Journal of High Energy Astrophysics最新文献

{"title":"VegasAfterglow: A high-performance framework for gamma-ray burst afterglows","authors":"Yihan Wang ,&nbsp;Connery Chen ,&nbsp;Bing Zhang","doi":"10.1016/j.jheap.2025.100490","DOIUrl":"10.1016/j.jheap.2025.100490","url":null,"abstract":"<div><div>Gamma-ray bursts (GRBs) are the most luminous astrophysical transients, known to be associated with core collapse of massive stars or mergers of two compact objects such as two neutron stars. They are followed by multi-wavelength afterglow emission originating from the deceleration of the relativistic jets by the ambient medium. The study of afterglow emission offers crucial insights into the physics of relativistic shocks, the properties of the circumburst environment, the physical and geometrical structure of relativistic jets, as well as the viewing geometry of the observer. We present <span>VegasAfterglow</span>, a newly developed, high-performance C++ framework designed for modeling GRB afterglows with flexibility and computational efficiency as key features of design. The framework self-consistently solves forward and reverse shock dynamics and calculates synchrotron (including self-absorption or all spectral regimes) and inverse Compton radiation (including Klein–Nishina corrections); it can handle arbitrary user-defined ambient density profiles, central engine activity histories, viewing angles, and the jet structures of energy, Lorentz factor, and magnetization profiles. It supports both relativistic and non-relativistic regimes and includes lateral jet spreading effects. In this paper, we describe the numerical implementation of the framework and assess its computational performance. Our results demonstrate that <span>VegasAfterglow</span> is well-suited for interpreting current and future multi-wavelength observations in the era of multi-messenger astronomy.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100490"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145269259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Black hole topologies and geodesic structures in symmetric teleparallel f(Q) gravity","authors":"G.G.L. Nashed ,&nbsp;A. Eid","doi":"10.1016/j.jheap.2025.100508","DOIUrl":"10.1016/j.jheap.2025.100508","url":null,"abstract":"<div><div>In this work, we investigate black hole solutions in the context of symmetric teleparallel gravity, specifically within <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> theory, where <em>Q</em> denotes the non-metricity scalar. We focus on static, circularly symmetric spacetimes in <span><math><mo>(</mo><mn>2</mn><mo>+</mo><mn>1</mn><mo>)</mo></math></span>-dimensions, analyzing both charged and uncharged cases. By adopting a power-law form for <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span>, we derive exact black hole solutions and explore their thermodynamic and geometric properties. Curvature and non-metricity scalars reveal central singularities stronger than those in general relativity. We find that the horizon radii increase with the charge parameter while higher values of the non-metricity coefficient, <span><math><msub><mrow><mi>c</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span>, or the cosmological constant Λ tend to merge or eliminate horizons, reducing their total number and altering the near-origin structure of the spacetime. We perform a detailed topological analysis based on the Euler characteristic and examine the geodesic completeness of the spacetime. Our findings show that, depending on the presence of electric charge, the singularity may or may not be reachable by geodesics. The thermodynamic stability is confirmed via temperature, entropy, and heat capacity calculations. This study highlights the rich structure of <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> gravity in lower-dimensional settings and offers new insights into the nature of singularities and black hole topologies in modified gravity theories.