storm intensity was primarily established by the coronal MAGNETic configuration, whereas storm duration was controlled by the ambient solar wind.
[abstract 26 / 43] (score: 3) - Title: ModeCast: One-Shot Prediction of Linear MHD Eigenmodes and Growth Rates in TokamaksAuthors: Alex Higginbottom, Zara Z. Ercan, Abetharan Antony, Guzman Sanchez Gonzalez, Rafael Grazzini Placucci, Armand Kassaï Koupaï, Artur P. Toshev,Comments: 40th Conference on Neural Information Processing Systems (NeurIPS 2026). Workshop: Sim2Science: ML with Imperfect Scientific ModelsSubjects: physics.plasm-phCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Large-scale MAGNETohydrodynamic instabilities break plasma confinement, can trigger disruptions, and constrain fusion reactor design; modeling a single configuration against them takes hours with a reference solver such as JOREK, and a design study requires thousands of hours. ModeCast is the first learned surrogate to return the complete linear stability assessment for MHD modes. Trained on a comprehensive dataset of over 45,000 JOREK simulations across thousands of equilibria, it screens stability across toroidal mode numbers n=1-4 and predicts the full spatial structure and growth rate of unstable modes. Excluding the equilibrium solve, inference on a single GPU is over 10,000x faster than multi-core JOREK linear stability runs. The gain comes from building the linear-phase physics into the formulation, objective, and inputs, yielding up to six times more training data. ModeCast misses none of the unstable held-out cases, and its predicted fields reproduce the simulation's measured physics, from MAGNETic island topology to resistivity trends. On a fixed-geometry resistivity scan outside its training distribution, refitting only the 22k-parameter growth rate head of the 145M-parameter network on four simulation halves the held-out internal kink growth rate error, and fine-tuning the whole network adds little. Because it is differentiable and returns full fields, ModeCast could in the future assimilate experimental measurements, providing a bridge to real devices and accelerating progress toward commercial fusion. Project page: zenithon.ai/research/modecast.
[abstract 27 / 43] (score: 2) - Title: On the stability and emittance growth of different particle phase-space distributions in a long MAGNETic quadrupole channelAuthors: Jürgen Struckmeier, Jürgen Klabunde, Martin Reiser,Comments: 22 pages, 10 figuresSubjects: physics.plasm-ph physics.acc-phCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
The behavior of K-V, waterbag, parabolic, conical and Gaussian distributions in periodic quadrupole channels is studied by particle simulations. In the parameter range studied, the response associated with the K-V instabilities becomes progressively less pronounced toward the Gaussian distribution. For the third-order instability studied here, the emittance growth factor of an initially Gaussian beam after a large number of periods is considerably lower than that of an equivalent K-V distribution.\newline\indent In addition, the non-K-V distributions exhibit a rapid initial emittance growth within approximately one period of the channel, which becomes very significant at high beam intensities. This growth is attributed to the homogenization of the space-charge density, resulting in a conversion of electric-field energy into transverse kinetic and potential energy. Two simple analytical formulae based on different energy-partition assumptions are derived as estimates for this effect and are compared with the results obtained from particle simulations. They are not rigorous lower and upper bounds for arbitrary beam evolution. \\[6pt] Original publication in Particle Accelerators {\bf 15}, 47--65 (1984)}
[abstract 28 / 43] (score: 2) - Title: Clustering effects on the Dark Siren determination of $H_0$: A simulation studyAuthors: Marios Kalomenopoulos, Riccardo Barbieri, Sadegh Khochfar, Jonathan Gair, Robert J. McGibbon,Comments: Updated version, accepted in MNRASSubjects: astro-ph.CO astro-ph.GA gr-qcCreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
We investigate the cosmological power of gravitational wave (GWs) events without electroMAGNETic counterparts using high-resolution, cosmological simulations that include realistic clustering. We assume a near-future detector network (LVK + LIGO India in O5), with sky localisation and distance uncertainty capabilities for binary BLACK HOLEs, of the order of $60$ deg. squared and $10\%$ respectively, and with a range of about $1600$ Mpc/h. We find that clustering leads to increased convergence of the $H_0$ posteriors, with clear recovery of the input value as early as $N_{\rm gw}=40$ events (a very conservative estimate for O5, which expects thousands of BBHs/year). In contrast, even with $N_{\rm gw}=100$ events in uniform catalogues, the posterior remains largely unconstrained. Additionally, we quantify the role of catalogue completeness and show that levels as low as $f=25\%$ can be competitive with fully complete catalogues, confirming the impact of clustering. Completeness levels of $f=50\%$ perform statistically similar to complete catalogues with as few as $N_{\rm gw}=40$ events. We conclude that improving GWs detection capabilities yields better results than more complete galaxy catalogues.Finally, we find that 1) physical weights do not provide significant additional constraining power on top of clustering, 2) luminosity distance errors contribute more for small cone openings, 3) the $H_0$ prior range does not introduce any biases in the $H_0$ posterior, 4) closer events ($\lesssim 100$ Mpc/h) yield about two times better precision than more distant events ($\lesssim 1600$ Mpc/h), and 5) our method is robust to different modelling choices.
