Current date: 2025-12-24

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Datestamp limit: 2025-12-24 (0 days ago)

Created/updated limit: 2025-12-17 (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=2025-12-24&until=2025-12-24&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 675

Keyword score statistics

score 7 -- 1 abstracts

score 6 -- 4 abstracts

score 4 -- 2 abstracts

score 3 -- 9 abstracts

score 2 -- 16 abstracts

in total -- 32 abstracts

Articles that appeared on 2025-12-24

[abstract 1 / 32] Wow! (score: 7)
arXiv:2509.25877 [pdf, ps, other]

Title: A fast powerful X-ray transient from possible tidal disruption of a white dwarf

Authors: Dongyue Li, Wenda Zhang, Jun Yang, Jin-Hong Chen, Weimin Yuan, Huaqing Cheng, Fan Xu, Xinwen Shu, Rong-Feng Shen, Ning Jiang, Jiazheng Zhu, Chang Zhou, Weihua Lei, Hui Sun, Chichuan Jin, Lixin Dai, Bing Zhang, Yu-Han Yang, Wenjie Zhang, Hua Feng, Bifang Liu, Hongyan Zhou, Haiwu Pan, Mingjun Liu, Stephane Corbel, Sitha K. Jagan, Maria Cristina Baglio, Christopher R. Burns, Floriane Cangemi, Chun Chen, Yehao Cheng, Alexis Coleiro, Francesco Coti Zelati, Sourya R. Das, Zhongnan Dong, Luis Galbany, Noa Grollimund, Daniel Kelson, Dong Lai, Xia Li, Yuan Liu, Alessio Marino, Brenna Mockler, Paul O'Brien, Erlin Qiao, Nanda Rea, Resmi, Jérome Rodriguez, Richard Saxton, Luming Sun, Lian Tao, Tinggui Wang, Yilong Wang, Xuefeng Wu, Dong Xu, Yijia Zhang, Guoying Zhao, Congying Bao, Zhiming Cai, Yehai Chen, Yong Chen, Bertrand Cordier, Chenzhou Cui, Weiwei Cui, Zhou Fan, He Gao, Giancarlo Ghirlanda, Ju Guan, Dawei Han, Jinxin Hao, Jingwei Hu, Maohai Huang, Yong-Feng Huang, Shumei Jia, Ge Jin, Stefanie Komossa, Chengkui Li, Zhixing Ling, Congzhan Liu, Heyang Liu, Huaqiu Liu, Fangjun Lu, Kirpal Nandra, Jan-Uwe Ness, Arne Rau, Jeremy Sanders, Liming Song, Roberto Soria, Shengli Sun, Xiaojin Sun, Yuyin Tan, Eleonora Troja, Sixiang Wen, Haitao Xu, Changbin Xue, Yongquan Xue, Yi-Han Iris Yin, Chen Zhang, Shuang-Nan Zhang, Yonghe Zhang,

Comments: submitted on 19 October 2025, accepted for publication in Science Bulletin on 12 December 2025

Subjects: astro-ph.HE

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

Stars captured by BLACK HOLEs (BHs) can be torn apart by strong tidal forces, producing electroMAGNETic flares. To date, more than 100 tidal disruption events (TDEs) have been observed, each involving invariably normal gaseous stars whose debris falls onto the BH, sustaining the flares over years. White dwarfs (WDs), which are the most prevalent compact stars and a million times denser--and therefore tougher--than gaseous stars, can only be disrupted by intermediate-mass BLACK HOLEs (IMBHs) of 10^2--10^5 solar masses. WD-TDEs are considered to generate more powerful and short-lived flares, but their evidence has been lacking. Here we report observations of a fast and luminous X-ray transient EP250702a detected by Einstein Probe. Its one-day-long X-ray peak as luminous as 10^(47-49) erg/s showed strong recurrent flares with hard spectra extending to several tens of MeV gamma-rays, as detected by FERMI/GBM and Konus-Wind, indicating RELATIVISTIC JET emission. The JET's X-ray dropped sharply from 3 x 10^49 erg/s to around 10^44 erg/s within 20 days (10 days in the source rest frame). These characteristics are inconsistent with any known transient phenomena other than a JETted-TDE evolving over an unprecedentedly short timescale, indicating the disruption of a WD by an IMBH. At late times, a new soft component progressively dominates the X-ray spectrum, exhibiting an extreme super-Eddington luminosity, which possibly originates from an accretion disc. WD-TDEs open a new window for investigating the elusive IMBHs and their surrounding stellar environments, and they are prime sources of gravitational waves in the band of space-based interferometers.

[abstract 2 / 32] Yes (score: 6)
arXiv:2506.04196 [pdf, ps, other]

Title: Lense-Thirring Precession Modulates Repeated Lensing of Continues Gravitational Wave Source from AGN Disks

Authors: Yu-Zhe Li, Wen-Long Xu, Yi-Gu Chen, Wei-Hua Lei,

Comments: Accepted for publication in Physical Review D

Subjects: astro-ph.HE

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

Gravitational lensing of gravitational waves (GWs) offers a novel observational channel that complements traditional electroMAGNETic approaches and provides unique insights into the astrophysical environments of GW sources. In this work, we investigate the repeated lensing of continuous gravitational wave (CW) sources in ACTIVE GALACTIC NUCLEus (AGN) disks by central supermassive BLACK HOLEs (SMBHs), focusing on the imprint of SMBH spin via the Lense-Thirring (LT) effect. Although typically weak and challenging to observe, the spin-induced precession of source orbits can accumulate over time, thereby modulating the lensing geometry. Such modulations influence the magnification, duration, and waveform structure of each repeated lensing event, and enhance the overall probability of lensing occurrences. Using matched filtering, we demonstrate that spin-dependent signatures may be detectable, suggesting that lensed CW signals could serve as an indirect probe of SMBH spin in AGNs.

[abstract 3 / 32] Yes (score: 6)
arXiv:2509.22843 [pdf, ps, other]

Title: Can GRB 250702B be explained as the tidal disruption of a white dwarf by an intermediate mass BLACK HOLE? Yes

Authors: Rob AJ Eyles-Ferris, Andrew King, Rhaana LC Starling, Peter G Jonker, Andrew J Levan, Antonio Martin-Carrillo, Tanmoy Laskar, Jillian C Rastinejad, Nikhil Sarin, Nial R Tanvir, Benjamin P Gompertz, Nusrin Habeeb, Paul T O'Brien, Massimiliano De Pasquale,

Comments: 8 pages, 2 figures. Third revision

Subjects: astro-ph.HE

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

GRB 250702B is a unique astrophysical transient characterised by its nature as a repeating gamma-ray trigger. Its properties include possible periodicity in its gamma-ray light curve, an X-ray counterpart that rose prior to the gamma-ray outbursts and faded quickly, and radio and infrared counterparts. These features are difficult to reconcile with most models of high energy transients but we show that they are compatible with a white dwarf bound to an intermediate mass BLACK HOLE that is tidally stripped over multiple pericentre passages before being fully disrupted. Accretion onto the BLACK HOLE powers a mildly RELATIVISTIC JET that produces the X-rays through internal processes and the infrared and radio counterparts through thermal emission and external shocks respectively but is unable to produce the gamma-ray emission on its own. We propose that chaotic debris streams from the multiple stripping episodes can collide with a period roughly the same as the orbital period of the star. These shocks produce hard X-ray photons that are upscattered by the JET to produce the observed MeV gamma-ray emission. Future analysis of the JET properties will allow us to place firmer constraints on our model.