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100508"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145519811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"AstroSat's view of kHz quasi-periodic oscillations from 4U 1820−30","authors":"L. Giridharan,&nbsp;Neal Titus Thomas,&nbsp;S.B. Gudennavar,&nbsp;S.G. Bubbly","doi":"10.1016/j.jheap.2025.100494","DOIUrl":"10.1016/j.jheap.2025.100494","url":null,"abstract":"<div><div>This study presents the spectro-temporal analysis of the neutron star low mass X-ray binary 4U 1820−30, using data from three observations conducted by <em>AstroSat</em>'s Soft X-ray Telescope and Large Array X-ray Proportional Counter. Spectral analysis revealed that the source spectra could be modelled using an absorbed blackbody and a multi-temperature disk model along with a Comptonization model with Γ=1.24 − 1.89 and the inner accretion disk located at an distance of ∼17 km from the neutron star. This showed the source to be in the hard spectral state. Temporal analysis revealed the presence of kHz quasi-periodic oscillations (QPOs) with frequencies in the 640 − 1090 Hz range with root mean squared (RMS) amplitudes between 6 − 10 per cent and quality factors between 8 − 42. The RMS amplitude−energy and time lag−energy spectra of the upper and lower kHz QPOs hint them to be caused by modulations of photons having a common radiative mechanism. Moreover, the maximum RMS amplitude and time lag exhibited an anti-correlation with mass accretion rate. Using an analytical relation based on the relativistic precession model, the mass of the neutron star in the system was estimated to be 1.8 M_⊙. The emission radius of one of the detected kHz QPOs was estimated to be ∼ 17 km.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100494"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145364109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Triggering electron capture supernovae: Dark matter effects in degenerate white-dwarf-like cores of super-asymptotic giant branch stars","authors":"Vishal Parmar ,&nbsp;Domenico Scordino ,&nbsp;Ignazio Bombaci","doi":"10.1016/j.jheap.2025.100470","DOIUrl":"10.1016/j.jheap.2025.100470","url":null,"abstract":"<div><div>Electron-capture supernovae (ECSNe) have emerged as a compelling formation channel for low-mass neutron stars, bolstered by decades of theoretical work and increasingly supported by observational evidence, including the recent identification of SN 2018zd. Motivated by this, we investigate the influence of fermionic asymmetric dark matter (ADM) on the equilibrium structure of progenitor cores and the formation of their neutron star remnants. Using a general relativistic two-fluid formalism, we model the coupled evolution of ordinary matter (OM) and ADM, treated as separately conserved fluids interacting solely through gravity. Our analysis focuses on neon-rich white dwarfs (Ne WDs), which are typical progenitor cores for ECSNe. We assume conservation of both baryon number (<span><math><msub><mrow><mi>N</mi></mrow><mrow><mi>B</mi></mrow></msub></math></span>) and DM particle number (<span><math><msub><mrow><mi>N</mi></mrow><mrow><mi>D</mi></mrow></msub></math></span>) during collapse, allowing for a consistent mapping between progenitor and remnant configurations. We find that ADM significantly enhances the central density of the WD progenitor. This lowers the threshold gravitational mass <span><math><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> required to initiate electron capture, enabling ECSNe from lower-mass progenitors. The resulting remnants are stable, DM-admixed neutron stars with gravitational masses potentially well below current observational bounds. Moreover, we find that the conversion energy during the WD-to-NS conversion is also significantly reduced for higher ADM particle masses and fractions, suggesting that unusually low-energy ECSNe may serve as potential indicators of ADM involvement in stellar collapse.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100470"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145110181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"How many VHE gamma-ray binaries with young pulsars can be observed?","authors":"A.M. Bykov ,&nbsp;A.G. Kuranov ,&nbsp;A.E. Petrov ,&nbsp;K.A. Postnov","doi":"10.1016/j.jheap.2025.100484","DOIUrl":"10.1016/j.jheap.2025.100484","url":null,"abstract":"<div><div>A population of Galactic gamma-ray binaries is currently emerging due to ever increasing sensitivity of gamma-ray observatories. The detection of very high energy (VHE) photons with energies well above 10 TeV from a dozen of sources and the estimated power of those sources make them potentially interesting cosmic ray accelerators. Multi-wavelength observations of gamma-ray binaries revealed that most of them include a young massive star in pair with a relativistic companion, either a black hole or energetic pulsar. Fast stellar winds interacting with powerful relativistic outflows from pulsars or the black hole jets in microquasars are favorable sites for very high energy particle acceleration. To estimate the expected number of gamma-ray binaries, we present here results of population synthesis calculations predicting the