Current date: 2026-01-28

Setting default datestamp limit: 0

Datestamp limit: 2026-01-28 (0 days ago)

Created/updated limit: 2026-01-21 (7 days ago)

Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics

Setting default set: physics

OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-01-28&until=2026-01-28&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 697

Keyword score statistics

score 12 -- 1 abstracts

score 6 -- 1 abstracts

score 5 -- 4 abstracts

score 4 -- 7 abstracts

score 3 -- 15 abstracts

score 2 -- 18 abstracts

in total -- 46 abstracts

Articles that appeared on 2026-01-28

[abstract 1 / 46] Wow! (score: 12)
arXiv:2601.19135 [pdf, ps, other]

Title: Maximum Energy of Particles Accelerated in GRB Afterglow Shocks

Authors: Zhao-Feng Wu, Sofía Guevara-Montoya, Paz Beniamini, Dimitrios Giannios, Daniel Grošelj, Lorenzo Sironi,

Comments: 10 pages, 4 figures, submitted to ApJL

Subjects: astro-ph.HE physics.plasm-ph

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Particle acceleration in RELATIVISTIC collisionless shocks remains an open problem in high-energy astrophysics. Particle-in-cell (PIC) simulations predict that electron acceleration in weakly MAGNETized shocks proceeds via small-angle scattering, leading to a maximum electron energy significantly below the Bohm limit. This upper bound manifests observationally as a characteristic SYNCHROTRON cutoff, providing a direct probe of the underlying acceleration physics. Gamma-ray burst (GRB) afterglows offer an exceptional laboratory for testing these predictions. Here, we model the spectral evolution of GRB afterglows during the RELATIVISTIC deceleration phase, incorporating PIC-motivated acceleration prescriptions and self-consistently computing SYNCHROTRON and SYNCHROTRON self-Compton emission. We find that low-energy bursts in low-density environments, typical of short GRBs, exhibit a pronounced SYNCHROTRON cutoff in the GeV band within minutes to hours after the trigger. Applying our framework to GRB 190114C and GRB 130427A, we find that current observations are insufficient to discriminate between PIC-motivated acceleration and the Bohm limit, primarily due to large uncertainties in the FERMI-LAT band. Nevertheless, future MeV-TeV afterglow observations can break model degeneracies and place substantially tighter constraints on particle acceleration in RELATIVISTIC shocks.

[abstract 2 / 46] Yes (score: 6)
arXiv:2510.19132 [pdf, ps, other]

Title: Evidence of Energy Injection in the Short and Distant GRB 250221A in a High Density Environment

Authors: Camila Angulo-Valdez, Rosa L. Becerra, Ramandeep Gill, Noémie Globus, William H. Lee, Diego López-Cámara, Cassidy Mihalenko, Enrique Moreno-Méndez, Roberto Ricci, Karelle Siellez, Alan M. Watson, Muskan Yadav, Yu-han Yang, Dalya Akl, Sarah Antier, Jean-Luc Atteia, Stéphane Basa, Nathaniel R. Butler, Simone Dichiara, Damien Dornic, Jean-Grégoire Ducoin, Francis Fortin, Leonardo García-García, Kin Ocelotl López, Francesco Magnani, Brendan O'Connor, Margarita Pereyra, Ny Avo Rakotondrainibe, Fredd Sánchez-Álvarez, Benjamin Schneider, Eleonora Troja, Antonio de Ugarte Postigo,

Comments: Accepted to MNRAS

Subjects: astro-ph.HE

Created: 2026-01-23; Updated: 2026-01-28; Datestamp: 2026-01-28

We present the photometric and spectroscopic analysis of the short-duration GRB 250221A ($T_{90}=1.80\pm0.32$ s), using a data set from the optical facilities COLIBRÍ, the Harlingten 50~cm Telescope, and the Very Large Telescope. We complement these observations with data from the Neil Gehrels SWIFT Observatory and the Einstein Probe, as well as radio observations from the Very Large Array. GRB 250221A is among the few short GRBs with direct afterglow spectroscopy, which gives a secure redshift determination of $z=0.768$ and allows the unambiguous identification of the host as a galaxy with a star-formation rate of $\sim3\,M_\odot\,{\rm yr}^{-1}$. The X-ray and optical light curves up to $T_0+3\times 10^4$ s (where $T_0$ refers to the GRB trigger time) are well described by forward-shock SYNCHROTRON emission in the slow-cooling regime within the standard fireball framework. However, at $T_0 \sim 5\times 10^4$ s, both the X-ray and optical bands exhibit an excess over the same interval, which we interpret as evidence of energy injection into a JET with a half-opening angle of $θ_j=11.5^{\circ}$ through a refreshed shock powered by late central engine activity or a radially stratified ejecta. The burst properties (duration, spectral hardness, peak energy, and location in the Amati plane) all favour a compact binary merger origin. However, our modelling of the afterglow suggests a dense circumburst medium ($n\sim80$ cm$^{-3}$), which is more typical of a collapsar environment.

[abstract 3 / 46] Yes (score: 5)
arXiv:2509.10601 [pdf, ps, other]

Title: Active galactic nuclei do not exhibit strictly sinusoidal brightness variations

Authors: Kareem El-Badry, David W. Hogg, Hans-Walter Rix,

Comments: 18 pages, 3 figures, accepted to PASP

Subjects: astro-ph.GA astro-ph.HE

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Periodic variability in ACTIVE GALACTIC NUCLEi (AGN) light curves has been proposed as a signature of close supermassive BLACK HOLE (SMBH) binaries. Recently, 181 candidate SMBH binaries were identified in Gaia DR3 based on apparently stable sinusoidal variability in their $\sim$1000-day light curves. By supplementing Gaia photometry with longer-baseline light curves from the Zwicky Transient Facility (ZTF) and the Catalina Real Time Transient Survey (CRTS), we test whether the reported periodic signals persist beyond the Gaia DR3 time window. We find that in all 116 cases with available ZTF data, the Gaia-inferred periodic model fails to predict subsequent variability, which appears stochastic rather than periodic. The periodic candidates thus overwhelmingly appear to be false positives; red noise contamination appears to be the primary source of false detections. We conclude that truly periodic and sinusoidal AGN variability is exceedingly rare, with at most a few in $10^6$ AGN exhibiting it on 100 to 1000 day timescales. Models predict that the Gaia AGN light curve sample should contain dozens of true SMBH binaries with periods within the observational baseline, so the lack of strictly periodic light curves in the sample suggests that most short-period binary AGN do not have light curves dominated by simple sinusoidal periodicity.

[abstract 4 / 46] Yes (score: 5)
arXiv:2512.17539 [pdf, ps, other]

Title: Constraining BLACK HOLE spin in PG 1535+547 amidst complex multi-layered absorption

Authors: A. Madathil-Pottayil, D. J. Walton, Jiachen Jiang, T. Dauser, Andrew Fabian, D. Stern, Luigi C. Gallo, Mark T. Reynolds, Emanuele Nardini, Javier A. Garcia,

Comments: 14 pages, 9 figures, accepted for publication in MNRAS

Subjects: astro-ph.HE

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

We present a spectroscopic analysis of XMM-Newton and NUSTAR observations of the 'complex' NLS1 PG 1535+547 at redshift $z=0.038$. These observations span three epochs: 2002 and 2006 with XMM-Newton alone, covering the $0.3-10$ keV energy range, and a coordinated XMM-Newton and NUSTAR observation in 2016, covering the $0.3-60$ keV energy range. The X-ray spectra across all epochs exhibit both neutral and ionized absorption, along with reflection features from the accretion disc, including a prominent Compton hump in the broadband data. Notably, the spectral shape varies across epochs. Our analysis suggests this variability is attributed to changes in both line-of-sight absorption and the intrinsic emission from PG 1535+547. The source is obscured by multiple layers of partially and/or fully covering neutral and ionized absorbers, with neutral column densities ranging from undetectable levels in the least obscured phase to $\sim0.3-5\times10^{23}\mathrm{cm^{-2}}$ in the most obscured phase. A clear warm absorber is revealed during the least obscured phase. The continuum remains fairly consistent ($Γ\approx 2.2\pm0.1$) during the first two observations, followed by a substantial flux decrease (by a factor of $\sim7$ in the $2-10$ keV band) in 2016 compared to 2006. The 2016 data indicates the source is in a reflection-dominated state during this epoch, with a reflection fraction of $R>7$ and an X-ray source located at a height $\leq 1.72r_g$. Simultaneous fitting of the multi-epoch data suggests a rapidly rotating BLACK HOLE with a spin parameter, $a>0.99$. These findings imply that strong light-bending effects may account for the observed continuum flux reduction.

[abstract 5 / 46] Yes (score: 5)
arXiv:2601.18893 [pdf, ps, other]

Title: Hubble Study of the Proper Motion of HST-1 in the Jet of M87

Authors: Rameshan Thimmappa, Joey Neilsen, Daryl Haggard, Michael A. Nowak, Łukasz Stawarz,

Comments: Accepted for publication in ApJ. 13 pages, 8 figures, 1 table

Subjects: astro-ph.GA

Created: 2026-01-26; Updated: 2026-01-28; Datestamp: 2026-01-28

The RADIO GALAXy M87 is well known for its JET, which features a series of bright knots observable from radio to X-ray wavelengths. The most famous of these, HST-1, exhibits superluminal motion, and our analysis of {\it Chandra} data \citep{Thimmappa24} reveals a correlation between the X-ray flux of HST-1 and its separation from the core. This correlation likely arises from moving shocks in the JET, allowing measurement of the internal structure of HST-1 in the X-ray band. To follow up on these results, we use observations from the {\it Hubble} Space Telescope Advanced Camera for Surveys HRC/WFC/SBC channel and the Wide Field Camera 3 (WFC3)'s UVIS to analyze the image and flux variability of HST-1. Our analysis includes 245 ACS and 120 WFC3 observations from 2002-2022, with a total exposure time of $\sim345$ ks. We study the brightness profile of the optical JET and measure the relative separation between the core and HST-1 for comparison to the X-ray. We find that the X-ray and the UV/optical emission could arise from physically distinct regions. The measured proper motion of the knot HST-1 is 1.04$\pm$0.04 c from 2002-2005 and around 2.1$\pm$0.05 c from 2005-2022. We discuss the acceleration of the JET and the flaring SYNCHROTRON emission from HST-1 from optical to X-rays.