[abstract 29 / 43] (score: 2) - Title: Strong Lensing and Quasinormal modes of a Black Hole with a Global MonopoleAuthors: Irengbam Roshila Devi, Ningthoujam Media, Yenshembam Priyobarta Singh, Telem Ibungochouba Singh,Comments: 45 pagesSubjects: gr-qcCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
In this paper, we investigate various key aspects of a static and spherically symmetric BLACK HOLE with a global monopole. Firstly, we analyze the deflection angle in the strong field limit of a spacetime with a global monopole. It shows that the angle of deflection increases when the two characteristic parameters for the monopole configuration, $η$ and $λ$, increase. The influence of the global monopole parameter on the lensing observables and the BLACK HOLE shadow is studied. This shows that a larger monopole parameter corresponds to larger shadow radii. The dynamics of timelike geodesics is also investigated in the spacetime. General circular orbits and the innermost stable circular orbits (ISCO) of timelike particles are discussed, highlighting that the monopole parameter significantly affects the circular orbits and the ISCO. In particular, it is observed that the radius of ISCO rises monotonically with $η$. In addition, the Lyapunov exponent is used to analyze the stability of timelike geodesics. We also determine the quasinormal modes under electroMAGNETic perturbations for different values of $η$. Our findings indicate that increasing the monopole parameter gives rise to electroMAGNETic perturbations with more slowly damped oscillations. To further validate the derived quasinormal mode spectrum, we discuss the time-domain evolution of the perturbation, confirming the presence of the characteristic quasinormal ringing followed by late-time power-law tails. Finally, comparison with the EHT observations of M87* and Sgr A* determines the parameter combinations of $η$ and $λ$ compatible with current observations, and the observational prospects of the strong-lensing observables are discussed.
[abstract 30 / 43] (score: 2) - Title: Pair-exchange dynamics of MAGNETohydrodynamic turbulenceAuthors: Jean-Mathieu Teissier, Wolf-Christian Müller,Comments:Subjects: physics.flu-dyn astro-ph.IM astro-ph.SR physics.plasm-phCreated: 2026-10-15; Updated: 2026-10-19; Datestamp: 2026-10-19
Nonlinear interactions in incompressible MAGNETohydrodynamic (MHD) and Navier-Stokes turbulence involve three spatial fluctuations conservatively exchanging, e.g., energy. The mathematical structure of a triad interaction does not allow to unambigously determine the specific contribution of each of the participating fluctuations to the resulting exchanges. Presently, only additional assumptions allow for the deconstruction of triad interactions into a sum of pair exchanges. This work proves that in incompressible MHD the simultaneous nonlinear transfer of cross-helicity sufficiently constrains the triad dynamics such that a mathematically unique pair-exchange representation of nonlinear energy and cross-helicity transfer is possible.
[abstract 31 / 43] (score: 2) - Title: Azimuthal Instability in Oscillating Liquid Jets by the Weber Number VariationsAuthors: Hyoungwoo Kim, Seungwon Shin, Hyosang Yoon, Sanghyuen Park, Dong-hyuk Shin,Comments: The following article has been submitted to Physics of FluidsSubjects: physics.flu-dyn physics.comp-phCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
This paper investigates the dependence of azimuthal mode growth rate of oscillating liquid laminar JETs on the Weber number. The oscillating liquid laminar JETs were simulated over a range of Weber numbers. The simulation setup was validated by comparing the instantaneous interface shapes and the visible azimuthal mode from experimental measurements. As the Weber number increases, the spreading angle rises due to the small surface tension, and higher azimuthal modes are observed. Fourier Transform analysis is used to find the exact azimuthal mode of the simulation results. The dominant azimuthal mode increases as the Weber number increases. A power-law dependence of the growth rate on the Weber number is identified, with the obtained exponents showing good agreement with linear instability analysis. Furthermore, the rescaled Fast Fourier Transform (FFT) results collapse onto a single growth curve for each azimuthal mode, validating the proposed power-law for predicting the growth rates of oscillating liquid JETs.