number of Galactic binaries in which a young massive OB- or Be-star is accompanied by a pulsar capable of producing a powerful relativistic outflow. The distributions over the binary eccentricities, orbital periods, Be-disk inclinations, and the pulsar braking energy losses are taken into account. Conditions for a binary to accelerate very high energy particles, radiate and absorb the non-thermal photons that may reach the observer are discussed. We model the anisotropic structure of the zone of interaction of the relativistic pulsar wind with the strongly magnetized massive star's wind. The stellar winds with strong (in a Gauss range) magnetic fields at ∼ AU distances colliding with powerful pulsar outflows are capable of accelerating particles up to PeV energies at some orbital configurations and phases. The strong magnetic field in the interaction region produces a highly anisotropic structure of the particle accelerator and the emitter in the pulsar outflow. The anisotropic radiation pattern may affect the gamma-ray photon absorption and the number of the observed gamma-ray loud systems.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100484"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification of vortical coherent modes during relativistic jet propagation from active galactic nuclei using data-driven techniques","authors":"Ribhu Pal,&nbsp;Arnab Roy","doi":"10.1016/j.jheap.2025.100485","DOIUrl":"10.1016/j.jheap.2025.100485","url":null,"abstract":"<div><div>In this article, two-dimensional numerical simulations of magnetized relativistic jets propagating through a uniform interstellar medium (ISM) were conducted by solving the relativistic magnetohydrodynamic (RMHD) equations using a high-order finite volume method in PLUTO solver <span><span>Mignone et al. (2007)</span></span>. Vortical coherent structures generated by jet–ISM interactions were identified through the application of both standard Dynamic Mode Decomposition (DMD) and Hankel DMD. While dominant coherent modes were extracted using linear DMD, transient and nonlinear structures were more effectively captured by Hankel DMD due to its time-delay embedding formulation. A parametric study was performed to investigate the mechanisms governing energy dissipation, with variations introduced in jet Lorentz factor, magnetization strength, and the comparison between relativistic hydrodynamic (RHD) and magnetized (RMHD) configurations. Across all cases, eigenvalues were consistently located within the unit circle, signifying temporal decay of vortical modes due to strong dissipation imposed by the jet head shock. It was shown that dissipation was sustained with increasing Lorentz factor, that magnetization exerted control over the stability and coherence of vortical structures, and that RMHD jets followed distinct dissipation pathways relative to RHD jets. Overall, nonlinear coherent dynamics were more effectively revealed through Hankel DMD, and dissipation trends were elucidated via systematic parametric variation.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100485"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"X-ray emission of the Nuclear Stellar Disk as seen by SRG/ART-XC","authors":"Valentin Nezabudkin ,&nbsp;Roman Krivonos ,&nbsp;Sergey Sazonov ,&nbsp;Rodion Burenin ,&nbsp;Alexander Lutovinov ,&nbsp;Ekaterina Filippova ,&nbsp;Alexey Tkachenko ,&nbsp;Mikhail Pavlinsky","doi":"10.1016/j.jheap.2025.100473","DOIUrl":"10.1016/j.jheap.2025.100473","url":null,"abstract":"<div><div>The Nuclear Stellar Disk (NSD), together with the Nuclear Stellar Cluster and the supermassive black hole Sgr A*, forms the central region of the Milky Way. Galactic X-ray background emission is known to be associated with the old stellar population, predominantly produced by accreting white dwarfs. In this work we characterize the X-ray emission of the Galactic Center (GC) region using wide-field observations with the ART-XC telescope on-board the <em>SRG</em> observatory in the 4−12 keV energy band. Our analysis demonstrates that the X-ray emission of the GC at a spatial scale of a few hundred parsecs is dominated by the regularly-shaped NSD aligned in the Galactic plane, and characterized by latitudinal and longitudinal scale heights of ∼20 pc and ∼100 pc, respectively. The measured flux <span><math><mo>(</mo><msubsup><mrow><mn>6.8</mn></mrow><mrow><mo>−</mo><mn>0.3</mn></mrow><mrow><mo>+</mo><mn>0.1</mn></mrow></msubsup><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>10</mn></mrow></msup></math></span>erg s⁻¹ cm⁻² in the 4−12 keV band corresponds to a luminosity of <span><math><msub><mrow><mi>L</mi></mrow><mrow><mn>4</mn><mtext>–</mtext><mn>12</mn><mspace></mspace><mrow><mi>keV</mi></mrow></mrow></msub><mo>=</mo><mo>(</mo><msubsup><mrow><mn>5.9</mn></mrow><mrow><mo>−</mo><mn>0.3</mn></mrow><mrow><mo>+</mo><mn>0.1</mn></mrow></msubsup><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>36</mn></mrow></msup></math></span>erg s⁻¹, assuming the GC distance of 8.178 kpc. The average mass-normalized X-ray emissivity of the NSD, <span><math><mo>〈</mo><mi>L</mi><mo>/</mo><mi>M</mi><mo>〉</mo><mo>=</mo><mo>(</mo><msubsup><mrow><mn>5.6</mn></mrow><mrow><mo>−</mo><mn>0.7</mn></mrow><mrow><mo>+</mo><mn>0.5</mn></mrow></msubsup><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>27</mn></mrow></msup></math></span>erg s⁻¹ M<span><math><msubsup><mrow></mrow><mrow><mo>⊙</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></math></span>, exceeds the corresponding value for the Galactic ridge by a factor of <span><math><msubsup><mrow><mn>3.3</mn></mrow><mrow><mo>−</mo><mn>0.5</mn></mrow><mrow><mo>+</mo><mn>0.4</mn></mrow></msubsup></math></span>, confirming other studies. We also perform a deprojection of the observed NSD surface brightness distribution in order to construct a three-dimensional X-ray luminosity density model, which can be directly compared to the existing 3D stellar mass models. Finally, we conclude that the spatial distribution of the X-ray emission from the NSD is consistent with the most recent stellar mass density distribution model within 30%, which suggests that this emission is dominated by unresolved point X-ray sources rather than by diffuse X-ray emission.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100473"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structure formation in a non-canonical scalar field model of clustering dark energy","authors":"Zanyar Ebrahimi ,&nbsp;Kayoomars Karami","doi":"10.1016/j.jheap.2025.100496","DOIUrl":"10.1016/j.jheap.2025.100496","url":null,"abstract":"<div><div>This paper examines the growth of dark matter and dark energy perturbations within a non-canonical scalar field model characterized by an exponential potential. Through dynamical system analysis, we identify critical points and track the background evolution of a spatially flat FLRW universe dominated by dark energy and pressureless dark matter. We systematically derive key cosmological quantities, including the Hubble parameter, deceleration parameter, density parameters, and the scalar field's equation of state, and explore their dependence on model parameters. Within the linear perturbation framework, employing the pseudo-Newtonian formalism, we compute the growth factor of matter density perturbations. To investigate the non-linear regime of structure formation, we employ the spherical collapse model and derive its key parameters. Building on these findings, we compute the function <span><math><mi>f</mi><mo>(</mo><mi>z</mi><mo>)</mo><msub><mrow><mi>σ</mi></mrow><mrow><mn>8</mn></mrow></msub><mo>(</mo><mi>z</mi><mo>)</mo></math></span> and the relative number density of halo objects exceeding a given mass threshold. Our results indicate that non-canonical scalar field models can effectively account for both background cosmic evolution and the growth of structure, offering potential insights into observational constraints and large-scale dynamics.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100496"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145364076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dispersion relation for the linear theory of relativistic Rayleigh–Taylor instability in a magnetized medium revisited","authors":"Qiqi Jiang ,&nbsp;Guang-Xing Li ,&nbsp;Chandra B. Singh","doi":"10.1016/j.jheap.2025.100488","DOIUrl":"10.1016/j.jheap.2025.100488","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Rayleigh–Taylor instability (RTI) arises at the interface between two fluids of different densities, notably when a heavier fluid lies above a lighter one in an effective gravitational field. In astrophysical systems with high velocities, relativistic corrections are necessary. We investigate the linear theory of the relativistic Rayleigh-Taylor instability (R-RTI) in a magnetized medium, where fluids can move with relativistic velocities. We chose an “intermediate frame” in which the fluids on each side of the interface move in opposite directions with identical Lorentz factors &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⁎&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and derive the new dispersion relation of the R-RTI. This symmetry facilitates