[abstract 6 / 46] Yes (score: 5)
arXiv:2601.18988 [pdf, ps, other]

Title: Energy partition in collisionless counterstreaming plasmas

Authors: Alexis Marret, Frederico Fiuza,

Comments:

Subjects: physics.plasm-ph astro-ph.HE

Created: 2026-01-26; Updated: 2026-01-28; Datestamp: 2026-01-28

Fast, counter-streaming plasma outflows drive MAGNETic field amplification, plasma heating, and particle acceleration in numerous astrophysical environments, from SUPERNOVA remnant shocks to ACTIVE GALACTIC NUCLEi JETs. Understanding how, in the absence of Coulomb collisions, energy is redistributed between the different plasma species remains a fundamental open question. We use 3D fully-kinetic simulations to investigate energy partition in weakly MAGNETized counter-propagating plasmas. Our results reveal a complex interplay between different processes, where at early times the Weibel instability drives a first stage of MAGNETic field amplification and at late times the kinking of current filaments drives a second amplification stage via a dynamo-type mechanism. Electrons are heated primarily during the latter phase through MAGNETic pumping. By the time the flows thermalize, we observe that the final temperature ratio $T_e/T_i$ and energy partition depend on the ion-to-electron mass ratio. For electron-proton flows, the electron thermal energy only reaches up to a few percent of the initial ion kinetic energy.

[abstract 7 / 46] Yes (score: 4)
arXiv:2407.18188 [pdf, ps, other]

Title: Evolution of RECONNECTion flux during eruption of MAGNETic flux ropes

Authors: Samriddhi Sankar Maity, Piyali Chatterjee, Ranadeep Sarkar, Ijas S. Mytheen,

Comments: 12 pages, 10 figures, 1 animation, Accepted in The Astrophysical Journal (ApJ)

Subjects: astro-ph.SR physics.space-ph

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Coronal mass ejections (CMEs) are powerful drivers of space weather, with MAGNETic flux ropes (MFRs) widely regarded as their primary precursors. However, the variation in RECONNECTion flux during the evolution of MFR during CME eruptions remains poorly understood. In this paper, we develop a realistic 3D MAGNETo-hydrodynamic model using which we explore the temporal evolution of RECONNECTion flux during the MFR evolution using both numerical simulations and observational data. Our initial coronal configuration features an isothermal atmosphere and a potential arcade MAGNETic field beneath which an MFR emerges at the lower boundary. As the MFR rises, we observe significant stretching and compression of the overlying MAGNETic field beneath it. Magnetic RECONNECTion begins with the gradual formation of a current sheet, eventually culminating with the impulsive expulsion of the flux rope. We analyze the temporal evolution of RECONNECTion fluxes during two successive MFR eruptions while continuously emerging the twisted flux rope through the lower boundary. We also conduct a similar analysis using observational data from the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) for an eruptive event. Comparing our MHD simulation with observational data, we find that RECONNECTion flux play a crucial role in determination of CME speeds. From the onset to the eruption, the RECONNECTion flux shows a strong linear correlation with the velocity. This nearly realistic simulation of a solar eruption provides important insights into the complex dynamics of CME initiation and progression.

[abstract 8 / 46] Yes (score: 4)
arXiv:2507.19987 [pdf, ps, other]

Title: Perseus cluster in its X-ray entirety with SRG/eROSITA. Merger and Radio-Uroboroses

Authors: Eugene Churazov, Ildar Khabibullin, Natalya Lyskova, Rashid Sunyaev, Klaus Dolag,

Comments: A&A accepted

Subjects: astro-ph.HE

Created: 2026-01-26; Updated: 2026-01-28; Datestamp: 2026-01-28

The Perseus cluster (Abell 426) is a nearby massive galaxy cluster that spans several degrees. We combined SRG/eROSITA, XMM-Newton, and Chandra data to get a complete coverage of this cluster in X-rays up to $R_{\rm 200c}$ and beyond, although at the largest radii, spatial non-uniformities of the X-ray sky background and foreground dominate. While the Perseus central part represents a canonical cool-core structure with clear signs of AGN Feedback, the outskirts, in turn, serve as a convincing example of a merger-perturbed system. X-ray data suggest that IC310 is the main galaxy of a subcluster that merges with Perseus over the past $\sim 4\,{\rm Gyr}$. Overall, this configuration resembles the merger between the Coma cluster and the NGC4839 group. It is statistically more likely to find a merging group near the apocenter of its orbit. Therefore, it is not surprising that IC310 in Perseus has a relatively small velocity relative to the main cluster, similarly to NGC4839 in Coma. Perseus also hosts a high-velocity RADIO GALAXy, NGC1265 (line-of-sight velocity is almost twice the virial velocity of the main cluster), which is known for its spectacular radio tail. Unless this galaxy has been accelerated by a time-variable potential associated with the merger, it has to move almost along the line of sight through the entire cluster, which would be a rare, but not a truly exceptional configuration. Both galaxies, IC310 and NGC1265, have remarkable radio tails with sharp bends that are reminiscent of a "snake biting its tail". We speculate that these curious shapes are natural consequences of their (different) orbits in Perseus. For IC310, the proximity to the apocenter and the reversal of its radial velocity might play a role. For NGC1265, the nearly line-of-sight motion coupled with the gas motions in the merging system might be important.

[abstract 9 / 46] Yes (score: 4)
arXiv:2511.22319 [pdf, ps, other]

Title: The life of central RADIO GALAXies in clusters: AGN-ICM studies of eRASS1 clusters in the ASKAP fields

Authors: Angie Veronica, Thomas H. Reiprich, Florian Pacaud, Marcus Brüggen, Bärbel Koribalski, Thomas Pasini, Tessa Vernstrom, Stefan W. Duchesne, Kathrin Böckmann, Jeremy S. Sanders, Y. Emre Bahar, Fabian Balzer, Lachlan J. Barnes, Esra Bulbul, Nicolas Clerc, Jessica E. M. Craig, Johan Comparat, Simon Dannhauer, Jakob Dietl, Klaus Dolag, Vittorio Ghirardini, Sebastian Grandis, Duy Hoang, Andrew M. Hopkins, Zsofi Igo, Matthias Kluge, Ang Liu, Konstantinos Migkas, Vanessa A. Moss, Miriam E. Ramos-Ceja, Chris Riseley, Lawrence Rudnick, Mara Salvato, Stanislav Shabala, Riccardo Seppi, Jacco van Loon, Tayyaba Zafar, Xiaoyuan Zhang,

Comments: Accepted for publication in PASA on 25-Nov-2025: 22 pages, 7 figures (main text), 6 figures (appendix)

Subjects: astro-ph.CO astro-ph.GA

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

The mechanical feedback from the central AGNs can be crucial for balancing the radiative cooling of the intracluster medium at the cluster centre. We aim to understand the relationship between the power of AGN feedback and the cooling of gas in the centres of galaxy clusters by correlating the radio properties of the brightest cluster galaxies (BCGs) with the X-ray properties of their host clusters. We used catalogues from the first SRG/eROSITA All-Sky Survey (eRASS1) along with ASKAP radio data. In total, we identified 134 radio sources associated with BCGs of the 151 eRASS1 clusters located in the PS1, PS2, and SWAG-X ASKAP fields. Non-detections were treated as upper limits. We correlated BCG radio luminosity, largest linear size (LLS), and BCG offset with the integrated X-ray luminosity of their host clusters. To characterise cool cores (CCs) and non-cool cores (NCCs), we used the concentration parameter $c_{R_{500}}$ and combined it with the BCG offset to assess cluster dynamical state. We analysed the correlation between radio mechanical power and X-ray luminosity within the CC subsample. We observe a potential positive trend between LLS and BCG offset, suggesting an environmental effect on radio-source morphology. We find a weak trend where more luminous central RADIO GALAXies are found in clusters with higher X-ray luminosity. Within the CC subsample, there is a positive but highly scattered relationship between the mechanical luminosity of AGN JETs and the X-ray cooling luminosity. This finding is supported by bootstrap resampling and flux-flux analyses. The correlation indicates that AGN feedback is ineffective in high-luminosity (high-mass) clusters. At a cooling luminosity of $L_{\mathrm{X},~rAGN feedback appears to contribute only about 13%-22% of the energy needed to offset the radiative losses in the ICM.

[abstract 10 / 46] Yes (score: 4)
arXiv:2601.16977 [pdf, ps, other]

Title: ReveaLLAGN 1: JWST Emission-Line Spectra Reveal Low-Luminosity AGN with UV-Deficient SEDs and Warm Molecular Gas

Authors: Kameron Goold, Anil Seth, Mallory Molina, David Ohlson, Nischal Acharya, Torsten Böker, Antoine Dumont, Michael Eracleous, Anja Feldmeier-Krause, Juan Antonio Fernández-Ontiveros, Elena Gallo, Andy D. Goulding, Kayhan Gültekin, Luis C. Ho, Nadine Neumayer, Richard M. Plotkin, Almudena Prieto, Jessie C. Runnoe, Shobita Satyapal, Glenn van de Ven, Jonelle L. Walsh, Feng Yuan, Nora Lützgendorf,

Comments: Submitted to The Astrophysical Journal; under review after addressing referee comments. 25 pages, 10 figures

Subjects: astro-ph.GA

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

We present near- and mid-infrared spectra of eight Low-Luminosity Active Galactic Nuclei (LLAGN), spanning nearly four orders of magnitude in BLACK HOLE mass and Eddington ratio, obtained with JWST/NIRSpec and MIRI as part of the ReveaLLAGN program along with identical archival data of Cen A. The high spatial resolution of JWST cleanly separates AGN emission from host-galaxy contamination, enabling detections of high-ionization potential lines more than an order of magnitude fainter than previously measured. Emission-line diagnostics reveal a transition at log($L_{bol}/L_{Edd}$) ~ -3.5, where the spectral energy distribution becomes increasingly deficient in ultraviolet photons. We find that rotational H$_2$ excitation temperatures are elevated (~500 K higher) compared to both higher-luminosity AGN and star-forming galaxies, while the H$_2$(0-0)S(3)/PAH$_{11.3 μm}$ ratios are consistent with those observed in the AGN population. We discuss the possible roles of outflows, JETs, and X-ray dominated regions in shaping the interstellar medium surrounding LLAGN. Silicate emission at ~10 $μ$m, localized to the nuclear region, is detected in most ReveaLLAGN targets. This dataset offers the first comprehensive JWST-based characterization of infrared emission lines in the nuclear regions of LLAGN.