[abstract 4 / 32] Yes (score: 6)
arXiv:2512.19876 [pdf, ps, other]

Title: Double-hump spectrum, pulse profile dip, and pulsed fraction spectra from the low-accretion regime in the X-ray pulsar MAXI J0655-013

Authors: C. Malacaria, S. N. Pike, A. D'Aì, G. L. Israel, L. Ducci, R. E. Rothschild, L. Stella, R. Amato, E. Ambrosi, J. B. Coley, F. Fürst, M. Imbrogno, P. Kretschmar, D. K. Maniadakis, A. Papitto, P. Pradhan, A. Rouco Escorial, A. Simongini, J. Stierhof, B. F. West, N. Zalot,

Comments: 10 pages, accepted on A&A

Subjects: astro-ph.HE

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

Accreting X-ray pulsars (XRPs) undergo different physical regimes depending on the mass accretion rate. Recent observations have shown a dramatic change in the emission properties of this class of sources observed at low luminosity. We explore the timing and spectral properties of the XRP MAXI J0655-013 observed in the low-luminosity regime (about 5x$10^{33}$ erg/s) to witness the corresponding spectral shape and pulse profiles. We employ recent $XMM$ and $NUSTAR$ pointed observations of the MAXI J0655-013 X-ray activity during the low-luminosity stage. We explore several spectral models to fit the data and test theoretical expectations of the dramatic transition of the spectral shape. We study the pulsating nature of the source and find a phase-connected timing solution. We explore the energy-resolved pulse profiles and the derived energy-dependence of different pulsed fraction estimators ($PF_{minmax}$ and $PF_{rms}$). We also obtain $NUSTAR$ pulsed fraction spectra (PFS) at different luminosity regimes. MAXI J0655-013 spectrum is well fitted by a double Comptonization model, in agreement with recent observational results and theoretical expectations that explain the observed spectrum as being composed of two distinct bumps, each dominated by different POLARIZATION modes. We measure a spin period of $1081.86\pm0.02$ s, consistent with the source spinning-up compared to previous observations, yielding an upper limit for the MAGNETic field strength of B<9x$10^{13}$ G. The pulse profiles show a single broad peak interrupted by a sharp dip that coincides with an increase in the hardness ratio. For the low-luminosity observation, the $PF_{minmax}$ increases with energy up to $\sim100\%$ in the 10-30 keV band, while the $PF_{rms}$ remains steady at $\sim60\%$. The PFS obtained at high luminosity shows evidence of an iron $Kα$ emission line but no indications of a cyclotron line.

[abstract 5 / 32] Yes (score: 6)
arXiv:2512.19892 [pdf, ps, other]

Title: Superluminal Wave Activation at Relativistic Magnetized Shocks

Authors: Jens F. Mahlmann, Logan Eskildsen, Arno Vanthieghem, Dawei Dai, Lorenzo Sironi,

Comments: 13 pages, 6 figures, submitted to ApJL

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

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

Fast radio bursts (FRBs) are extremely energetic radio transients, some are generated in MAGNETar MAGNETospheres and winds. Despite a growing number of observations, their emission mechanisms remain elusive. It has recently been proposed that Alfvénic perturbations can convert into superluminal O-modes at MAGNETized shocks and propagate in the downstream as a radio signal. We validate this superluminal wave activation mechanism using pair-plasma theory and particle-in-cell simulations. Theory predicts two different downstream modes: non-propagating Alfvénic perturbations and propagating superluminal O-modes. Superluminal wave activation occurs if the frequency of upstream perturbations in the shock frame exceeds the downstream plasma frequency. 1D particle-in-cell simulations confirm wavenumber and frequency jumps across the shock for upstream perturbations with frequencies well above the plasma frequency. Our simulations model both monochromatic upstream waves and broadband spectra with the downstream plasma frequency acting like a high-pass filter for superluminal O-modes. We discuss implications for FRB generation in RELATIVISTIC MAGNETized winds.

[abstract 6 / 32] Yes (score: 4)
arXiv:2512.19792 [pdf, ps, other]

Title: A multiwavelength study of an early galaxy group merger in COSMOS revealed by two tailed RADIO GALAXies at z = 0.35

Authors: Paula Vulić, Vernesa Smolčić, Ghassem Gozaliasl, Ivan Delvecchio, Alexis Finoguenov,

Comments:

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

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

We report the discovery of two tailed RADIO GALAXies in the COSMOS field, associated with a massive, dynamically unrelaxed galaxy group detected in X-rays at z = 0.349. One of them is a wide-angle tail (WAT) galaxy, supporting the role of WATs as tracers of dynamically young groups and clusters. Our multiwavelength analysis combines VLA radio data, HST-ACS imaging, COSMOS2020 photometric redshifts, COSMOS2015 photometry, the newest compilation of spectroscopic redshifts in COSMOS, and X-ray observations from Chandra and XMM-Newton. We used these data to study the tailed RADIO GALAXies, their host galaxies, and the group environment. Both RADIO GALAXies are hosted by massive ($\log_{10}(M_*/M_{\odot})=11.88\pm0.03$ and $\log_{10}(M_*/M_{\odot})=11.49\pm0.06$), red, elliptical galaxies with extended stellar halos, as revealed by a color, magnitude, and stellar mass analysis combined with GALFIT modeling and surface-brightness profiles. One corresponds to the brightest group galaxy (BGG), while the other is the second-brightest. A diffuse intragroup medium (IGM) is characterized by its irregular shape and the analysis of the X-ray spectra of the group core reveals high temperature ($T_X=2.4\pm0.6\hspace{0.1cm}\mathrm{keV}$) and an electron density of $(8.2\pm0.3)\times 10^{-4}\hspace{0.1cm}\mathrm{cm^{-3}}$. A galaxy overdensity associated with the group was detected via Voronoi tessellation, using COSMOS2020 CLASSIC photometric redshifts, displaying an irregular morphology, along with evidence of substructure. Assuming the JET bending results from interaction with the IGM, we find a high relative velocity between the BGG and the IGM ($v_{\mathrm{BGG/IGM}} \gtrsim 540$ km/s), primarily due to bulk gas motion. Our findings indicate a dynamically young system in the early stages of assembly via group-group merging.

[abstract 7 / 32] Yes (score: 4)
arXiv:2512.19816 [pdf, ps, other]

Title: Obtaining Magnetization of Super-Alfvénic Turbulence with the Structure Functions of Gradient Directions

Authors: A. Lazarian, Yue Hu, D. Pogosyan,

Comments: 8 pages, 1 figure

Subjects: astro-ph.GA

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

Super-Alfvénic turbulence is widespread in astrophysical environments, including molecular clouds and the diffuse plasma of galaxy clusters. At large scales, MAGNETic fields play only a minor dynamical role; however, for sufficiently extended turbulent cascades, the motions transition into the MHD regime at a characteristic scale $l_A$. We introduce a new diagnostic based on the structure functions of the gradient directions, which can be obtained directly from spectroscopic and SYNCHROTRON intensity observations. We demonstrate that the new measure robustly recovers the transition scale $l_A$. Building on this result, we propose a generalized expression that replaces the traditional Davis-Chandrasekhar-FERMI (DCF) method for estimating MAGNETic field strength in the super-Alfvénic regime, where the DCF approach fails. We further show how the MAGNETization and MAGNETic field strength of diffuse media, such as the intracluster medium, can be inferred using SYNCHROTRON intensity maps. Our theoretical predictions are validated through numerical simulations.