analytical derivations and the study of relativistic effects on the dynamics of instabilities. We find that the instability is activated when the Atwood number &lt;span&gt;&lt;math&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; = &lt;span&gt;&lt;math&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ρ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ρ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ρ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ρ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/math&gt;&lt;/span&gt;, where &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ρ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ρ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; are densities measured in the rest of the fluids. The relativistic effect is mostly contained in the Lorentz transformation of the effective acceleration &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⁎&lt;/mo&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;, which, combined with time dilation, leads to a much slower growth of instability (&lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;ω&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⁎&lt;/mo&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ω&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;), and a slightly elongated length of the unstable patch, due to weaker &lt;em&gt;g&lt;/em&gt; in the intermediate frame. Taking time dilation into account, when viewed in the rest frame of the medium, we expect the instability to grow at a much reduced rate. The analytical results should guide further explorations of instability in systems such as microquasars (&lt;em&gt;μ&lt;/em&gt;QSOs), Active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and radio pulsars (PSRs), where the apparent stability of the jet can be attributed to either the intrinsic stability (e.g. the Atwood number)","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100488"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145364148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First-principles formulation of high-energy radiation from magnetar giant flares","authors":"Umer Rehman ,&nbsp;Joseph Zhao Zhang ,&nbsp;Bin-Bin Zhang","doi":"10.1016/j.jheap.2025.100489","DOIUrl":"10.1016/j.jheap.2025.100489","url":null,"abstract":"<div><div>We develop a first-principles atmosphere model for neutron stars with ultra-strong magnetic fields (<span><math><mi>B</mi><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>14</mn></mrow></msup><mo>,</mo><mi>G</mi></math></span>). In this framework, a magnetar giant flare (MGF) arises when a large energy release into confined field lines launches an expanding fireball (FB); thermal photons from the FB are Comptonized by relativistic <span><math><msup><mrow><mi>e</mi></mrow><mrow><mo>±</mo></mrow></msup></math></span> pairs, producing a modified blackbody spectrum with a Rayleigh–Jeans low-energy slope and a high-energy tail. We derive polarization-dependent opacities for a magnetized <span><math><msup><mrow><mi>e</mi></mrow><mrow><mo>±</mo></mrow></msup></math></span> pair plasma (including plasma and vacuum polarization effects) and formulate the coupled radiative-transfer equations for the ordinary and extraordinary modes. The calculations show that, in deep magnetospheric layers with <span><math><mi>n</mi><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>24</mn></mrow></msup></math></span>–<span><math><msup><mrow><mn>10</mn></mrow><mrow><mn>28</mn></mrow></msup><mo>,</mo><mrow><mi>c</mi><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></mrow></math></span> and path length <span><math><mi>l</mi><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>3</mn></mrow></msup></math></span>–<span><math><msup><mrow><mn>10</mn></mrow><mrow><mn>6</mn></mrow></msup><mo>,</mo><mrow><mi>cm</mi></mrow></math></span>, plasma effects substantially reshape the opacities and generate a broad spectral feature (<span><math><mi>Δ</mi><mi>ω</mi><mo>/</mo><mi>ω</mi></math></span>) around the electron cyclotron frequency <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mi>B</mi></mrow></msub></math></span> via resonant polarization/mode conversion. Identifying this feature in data would enable a direct estimate of the surface magnetic field. Despite current observational limitations, the model reproduces key spectral properties of GRB200415A and GRB231115A, providing insight into their radiation mechanisms and the emission physics of MGFs.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100489"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}