[abstract 11 / 46] Yes (score: 4)
arXiv:2601.18865 [pdf, ps, other]

Title: Induced Scattering of Fast Radio Bursts in Magnetar Magnetospheres

Authors: Rei Nishiura, Shoma F. Kamijima, Kunihito Ioka,

Comments: 8 pages, 4 figures. Comments welcome!

Subjects: astro-ph.HE physics.plasm-ph

Created: 2026-01-26; Updated: 2026-01-28; Datestamp: 2026-01-28

We investigate induced Compton/Brillouin scattering of electroMAGNETic waves in MAGNETized electron and positron pair plasma by verifying kinetic theory with Particle-in-Cell simulations. Applying this to fast radio bursts (FRBs) in MAGNETar MAGNETospheres, we find that the scattering--although suppressed by the MAGNETic field--inevitably enters the linear growth stage. The subsequent evolution bifurcates: full scattering occurs when the density exceeds a critical value, whereas below it the scattering saturates and the FRB can escape. This eases the tension with observations of compact emission regions and may explain the observed diversity, including the presence or absence of FRBs associated with X-ray bursts.

[abstract 12 / 46] Yes (score: 4)
arXiv:2601.19609 [pdf, ps, other]

Title: A Catalog of 971 FR-I Radio Galaxies from the FIRST Survey via Hybrid Deep Learning and Ridgeline Flux Density Distribution Analysis

Authors: Baoqiang Lao, Xiaolong Yang, Wenjun Xiao, Tapan K. Sasmal, Yanli Zou, Didi Liu, Zhixian Liao, Ye Lu, Rushuang Zhao,

Comments: 18 pages, 10 figures, 2 tables; accepted for publication in ApJS

Subjects: astro-ph.GA

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

We present a catalog of 971 FR-I RADIO GALAXies (FR-Is) identified from the Very Large Array Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. The identifications were made using a hybrid method that combines deep learning with ridgeline flux density distribution analysis. Among these sources, 845 are new discoveries. The catalog comprises sources characterized by edge-darkened double JETs, an absence of significant bent morphology, and angular sizes ranging from 23 to 159 arcseconds. Optical and/or infrared counterparts have been identified for 813 FR-Is. Among these, the host galaxies are predominantly (88.1\%) red galaxies, with the remainder (11.9\%) being blue galaxies; notably, most blue galaxies exhibit high radio power. The FR-I sample spans a radio power range of $1.20 \times 10^{21} \leq P_{\rm 1400} \leq 3.55 \times 10^{27} \, {\rm W\,Hz}^{-1}$ at 1400 MHz and reaches redshifts up to $z = 2.307$. The host galaxies have $r$-band absolute magnitudes in the range $-24 \lesssim M_r \lesssim -20$ mag. For the 512 FR-Is with estimates, the BLACK HOLE masses fall within $10^7 \lesssim M_{\rm BH} \lesssim 7.94 \times 10^9 \, M_{\odot}$. Based on optical emission-line ratios and mid-infrared colors, spectroscopic classification shows that 571 hosts are low-excitation RADIO GALAXies (LERGs) and 59 are high-excitation RADIO GALAXies (HERGs).

[abstract 13 / 46] Yes (score: 4)
arXiv:2601.19616 [pdf, ps, other]

Title: On the rarity of rocket-driven Penrose extraction in Kerr spacetime

Authors: An T. Le,

Comments: 17 pages, 6 figures, 8 tables, submitted to Physical Review D

Subjects: astro-ph.HE cs.SY eess.SY gr-qc physics.comp-ph

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

We present a Monte Carlo study of energy extraction from rotating (Kerr) BLACK HOLEs via the Penrose process using rocket propulsion. Through over 250,000 trajectory simulations, we establish sharp constraints on when Penrose extraction with escape to infinity succeeds. The mechanism requires that exhaust ejected inside the ergosphere carries negative Killing energy, which is kinematically accessible only via ultra-RELATIVISTIC ejection deep within the ergosphere. We find that successful extraction with escape is statistically rare ($\sim$1% in broad parameter scans) and is governed by strict thresholds: it requires high BLACK HOLE spin (empirically $a/M \gtrsim 0.89$) and ultra-RELATIVISTIC exhaust velocity (onset at $v_e \approx 0.91c$). When conditions are highly tuned to a specific "sweet spot," success rates can reach 88.5%, representing a narrow extraction window rather than generic behavior. Furthermore, single-impulse thrust at periapsis achieves significantly higher cumulative efficiency ($η_{\rm cum} \approx 19\%$) compared to continuous thrust ($\sim$2--4%) due to path-averaging penalties. These constraints quantify the extreme fine-tuning required for material-based Penrose extraction, consistent with the astrophysical dominance of electroMAGNETic mechanisms. Simulation code is available at https://github.com/anindex/penrose_process.

[abstract 14 / 46] (score: 3)
arXiv:2503.04727 [pdf, ps, other]

Title: A sudden dramatic change and recovery of MAGNETo-environment of a repeating fast radio burst

Authors: Y. Li, S. B. Zhang, Y. P. Yang, C. W. Tsai, X. Yang, C. J. Law, R. Anna-Thomas, X. L. Chen, K. J. Lee, Z. F. Tang, D. Xiao, H. Xu, X. L. Yang, G. Chen, Y. Feng, D. Z. Li, R. Mckinven, J. R. Niu, K. Shin, B. J. Wang, C. F. Zhang, Y. K. Zhang, D. J. Zhou, Y. H. Zhu, Z. G. Dai, C. M. Chang, J. J. Geng, J. L. Han, L. Hu, D. Li, R. Luo, C. H. Niu, D. D. Shi, T. R. Sun, X. F. Wu, W. W. Zhu, P. Jiang, B. Zhang,

Comments: 95 pages, 14 figures. Published in Science, 15 January 2026. Authors' version

Subjects: astro-ph.HE astro-ph.GA astro-ph.SR

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Fast radio bursts (FRBs) are millisecond-duration radio bursts with unidentified extra-galactic origin. Some FRBs exhibit mild MAGNETo-ionic environmental variations, possibly attributed to plasma turbulence or binary configuration. We report an abrupt MAGNETo-ionic variation of FRB 20220529, a repeating FRB from a disk galaxy at redshift $0.1839 \pm 0.0001$. Initially, the Faraday rotation measure (RM) had a median of $17~{\rm rad~m^{-2}}$ and a scatter of $101~{\rm rad~m^{-2}}$ over 17 months. In December 2023, it jumped to $1977 \pm 84~{\rm rad~m^{-2}}$, and returned to typical values within two weeks. This drastic RM variation suggests that a dense MAGNETized clump enters and exits the line of sight in week timescales. One plausible scenario invokes a coronal mass ejection from a companion star, while other scenarios invoking extreme turbulence or binary orbital motion are also possible.

[abstract 15 / 46] (score: 3)
arXiv:2505.04625 [pdf, ps, other]

Title: First Observations of Solar Halo Gamma Rays Over a Full Solar Cycle

Authors: Tim Linden, Jung-Tsung Li, Bei Zhou, Isabelle John, Milena Crnogorčević, Annika H. G. Peter, John F. Beacom,

Comments: 17 pages, 11 figures. Appendix adds 3 pages and 3 figures. Matches journal version

Subjects: astro-ph.HE astro-ph.SR hep-ph

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

We analyze 15 years of FERMI-LAT data and produce a detailed model of the Sun's inverse-Compton scattering emission (solar halo), which is powered by interactions between ambient cosmic-ray electrons and positrons with sunlight. By developing a novel analysis method to analyze moving sources, we robustly detect the solar halo at energies between 31.6 MeV and 100 GeV, and angular extensions up to 45$^\circ$ from the Sun, providing new insight into spatial regions where there are no direct measurements of the galactic cosmic-ray flux. The large statistical significance of our signal allows us to sub-divide the data and provide the first $γ$-ray probes into the time-variation and azimuthal asymmetry of the solar modulation potential, finding time-dependent changes in solar modulation both parallel and perpendicular to the ecliptic plane. Our results are consistent with (but with independent uncertainties from) local cosmic-ray measurements, unlocking new probes into both astrophysical and beyond-standard-model processes near the solar surface.

[abstract 16 / 46] (score: 3)
arXiv:2506.16544 [pdf, ps, other]

Title: Black holes as telescopes: Discovering supermassive binaries through quasi-periodic lensed starlight

Authors: Hanxi Wang, Miguel Zumalacárregui, Bence Kocsis,

Comments: 26 pages, 10 figures, accepted for publication in PRL

Subjects: astro-ph.GA astro-ph.CO gr-qc

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Supermassive BLACK HOLE (SMBH) binary systems are unavoidable outcomes of galaxy mergers. Their dynamics encode information about their formation and growth, the composition of their host galactic nuclei, the evolution of galaxies, and the nature of gravity. Many SMBH binaries with separations pc-kpc have been found, but closer (sub-parsec) binaries remain to be confirmed. Identifying these systems may elucidate how binaries evolve past the ``final parsec'' until gravitational radiation drives them to coalescence. Here we show that SMBH binaries in non-ACTIVE GALACTIC NUCLEi can be identified and characterized by the gravitational lensing of individual bright stars, located behind them in the host galaxy. The rotation of `caustics' -- regions where sources are hugely magnified due to the SMBH binary's orbit and inspiral -- leads to Quasi-Periodic Lensing of Starlight (QPLS). The extreme lensing magnification of individual bright stars produces a significant variation in the host galaxies' luminosity; their lightcurve traces the orbit of the SMBH binary and its evolution. QPLS probes the population of sources observable by pulsar timing arrays and space detectors (LISA, TianQin), offering advance warning triggers for merging SMBHs for coincident or follow-up GW detections. SMBH population models predict $1-50\; [190-5,000] \left({n_\star}/{\rm pc}^{-3}\right)$ QPLS binaries with period less than $10\; [40]$ yr with comparable masses and $z<0.3$, where $n_\star$ is the stellar number density. Additionally, stellar and orbital motion will lead to frequent instances of single/double flares caused by SMBHBs with longer periods. This novel signature can be searched for in a wealth of existing and upcoming time-domain photometric data: identifying quasi-periodic variability in galactic lightcurves will reveal an ensemble of binary systems and illuminate outstanding questions around them.