[abstract 32 / 43] (score: 2) - Title: Geometric Capture and Optical Critical Curves of Purely Electric, Magnetic and Dyonic Black Holes in Einstein-Euler-Heisenberg TheoryAuthors: Yong-Zhuang Li, An-Hao Xu, Haoyuan Luo, Xiao Yan Chew,Comments: 12 pages, 3 figures, comments are welcomeSubjects: gr-qcCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
We examine background null capture in the electric, MAGNETic, and dyonic solutions of Einstein gravity coupled to a quartic Euler-Heisenberg-type electroMAGNETic Lagrangian. The calculation uses the exact hypergeometric electric solution, the closed-form MAGNETic solution, and a numerical dyonic solution. Relative to the Reissner-Nordström value at fixed total charge, the EEH correction increases the geometric critical impact parameter in the parameter ranges considered. For the purely MAGNETic case, the disappearance of the two outer horizons can expose an additional capture barrier and thus forms an unstable circular orbit with a very small radius. In the dyonic case, for a fixed MAGNETic-to-electric charge ratio, the behavior is consistent with that of the pure electric solution while preserving the phase transition between single- and multi-horizon BLACK HOLE phases. Moreover, when the coupling parameter is fixed, the effect of the MAGNETic-to-electric charge ratio depends on the electric charge. The present findings establish that the multi-horizon phase can impart pronounced signatures to geometric photon observables, whereas, in the off-transition regime, the purely electric, purely MAGNETic, and dyonic solutions remain characterized by clearly distinguishable trends.
[abstract 33 / 43] (score: 2) - Title: A Unified Solution to the Low-Mass X-ray Binary Diversity Puzzle: Saturated Magnetic Braking Coupled with Irradiation-Driven WindsAuthors: Zhu-Ling Deng, Xiang-Dong Li, Bo Wang, Philipp Podsiadlowski, Yong Shao, Dong-Dong Liu, Zhan-Wen Han,Comments:Subjects: astro-ph.HE astro-ph.SRCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
The standard MAGNETic braking (MB) model has long failed to explain key properties of low-mass X-ray binaries (LMXBs)---including their accretion rates, the formation of ultracompact binaries, and orbital expansion---casting doubt on binary evolution and gravitational-wave progenitor predictions. Phenomenological modifications exist, but a unified, physically grounded mechanism has been missing. Here we show that the overlooked coupling between MAGNETic saturation and irradiation-driven winds (IDW) provides this missing framework. Accretion-powered irradiation enhances the donor wind, which in turn amplifies MB exactly where needed. Our Saturated MB + IDW (SMB+IDW) model simultaneously resolves three outstanding discrepancies with no fine-tuning: (1) it reproduces the full observed distribution of accretion rates across persistent and transient LMXBs; (2) it naturally explains ultracompact X-ray binary formation; and (3) it quantitatively matches the orbital period distribution of descendant millisecond pulsar (MSP) binaries---a critical independent test failed by all previous models. Critically, the SMB+IDW model transforms MB from an externally imposed condition into a self-consistently regulated process tied to the accretion history. By unifying LMXB evolution to MSPs in a single physical picture, our work resolves the long-standing diversity puzzle and establishes a physics-based foundation for next-generation population synthesis, gravitational-wave progenitor predictions, and compact binary interpretation across cosmic time.
