Journal of High Energy Astrophysics最新文献

{"title":"Search for spatial coincidences between galaxy mergers and Fermi-LAT 4FGL-DR4 sources","authors":"Siddhant Manna,&nbsp;Shantanu Desai","doi":"10.1016/j.jheap.2025.100460","DOIUrl":"10.1016/j.jheap.2025.100460","url":null,"abstract":"<div><div>We present a systematic search for spatial association between a high confidence sample of 3,166 morphologically selected galaxy mergers drawn from the initial convolutional neural network (CNN) catalog of 328,151 candidate mergers (<span><span>Ackermann et al., 2018</span></span>) and refined through SDSS cross-matching and the Fermi Large Area Telescope Fourth Source Catalog Data Release 4 (4FGL-DR4) catalog of gamma-ray sources detected by the Fermi Large Area Telescope (LAT). Using a conservative 4<em>σ</em> positional uncertainty threshold and a Poisson based statistical framework, we identify 21 statistically significant associations with match probabilities <span><math><mi>p</mi><mo>&lt;</mo><mn>0.05</mn></math></span>. Among these are known classes of gamma-ray emitters such as Flat-Spectrum Radio Quasars (FSRQs), BL Lacertae objects (BLL), and radio galaxies bolstering the hypothesis that merger driven processes can fuel high energy activity. Intriguingly, five of the associated sources remain unclassified in 4FGL-DR4, hinting at a possible link between galaxy mergers and a hitherto unrecognized population of gamma-ray sources. The dominance of AGN like matches supports the scenario in which mergers trigger accretion onto central supermassive black holes, initiating AGN activity observable at gamma-ray energies. Moreover, the recurrent presence of unassociated sources among secure matches underscores the potential of merger catalogs as physically motivated priors in gamma-ray source identification efforts. This work constitutes the first dedicated effort to explore associations between gamma-ray sources and a large, morphologically selected sample of galaxy mergers (<span><span>Ackermann et al., 2018</span></span>) catalog, opening new avenues for understanding the role of galaxy interactions in high-energy astrophysics. We additionally examined the sample of 70 galaxy pairs from the Canadian Network for Observational Cosmology Field Galaxy Redshift Survey and found no statistically significant matches, with <span><math><mi>p</mi><mo>&lt;</mo><mn>0.05</mn></math></span> within the 4<em>σ</em> positional uncertainty threshold.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"49 ","pages":"Article 100460"},"PeriodicalIF":10.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145049371","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":"High mass pulsars as hybrid stars: Phase transitions and oscillation modes","authors":"Soumen Podder ,&nbsp;Sujan Kumar Roy ,&nbsp;Suman Pal ,&nbsp;Gargi Chaudhuri","doi":"10.1016/j.jheap.2025.100457","DOIUrl":"10.1016/j.jheap.2025.100457","url":null,"abstract":"<div><div>Recent observations of high-mass pulsars justify the investigation of the internal composition of neutron stars. At the extreme densities relevant to such objects, quantum chromodynamics predicts a phase transition in neutron star matter to deconfined quark matter. However, the nature of this phase transition remains uncertain due to the absence of direct observational evidence. In this work, we investigate the possibility of such a transition inside neutron stars, focusing on the scenario of a first-order phase transition. In particular, we consider the slow conversion of the hadronic phase into the deconfined quark phase. For comparison, we also construct hybrid stars using a continuous Gibbs phase transition description. Our findings indicate that the neutron star structure is significantly influenced by the adopted phase transition model. In the context of gravitational wave observations, we analyze the non-radial f-mode oscillations in high-mass pulsars. We find that these oscillations are sensitive to both the nature of the phase transition and the underlying neutron star structure. Consequently, we explore neutron star oscillations as a potential probe of the internal composition of high-mass pulsars, as these oscillation modes can provide signatures of phase transitions.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"49 ","pages":"Article 100457"},"PeriodicalIF":10.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145049370","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":"Does DESI 2024 confirm ΛCDM?","authors":"E. Ó Colgáin ,&nbsp;M.G. Dainotti ,&nbsp;S. Capozziello ,&nbsp;S. Pourojaghi ,&nbsp;M.M. Sheikh-Jabbari ,&nbsp;D. Stojkovic","doi":"10.1016/j.jheap.2025.100428","DOIUrl":"10.1016/j.jheap.2025.100428","url":null,"abstract":"<div><div>We demonstrate that a <span><math><mo>∼</mo><mn>2</mn><mi>σ</mi></math></span> discrepancy with the Planck-ΛCDM cosmology in DESI Luminous Red Galaxy (LRG) data in the redshift range <span><math><mn>0.4</mn><mo>&lt;</mo><mi>z</mi><mo>&lt;</mo><mn>0.6</mn></math></span> with effective redshift <span><math><msub><mrow><mi>z</mi></mrow><mrow><mtext>eff</mtext></mrow></msub><mo>=</mo><mn>0.51</mn></math></span> translates into an unexpectedly large <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>m</mi></mrow></msub></math></span> value, <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>=</mo><msubsup><mrow><mn>0.67</mn></mrow><mrow><mo>−</mo><mn>0.17</mn></mrow><mrow><mo>+</mo><mn>0.18</mn></mrow></msubsup></math></span>. We