[abstract 17 / 46] (score: 3)
arXiv:2508.21100 [pdf, ps, other]

Title: The Influence of Uniform Magnetic Fields on Strong Field Gravitational Lensing by Kerr Black Holes

Authors: Amnish Vachher, Arun Kumar, Sushant G. Ghosh,

Comments: 17 pages, 7 figures, 5 tables, Matched with the published version

Subjects: gr-qc

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

We investigate strong gravitational lensing using MAGNETized Kerr BLACK HOLEs (MKBHs), which are accurate Kerr-Bertotti-Robinson solutions for Kerr BLACK HOLEs in a uniform MAGNETic field with additional MAGNETic field strength $B$ apart from mass $M$ and spin $a$. Unlike previous MAGNETized spacetimes, the MKBH geometry is Petrov type D, devoid of conical singularities, allowing photons to reach asymptotic infinity and making the concept astrophysically feasible. We use the strong deflection limit formalism to calculate the photon sphere radius, critical impact parameter, deflection angle, and lensing observables including the image position $θ_\infty$, angular separation $s$ and relative magnification $r_{\text{mag}}$, as well as their relationships with the parameters $a$ and $B$. Our results reveal that the RELATIVISTIC image's photon sphere and angular size increase with $B$, whereas lensing observables deviate significantly from the Kerr scenario. For M87*, with $a=0.9$, the angular position of RELATIVISTIC images increases from $10.8~μ$as (Kerr) to $12.02~μ$as, and the time delay between the first two images increases from $158.5$ h to $176$ h at $B=0.4$. Similarly, for Sgr A*, the image position increases from $14.4~μ$as to $16~μ$as, with time delays enhanced by approximately $0.7$ minutes. The relative magnification $r_{\text{mag}}$ grows with $B$ and deviates by $0.53$ from Kerr BLACK HOLEs at $B=0.4$. Our findings highlight strong gravitational lensing as a powerful tool to probe the presence of MAGNETic fields around astrophysical BLACK HOLEs, and in particular, we demonstrate that the MKBH spacetime enables constraints on the parameters $a$ and $B$.

[abstract 18 / 46] (score: 3)
arXiv:2509.11631 [pdf, ps, other]

Title: Hurst index of GAMMA-RAY BURST light curves and its statistical study

Authors: Ruo-Yu Guan, Fei-Fei Wang, Yuan-Chuan Zou,

Comments: 34 pages, 14 figures, accepted by Journal of High Energy Astrophysics (JHEAP)

Subjects: astro-ph.HE

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Gamma-ray bursts (GRBs) rank among the most powerful astrophysical phenomena, characterized by complex and highly variable prompt emission light curves that reflect the dynamics of their central engines. In this work, we analyze a sample of 163 long-duration GRBs detected by the Burst and Transient Source Experiment (BATSE), applying detrended fluctuation analysis (DFA) to derive the Hurst index as a quantitative descriptor of temporal correlations in the light curves. We further explore statistical correlations between the Hurst index and 12 other observational parameters through regression and correlation analyses. Our results reveal anti-correlations between the Hurst index and the burst durations ($T_{50}$, $T_{90}$), and moderate positive correlations with peak photon flux proxies ($P_{pk1}$--$P_{pk3}$). By contrast, the standard spectral parameters (including the low-energy index $α$) show no evidence for a linear dependence on the Hurst index in our sample. We do not find a clear monotonic weakening of the correlation strength from 64 ms to 1024 ms peak-flux measures; rather, the correlation coefficients for $P_{pk1}$--$P_{pk3}$ are comparable within uncertainties. The results offer new perspectives on the temporal structure of the GRB emission and its potential link to the underlying physical mechanisms driving these bursts.

[abstract 19 / 46] (score: 3)
arXiv:2601.17416 [pdf, ps, other]

Title: The rest ultraviolet to infrared spectral energy distributions of heavily reddened QUASARs are "V-shaped" and hot-dust poor

Authors: Matthew Stepney, Manda Banerji, Shenli Tang, Matthew J. Temple, Paul C. Hewett,

Comments: 19 pages, 13 figures, Accepted by MNRAS: 23 Jan 2025

Subjects: astro-ph.GA

Created: 2026-01-24; Updated: 2026-01-28; Datestamp: 2026-01-28

We present a rest-ultraviolet to infrared spectral energy distribution (SED) analysis of 63 heavily reddened QUASARs (HRQs) at redshifts z=0.7-2.7 and with dust extinctions E(B-V)=0.4-1.8. Our analysis demonstrates that SEDs with red optical and blue UV continua are very common in HRQs, with more than 82 per cent of the sample showing a UV-excess relative to the reddened QUASAR continuum. We model the SEDs by combining a reddened QUASAR and an unobscured scattered light component, though contributions from a star-forming host galaxy cannot be ruled out. The average scattering fraction is small (0.3 per cent). Higher scattering fractions are ruled out by the (i-K)=2.5 colour-cut used to select HRQs which pre-dates the discovery of the JWST "Little Red Dot" (LRD) population. Hence, LRDs generally have bluer UV continua. Nevertheless, four HRQs satisfy the LRD UV/optical continuum slope selections and are therefore massive, cosmic noon analogues of LRDs. Analysis of the near-infrared SEDs of HRQs reveals a deficit of hot dust relative to blue QUASARs, similar to what is observed in LRDs. This suggests HRQs trace a phase where strong AGN feedback processes eject dust from the inner torus. The UV scattering fraction of HRQs is weakly correlated with the amount of hot dust emission and anti-correlated with the line-of-sight extinction, E(B-V). This is consistent with the hot dust acting as the scattering medium, and the line-of-sight extinction being dominated by dust on interstellar medium scales in the host galaxy.

[abstract 20 / 46] (score: 3)
arXiv:2601.18859 [pdf, ps, other]

Title: Energetic Ceilings of Astrophysical Gravitational-Wave Backgrounds

Authors: Chiara M. F. Mingarelli,

Comments: This is "Paper 1". Paper 2 was uploaded simultaneously. Online plotter here, https://gwbceilings.streamlit.app. Comments welcome

Subjects: astro-ph.HE gr-qc

Created: 2026-01-26; Updated: 2026-01-28; Datestamp: 2026-01-28

Every astrophysical stochastic gravitational wave (GWB) is limited by the amount of rest mass available to be converted into gravitational radiation. Here we derive a population-agnostic scaling law that places an absolute energetic ceiling on stochastic backgrounds across the entire GW frequency spectrum, from nanoHertz to kilohertz. We apply this framework to bound the backgrounds from supermassive BLACK HOLE binaries, intermediate-mass BLACK HOLE captures by supermassive BLACK HOLEs in AGN disks, extreme mass-ratio inspirals, binary neutron stars, Population III remnants, and stellar-mass binary BLACK HOLEs. We find that the energetic ceiling for supermassive BLACK HOLE binaries is $A \leq 1.6^{+0.3}_{-0.3} \times 10^{-15}$ at a reference frequency of $1\,{\rm yr}^{-1}$. This astrophysical GWB ceiling is within $1σ$ with the GWB amplitude reported by NANOGrav, EPTA, and PPTA, implying that the current observed signal is consistent with being powered by a population of ultramassive BLACK HOLEs ($M_\bullet \gtrsim 10^{10}\,M_\odot$). Finally, we demonstrate that the total astrophysical background from all channels combined cannot exceed $Ω_{\rm gw} \sim 10^{-7}$.

[abstract 21 / 46] (score: 3)
arXiv:2601.18986 [pdf, ps, other]

Title: Progenitor of the recoiling super-massive BLACK HOLE RBH-1 identified using HST/JWST imaging

Authors: Tousif Islam, Tejaswi Venumadhav, Digvijay Wadekar,

Comments: 9 pages, 8 figures

Subjects: astro-ph.HE gr-qc

Created: 2026-01-26; Updated: 2026-01-28; Datestamp: 2026-01-28

Using a combination of \textit{Hubble Space Telescope} and \textit{James Webb Space Telescope} imaging, a runaway supermassive BLACK HOLE (RBH-1) was recently identified with an inferred velocity of $954^{+110}_{-126}\,\mathrm{km\,s^{-1}}$, likely ejected from a compact star-forming galaxy (denoted as GX) at $z \approx 0.96$. Assuming the runaway BLACK HOLE was the outcome of the gravitational-wave-driven merger of two BLACK HOLEs, we use its measured runaway velocity together with gravitational-wave recoil predictions from numerical relativity and BLACK HOLE perturbation theory to constrain the mass ratio and spin configuration of the progenitor SMBHs that overcame the final-parsec problem and merged $\sim 70$~Myr ago. We find that the progenitor binary must have been precessing, with a mass ratio $m_1/m_2\lesssim 6$, and that the more massive SMBH must have possessed a high spin (dimensionless spin magnitude $\sim 0.75$) in order to generate a recoil of this magnitude. This has important astrophysical implications as similar SMBH mergers can be an interesting source population for the upcoming LISA mission with signal-to-noise ratios $\gtrsim$ 1000. Furthermore, the progenitor SMBH properties imply that GX was likely formed through a major, gas-rich (``wet'') merger between two galaxies of comparable mass, with a mass ratio $\lesssim 4$.

[abstract 22 / 46] (score: 3)
arXiv:2601.19140 [pdf, ps, other]

Title: Latent characterisation of the complete BATSE gamma ray bursts catalogue using Gaussian mixture of factor analysers and model-estimated overlap-based syncytial clustering

Authors: Fan Dai, Ranjan Maitra,

Comments:

Subjects: astro-ph.HE stat.AP stat.CO stat.ME

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Characterising and distinguishing GAMMA-RAY BURSTs (GRBs) has interested astronomers for many decades. While some authors have found two or three groups of GRBs by analyzing only a few parameters, recent work identified five ellipsoidally-shaped groups upon considering nine parameters $T_{50}, T_{90}, F_1, F_2, F_3, F_4, P_{64}, P_{256}, P_{1024}$. Yet others suggest sub-classes within the two or three groups found earlier. Using a mixture model of Gaussian factor analysers, we analysed 1150 GRBs, that had nine parameters observed, from the current Burst and Transient Source Experiment (BATSE) catalogue, and again established five ellipsoidal-shaped groups to describe the GRBs. These five groups are characterised in terms of their average duration, fluence and spectrum as shorter-faint-hard, long-intermediate-soft, long-intermediate-intermediate, long-bright-intermediate and short-faint-hard. The use of factor analysers in describing individual group densities allows for a more thorough group-wise characterisation of the parameters in terms of a few latent features. However, given the discrepancy with many other existing studies that advocated for two or three groups, we also performed model-estimated overlap-based syncytial clustering (MOBSynC) that successively merges poorer-separated groups. The five ellipsoidal groups merge into three and then into two groups, one with GRBs of low durations and the other having longer duration GRBs. These groups are also characterised in terms of a few latent factors made up of the nine parameters. Our analysis provides context for all three sets of results, and in doing so, details a multi-layered characterisation of the BATSE GRBs, while also explaining the structure in their variability.