[abstract 34 / 43] (score: 2) - Title: $\texttt{GASTRO-BH}$: Effects of a Central Black Hole in GSE-like Dwarf-galaxy Mergers Around Milky Way-like HostsAuthors: Pedro Naethe Motta, João A. S. Amarante, Guilherme Limberg, Lais Borbolato, Chervin F. P. Laporte, Zhao-Yu Li, Reinaldo Santos-Lima, Victor P. Debattista, Marcelo C. Vicentin,Comments: 23 pages, 11 figures. Comments are welcome! Submitted to ApJSubjects: astro-ph.GA astro-ph.HECreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Recent evidence points to an intermediate-mass BLACK HOLE (IMBH) in the most massive globular cluster of the Milky Way, $ω$ Centauri. This globular cluster is commonly associated with the Gaia-Sausage/Enceladus (GSE) dwarf galaxy, the last major merger event of our Galaxy, as its nuclear star cluster remnant. Motivated by this, we investigate whether the interaction between a bright GSE-like dwarf galaxy with stellar mass in the range $10^{8.5}$--$10^{9.7}$ solar masses and a Milky Way-like host can either suppress or enhance the growth of a central BLACK HOLE (BH) during the merger process. To this end, we perform high-resolution $N$-body and smoothed particle hydrodynamics (SPH) simulations with the ChaNGa framework and a modified, angular-momentum-aware Bondi-Hoyle accretion prescription, considering both isolated dwarf galaxies and merger simulations with different stellar feedback efficiencies. The merger simulations show that the interaction does not halt BH accretion; instead, tidal interactions and gas inflows during pericentric passages strongly enhance accretion, leading to BH mass growth by more than two orders of magnitude in both low- and high-feedback models. The enhanced accretion is accompanied by suppressed STAR FORMATION in the dwarf galaxy. Our results suggest that mergers similar to the GSE event can efficiently fuel IMBH growth in satellite galaxies rather than suppress it. This may be in tension with the estimated low mass of the proposed IMBH in $ω$ Centauri, but it could provide a mechanism for triggering ACTIVE GALACTIC NUCLEus activity in dwarf galaxies.
[abstract 35 / 43] (score: 2) - Title: Role of Device Size on Island Divertor Performance of W7-X-like ConfigurationsAuthors: K. A. Garcia, F. Reimold, Y. Feng, H. Frerichs, V. R. Winters, the W7-X team,Comments:Subjects: physics.plasm-phCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
To examine how the island divertor performs in future low-shear stellarator reactors, we simulate (using EMC3-Eirene [1]) 3 different scales of W7-X: its current size, increased by a factor 2, and increased by a factor 4, where 4 times W7-X corresponds roughly to a reactor-scale device. For a single MAGNETic configuration, the standard MAGNETic configuration in W7-X, we examine how increasing the size of W7-X alters the divertor performance of the island divertor. We analyze how device scale shifts the location of the ionization source and the downstream density and temperature trends in the island divertor for achieving detachment. Local field line analysis shows that factor 2 and factor 4 size scalings achieve target densities $>10^{21} \ \mathrm{m}^{-3}$ via plasma ``self-baffling" within the open island divertor geometry. Finally, the heat and particle flux deposition on the scaled-up island divertor configurations are calculated. We observe a separation in the target heat and particle flux distribution with increased machine size in agreement with [2]. The target heat fluxes are $<5 \ \mathrm{MW}/\mathrm{m}^2$ at high separatrix densities. This shows that the separation of the heat and particle flux channels remains to be largely unproblematic. This analysis helps guide how to improve the open island divertor geometries for future stellarator reactors.
[abstract 36 / 43] (score: 2) - Title: A new submillimeter Class I methanol maser at 345.903 GHz near the massive protostar S255IR NIRS3Authors: Svetlana Salii, Igor Zinchenko, Andrej Sobolev,Comments: 6 pages, 3 figures, 2 tablesSubjects: astro-ph.GACreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
We present results of further investigation of radio emission from the remarkable molecular core S255IR-SMA1 harboring a \(\sim\) 20 Msun young stellar object NIRS3 which exhibited a disk-mediated accretion burst in 2015. Our study is based on observations of this object with ALMA in Band 7 with the longest baselines, which provide an angular resolution of \(\sim\)15 mas. The obtained data reveal several spots in the bright and narrow methanol 16(1) \(-\) 15(2) A\(-\) line emission at 345.903 GHz. These spots are located close to H_2O masers, knots in the JET and arc-like structures seen in submillimeter continuum. At the same time, they are far away from the peaks of the Class II methanol maser spots. High brightness temperatures and small line widths of the 345.903 GHz line emission indicate that this emission has a maser nature. Association with the shock tracers tells that these masers belong to Class I methanol maser category. Non-LTE analysis of the physical parameters which lead to population inversion of 16(1) \(-\) 15(2) A\(-\) transition shows that some known rare Class I methanol maser transitions are also inverted under these conditions.