[abstract 8 / 32] (score: 3)
arXiv:2501.05732 [pdf, ps, other]

Title: Relativistic MAGNETohydrodynamics in the early Universe

Authors: Alberto Roper Pol, Antonino Salvino Midiri,

Comments: 65 pages, 2 figures, 1 table, updated version submitted to JCAP

Subjects: gr-qc astro-ph.CO

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

We review the conservation laws of MAGNETohydrodynamics (MHD) in an expanding homogeneous and isotropic Universe that can be applied to the study of early Universe physics during the epoch of radiation domination. The conservation laws for a conducting perfect fluid with RELATIVISTIC bulk velocities in an expanding background are presented, extending previous results that apply in the limit of subRELATIVISTIC bulk motion. Furthermore, it is shown that the subRELATIVISTIC limit presents new corrections that have not been considered in previous work. We discuss the conformal invariance of the MHD equations for a radiation-dominated fluid and different types of scaling of the fluid variables that are relevant for other equations of state when the bulk velocity is subRELATIVISTIC. In particular, we review the super-comoving coordinates that scale the time coordinate with the Universe expansion, and present a particular choice that allows the equations to become conformally flat for any choice of the equation of state. Imperfect RELATIVISTIC fluids are briefly described but their detailed study is not included in this work. We review the propagation of sound waves, Alfvén waves, and MAGNETosonic waves in the early Universe plasma. The Boris correction for RELATIVISTIC Alfvén speeds is presented and adapted for early Universe applications. This review is an extension, including new results, of part of the lectures presented at the minicourse ``Simulations of Early Universe Magnetohydrodynamics'' lectured by A. Roper Pol and J. Schober at EPFL, as part of the six-week program ``Generation, evolution, and observations of cosmological MAGNETic fields'' at the Bernoulli Center in May 2024.

[abstract 9 / 32] (score: 3)
arXiv:2504.19281 [pdf, ps, other]

Title: A novel sub-grid model for super-Eddington accretion of spinning BLACK HOLEs in galaxy-scale simulations

Authors: Wei-Bo Kao, Pedro R. Capelo, Elia Cenci, Lucio Mayer, Alessandro Lupi, Luca Sala,

Comments: 36 pages, 18 figures, accepted by MNRAS

Subjects: astro-ph.GA

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

Super-Eddington accretion has been proposed to explain the existence of BLACK HOLEs (BHs) with masses exceeding a billion solar masses within the first billion years after the Big Bang. We present a novel accretion disc-based sub-grid model for BH mass and spin evolution in the super-Eddington regime, implemented in the hydrodynamics code GIZMO. In our model, motivated by results of radiation-hydrodynamics simulations of accretion discs, the growth of the BH is mediated by a sub-grid accretion disc, comprising an inner photon-trapping region described by simulation-based fitting formulae and an outer thin $α$-disc with three regions. We incorporate a self-consistent spin evolution prescription that transitions between the Bardeen-Petterson effect and inner thick-disc precession, depending on the accretion rate. We perform a suite of idealised simulations of a BH embedded in a gaseous circumnuclear disc and a spherically distributed stellar component to explore the conditions under which super-Eddington accretion can be sustained in the environment of a realistic galactic nucleus. Simulations with misaligned gas inflows onto an initially aligned BH-disc system yield very high Eddington ratios, triggered by the rapid removal of disc angular momentum via inflows. These results highlight the importance of angular momentum misalignment in enabling super-Eddington accretion and suggest that such episodes are difficult to trigger unless the system resides in a highly dynamical environment -- a condition more likely to occur in high-redshift galaxies. Our model potentially provides a way to grow moderate-mass BH seeds to the sizes required to explain the bright high-redshift QUASARs.

[abstract 10 / 32] (score: 3)
arXiv:2506.16197 [pdf, ps, other]

Title: X-ray and Radio Analysis of Abell 1644: Constraints on Cluster Dynamics

Authors: Humaira Bashir, R. Kale, Asif Iqbal, Manzoor A. Malik,

Comments:

Subjects: astro-ph.GA

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

We present the first band-2 (120--250\,MHz) uGMRT (upgraded Giant Metrewave Radio Telescope) observations of the bimodal galaxy cluster Abell\,1644 (\(z = 0.0471\)), complemented by Chandra X-ray data. While weak lensing measurements reveal a third substructure in Abell 1644, our radio analysis reveals only two compact sources coinciding with the respective brightest cluster galaxies (BCGs) of the northern (A1644N1) and southern (A1644S) substructures, seen in the X-ray observations. Radio analysis yields compact ACTIVE GALACTIC NUCLEi (AGN) powered sources with radio power $P_{A1644S} = 1.1\times 10^{23} W/Hz$ and $P_{A1644N} = 7.3\times 10^{23} W/Hz$ at 200MHz. We find no evidence of non-thermal diffuse radio emission, such as halos or relics, within the sensitivity of our band-2 image. We measured the flux density of each radio source and performed spectral analysis. A1644N1 exhibits a SYNCHROTRON power law spectrum while A1644S shows spectral turnover suggestive of SYNCHROTRON self-absorption. Our X-ray analysis confirms the presence of a cold front east of the A1644S subcluster core. The temperature map further reveals a previously unreported asymmetry, with a hot intracluster medium (ICM) region to the east of A1644S and cooler gas to the west, likely representing residual signatures of earlier merger activity. Together, these features indicate that Abell 1644 preserves clear imprints of its merger history through long-lived sloshing motions, while the absence of diffuse radio emission suggests that the past merger was relatively minor not injecting enough turbulence for large scale reacceleration or the cluster is approaching a late stage of ICM relaxation.

[abstract 11 / 32] (score: 3)
arXiv:2510.23886 [pdf, ps, other]

Title: Vacuum breakdown around a Kerr BLACK HOLE surrounded by a MAGNETic field

Authors: C. Cherubini, R. Moradi, J. A. Rueda, R. Ruffini,

Comments: Typo in previous Eq. (15) corrected, and quantitative estimates updated accordingly. Conclusions remain the same

Subjects: gr-qc astro-ph.HE

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

We present the invariant characterization of the region where vacuum breakdown into electron-positron ($e^+e^-$) pairs occurs due to an overcritical electric field, the dyadoregion, in the case of a Kerr BLACK HOLE (BH) in the presence of an external, asymptotically uniform test MAGNETic field aligned with the BH rotation axis, using the Wald solution. We calculate the dyadoregion morphology, the electroMAGNETic energy available to the pairs, the pair-creation rate, the pair number density, the average energy per pair, and the pair energy density and pressure. These results provide initial conditions for simulating the subsequent dynamics of the pair-produced plasma and astrophysical applications in the context of high-energy transients involving BHs in strong electroMAGNETic fields.