[abstract 23 / 46] (score: 3)
arXiv:2601.19291 [pdf, ps, other]

Title: Magnetic Compression of Compact Tori Experiment and Simulation

Authors: Carl Dunlea,

Comments: PhD thesis

Subjects: physics.plasm-ph

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

The MAGNETic compression experiment at General Fusion was a repetitive non-destructive test to study plasma physics applicable to MAGNETic target fusion compression. A compact torus (CT) is formed with a co-axial gun into a containment region with an hour-glass shaped inner flux conserver, and an insulating outer wall. External coil currents keep the CT off the outer wall (radial levitation) and then rapidly compress it inwards. The optimal external coil configuration greatly improved both the levitated CT lifetime and the recurrence rate of shots with good compressional flux conservation. As confirmed by spectrometer data, the improved levitation field profile reduced plasma impurity levels by suppressing the interaction between plasma and the insulating outer wall during the formation process. Significant increases in MAGNETic field, electron density, and ion temperature were routinely observed at MAGNETic compression in the final external coil configuration tested, despite the prevalence of an instability, thought be an external kink mode, at compression. Matching the decay rate of the levitation currents to that of the CT currents resulted in a reduced level of MHD activity associated with unintentional compression by the levitation field, and a higher probability of long-lived CTs. The DELiTE (Differential Equations on Linear Triangular Elements) framework was developed for spatial discretisation of partial differential equations on an unstructured triangular grid in axisymmetric geometry. The framework is based on discrete differential operators in matrix form, which are derived using linear finite elements and mimic some of the properties of their continuous counterparts. A single-fluid two-temperature MHD model is implemented in this framework.

[abstract 24 / 46] (score: 3)
arXiv:2601.19328 [pdf, ps, other]

Title: STONKS first results: Long-term transients in the XMM-Newton Galactic plane survey

Authors: Robbie Webbe, E. Quintin, N. A. Webb, Gabriele Ponti, Tong Bao, Chandreyee Maitra, Shifra Mandel, Samaresh Mondal,

Comments: 15 pages, 10 figures, Accepted by A&A

Subjects: astro-ph.HE

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

The study of astronomical transients at high energies provides insights into some of the most extreme physical events in the universe; however, carrying out their detection and fast follow-up studies are limited by instrumental constraints. Search for Transient Object in New observations using Known Sources (STONKS) is a near-real-time transient detection system for XMM-Newton offering the capability to detect transients in XMM-Newton observations at fainter fluxes than can be achieved with wide survey instruments. We present the transients detected with the STONKS pipeline found in an XMM-Newton multi-year heritage survey of the Galactic plane to identify and classify highly variable X-ray sources that have recently been reported in this region. We examined the alerts created by the STONKS pipeline from over 200 XMM observations of the Galactic plane, screening for instrumental effects. The 78 alerts associated with 70 real astrophysical sources were then subjected to further temporal and spectral analysis. From the 70 sources we identified, we were able to classify 32 with a high degree of confidence, including 7 X-ray binaries, 1 $γ$-Cas analogue, and 1 MAGNETar candidate. Of the 70 sources, 23 were detected for the first time in X-rays. This systematic analysis of publicly available data has shown the value and potential of STONKS in the application to XMM-Newton observations. It will enable the community to detect transient and highly variable sources at fainter fluxes than with any other X-ray transient detection systems.

[abstract 25 / 46] (score: 3)
arXiv:2601.19386 [pdf, ps, other]

Title: Constraints on Primordial Black Holes from Galactic Diffuse Synchrotron Emissions

Authors: Chen-Wei Du, Yu-Feng Zhou,

Comments: 51 pages, 17 figures and 2 tables

Subjects: hep-ph astro-ph.HE

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

We investigate the possibility of constraining primordial BLACK HOLEs (PBHs) with masses $M_\mathrm{PBH}\gtrsim 10^{15}\,\mathrm{g}$ through Galactic diffuse SYNCHROTRON emissions. Due to Hawking radiation, these types of PBHs are expected to be stable sources of cosmic-ray (CR) electrons and positrons with energies below $\mathcal{O}(10\,\mathrm{MeV})$. In many CR propagation models with diffusive re-acceleration characterized by a significant Alfvén velocity $V_a\sim \mathcal{O}(10)\,\mathrm{km/s}$, the energies of the evaporated electrons/positrons can be further enhanced to $\mathcal{O}(100)\,\mathrm{MeV}$ through their scattering with the Galactic random MAGNETic fields. Consequently, the observation of Galactic SYNCHROTRON emissions at frequencies above $\sim 20\,\mathrm{MHz}$ can provide useful constraints on the abundance of PBHs. Using the AMS-02 and Voyager-1 data on the boron-to-carbon nuclei flux ratio, we confirm that a significant Alfvén velocity $V_a \sim 20\,\mathrm{km/s}$ is favored in several benchmark diffusive re-acceleration models. We show that, in this scenario, the observed low-frequency SYNCHROTRON emissions (from 22 MHz to 1.4 GHz) can provide stringent constraints on PBH abundance. The obtained conservative constraints are stronger than those derived from the Voyager-1 all-electron (electron plus positron) data by more than one order of magnitude for $M_\mathrm{PBH}\gtrsim 1\times 10^{16}\,\mathrm{g}$, and also stronger than our previous constraints derived from the AMS-02 positron data for $M_\mathrm{PBH}\gtrsim 2\times 10^{16}\,\mathrm{g}$.

[abstract 26 / 46] (score: 3)
arXiv:2601.19405 [pdf, ps, other]

Title: Numerical simulations of BLACK HOLE-neutron star mergers with equal and near-equal mass ratios

Authors: Ivan Markin, Mattia Bulla, Tim Dietrich,

Comments: 19 pages, 9 figures, to be submitted to PRD

Subjects: astro-ph.HE gr-qc

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

The detection of GW230529_181500 suggested the existence of more symmetric BLACK HOLE-neutron star mergers where the BLACK HOLE mass can be as low as 2.6 times that of the neutron star. Black hole-neutron star binaries with even more symmetric mass ratios are expected to leave behind massive disks capable of driving bright electroMAGNETic transients like kilonovae. Currently, there is only a limited number of numerical-relativity simulations of BLACK HOLE-neutron star mergers in this regime, which are vital for accurate gravitational waveform models and analytical fitting formulas for the remnant properties. Insufficient accuracy of these may lead to misclassification of real events and potentially missed opportunities to locate their electroMAGNETic counterparts. To fill this gap in the parameter space coverage, we perform simulations of BLACK HOLE-neutron star mergers with mass ratios $q \in \{1, 1/2, 1/3\}$. We find the gravitational waveform models do not show good agreement with the numerical waveforms, with dephasing at the level of around 1 rad at the merger. We find that the masses of the dynamical ejecta and disk are in good agreement with the available fitting formulas. The analytical formulas for the remnant BLACK HOLE are in excellent agreement for the BLACK HOLE mass, but are less accurate with the predictions for its spin. Moreover, we analyze the remnant disk structure and dynamics, deriving the rotation law and identifying global trapped $g$-mode density oscillations. We distinguish three types of accretion in the postmerger and find modulation of the accretion rate by the global oscillations of the disk. Finally, we model the kilonova emission these systems would produce and find that most of them are potentially detectable by Vera C. Rubin Observatory within four days after merger, and by DECam within two days after merger if located at a distance of 200 Mpc.

[abstract 27 / 46] (score: 3)
arXiv:2601.19409 [pdf, ps, other]

Title: Dynamical and observational properties of weakly Proca-charged BLACK HOLEs

Authors: Abylaikhan Tlemissov, Arman Tursunov, Jiří Kovář, Zdeněk Stuchlík,

Comments: 16 pages, 8 figures. To appear in EPJC

Subjects: gr-qc astro-ph.HE

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

The simplest approach to include a mass into the electroMAGNETic vector potential is to modify the Einstein-Maxwell action to the Einstein-Proca form. There are currently no exact analytical solutions for this scenario. However, by using perturbation theory, where both the Proca mass and the BLACK HOLE charge are small parameters, it is possible to find an exact analytical solution. In this solution, the metric tensor remains unchanged, but the vector potential deviates from the Coulomb potential. In particular, even if the Proca mass is limited by the value $m_γ<10^{-48}\text{g}$, which is the current experimental upper limit for photon mass, it makes a significant contribution to the dynamical equations. In this paper, we study the motion of neutral and charged particles in the vicinity of a weakly Proca-charged BLACK HOLE, and test the observational implications of the solution of the Einstein-Proca equations for gravitational bending, the BLACK HOLE shadow, and the fit to the orbits of the Galactic center flares observed by the near-infrared GRAVITY instrument. We find that only extremely cold photons, which are likely scattered before reaching a distant observer, could reveal the non-zero photon mass effect through the BLACK HOLE shadow. For the Galactic center flare analysis we obtained constraints on the dimensionless Proca parameter to $μ\leq 0.125$ for the electric interaction parameter in the range $-1.1 < \mathrm{Q} < 0.5$, which can be potentially tested by future GRAVITY flare astrometry. Since the Proca parameter is coupled to the BLACK HOLE mass, the effect of the Proca charge becomes more pronounced for supermassive BLACK HOLEs compared to stellar-mass objects. Our perturbative treatment remains valid essentially up to the horizon, with divergences appearing only in the immediate near-horizon region, where a fully non-perturbative analysis would be required.