independently confirm that this anomaly drives the preference for <span><math><msub><mrow><mi>w</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>&gt;</mo><mo>−</mo><mn>1</mn></math></span> in DESI data <em>alone</em> confronted to the <span><math><msub><mrow><mi>w</mi></mrow><mrow><mn>0</mn></mrow></msub><msub><mrow><mi>w</mi></mrow><mrow><mi>a</mi></mrow></msub></math></span>CDM model. Given that LRG data at <span><math><msub><mrow><mi>z</mi></mrow><mrow><mtext>eff</mtext></mrow></msub><mo>=</mo><mn>0.51</mn></math></span> is at odds with Type Ia supernovae in overlapping redshifts, we expect that this anomaly will decrease in statistical significance with future DESI data releases leaving an increasing <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>m</mi></mrow></msub></math></span> trend with effective redshift at higher redshifts. We estimate the current significance of the latter in DESI data at <span><math><mo>∼</mo><mn>1.8</mn><mi>σ</mi></math></span> and comment on how it dovetails with independent observations. It is imperative to understand what makes DESI LRG data at <span><math><msub><mrow><mi>z</mi></mrow><mrow><mtext>eff</mtext></mrow></msub><mo>=</mo><mn>0.51</mn></math></span> an outlier when it comes to <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>m</mi></mrow></msub></math></span> determinations.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"49 ","pages":"Article 100428"},"PeriodicalIF":10.2,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144713684","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":"The role of r-modes in pulsar spin-down, pulsar timing, and gravitational waves","authors":"Xiyuan Li ,&nbsp;Shahram Abbassi ,&nbsp;Varenya Upadhyaya ,&nbsp;Xiyang Zhang ,&nbsp;S.R. Valluri","doi":"10.1016/j.jheap.2025.100446","DOIUrl":"10.1016/j.jheap.2025.100446","url":null,"abstract":"<div><div>We investigate the role of r-mode oscillations in pulsar spin-down and their implications for gravitational wave emission and pulsar timing analysis. Using a non-linear differential framework that includes r-mode contributions, we derive time-dependent solutions for rotational frequency and period evolution. These expressions are validated using observational data from the Crab pulsar with high precision. By analytically fitting braking indices and spin-down coefficients, we link measurable pulsar properties to gravitational wave signatures. Furthermore, we present closed-form expressions for neutron star compactness and tidal deformability using Lambert W and Lambert–Tsallis functions, enabling model-independent inferences from r-mode gravitational wave frequencies. Our results show that incorporating r-modes significantly improves the accuracy of spin-down models and continuous wave detectability, particularly through the inclusion of high-order frequency terms. This framework supports the modeling of timing residuals, glitch quantification, and gravitational wave constraints. Our findings have direct relevance for data analysis in ongoing and future gravitational wave observatories.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"49 ","pages":"Article 100446"},"PeriodicalIF":10.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144831592","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":"Quasi-Periodic Oscillations due to radiative feedback mechanism between the disc and corona","authors":"Akash Garg ,&nbsp;Ranjeev Misra ,&nbsp;Somasri Sen","doi":"10.1016/j.jheap.2025.100426","DOIUrl":"10.1016/j.jheap.2025.100426","url":null,"abstract":"<div><div>Compact object systems exhibit Quasi-Periodic Oscillations (QPOs) as revealed by peaked features in their power density spectra. It has been known that stochastic variations in the accretion disc will propagate to the corona after a time delay and that the hard X-rays from the corona impinge back on the disc, giving reflection spectral features. Here, we show that the combination of these two effects makes a simple radiative feedback system between the corona and the disc, which naturally produces the observed QPOs whose primary frequency corresponds to the inverse of the time delay. The analytical form of the expected power spectra can be statistically compared with the observed ones. Hence for the first time, a physical model is used to describe and fit the AstroSat observed power spectra of the black hole systems MAXI J1535-571 and GRS 1915+105, including the QPO, its harmonics as well as the broadband components.