[abstract 12 / 32] (score: 3)
arXiv:2512.19768 [pdf, ps, other]

Title: A Dynamical-Time Framework for the Dynamics of Charged Particles

Authors: Zui Oporto, Gonzalo Marcelo Ramírez-Ávila,

Comments: 11 pages, 4 figures

Subjects: physics.class-ph physics.plasm-ph

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

We present a dynamical framework for modeling the motion of point-like charged particles, with or without mass, in general external electroMAGNETic fields. A key feature of this formulation is the treatment of the time coordinate as a dynamical variable. The framework applies to the RELATIVISTIC regime while consistently admitting a nonRELATIVISTIC limit. We also present a representation of particle trajectories in velocity space, which provides a clear insight into the nature and asymptotic behavior of the dynamics. As an application, we compare the motion of massive and massless particles in a constant electroMAGNETic field and find that, for identical field configurations, their asymptotic behavior is independent of both mass and initial conditions. Finally, we explore the computational advantages of the dynamical-time formulation over the conventional uniform-time approach in two study cases: an uniform electroMAGNETic field and an elliptically polarized wave propagating along a uniform MAGNETic field. In both scenarios, the proposed scheme exhibits improvements in accuracy and computational efficiency.

[abstract 13 / 32] (score: 3)
arXiv:2512.19800 [pdf, ps, other]

Title: New and updated timing models for seven young energetic X-ray pulsars, including the Big Glitcher PSR J0537-6910

Authors: Wynn C. G. Ho, Lucien Kuiper, Cristobal M. Espinoza, Timothy Leon, Bennett Waybright, Sebastien Guillot, Zaven Arzoumanian, Slavko Bogdanov, Alice K. Harding,

Comments: 16 pages, 17 figures; accepted for publication in MNRAS

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

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

We present new timing models and update our previous ones for the rotational evolution of seven young energetic pulsars, including four of the top five in spin-down luminosity Edot among all known pulsars. For each of the six pulsars that were monitored on a regular basis by NICER, their rotation phase-connected timing model covers the entire period of NICER observations, in many cases from 2017-2025. For PSR J0058-7218, which was only identified in 2021, we extend the baseline of its timing model by 3 years and report detections of its first three glitches. The timing model for PSR J0537-6910 over the entire 8 years of NICER monitoring is presented, including a total of 23 glitches; we also report its spin frequency and pulsed spectrum from a 2016 NUSTAR observation. For PSR B0540-69, its complete timing model from 2015-2025 is provided, including a braking index evolution from near 0 to 1.6 during this period. The 8-year timing model for PSR J1412+7922 (also known as Calvera) is reported, which includes a position that is consistent with that measured from imaging. For PSR J1811-1925, we present its 3.5-year timing model. For PSR J1813-1749, its incoherent timing model is extended through early 2025 using new Chandra observations. For PSR J1849-0001, its 7-year timing model is provided, including a position that is consistent with and more accurate than its imaging position and its first glitch that is one of the largest ever measured. Our timing models of these seven X-ray pulsars enable their study at other energies and in gravitational wave data.

[abstract 14 / 32] (score: 3)
arXiv:2512.19825 [pdf, ps, other]

Title: On the Stability of Anisotropic Neutron Stars

Authors: L. M. Becerra, E. A. Becerra-Vergara, F. D. Lora-Clavijo, J. F. Rodriguez,

Comments: 13 pages, 11 figures. Summited in Physical Review D

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

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

We model anisotropic neutron stars using three distinct prescriptions for pressure anisotropy, the Horvat, Bowers-Liang, and Covariant models, and three equations of state with different particle compositions, each described by a piecewise polytropic parametrization with continuous sound speed. The stability of these configurations is assessed through their dynamical evolution using a fully non-linear RELATIVISTIC code. For stable configurations, we compute the oscillation spectrum and identify the fundamental mode frequency. We found that, while the isotropic and Horvat models become unstable close to the maximum-mass point, the Bowers-Liang and Covariant models become unstable at lower central densities, indicating that the standard turning-point criterion may not reliably predict the onset of dynamical instability in anisotropic stars. Based on our results, we also determine the neutral-stability line and verify that configurations lying to the right of this line are indeed unstable under radial perturbations and collapse. Overall, given an equation of state, pressure anisotropy can increase the maximum mass of an stable configuration by up to ~30 % compared to the isotropic case. It also allows for more compact stable configurations that may collapse on longer timescales once they become unstable. Finally, we show that these compact stars could initially mimic a BLACK HOLE's gravitational-wave ringdown. However, the production of subsequent echoes is not guaranteed by high compactness; instead, it depends critically on the star's specific internal structure and equation of state.

[abstract 15 / 32] (score: 3)
arXiv:2512.19845 [pdf, ps, other]

Title: The EUV Late-Phase: Statistical Results from 15 Years of Solar Dynamics Observatory Observations

Authors: Harry J. Greatorex, Aisling N. O'Hare, Susanna Bekker, Ryan C. Campbell, Daniel C. Keane, Ryan O. Milligan,

Comments:

Subjects: astro-ph.SR

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

Since its launch in 2010, the Solar Dynamics Observatory (SDO) has provided continuous high-cadence, multi-wavelength observations of the Sun, capturing thousands of solar flares and offering new insights into coronal dynamics. Among the discoveries enabled by SDO is the EUV late-phase (ELP), characterised by a secondary enhancement in warm coronal emission occurring tens of minutes after the main flare. While recent work has demonstrated the relevance of the ELP for space weather, its statistical behaviour and physical origin remain poorly constrained. Here, we present the most comprehensive review of the ELP to date, based on 15 years of Fe XVI observations from the Atmospheric Imaging Assembly onboard SDO (SDO/AIA). From a sample of 5335 isolated flares between 2010 and 2025, we identify and validate 467 ELP events. The overall ELP occurrence rate is 8 percent, with no significant dependence on the solar cycle and only a modest enhancement in the low-to-mid M-class range. The ELP typically exhibits and onset delay of 19 minutes, a peak-to-peak delay of 88 minutes, and a duration of 93 minutes. Strong correlations are found between ELP rise and decay rates (p=0.76), and between flare and ELP impulsivity (p=0.61), while no significant correlation is observed between flare and ELP phases. A Principal Component Analysis revealed three dominant axes of variation, corresponding to a timescale component, an energy-release intensity axis, and a partitioning of energy between the flare and ELP. These results suggest that ELP evolution is governed by both flare loop properties and RECONNECTion-driven energetics, likely modulated by a finite MAGNETic energy budget, and highlight the importance of SDO's long-term observations for understanding flare evolution and the Sun-Earth connection.