[abstract 28 / 46] (score: 3)
arXiv:2601.19412 [pdf, ps, other]

Title: A thin disk and a nearly universal accretion rate in luminous QUASARs

Authors: G. Risaliti, B. Trefoloni, M. Salvati,

Comments: 9 Pages, 8 Figures. Submitted to Astronomy & Astrophysics. Comments are very welcome

Subjects: astro-ph.CO

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Quasars accretion models predict a broad range of optical and ultraviolet properties that depend primarily on BLACK HOLE mass and accretion rate. Yet, most optically selected luminous QUASARs display strikingly similar continuum spectra. We show that this uniformity can be explained by a nearly constant luminosity to mass (Eddington) ratio, L_EDD and by thermal emission from a standard, optically thick, geometrically thin accretion disc. A standard disk with an Eddington ratio L_EDD=0.1 reproduces both the BLACK HOLE mass/luminosity distribution of Sloan Digital Sky Survey (SDSS) QUASARs and their principal continuum properties. In this framework, the spectral energy distribution peaks beyond the observable ultraviolet range for nearly all sources. We show that the few QUASARs, expected to be cold enough to shift the peak into the observable region, indeed show this behaviour. This scenario is further supported by an analysis of the relation between the luminosity of the main broad emission lines and the continuum luminosity (i.e. the Baldwin effect). We find that 1) the observed slopes of the line to continuum relations match the expectations from the standard disk model, if we assume that the line emission is a good proxy of the ionizing luminosity; 2) the dispersions of the line-continuum luminosity relations are very small (as small as 0.13 dex), suggesting that the physics of the disk-broad line region system is dominated by only one parameter (the BLACK HOLE mass) with a nearly constant Eddington ratio. Finally, we notice that our hypothesis of constant L_EDD=0.1 provides a BLACK HOLE mass estimate (based on the observed luminosity) with a smaller error than the virial estimate.

[abstract 29 / 46] (score: 2)
arXiv:2503.09773 [pdf, ps, other]

Title: Constraining the neutron star-BLACK HOLE merger rate

Authors: Ian Harry, Charlie Hoy,

Comments: 8 pages, 2 figures. Supplementary Material available at http://link.aps.org/supplemental/10.1103/cqqn-gl4y. Matches published version

Subjects: hep-ex astro-ph.CO astro-ph.HE gr-qc

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Current template-based gravitational-wave searches for compact binary mergers neglect the general RELATIVISTIC phenomenon of spin-induced orbital precession. Owing to their asymmetric masses, gravitational-waves from neutron star-BLACK HOLE (NSBH) binaries are prime candidates for displaying strong imprints of spin-precession. Current searches may therefore miss a significant fraction of the astrophysical population, and the detected NSBH population may be significantly suppressed or biased. Here we report the most sensitive search for NSBH binaries to date by including spin-precession for the first time. We analyze data from the entirety of the third LIGO--Virgo--KAGRA gravitational-wave observing run and show that when accounting for spin-precession, our search is up to 100% more sensitive than the search techniques currently adopted by the LIGO--Virgo--KAGRA collaboration (for systems with strong precessional effects). This allows us to more tightly constrain the rate of NSBH mergers in the local Universe. When focusing on a potentially precessing subpopulation of NSBH mergers, the lack of observed candidates allows us to place an upper limit on the merger rate of $R_{90} = 79\, \mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$ with 90% confidence. We then show that if there is no preferred direction of component spin, the overall rate of NSBH mergers is on average 16% smaller than previously believed. Finally, we report four new subthreshold NSBH candidates, all with strong imprints of spin precession, but note that these are most likely to be of terrestrial origin.

[abstract 30 / 46] (score: 2)
arXiv:2507.05596 [pdf, ps, other]

Title: Investigating the transverse-momentum- and pseudorapidity-dependent flow vector decorrelation in p--Pb collisions with a Multi-Phase Transport model

Authors: Siyu Tang, Zuman Zhang, Chao Zhang, Liang Zheng, Renzhuo Wan,

Comments: accepted by Chinese Physics C

Subjects: hep-ph

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

The event-by-event fluctuations in the initial energy density of the nuclear collisions lead to the decorrelation of second order flow vector, as known as its transverse-momentum ($p_{\mathrm{T}}$) and pseudorapidity ($η$) dependence as observed in high-energy heavy-ion collisions. Existing measurements at the CERN Large Hadron Collider shown that these decorrelations are also observed in small collision systems. In this work, a systematic study of the transverse-momentum- and pseudorapidity-dependent flow vector decorrelation is performed in p--Pb collisions at the 5.02 TeV with A Multi-Phase Transport (AMPT) model using different tunings of the initial conditions, partonic and hadronic interactions. It is found that the string-melting version of the AMPT model provides a reasonable description of the measured flow vector decorrelation as a function of $p_{\mathrm{T}}$ and $η$. We demonstrate that the hadronic scatterings do not have significant impact on decorrelation in p--Pb collisions for different centrality selections, while both initial conditions and partonic interactions influence the magnitude of the decorrelations. In addition, we found that the subtraction of the nonflow, especially the long-range JET correlation, is crucial for the accurate extraction of the flow vector decorrelation in small collision systems. The comparison of data and model presented in this paper provide further insights in understanding the fluctuations of the flow vector with $p_{\mathrm{T}}$ and $η$ in small collision systems and has referential value for future measurements.

[abstract 31 / 46] (score: 2)
arXiv:2508.13296 [pdf, ps, other]

Title: DIPLODOCUS I: Framework for the evaluation of RELATIVISTIC transport equations with continuous forcing and discrete particle interactions

Authors: Christopher N. Everett, Garret Cotter,

Comments: 16 pages, 7 figures. Published in the Open Journal of Astrophysics

Subjects: astro-ph.HE

Created: 2026-01-26; Updated: 2026-01-28; Datestamp: 2026-01-28

DIPLODOCUS (Distribution-In-PLateaux methODOlogy for the CompUtation of transport equationS) is a novel framework being developed for the mesoscopic modelling of astrophysical systems via the transport of particle distribution functions through the seven dimensions of phase space, including continuous forces and discrete interactions between particles. This first paper in a series provides an overview of the analytical framework behind the model, consisting of an integral formulation of the RELATIVISTIC transport equations (Boltzmann equations) and a discretisation procedure for the particle distribution function (Distribution-In-Plateaux). The latter allows for the evaluation of anisotropic interactions, and generates a conservative numerical scheme for a distribution function's transport through phase space.

[abstract 32 / 46] (score: 2)
arXiv:2508.15862 [pdf, ps, other]

Title: Parameter estimation of Kerr-Bertotti-Robinson BLACK HOLEs using their shadows

Authors: Heena Ali, Sushant G. Ghosh,

Comments: 18 pages, 8 figures, 2 tables, matched with the published version

Subjects: gr-qc

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

We investigate the shadow of Kerr-Bertotti-Robinson BLACK HOLEs (KBRBHs), which have a deviation parameter $B$ that captures the effect of an external MAGNETic field on the spacetime geometry. These spacetimes of Petrov type $D$ are asymptotically non-flat. We utilise the separability of the Hamilton-Jacobi equation to generate null geodesics and examine the crucial impact parameters for unstable photon orbits that define the BLACK HOLE shadow. We carefully investigate how the MAGNETic field strength $B$ and spin parameter $a$ influence BLACK HOLE shadows, discovering that increasing $B$ increases the shadow size while also introducing additional distortions, especially at high spins. We calculate the shadow observables, viz., area $A$ and oblateness $D$ and create contour plots in the parameter space $(a, B)$ to facilitate parameter estimation. We also investigate the dependence of the shadow on the observer's position, specifically by altering the radial coordinate $r_O$ and the inclination angle $θ$. For far viewers, the shadow approaches its asymptotic shape, but finite-distance observers perceive substantial deviations. The energy emission rate analysis reveals that the MAGNETic field parameter $B$ modifies the Hawking radiation spectrum, with increasing $B$ suppressing emission via backreaction, which lowers the Hawking temperature. Our findings confirm that KBRBH shadows encode imprints of MAGNETic deviations, thereby offering a potential avenue to distinguish Kerr from non-Kerr spacetimes and to probe MAGNETic effects in the strong-gravity regime.

[abstract 33 / 46] (score: 2)
arXiv:2512.17204 [pdf, ps, other]

Title: A Search for Binary Black Hole Mergers in LIGO O1-O3 Data with Convolutional Neural Networks

Authors: Ethan Silver, Plamen Krastev, Edo Berger,

Comments:

Subjects: gr-qc astro-ph.HE astro-ph.IM

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Since the first detection of gravitational waves in 2015 by LIGO from the binary BLACK HOLE merger GW150914, gravitational-wave astronomy has developed significantly, with over 200 compact binary merger events cataloged. The use of neural networks has the potential to significantly speed up the detection, classification, and especially parameter estimation for gravitational wave events, compared to current techniques, quite important for electroMAGNETic follow-up of events. In this work, we present a machine learning pipeline using neural networks to detect gravitational wave events. We generate training data using real LIGO data to train and refine neural networks that can detect binary BLACK HOLE (BBH) mergers, and apply these models to search through LIGO's first three observing runs. We detect 57 out of the 75 total cataloged BBH events with two detectors of data in O1, O2, and O3, with 57 false positives that can mostly be ruled out with parameter inference and human inspection. Finally, we extensively test this pipeline on time-shifted data to characterize its False Alarm Rate (FAR). These results are an important step in developing machine learning-based GW searches, enabling low-latency detection and multi-messenger astronomy.

[abstract 34 / 46] (score: 2)
arXiv:2512.17214 [pdf, ps, other]

Title: Pulsed radio emission from a Central Compact Object

Authors: Lei Zhang, Alessandro Ridolfi, Di Li, Erbil Gugercinoglu, Fernando Camilo, Wynn C. G. Ho, Matthew Bailes, Ping Zhou, Craig O. Heinke, Marcus E. Lower,

Comments:

Subjects: astro-ph.HE

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

The high MAGNETic fields and rapid spins of young pulsars associated with SUPERNOVA remnants, such as the Crab and the Vela, established the standard pulsar model in which massive stellar explosions produce rapidly rotating, radio-luminous neutron stars. Central Compact Objects (CCOs), identified in X-rays at the centers of other remnants, challenged this view, as decades of searches yielded no radio detections. Here we show that the prototypical young CCO 1E 1207.4-5209 is in fact a faint radio pulsar rotating at the 0.4s X-ray period. Analysis of its POLARIZATION indicates that the radio beam intersects our line of sight near the MAGNETic pole, affirming its radio faintness' being intrinsic. Once its SUPERNOVA remnant dissipates, this source would be misidentified as an apparently gigayear-old pulsar. The CCO's low radio flux density may explain why many SUPERNOVA remnants lack detectable radio pulsars and suggests a hidden population of young, slowly rotating neutron stars.