[abstract 37 / 43] (score: 2) - Title: The Dancing Bonfire: An Unusual Persistent X-ray Source in M81 Exhibiting Recurrent Luminous FlaresAuthors: Jiachang Zhang, Zhiyuan Li, Xiangdong Li, Tong Bao, Ziqian Hua, ShanShan Weng,Comments: 22 pages, 6 figures. Revised version submitted to ApJSubjects: astro-ph.HECreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Short-timescale X-ray variability provides a direct probe of unstable accretion onto compact objects, yet extragalactic X-ray binaries (XRBs) with recurrent flaring remain largely unexplored. Here we present a detailed X-ray study of M81F4 (2CXO J095524.2+690957), a persistently luminous X-ray source towards M81 that exhibits recurrent short X-ray flares. Based on multi-mission X-ray observations spanning two decades, it is found that M81F4 remains persistently bright at $L_{0.5-8.0\rm~keV}\sim10^{38}-10^{39}\rm~erg~s^{-1}$, while producing flares lasting a few hundred seconds and reaching peak luminosities of a few $10^{39}\rm~erg~s^{-1}$, with an observed mean (minimum) recurrence time of $\sim0.5$ day ($\sim$6 ks). The stacked flare profile shows a rapid rise followed by a slower decay, but no significant hardness evolution. Spectral analysis reveals that both the flare and non-flare states are dominated by a hard power-law continuum, with evidence of highly ionized Fe lines in the non-flare state spectrum. These properties disfavor classical Type I and Type II bursts and have no close analog among known XRBs. We favor a MAGNETized neutron star accreting from an intermediate mass donor at a persistently high rate with the flares arising from instabilities at the disk-MAGNETosphere boundary. If confirmed, M81F4 might represent a hidden population of XRBs in which sustained, MAGNETically-regulated accretion can lead to brief episodes of super-Eddington emission.
[abstract 38 / 43] (score: 2) - Title: Path-integrated electrostatic energization in LASER-driven collisionless cylindrical convergenceAuthors: Diya Pan, Masakatsu Murakami, Shinsuke Fujioka, Hideo Nagatomo,Comments:Subjects: physics.plasm-phCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Collisionless converging ion flows can sustain particle energization over an extended path, but the field channel responsible for the energy gain is not always identifiable. In LASER-driven bladed microtube implosion, energetic carbon ions were previously observed alongside a self-generated gigagauss-class axial MAGNETic field [D. Pan and M. Murakami, Phys. Plasmas 32, 072107 (2025)], leaving the origin of their energization unresolved. Using two-dimensional particle-in-cell simulations, field-particle power decomposition and trajectory-resolved work accounting show that radial electrostatic work accumulated along the converging path supplies more than 98% of the net in-plane electric work, whereas the azimuthal channel associated with the time-varying MAGNETic field remains subdominant. The peak local mean ion energy factorizes, to good approximation, into an incident-flow contribution controlled by LASER intensity and a geometric enhancement that grows approximately linearly with the inner radius because ions accumulate electrostatic work over a longer convergence path. The path-averaged radial electric field $\langle E_r\rangle$ scales with the peak LASER intensity $I_L$ as $\langle E_r\rangle \propto I_L^{0.47}$, favoring a geometry-pinned, comoving charge-separation structure over Debye-limited scaling. The peak local mean carbon-ion energy reaches 0.89 GeV. A smooth-cylinder control exhibits comparable peak energization, showing that blade modulation mainly affects poststagnation ion residence rather than the energy source.
[abstract 39 / 43] (score: 2) - Title: Conservative Numerical Construction of Vlasov-Maxwell Equilibria and an Exact Cancellation of $E\times B$ Flow by an Electrostatic Pressure-Gradient FlowAuthors: Benjamin J. Sturdevant, Hong Qin,Comments:Subjects: physics.plasm-phCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
A class of Vlasov-Maxwell equilibria with pressure gradients is considered under symmetry assumptions that reduce the equilibrium equations to a nonlinear system of ordinary differential equations. Such equilibria provide self-consistent kinetic states with nonuniform thermodynamic profiles and potentially strong equilibrium electric fields, useful for fully kinetic stability studies of gradient-driven instabilities in the presence of equilibrium flows. The reduced equilibrium problem is posed as a nonlinear boundary-value problem for numerical solution, and a discretization is developed that preserves an associated energy invariant exactly at the discrete level. The resulting method provides a systematic means of computing nontrivial equilibria without relying on scale separation, and an alternative to constructing only approximately self-consistent initial states. A key property of the species flows, identified within this model for any distribution function of the constants of motion, is an exact cancellation between the $E\times B$ flow and an electrostatically generated component of the pressure-gradient-driven flow. This follows directly from a structural property of the species force balance that arises from this type of symmetry reduction, and is verified numerically. Additional numerical results demonstrate the conservative properties of the discretization. Representative equilibrium configurations, relevant to future kinetic instability studies, are also presented. An asymptotic approximation for the interior equilibrium, derived in the well-MAGNETized, quasi-neutral regime, provides an independent check on these results. The present setting is deliberately simple, providing a controlled framework for constructing and analyzing self-consistent kinetic equilibria and a starting point for extensions to more general symmetry-reduced configurations.