[abstract 16 / 32] (score: 3)
arXiv:2512.19942 [pdf, ps, other]

Title: Observation of Large-Scale Kelvin-Helmholtz Instability Wave Driven by a Coronal Mass Ejection

Authors: Leon Ofman, Olga Khabarova, Ryun-Yong Kwon, Yogesh, Eyal Heifetz, Katariina Nykyri,

Comments: Accepted for publication in Astrophysical Journal Letters

Subjects: astro-ph.SR

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

The Kelvin-Helmholtz instability (KHI) can occur when there is a relative motion between two adjacent fluids. In the case of MAGNETized plasma, the shear velocity must exceed the local Alfvén speed for the instability to develop. The KHI produces nonlinear waves that eventually roll up into vortices and contribute to turbulence and dissipation. In the solar atmosphere KHI has been detected in coronal mass ejections (CMEs), JETs, and prominences, mainly in the low corona. Only a few studies have reported the KHI in the upper corona, and its vortex development there has not been previously observed. We report the event with large-scale KHI waves observed from $\sim 6$ to 14~$R_{\odot}$ on 2024-Feb-16 using SOHO/LASCO and STEREO-A coronagraphs. KHI appeared during the passage of a fast CME and evolved into the nonlinear stage showing evidence of vortices. A closely timed subsequent CME in the same region has further developed the fully nonlinear KHI waves along its flank. We find that the radial speed of the CMEs exceeds the estimated local Alfven speed obtained from in-situ Parker Solar Probe (PSP) MAGNETic field data at perihelia. We propose that such events are rare because the fast CME created specific conditions favorable for instability growth in its trailing edge, including radial elongation of MAGNETic-field lines, reduced plasma density, and enhanced velocity and MAGNETic-field shear along the developing interface. The observed growth rate of KHI wave is in qualitative agreement with the theoretical predictions.

[abstract 17 / 32] (score: 2)
arXiv:2407.04256 [pdf, ps, other]

Title: Dynamics of Heatwave Intensification over the Indian Region

Authors: Lekshmi S, Rajib Chattopadhyay, D. S. Pai,

Comments:

Subjects: physics.ao-ph

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

In a warming world, heatwaves over India have become intense and are causing severe health impacts. Studies have identified the presence of amplified Rossby waves and their association with the intensification of heatwaves. Earlier studies have identified two dominant modes of temperature variability in India and their possible role in the development of dry (mode 1) and moist (mode 2) heatwaves. These modes are associated with midlatitude Rossby waves intruding over the Indian region. However the role of regional forcing and the teleconnection behind the intensification of the heatwaves over India is missing. The present study has analyzed the dynamical mechanisms for the regional intensification of the circulation features associated with the dominant moist heatwave mode (mode 2). Considering the predominant barotropic nature of the observed circulation features of the mode, a simple barotropic vorticity equation model forced with extratropical and regional vorticity sources is used to understand the intensification of the heat waves. It was found that a wave response initiated by a cyclonic vorticity over the Bay of Bengal superimposes with the mid-latitude anticyclonic vorticity generated Rossby waves intruding over India. This superimposition results in the amplification and persistence of the anticyclonic vorticity phase over the Northwest Indian region, leading to the intensification of circulation. It was also found that the barotropically forced intensified circulation leads to the intensification of the heat stress. Under a climate change scenario, different circulation regimes, characterized by zonal stationary wave number and JET speed, which can favor the intensification are also identified.

[abstract 18 / 32] (score: 2)
arXiv:2502.20452 [pdf, ps, other]

Title: Full-sky Models of Galactic Microwave Emission and Polarization at Sub-arcminute Scales for the Python Sky Model

Authors: Experiment Galactic Science Group, Julian Borrill, Susan E. Clark, Jacques Delabrouille, Andrei V. Frolov, Shamik Ghosh, Brandon S. Hensley, Monica D. Hicks, Nicoletta Krachmalnicoff, King Lau, Myra M. Norton, Clement Pryke, Giuseppe Puglisi, Mathieu Remazeilles, Elisa Russier, Benjamin Thorne, Jian Yao, Andrea Zonca,

Comments: Updated to match version published in ApJ. 35 pages, 15 figures. A supplement describing author contributions to this paper can be found at https://pysm3.readthedocs.io/en/latest/pysm_methods_author_contributions.html

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

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

Polarized foreground emission from the Galaxy is one of the biggest challenges facing current and upcoming cosmic microwave background (CMB) POLARIZATION experiments. We develop new models of polarized Galactic dust and SYNCHROTRON emission at CMB frequencies that draw on the latest observational constraints, that employ the ``POLARIZATION fraction tensor'' framework to couple intensity and POLARIZATION in a physically motivated way, and that allow for stochastic realizations of small-scale structure at sub-arcminute angular scales currently unconstrained by full-sky data. We implement these models into the publicly available Python Sky Model (PySM) software and additionally provide PySM interfaces to select models of dust and CO emission from the literature. We characterize the behavior of each model by quantitatively comparing it to observational constraints in both maps and power spectra, demonstrating an overall improvement over previous PySM models. Finally, we synthesize models of the various Galactic foreground components into a coherent suite of three plausible microwave skies that span a range of astrophysical complexity allowed by current data.

[abstract 19 / 32] (score: 2)
arXiv:2507.14711 [pdf, ps, other]

Title: Investigating FRB 20240114A with FAST: Morphological Classification and Drifting Rate Measurements in a Burst-Cluster Framework

Authors: Long-Xuan Zhang, Shiyan Tian, Junyi Shen, Jun-Shuo Zhang, Dejiang Zhou, Lin Zhou, Po Ma, Tian-Cong Wang, Dengke Zhou, Jinlin Han, Yunpeng Men, Fayin Wang, Jiarui Niu, Pei Wang, Weiwei Zhu, Bing Zhang, Di Li, Yuan-Chuan Zou, Wei-Yang Wang, Yuan-Pei Yang, Qin Wu, He Gao, Ke-Jia Lee, Jia-Wei Luo, Rui Luo, Chao-Wei Tsai, Lin Lin, Wanjin Lu, Jintao Xie, Jianhua Fang, Jinhuang Cao, Chen-Chen Miao, Yuhao Zhu, Yunchuan Chen, Yong-Kun Zhang, Shuo Cao, Zi-Wei Wu, Chunfeng Zhang, Silu Xu, Huaxi Chen, Xiang-Lei Chen, Xianghan Cui, Yi Feng, Yu-Xiang Huang, Weicong Jing, Dong-Zi Li, Jian Li, Ye Li, Chen-Hui Niu, Yong-Feng Huang, Qingyue Qu, Yuanhong Qu, Bojun Wang, Yi-Dan Wang, Suming Weng, Xuefeng Wu, Heng Xu, Shihan Yew, Aiyuan Yang, Wenfei Yu, Lei Zhang, Rushuang Zhao,

Comments: 23 pages, 14 figures, 1 tables, the 3rd of papers from the FAST FRB Key Science Project Collaboration on FRB 20240114A: Burst Morphology Analysis

Subjects: astro-ph.HE

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

This study investigates the morphological classification and drifting rate measurement of the repeating fast radio burst (FRB) source FRB20240114A using the Five-hundred-meter Aperture Spherical Telescope (FAST). Detected on January 14, 2024, FRB20240114A showed an exceptionally high burst rate. During a continuous 15,780-second monitoring session on March 12, 2024, 3,203 bursts (2,109 burst-clusters) were detected. We refine the definitions of sub-bursts, bursts, and burst-clusters. Using an average dispersion measure (DM) of 529.2 pc cm$^{-3}$, burst-clusters were classified into Downward Drifting, Upward Drifting, No Drifting, No Evidence for Drifting, Not-Clear, and Complex categories. Notably, 233 (23.82%) of the 978 drifting burst-clusters showed upward drifting. Excluding 142 upward drifting single-component clusters, the remaining 91 upward drifting double- or multiple-components clusters account for 10.89% of the drifting sample. Further restricting to those with consecutive time intervals, only 9 upward drifting bursts remain. An inverse correlation is found between drifting rate and sub-burst effective width. Upward drifting single-component clusters tend to have smaller effective widths, bandwidths, and fluxes than downward drifting ones. For these upward drifting clusters, drifting rate increases with peak frequency. A Kolmogorov-Smirnov test reveals longer consecutive intervals in upward drifting clusters compared to downward ones, suggesting differing underlying mechanisms.