[abstract 35 / 46] (score: 2)
arXiv:2601.18864 [pdf, ps, other]

Title: Inside the cocoon: a comprehensive explanation of the spectra of Little Red Dots

Authors: A. Sneppen, D. Watson, J. H. Matthews, G. Nikopoulos, N. Allen, G. Brammer, R. Damgaard, K. E. Heintz, C. Knigge, K. S. Long, V. Rusakov, S. A. Sim, J. Witstok,

Comments: 40 pages, 22 figures, 2 tables

Subjects: astro-ph.GA astro-ph.HE

Created: 2026-01-26; Updated: 2026-01-28; Datestamp: 2026-01-28

JWST has revealed a population of compact galaxies in the early Universe with broad emission lines and strong Balmer breaks; among them the so-called ''little red dots'' (LRDs). Their nature remains uncertain with hypotheses including exotic phenomena. We assemble a sample of LRD-like objects at $z>3$ and use self-consistent radiative-transfer calculations to show that a supermassive BLACK HOLE accreting from a dense gas cocoon accurately reproduces the detailed spectra. We show that the cocoons must be non-spherical, with comparable amounts of inflowing and outflowing material. And we predict correlations between Balmer break strength, Balmer line-absorption and scattering line width, which we confirm in our observed sample. We reproduce all LRD-like properties without requiring star-like atmospheres and we determine the typical BLACK HOLE in our sample to be of order a million solar masses, with ionized cocoon masses of tens of solar masses potentially supplied from a much larger cold-gas reservoir.

[abstract 36 / 46] (score: 2)
arXiv:2601.18916 [pdf, ps, other]

Title: Reconsidering the consistent use of precessing, higher order multipole models for gravitational wave analyses

Authors: Charlie Hoy,

Comments: 15 pages, 9 figures, 4 appendices

Subjects: gr-qc astro-ph.HE astro-ph.IM

Created: 2026-01-26; Updated: 2026-01-28; Datestamp: 2026-01-28

The growing number of gravitational-wave (GW) observations allows for constraints to be placed on the underlying population of BLACK HOLEs; current estimates show that BLACK HOLE spins are small, with binaries more likely to have comparable component masses. Since general RELATIVISTIC effects, such as spin-induced orbital precession and higher order multipole moments, are more likely to be observed for asymmetric binary systems, a direct measurement remains unlikely. Nevertheless, we continue to consistently probe these effects by performing Bayesian inference with our most accurate and computationally expensive models. As the number of GW detections increases, it may soon become infeasible to consistently use these models for analyses. In this paper, we provide a selection criterion that determines when less accurate and computationally cheaper models can be used without giving biased estimates for the population properties of BLACK HOLEs in the Universe. We show that when using our selection criterion, comparable estimates can be obtained for the underlying mass and spin distribution of BLACK HOLEs for a simulated "worst-case" scenario population, while reducing the overall cost of performing Bayesian inference on our population by $\sim 20\%$. We anticipate a reduction of up to $78\%$ in the overall cost for an astrophysically motivated population, since there are fewer events with observable spin-precession and higher order multipole power.

[abstract 37 / 46] (score: 2)
arXiv:2601.18926 [pdf, ps, other]

Title: Multiwavelength Analysis of Six Luminous, Fast Blue Optical Transients

Authors: Cassie Sevilla, Anna Y. Q. Ho, Nayana A. J., Steve Schulze, Daniel A. Perley, Michael Bremer, Igor Andreoni, Ivan Altunin, Thomas G. Brink, Poonam Chandra, Ping Chen, Ashley A. Chrimes, Michael W. Coughlin, Kaustav K. Das, Andrew Drake, Alexei V. Filippenko, Christoffer Fremling, James Freeburn, Avishay Gal Yam, Mary Gerhart, Matthew J. Graham, George Helou, K-Ryan Hinds, Natalya Johnson, Mansi M. Kasliwal, Harsh Kumar, Russ R. Laher, Natalie LeBaron, Maggie L. Li, Chang Liu, Ben Margalit, Yu-Jing Qin, Nabeel Rehemtulla, Sophia Risin, Sam Rose, Rupak Roy, Ben Rusholme, Genevieve Schroeder, Jesper Sollerman, Kailai Wang, Jacob L. Wise, Yi Yang, Yuhan Yao, WeiKang Zheng,

Comments: 42 pages, 12 figures

Subjects: astro-ph.HE astro-ph.GA

Created: 2026-01-26; Updated: 2026-01-28; Datestamp: 2026-01-28

We present multiwavelength observations and analysis of six luminous fast blue optical transients (LFBOTs) discovered in Zwicky Transient Facility (ZTF) survey data. We identified these LFBOTs from their fast light-curve evolution ($t_{1/2}\leq 12 $d), blue colors at peak brightness ($g-r\leq-0.5 $mag), a visible host galaxy, high optical luminosity ($M_g<-20$), and an X-ray or radio detection. With the exception of AT2024aehp (ZTF24abygbss), these transients exhibit peaks in their $10\,$GHz radio light curves at $t_{\text{rest}} \approx 50-100$ d, with peak radio luminosities ranging from $10^{38}-10^{40}$ erg s$^{-1}$. Modeling the radio emission as SYNCHROTRON radiation indicates a fast ($v=0.1-0.3c$) shock in a dense ($n_e\approx10^{3}-10^{4}$ cm$^{-3}$) medium. The X-ray emission varies by $\approx2$ orders of magnitude in luminosity ($10^{42}-10^{44}$ erg s$^{-1}$) at $t_{\text{rest}}\sim20 $d. Analysis of the host-galaxy photometry and spectroscopy for each transient shows that they are predominantly nonnuclear (a few kpc offset) with star-forming host galaxies of stellar masses $10^{9}-10^{11} ,M_\odot$. Unlike all other LFBOTs to date, AT2024aehp exhibited a luminous ($M<-19 $mag) plateau in the optical light curve; spectra during this plateau phase showed a featureless blue continuum. The $6-15$ GHz radio emission of AT2024aehp brightened by over an order of magnitude from $t_{\text{rest}} \approx70 $d to $t_{\mathrm{rest}} \approx130 $d. The mostly consistent radio behavior between optically selected LFBOTs implies a similar circumburst medium, leading us to prefer a progenitor scenario in which mass is lost in a consistent way shortly prior to the terminal event, such as a massive star merging with a compact object.

[abstract 38 / 46] (score: 2)
arXiv:2601.19073 [pdf, ps, other]

Title: Effect of Controlled Magnetic Island Bifurcation on Electron Diffusion

Authors: Jessica Eskew, D. M. Orlov, B. Andrew, E. Bursch, M. Koepke, F. Skiff, M. E. Austin, T. Cote, C. Marini, E. G. Kostadinova,

Comments: 20 pages, 12 figures

Subjects: physics.plasm-ph

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Magnetic islands strongly influence cross-field electron transport in MAGNETized plasmas. In particular, bifurcations of the island topology modify the number and location of O-points, X-points, and separatrix boundaries, thereby altering diffusion pathways. In recent DIII-D experiments, external MAGNETic perturbations were used to rotate and periodically bifurcate the island on the q = 2 surface, causing a switchback between a q = 2/1-dominated structure and a narrower q = 4/2-dominated structure. To investigate how this topological change affects electron transport, we employ the field line tracing code TRIP3D with an implemented collisional operator. Thermal, tracer electrons launched from O-points, X-points, and outside separatrix boundaries reveal distinct diffusion regimes, including classical, subdiffusive, and superdiffusive behavior, depending on both the dominant island mode and launch location. These results suggest that island bifurcation can alter electron diffusion across rational surfaces, with direct implications for particle confinement. While the present work emphasizes diffusion as a general framework, the findings provide insight into the conditions under which electron trapping into an island or stochastization of the island's separatrix can enable additional mechanisms, such as the generation of energetic electrons.

[abstract 39 / 46] (score: 2)
arXiv:2601.19104 [pdf, ps, other]

Title: Convolutional causal learning for aerodynamic flows

Authors: Ryo Koshikawa, Ryo Araki, Qiong Liu, Kai Fukami,

Comments:

Subjects: physics.flu-dyn physics.comp-ph

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

This study considers capturing aerodynamic causality from snapshot data with a time-varying mode decomposition technique referred to as information-theoretic machine learning. The current approach extracts time-dependent informative vortical structures, contributing to the future evolution of the aerodynamic coefficients. The present decomposition is employed with a convolutional neural network, enabling the identification of the spatial continuous mode. In addition, a low-order representation, characterizing the informative vortical structures and their corresponding aerodynamic coefficients, can also be identified by considering autoencoder-based data compression. The present technique is applied to a range of aerodynamic examples, including extreme vortex-gust airfoil interactions, experimentally measured transverse JET-wing interaction, and a turbulent separated wake. For the cases of gust-wing interaction, the time-varying gust effect on the lift response is extracted in an interpretable manner. With the example of a turbulent wake, the relationship between large-scale vortical motion and lift force is identified without any spatial length-scale information. The proposed approach could serve as a foundation for data-driven causal modeling and control for a range of unsteady flows.

[abstract 40 / 46] (score: 2)
arXiv:2601.19254 [pdf, ps, other]

Title: Constraining FRB Microstructure with Polarised Shot Noise

Authors: J. C. F. Balzan, A. Bera, C. W. James, B. Meyers,

Comments: 10 pages, 4 figures, 1 table. Submitted to PASA

Subjects: astro-ph.HE

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

We present FIRES, a polarised shot-noise framework that models fast radio burst (FRB) dynamic spectra as the incoherent superposition of Gaussian microshots. Applied to the CRAFT bursts FRB 20191001A and FRB 20240318A, FIRES reproduces key spectro-polarimetric behaviours: scattering suppresses position-angle (PA) variability on the trailing edge, while the leading edge preferentially retains intrinsic structure when sufficient signal-to-noise is present. We quantify this behaviour using the PA variance ratio $\mathcal{R}_ψ$ and explore the joint plane of measured linear polarisation fraction $Π_L$ versus PA variance to constrain the allowed parameter space of microshot number $N$, intrinsic PA dispersion $σ_ψ$, and intrinsic linear fraction $Π_{L,0}$ at fixed signal-to-noise. For FRB~20191001A, the data are consistent with an extended region spanning $σ_ψ\sim 10^\circ$--$30^\circ$ and $N \sim 5$--$1000$, reflecting degeneracies between intrinsic PA structure, microshot superposition, scattering, finite sampling, and noise. FRB~20240318A occupies a more restricted region, favouring fewer microshots ($N \lesssim 20$) and larger intrinsic PA dispersion ($σ_ψ\sim 15$--$23^\circ$), depending on $Π_{L,0}$, consistent with its observed PA variability. By combining an emission-mechanism-independent framework with minimal assumptions and observational constraints, FIRES provides direct, quantitative constraints on the space of viable FRB microphysical models and demonstrates that microshot superposition offers a natural explanation for the diverse polarimetric behaviours observed in FRBs.