[abstract 40 / 43] (score: 2) - Title: Galaxy bias of radio AGN and star-forming galaxies from MIGHTEE and CMB lensingAuthors: Joel Hamlett, Catherine L. Hale, Matt J. Jarvis, David Alonso, S. Lyla Jung, Natalia Stylianou, Rohan G. Varadaraj,Comments: 22 pages, 17 figures, 6 tables. Accepted for publication in MNRASSubjects: astro-ph.CO astro-ph.GACreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
Radio galaxies play a significant role in galaxy evolution through feedback mechanisms, making it important to characterize the environments in which they reside. We measure the cross-correlation between the positions of radio sources in the MIGHTEE survey and cosmic microwave background lensing measurements from the Atacama Cosmology Telescope over $20\ {\rm deg}^2$ to flux densities $S_{\rm 1.4\,GHz}>40\ {\rm μJy}$, detecting the signal at $\sim4σ$ significance. By combining this with auto-correlation measurements of low- and high-redshift radio samples, we constrain the redshift evolution of the galaxy bias parameter, $b(z)$. Fitting different models for the redshift evolution of the bias, we find that both a model inversely proportional to the linear growth factor, $b(z) = (1.63^{+0.19}_{-0.22})/D(z)$, and a model where bias grows linearly with redshift, $b(z) = (0.49^{+0.44}_{-0.32}) + (1.62^{+0.37}_{-0.51})z$, provide comparably good fits to the data, with the current measurements unable to distinguish between them. Using a radio luminosity function, we estimate the fraction of sources that are ACTIVE GALACTIC NUCLEi (AGNs) or star-forming galaxies (SFGs) as a function of redshift, and model the individual contributions of AGNs and SFGs to the total bias. This approach allows us to measure the bias of AGNs and SFGs without individual source classifications. Though no single model is favoured significantly, the best-fitting model gives $b_{\rm AGN}(z) = (2.60^{+0.65}_{-0.91})/D(z)$ compared to $b_{\rm SFG}(z) = (0.52^{+0.47}_{-0.34})/D(z)$. Incorporating SFG bias measurements from previous work as a prior tightens these constraints to $b_{\rm AGN}(z) = (1.96^{+0.37}_{-0.40})/D(z)$ and $b_{\rm SFG}(z) = (0.90^{+0.06}_{-0.06})/D(z)$.