[abstract 20 / 32] (score: 2)
arXiv:2508.10843 [pdf, ps, other]

Title: The explosion JETs of the core-collapse SUPERNOVA remnant Circinus X-1

Authors: Noam Soker, Muhammad Akashi,

Comments: Published in the Open Journal of Astrophysics

Subjects: astro-ph.HE

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

We propose that the recently analyzed opposite rings in the Circinus X-1 (Cir X-1) core collapse SUPERNOVA (CCSN) remnant resulted from a pair of opposite JETs at the final phases of the JET-driven explosion process of the progenitor of Cir X-1. We point out the similarity of the rings in the Cir X-1 CCSN remnant to a ring in the Cygnus Loop CCSN remnant. While the X-ray binary system Cir X-1 actively launches JETs, no such activity exists in the Cygnus Loop. In both CCSN remnants, we attribute the rings to JETs associated with the explosion process, within the framework of the jittering-JETs explosion mechanism (JJEM). We also identify such a ring in the CCSN remnant 107.7-5.1, which we also attribute to exploding JETs. We conduct three-dimensional hydrodynamical simulations of late JETs inside an exploding massive stellar core, and demonstrate the feasibility of this scenario for ring formation. The Cir X-1 CCSN remnant has a large blowout, similar to that of the Cygnus Loop and to a large protrusion in the CCSN remnant G0.9+0.1. Based on these similarities, we suggest that other exploding JETs inflated the blowout of the Cir X-1 nebula, consistent with an earlier claim regarding the formation of the blowout of the Cygnus Loop. We identify a point-symmetric structure in the Cir X-1 CCSN remnant, strengthening the JJEM. This study further demonstrates that the JJEM is a successful explosion mechanism to analyze CCSNe and CCSN remnants.

[abstract 21 / 32] (score: 2)
arXiv:2509.11631 [pdf, ps, other]

Title: Hurst Index of Gamma-Ray Burst Light Curves and Its Statistical Study

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

Comments: 33pages, 14 figures, submitted to Journal of High Energy Astrophysics

Subjects: astro-ph.HE

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

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 (T50, T90), and moderate positive correlations with peak photon flux proxies (P_{pk1}--P_{pk3}). In contrast, correlations between the Hurst index and standard spectral parameters (including the low-energy index α) are weak 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 22 / 32] (score: 2)
arXiv:2512.17787 [pdf, ps, other]

Title: Selected topics on: 1) proposal of interpreting the Crab SUPERNOVA with a GRB 2) progress in identifying the seven GRBs episodes 3) the role of Sagittarius A in identifying the DARK MATTER component (the X fermion)

Authors: R. Ruffini, C. Sigismondi, Y. Wang, H. Quevedo, S. Zhang, Y. Aimuratov, P. Chardonnet, C. L. Fryer, T. Mirtorabi, R. Moradi, M. Prakapenia, F. Rastegarnia, S. -S. Xue,

Comments:

Subjects: astro-ph.HE

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

As the fiftieth anniversary of our common effort in the field of RELATIVISTIC astrophysics is approaching, we offer a new look to some of our acquired knowledge in a more complete view, which evidence previous unnoticed connections. They are gaining due prominence in reaching a more complete picture evidencing the main results. We outline the history of GRB observations along with a summary of the contributions made by our group to develop the BdHN interpreting model. We show the seven Episodes characterizing the most powerful BdHNe I occurred to date: GRB 190114C and GRB 220101A. New inferences for the explanation of the highest energy radiation in the TeV are presented.

[abstract 23 / 32] (score: 2)
arXiv:2512.18637 [pdf, ps, other]

Title: A Framework for Lorentz-Dirac Dynamics and Post-Newtonian Interaction of Radiating Point Charges

Authors: Suhani Verma, Siddarth Mediratta, Nanditha Kilari, Prakhar Nigam, Ishaan Singh, Daksh Tamoli, Aakash Palakurthi, Valluru Ishan, Tanmay Golchha, Sanjay Raghav R, Sugapriyan S, Yash Narayan, P Devi, Prathamesh Kapase, G Prudhvi Raj, Lakshya Sachdeva, Shreya Meher, K Nanda Kishore, G Keshav, Jetain Chetan, Rickmoy Samanta,

Comments: 42 pages, 6 figures

Subjects: gr-qc astro-ph.HE hep-th

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

We examine classical radiation reaction by combining the covariant Lorentz--Dirac formulation, its Landau--Lifshitz (LL) order reduction, and a post-Newtonian (PN) Hamiltonian treatment of interacting and radiating charges. After reviewing the LL reduction and its removal of runaway and preacceleration behavior, we verify energy balance in several RELATIVISTIC single-particle scenarios by demonstrating agreement between the LL Larmor power and the loss of mechanical energy. We then construct an N-body framework based on the conservative Darwin Hamiltonian supplemented with the leading 1.5PN radiation--reaction term. Numerical simulations of charge-neutral binary systems of both symmetric and asymmetric mass configurations show orbital decay, circularization, and monotonic Hamiltonian decrease consistent with dipole radiative losses. The resulting framework provides a simple analogue of gravitational PN radiation reaction and a tractable system for studying dissipative and potentially chaotic electroMAGNETic dynamics.

[abstract 24 / 32] (score: 2)
arXiv:2512.19835 [pdf, ps, other]

Title: VERITAS contributions to the 39th International Cosmic Ray Conference

Authors: A. Archer, P. Bangale, J. T. Bartkoske, W. Benbow, Y. Chen, J. L. Christiansen, A. J. Chromey, A. Duerr, M. Escobar Godoy, J. Escudero Pedrosa, Q. Feng, S. Filbert, L. Fortson, A. Furniss, W. Hanlon, O. Hervet, C. E. Hinrichs, J. Holder, T. B. Humensky, M. Iskakova, W. Jin, M. N. Johnson, E. Joshi, M. Kertzman, M. Kherlakian, D. Kieda, T. K. Kleiner, N. Korzoun, S. Kumar, M. J. Lang, M. Lundy, G. Maier, C. E McGrath, P. Moriarty, R. Mukherjee, W. Ning, R. A. Ong, M. Pohl, E. Pueschel, J. Quinn, P. L. Rabinowitz, K. Ragan, P. T. Reynolds, D. Ribeiro, E. Roache, I. Sadeh, L. Saha, H. Salzmann, G. H. Sembroski, B. Shen, M. Splettstoesser, A. K. Talluri, J. V. Tucci, J. Valverde, V. V. Vassiliev, D. A. Williams, S. L. Wong, T. Yoshikoshi,

Comments:

Subjects: astro-ph.HE

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

Compilation of papers presented by the VERITAS Collaboration at the 39th International Cosmic Ray Conference (ICRC), held July 14 through July 24, 2025 in Geneva, Switzerland.