[abstract 41 / 46] (score: 2)
arXiv:2601.19289 [pdf, ps, other]

Title: Continued activity of the 25th cycle: largest in 20 years. Ground-level enhancement and Forbush decrease

Authors: B. Sargsyan, A. Chilingarian,

Comments:

Subjects: physics.ao-ph astro-ph.SR

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

After a very calm 24th solar activity cycle, the 25th cycle has already seen several interesting events. A Ground Level Enhancement GLE77 was observed on 11 November 2025 following an X5.1 class solar flare. A strong Forbush decrease occurred on 19 and 20 January 2026 during one of the most intense geoMAGNETic storms of Solar Cycle 25. Events were recorded coherently by the global neutron monitor network and by SEVAN detectors at multiple altitudes. Using spectrometric capabilities, we reconstruct energy spectra of missing neutrons and muons during the FD and compare them with corresponding spectra measured during GLE77. The analysis demonstrates that FD and GLE signatures are intrinsically asymmetric. FDs selectively suppress the preexisting galactic COSMIC RAY population, whereas GLEs introduce an additional, harder particle component. Neutron and muon channels exhibit markedly different spectral behavior, particularly at higher deposited energies, reflecting their sensitivity to different primary energy ranges. These results show that combined NM and SEVAN observations provide robust, complementary diagnostics of rigidity dependent COSMIC RAY modulation during extreme heliospheric disturbances.

[abstract 42 / 46] (score: 2)
arXiv:2601.19401 [pdf, ps, other]

Title: Sensitivity of External Magnetic Field on the Change in Cross-section of a Toroidal Current

Authors: Suman Aich, Joydeep Ghosh, Rakesh L. Tanna, D. Raju, Sameer Kumar, Aditya-U team,

Comments: 6 pages, 2 figures

Subjects: physics.plasm-ph

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Due to any toroidal current column, the MAGNETic field is found to be sensitive as well as insensitive to its cross-sectional area depending on location of subject point, as predicted by numerical approaches [S. Aich, J. Thakkar, and J. Ghosh, Plasma Fusion Res. 17, 2403055 (2022)], and hence the presence of an angle of invariance is found to be present for any toroidal geometry. Present study aims to validate those numerical observations using the measured MAGNETic field due to Aditya Upgrade tokamak plasma.

[abstract 43 / 46] (score: 2)
arXiv:2601.19480 [pdf, ps, other]

Title: A highly ionised outflow in the X-ray binary 4U 1624-49 detected with XRISM

Authors: M. Díaz Trigo, E. Caruso, E. Costantini, T. Dotani, T. Kohmura, M. Shidatsu, M. Tsujimoto, T. Yoneyama, J. Neilsen, T. Yaqoob, J. M. Miller,

Comments: 13 pages, 6 figures. Accepted for publication in A&A

Subjects: astro-ph.HE

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

The origin of accretion disc winds remains disputed to date. High inclination, dipping, neutron star Low Mass X-Ray Binaries (LMXBs) provide an excellent testbed to study the launching mechanism of such winds due to being persistently accreting and showing a nearly ubiquitous presence of highly-ionised plasmas. We aim to establish or rule out the presence of a wind in the high inclination LMXB 4U 1624-49, for which a highly ionised plasma has been repeatedly observed in X-ray spectra by Chandra and XMM-Newton, and a thermal-radiative pressure wind is expected. We leverage the exquisite spectral resolution of XRISM to perform phase-resolved spectroscopy of the full binary orbit to characterise the highly ionised plasma at all phases except during absorption dips. An outflow is clearly detected via phase-resolved spectroscopy of the source with XRISM/Resolve. Based on analysis of the radial velocity curve we determine an average velocity of ~200-320 km/s and a column density above 10$^{23}$ cm$^{-2}$. The line profiles are generally narrow, spanning from ~50 to ~100 km/s, depending on the orbital phase, pointing to a low velocity sheer or turbulence of the highly ionised outflow and a potential increase of turbulence as the absorption dip is approached, likely due to turbulent mixing. The line profiles, together with the derived launching radius and wind velocity are consistent with a wind being launched from the outskirts of the disc and without stratification, pointing to a thermal-radiative pressure origin.

[abstract 44 / 46] (score: 2)
arXiv:2601.19524 [pdf, ps, other]

Title: A complete survey of filaments in Cygnus X

Authors: Yingxi Li, Keping Qiu,

Comments: 17 pages, 17 figures

Subjects: astro-ph.GA

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Filamentary structures are widely observed in molecular clouds, yet most filament observations are biased toward case studies and small samples; a uniform census within a single giant molecular cloud is still missing. We do a complete census of filaments in Cygnus X and quantify their links to dense cores, the MAGNETic field (B field), and HII regions. Using the updated getsf algorithm on the Cygnus X column-density map, we extracted 2633 filaments and 6551 cores. We built CMFs for cores on and off filaments, compared filament orientations with the Planck B field, measured radial column-density profiles near HII-region boundaries, and computed distances between young stellar objects and filament spines. Filaments have a typical width of 0.5 pc in Cygnus X at a resolution of 0.12 pc and host > 93% of high-mass cores (>= 20 Msun). The on-filament CMF shows a high-mass (> 10 Msun) slope of -2.30, while the off-filament CMF is steeper (-2.83). The onCMF peak mass is well below the Bonnor-Ebert mass, whereas the outCMF peak is comparable to it. At 5' resolution, filaments are mostly perpendicular to the B field except at the lowest column densities; the transition occurs near Av = 10 mag. Prominent filaments and high-mass cores preferred to be located around HII-region boundaries or at intersections of multiple HII regions; filament profiles are steeper on the side facing the HII region. Massive-core formation depends strongly on filaments, which may provide reservoirs that feed cores via accretion. The B field likely regulates filament formation, consistent with the type-O mode (converging flows along an oblique MHD shock) and an HII-driven bubble-filament paradigm for Cygnus X.

[abstract 45 / 46] (score: 2)
arXiv:2601.19842 [pdf, ps, other]

Title: Dynamical Evidence for a Billion Solar Mass Black Hole in Galaxy NGC 4061 from ALMA $^{12}$CO(2-1) Kinematics

Authors: Dieu D. Nguyen, Long Q. T. Nguyen, Elena Gallo, Hai N. Ngo, Que T. Le, Fabio Pacucci, Tinh Q. T. Le, Tuan N. Le, Tien H. T. Ho,

Comments: 26 pages, 16 figures, 10 tables. Submitted to The Astrophysical Journal (ApJ)

Subjects: astro-ph.GA

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

We present the first robust dynamical measurement of the supermassive BLACK HOLE (SMBH) mass in the massive early-type galaxy NGC 4061 using high-spatial-resolution ALMA observations of the $^{12}$CO(2-1) emission. By combining archival Cycle 6 data with new Cycle 7 observations, we achieve a synthesized beam of $0''.16 \times 0''.13$, comparable to the expected sphere of influence of the central BLACK HOLE. The molecular gas forms a regularly rotating circumnuclear disk aligned with the prominent dust lane seen in HST imaging. We model the full three-dimensional ALMA data cube using the KinMS forward-modeling framework, exploring both data-driven and analytic prescriptions for the gas surface brightness distribution. Our Bayesian analysis yields a best-fitting SMBH mass of $M_{\rm BH} = (1.17^{+0.08}_{-0.10}\,[{\rm stat.}] \pm 0.43\,[{\rm syst.}]) \times 10^{9}$ M$_\odot$ and an $I$-band stellar mass-to-light ratio of $M/L_{\rm F814W} = 3.46^{+0.07}_{-0.06}\,[{\rm stat.}] \pm 0.10\,[{\rm syst.}]$ M$_\odot$/L$_\odot$. The inferred BLACK HOLE mass is fully consistent across different modeling assumptions and remains insensitive to plausible radial variations in the $M/L_{\rm F814W}$ profile. Our results resolve the long-standing discrepancy between previous indirect mass estimates based on conflicting stellar velocity dispersion measurements and demonstrate that the exceptionally large dispersion reported in the literature is likely spurious. This study highlights the power of high-resolution ALMA molecular gas kinematics for precision SMBH mass measurements at the high-mass end of the local BLACK HOLE mass function.

[abstract 46 / 46] (score: 2)
arXiv:2601.19858 [pdf, ps, other]

Title: Melvin--Bonnor and Bertotti--Robinson spacetimes with Baryonic charge

Authors: José Barrientos, Fabrizio Canfora, Adolfo Cisterna, Keanu Müller, Anibal Neira,

Comments: 9 pages, 6 figures

Subjects: gr-qc

Created: 2026-01-27; Updated: 2026-01-28; Datestamp: 2026-01-28

Recently, a novel dictionary relating solutions of the Einstein--Scalar--Maxwell theory to solutions of gauged Skyrme--Maxwell--Einstein models in $(3+1)$ dimensions has been established. This development provides a clear and systematic route to constructing new configurations with nontrivial Baryonic charge and MAGNETic field, leveraging the fact that the Einstein--Scalar--Maxwell system is considerably more tractable, thanks to powerful solution-generating techniques. In this work, we exploit the framework that allows compact sources dressed by scalar fields to be consistently embedded in external electroMAGNETic backgrounds, and we construct their dual counterparts carrying Baryonic charge in the Skyrme sector. The resulting Baryonic charge is expressed directly in terms of the parameters characterizing the seed spacetime, and a corresponding quantization condition involving these parameters is explicitly derived. Consequently, the mass and the Baryonic charge are not independent parameters. These results provide a closed analytic formula for the BLACK HOLE mass parameter in terms of the Baryonic charge and the MAGNETic field. This relation between the mass parameter and the Baryonic charge is linear for large values of the mass, while significant deviations from linearity arise if the mass takes intermediate values.