[abstract 41 / 43] (score: 2) - Title: Foreground dependence of the 20 GeV Galactic halo gamma-ray excess and its proposed connection to the LUX-ZEPLIN eventAuthors: Kevork N. Abazajian, Youyou Li, Oscar Macias,Comments: 24 pages, 6 figures, 14 tables. Code: https://github.com/kabazajian/totani (https://doi.org/10.5281/zenodo.23420779); data: https://doi.org/10.5281/zenodo.23420896Subjects: astro-ph.HE hep-phCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
We assess the DARK MATTER interpretation of the 20 GeV gamma-ray halo excess reported by Totani and its proposed connection to the LUX-ZEPLIN (LZ) high-energy nuclear-recoil event, which independently favors DARK MATTER masses above about 200 GeV. Using fifteen years of FERMI-LAT data, we reproduce the excess under the original assumptions and test it against 281 Galactic diffuse emission configurations, three descriptions of the FERMI bubbles, four of Loop I, and uniform and X-ray-brightness-weighted eROSITA bubbles templates. A component correlated with a Navarro-Frenk-White (NFW) annihilation template remains with finer spatial binning and the instrumental response included. Outside the FERMI bubbles footprint, it is detected at nominal significances of about 4-16$σ$ over 5.6-130 GeV, falling to 1-7$σ$ when the enlarged boundaries of a recent substructured bubbles model are also excluded. With the substructured model, which improves the fit substantially, the component remains at 7-18$σ$ in four of six representative foreground configurations. However, its amplitude and spectrum depend strongly on the foreground model, and no tested foreground yields a single NFW normalization across the sky, including with additional spatial freedom in the eROSITA bubbles. Simulations show that foreground mismodeling can produce spurious NFW-correlated emission of the observed amplitude, and that residual-derived bubbles templates can bias the recovered spectrum. The 420 GeV $W^+W^-$ spectrum motivated by the LZ connection describes the data for some foreground models but is disfavored by others. These results disfavor interpreting the full excess as annihilation in a smooth NFW halo and weaken the case for a common origin with the LZ event, but they do not exclude a DARK MATTER contribution to the persistent halo-like residual. [abridged]
[abstract 42 / 43] (score: 2) - Title: Eulerian ion energisation in three-dimensional hybrid-Vlasov-Maxwell turbulenceAuthors: L. Richard, S. S. Cerri, O. Pezzi, C. Granier, J. M. TenBarge,Comments: 27 pages, 10 figuresSubjects: physics.plasm-phCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
In collisionless plasma turbulence, energy is transferred from electroMAGNETic fluctuations to the particles. However, the relative contributions of different ion energisation mechanisms remain unclear. We investigate ion energisation in three-dimensional hybrid Vlasov--Maxwell simulations of decaying turbulence at $β_{i0}=0.25$ and $β_{i0}=4$, where $β_{i0}$ is the initial ratio of ion thermal to MAGNETic pressure. Using the exact ion momentum equation, we decompose the ion energisation rate $\mathbf{j}_i\mathbf{\cdot}\mathbf{E}$ into the work done on the parallel, diaMAGNETic, curvature, agyrotropic and polarisation ion currents. This decomposition requires neither gyrotropy nor scale separation and, therefore, remains valid where guiding-centre theory breaks down. We show that the agyrotropic term, which has no guiding-centre counterpart, accounts for $21\,\%$ of the energisation at $β_{i0}=0.25$ and $91\,\%$ at $β_{i0}=4$. We find that the dominant instantaneous energisation term changes with $β_{i0}$, from the polarisation current at low $β_{i0}$ to the diaMAGNETic and agyrotropic currents at high $β_{i0}$, at all resolved scales. In addition, we show that reversible exchange with the ion bulk flow dominates the instantaneous rate, so the time-integrated energy transfer is larger at $β_{i0}=4$ even though the instantaneous rate is smaller. Our results provide quantitative evidence that guiding-centre drifts alone cannot describe ion energisation in kinetic-scale turbulence and that the dominant energisation term depends on $β_i$. The results also highlight the key role of non-local thermodynamic-equilibrium effects in energy conversion in collisionless plasma turbulence.
[abstract 43 / 43] (score: 2) - Title: Clustering of JWST LRDs. Implications for PBHs and other early-forming seedsAuthors: Gert Hütsi,Comments: 11 pages, 6 figuresSubjects: astro-ph.CO astro-ph.GA astro-ph.HE gr-qcCreated: 2026-10-16; Updated: 2026-10-19; Datestamp: 2026-10-19
We use the observed abundance and spatial clustering of JWST little red dots (LRDs) over z = 4--8 to confront two formation scenarios: the standard picture in which LRDs form in virialized dark-matter halos, and one in which they are seeded by a dynamically subdominant population of primordial BLACK HOLEs (PBHs). The halo formation scenario accounts for both observables naturally and without fine-tuning. In the PBH scenario, matching the observed LRD abundance requires a negligibly small PBH mass fraction, and a power-spectrum analysis shows that such a Poisson isocurvature component predicts a clustering signal far below what is observed. The same conclusion holds for any population of dynamically subdominant early-forming seeds, unless their initial clustering is finely tuned or their activity is tied to massive host halos. We conclude that the spatial clustering of JWST LRDs strongly favours the standard halo formation picture and disfavours PBHs, or similar early-forming seeds, as a randomly activated LRD population; PBHs remain viable as seeds only if their activity is governed by massive host halos, in which case clustering alone cannot distinguish them from astrophysical seeds.
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