[abstract 25 / 32] (score: 2)
arXiv:2512.19924 [pdf, ps, other]

Title: Dynamics of JET formation and collapse for axisymmetric surface gravity waves: coupled 3D potential flow and SPH simulations

Authors: Taiga Kanehira, Peter K. Stansby, Benedict D. Rogers, Mark McAllister, T. S. van den Bremer, Samuel Draycott,

Comments: This paper is intended for submission to the Journal of Fluid Mechanics

Subjects: physics.flu-dyn

Created: 2025-12-22; Updated: 2025-12-24; Datestamp: 2025-12-24

Axisymmetric waves occur across a wide range of scales. This study analyses large-scale gravity-dominated axisymmetric waves, with JET heights of up to 6 m, for which surface-tension effects are negligible. The Bond number is O(10^5) and the Weber number ranges from O(10^4) to O(10^6). Our aim is to clarify the dynamics of highly nonlinear axisymmetric JET formation, cavity collapse and the consequent generation of secondary JETs. The newly developed three-dimensional framework OceanSPHysics3D, combining unsteady potential flow with smoothed particle hydrodynamics, enables full simulation of JET initiation and collapse. The computed free-surface elevations and JET evolution agree well with the experiments of McAllister et al. (Journal of Fluid Mechanics, 2022) and with an analytical JET-tip-angle formulation by Longuet-Higgins (Journal of Fluid Mechanics, 1983). The simulations elucidate how the falling primary JET induces a secondary JET. The mechanisms forming the pre-JET trough and the post-JET cavity are fundamentally different. The pre-JET trough arises geometrically from directional focusing of the constituent waves, yielding a self-similar shape when appropriately scaled. In contrast, the post-JET cavity is formed inertially by the falling continuous JET and lacks both spatial and temporal self-similarity. Its collapse also differs: the cavity pinches off at the neck to generate upward and downward secondary JETs, with local accelerations reaching approximately 150 times gravity. The primary JET scale governs the ensuing secondary-JET dynamics, including vortex-ring formation and strong vertical mixing. These findings illustrate the complexity of axisymmetric JET dynamics and demonstrate the ability of the present framework to reproduce the key coupled processes in such extreme free-surface events.

[abstract 26 / 32] (score: 2)
arXiv:2512.19962 [pdf, ps, other]

Title: Energy-conserving finite difference scheme for compressible MAGNETohydrodynamic flow at low Mach numbers using nonconservative Lorentz force

Authors: Hideki Yanaoka,

Comments: 34 pages, 27 figures. arXiv admin note: text overlap with arXiv:2407.01605

Subjects: physics.flu-dyn

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

In MAGNETohydrodynamic (MHD) flows, incompressibility is assumed for low Mach numbers. However, even at low Mach numbers, the Mach number influences flow and MAGNETic fields. Therefore, it is necessary to develop a method that can stably analyze low Mach number compressible MHD flows without using the incompressible assumption. This study constructs an energy-conserving finite difference method to analyze compressible MHD flows at low Mach numbers with the nonconservative Lorentz force. This analysis method discretizes the Lorentz force so that the transformation between conservative and nonconservative forms holds. This scheme simultaneously relaxes velocity, pressure, density, and internal energy, and stable convergence solutions can be obtained. In this study, we analyze four types of models and verify the accuracy and convergence of this numerical method. In the analyses of two- and three-dimensional ideal periodic inviscid MHD flows, it is clarified that momentum, MAGNETic flux density, and total energy are conserved discretely. The total energy is conserved even in a nonuniform grid. Even without correction for the MAGNETic flux density, the divergence-free condition of the MAGNETic flux density is satisfied discretely. Analysis of a Taylor decaying vortex under a MAGNETic field clarifies that the present numerical method can be applied to incompressible flows and can accurately predict the trend of energy attenuation. In the Orszag-Tang vortex analysis, an increase in Mach number reduces the magnitude of vorticity and current density. In addition, compression work increases more than expansion work, and the influence of compressibility appears. An increase in Mach number slightly delays the transition to turbulent flow. This numerical method has excellent energy conservation properties and can accurately predict energy conversion.

[abstract 27 / 32] (score: 2)
arXiv:2512.20054 [pdf, ps, other]

Title: Stable mass transfer in massive binaries leading to merging BLACK HOLEs

Authors: Xiao-Tian Xu, Norbert Langer, Jakub Klencki, Chen Wang, Xiang-Dong Li,

Comments: submitted

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

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

The vast majority of massive binary systems in the universe is evidently unsuited to produce merging binary BLACK HOLEs. However, several narrow evolutionary paths of isolated massive binaries towards this goal have recently been identified. Due to the high degree of simplification and assumptions applied in previous modelling of these paths, conclusions remained vague so far. For one of these paths, the stable mass transfer channel, we now construct detailed binary evolution models which include internal differential rotation as well as mass and angular momentum transfer between the stars, all the way from the zero-age main sequence to the formation of the BLACK HOLEs, only skipping the rapid late burning stages. This allows us to follow the mass and chemical structure evolution of the mass accreting component, which turns out to have a key influence on the phase of reverse mass transfer, that allows the obtained BLACK HOLE spins and mass ratios to naturally fall into the regime observed for the gravitational-wave source in the 10--25$M_\odot$ primary BLACK HOLE mass range. As for this channel, also a large number of progenitor binaries are known, we conclude that it likely contributes to the observed population of gravitational wave sources.

[abstract 28 / 32] (score: 2)
arXiv:2512.20072 [pdf, ps, other]

Title: Ultrahigh Charge-to-Spin Conversion and Tunneling Magnetoresistance in Quasi-Two-Dimensional d-wave AlterMAGNET

Authors: Qing Zhang, Siyun Wang, Jianting Dong, Jia Zhang,

Comments: 15 pages,4 figures,Supplementary Material included

Subjects: cond-mat.mtrl-sci cond-mat.str-el

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

The emergence of alterMAGNETs has driven groundbreaking advances in spintronics. Notably, d-wave alterMAGNETs support non-RELATIVISTIC spin transport, efficient charge-to-spin conversion, and T-odd spin currents. In addition, their integration as electrodes in antiferroMAGNETic tunnel junctions (AFMTJs) enables a tunneling MAGNEToresistance (TMR) effect, allowing electrical detection of Néel vectors for next-generation memory devices. In this work, we investigate the non-RELATIVISTIC spin transport properties of the quasi-two-dimensional (quasi-2D) d-wave alterMAGNET KV\textsubscript{2}Se\textsubscript{2}O and the TMR effect in KV\textsubscript{2}Se\textsubscript{2}O-based AFMTJs via first-principles calculations. Our results reveal that KV\textsubscript{2}Se\textsubscript{2}O exhibits a non-RELATIVISTIC longitudinal spin POLARIZATION and a spin Hall angle both exceeding 60\% at room temperature, while KV\textsubscript{2}Se\textsubscript{2}O-based AFMTJs achieve a giant TMR reaching approximately $10^{12}$\%, which remains robust against FERMI level shifts. These findings highlight the anisotropic spin POLARIZATION inherent to d-wave staggered MAGNETism and underscore the critical role of FERMI surface topology in enhancing T-odd spin transport and the TMR effect in AFMTJs.

[abstract 29 / 32] (score: 2)
arXiv:2512.20085 [pdf, ps, other]

Title: Unveiling the Dual Nature of V1180 Cas: UXor-like Dips and EXor-like Bursts Across a Decade

Authors: Tarak Chand, Saurabh Sharma, Koshvendra Singh, Joe P. Ninan, Arpan Ghosh, Devendra K. Ojha, Tapas Baug, D. K. Sahu, Bhuwan C. Bhatt, Pramod Kumar, Ram K. Yadav, Neelam Panwar, Aayushi Verma, Harmeen Kaur, Mamta, Manojit Chakraborty, Kartik Gokhe, Ajay Kumar Singh,

Comments: 31 pages, 14 figures, 8 tables. Accepted for for publication in The Astrophysical Journal

Subjects: astro-ph.SR

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

We present a detailed analysis of the long-term photometric and spectroscopic evolution of V1180 Cas over a decade, aiming to identify the dominant mechanisms behind its variability. We combine multi-band light curves from 1999 to 2025 with over 30 epochs of optical to near-infrared spectroscopy (0.5-2.5 $μ$m), analyzing variability patterns, color behavior, and emission line diagnostics. We investigate the temporal evolution of accretion and outflow indicators and their correlation with photometric states. The light curve reveals a transition from sporadic early dimming events to a quasi-periodic pattern since 2018, with eleven major dips showing asymmetry and stochastic sub-structure. Color-magnitude diagrams show classic UXor-like blueing during deep minima, while near-infrared and mid-infrared color changes indicate thermal evolution of disk. Spectroscopic analysis reveals persistent hydrogen, Ca II, He I, and forbidden line emission. Accretion diagnostics track photometric variability, and forbidden lines often intensify during dips, implying a physical link between extinction and outflows. Estimated accretion rates range from $\sim10^{-8}-10^{-7}$ $M_\odot$yr$^{-1}$; the outflow rate and density diagnostics are consistent with disk winds and shock-excited JETs. V1180 Cas demonstrates dual-mode variability driven by both variable circumstellar extinction and episodic accretion events. The hybrid UXor/EXor behavior, combined with evolving disk signatures and persistent outflows, suggests a young stellar object undergoing coupled accretion-extinction-outflow evolution. Continued monitoring will be essential to fully resolve the physical processes shaping its variability.

[abstract 30 / 32] (score: 2)
arXiv:2512.20150 [pdf, ps, other]

Title: Thermal wakefield structure in plasma acceleration processes: insights from fluid models and PIC simulations

Authors: Daniele Simeoni, Andrea Renato Rossi, Gianmarco Parise, Fabio Guglietta, Mauro Sbragaglia,

Comments: 12 pages, 7 figures

Subjects: physics.plasm-ph physics.acc-ph physics.app-ph

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

We focus on the process of plasma acceleration in the presence of non-negligible thermal effects, wherein a driver of RELATIVISTIC electrons perturbs a warm neutral plasma and generates a wakefield structure. We study the acceleration process via numerical simulations based on fluid models with different thermal closure assumptions, and also provide systematic comparisons against ground-truth data coming from particle-in-cell (PIC) simulations. The focus of the analysis is on the first electron depletion bubble after the driver, where we provide a detailed characterization of its size and the electroMAGNETic fields developed inside. Our results are instrumental in determining the correct thermal closure assumption to be used in fluid models for the numerical simulations of plasma acceleration processes, as well as elucidating the corresponding limits of applicability.

[abstract 31 / 32] (score: 2)
arXiv:2512.20175 [pdf, ps, other]

Title: Formation of an optically thick shocked shell in the very fast nova V1674 Herculis: the origin of superbrightness

Authors: Izumi Hachisu, Maiko Kato,

Comments: 22 pages, 10 figures, accepted for publication in ApJ

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

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

V1674 Her is the fastest ($t_2\sim 1$ day) classical nova in our Galaxy and its absolute $V$ peak of $M_{V,\rm max}\sim -10.2$ is one magnitude brighter than typical very fast novae. Such a nova is sometimes called a superbright nova. Using our fully self-consistent nova outburst model combined with the optically thick winds on a $1.35 ~M_\odot$ white dwarf (WD) with a mass accretion rate of $1\times 10^{-11} ~M_\odot$ yr$^{-1}$, we have clarified that a strong reverse shock arises $0.3$ days after the outburst, which is just after the maximum expansion of the WD photosphere. The shocked shell is optically thick and expanding with the velocity of $\sim 3500$ km~s$^{-1}$. Its $V$ brightness reaches maximum of $M_{V,\rm max}=-10.2$ when the shocked shell expands to $R_{\rm shell}\sim 300 ~R_\odot$ on day $\sim 0.7$. After that, the shocked shell turns to optically thin and becomes fainter than the brightness of free-free emission from the nova wind. In chronological order, the optical brightness of free-free emission reaches maximum of $M_V=-9$ on day 0.3. However, it is overtaken on day 0.5--0.7 by the $\sim$1 mag brighter luminosity of the optically thick shocked shell. The GeV gamma-ray flux reaches maximum on day 0.4 because the gamma-rays are emitted by the shock that arises on day 0.3. Our model consistently explains both the superbrightness and chronological order that the gamma-ray peak precedes substantially before the optical $V$ peak. We also present a similar light curve model for another superbright nova V1500 Cyg.

[abstract 32 / 32] (score: 2)
arXiv:2512.20265 [pdf, ps, other]

Title: Super-Eddington Accretion through a Multiwavelength Lens: Searching for Counterparts of Ultraluminous X-ray Sources

Authors: R. Amato, M. Bachetti, R. Soria, A. Gúrpide, M. Imbrogno, C. Salvaggio, R. Salvaterra, M. Del Santo, S. Scaringi, P. Casella, A. Wolter,

Comments: 4 pages. White paper submitted to the ESO call "Expanding Horizons: Transforming Astronomy in the 2040s"

Subjects: astro-ph.HE

Created: 2025-12-23; Updated: 2025-12-24; Datestamp: 2025-12-24

Ultraluminous X-ray sources (ULXs) represent the closest and most accessible laboratories to study sustained super-Eddington accretion onto compact objects. Over the past decade, the discoveries of coherent pulsations in a few ULXs has proved that these systems can be powered by accreting neutron stars, while the most luminous and distant ones remain strong candidates for hosting intermediate-mass BLACK HOLEs. Despite the increasing number of available X-ray data and the significant progress in theoretical modeling and simulations, our understanding of ULXs remains incomplete. Key open questions include the nature and mass distribution of the compact objects, the type of the donor stars, the geometry of the accretion disc and its contribution to the observed broadband emission, the mechanisms responsible for the wide spectral and temporal phenomenology, the duration of the super-Eddington accretion phase and its feedback on the host-galaxy environment. Future ground-based facilities will play a crucial role in addressing these issues.