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"49 ","pages":"Article 100426"},"PeriodicalIF":10.2,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144687015","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":"NuSTAR discovers a long type-I X-ray burst from the clocked burster GS 1826-24","authors":"Aditya S. Mondal ,&nbsp;Mayukh Pahari ,&nbsp;Gulab C. Dewangan","doi":"10.1016/j.jheap.2025.100450","DOIUrl":"10.1016/j.jheap.2025.100450","url":null,"abstract":"<div><div>The source GS 1826-24 is a neutron star low mass X-ray binary known as the “clocked burster” because of its extremely regular bursting behavior. We report on the detection of a long type-I X-ray burst from this source. We perform a detailed spectroscopic analysis of the long X-ray burst, lasting for ∼600 s, seen in the <em>NuSTAR</em> observation carried out on 2022 September. The persistent emission is well described by an absorbed thermal Comptonization model <span>nthcomp</span>, and the source exhibits a soft spectral state during this observation. The observed burst exhibits a rise time of ∼25 s and a decay time of ∼282 s. The time-resolved spectroscopy of the burst shows a significant departure from a pure thermal spectrum and is described with a model consisting of a varying-temperature blackbody plus an evolving persistent emission component. We observe a significant enhancement in the persistent emission during the burst. The enhancement of the pre-burst persistent flux is possibly due to Poynting-Robertson drag or coronal reprocessing. At the peak of the burst, the blackbody temperature and the blackbody emitting radius reached a maximum of <span><math><mn>2.10</mn><mo>±</mo><mn>0.07</mn></math></span> keV and <span><math><mn>5.5</mn><mo>±</mo><mn>2.1</mn></math></span> km, respectively. The peak flux (<span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>p</mi><mi>e</mi><mi>a</mi><mi>k</mi></mrow></msub></math></span>) during the burst is <span><math><mo>≈</mo><mn>2.4</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>8</mn></mrow></msup></math></span> ergs cm⁻² s⁻¹, which corresponds to a luminosity of <span><math><mo>≈</mo><mn>9.7</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>37</mn></mrow></msup></math></span> ergs s⁻¹.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"49 ","pages":"Article 100450"},"PeriodicalIF":10.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144863744","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":"Balancing accessibility and quality: How high energy astrophysics supports a diverse scientific community","authors":"","doi":"10.1016/j.jheap.2025.100423","DOIUrl":"10.1016/j.jheap.2025.100423","url":null,"abstract":"","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"49 ","pages":"Article 100423"},"PeriodicalIF":10.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145095332","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":"Maximum mass of singularity-free anisotropic compact stars in Rastall theory of gravity","authors":"Sourav Biswas,&nbsp;Debadri Bhattacharjee,&nbsp;Pradip Kumar Chattopadhyay","doi":"10.1016/j.jheap.2025.100445","DOIUrl":"10.1016/j.jheap.2025.100445","url":null,"abstract":"<div><div>The current model explores spherically symmetric anisotropic compact stars within the Rastall theory of gravity. By employing the Krori and Barua metric ansatz <span><span>Krori and Barua (1975)</span></span>, we derive a set of tractable, singularity-free relativistic solutions to the Einstein field equations. Using a best-fit equation for the numerical solution of the TOV equation, we determine the maximum mass and corresponding radius in this model. Our findings reveal that an increase in the Rastall parameter (<em>ξ</em>) leads to a higher maximum mass, indicating a stiffer nature of the equation of state. For <em>ξ</em> values ranging from 0.01 to 0.09, we calculate the maximum mass to be between <span><math><mn>2.24</mn><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span> and <span><math><mn>2.36</mn><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span>, with corresponding radii from 9.48 to 10.15 km. Furthermore, our model's predictions for the radii of recently observed pulsars are consistent with observational data. The model satisfies essential criteria for causality, energy conditions, and stability, confirming its viability and physical acceptability as a stellar structure.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"49 ","pages":"Article 100445"},"PeriodicalIF":10.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144809397","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":"A set of distinctive properties ruling the prompt emission of GRB 230307A and other long γ-ray bursts from compact object mergers","authors":"R. Maccary ,&nbsp;C. Guidorzi ,&nbsp;M. Maistrello ,&nbsp;S. Kobayashi ,&nbsp;M. Bulla ,&nbsp;R. Moradi ,&nbsp;S.-X. Yi ,&nbsp;C.W. Wang ,&nbsp;W.L. Zhang ,&nbsp;W.-J. Tan ,&nbsp;S.-L. Xiong ,&nbsp;S.-N. Zhang","doi":"10.1016/j.jheap.2025.100456","DOIUrl":"10.1016/j.jheap.2025.100456","url":null,"abstract":"<div><div>Short gamma-ray bursts (SGRBs), occasionally followed by a long and spectrally soft extended emission, are associated with compact object mergers (COMs). Yet, a few recent long GRBs (LGRBs) show compelling evidence for a COM origin, in contrast with the massive-star core-collapse origin of most LGRBs. While possible COM indicators were found, such as the minimum variability timescale (MVT), a detailed and unique characterisation of their <em>γ</em>-ray prompt emission that may help identify and explain their deceptively long profile is yet to be found. Here we report the discovery of a set of distinctive properties that rule the temporal and spectral evolution of GRB 230307A, a LGRB with evidence for a COM origin. Specifically, the sequence of pulses that make up its profile is characterised by an exponential evolution of (i) flux intensities, (ii) waiting times between adjacent pulses, (iii) pulse durations, and (iv) spectral peak energy. Analogous patterns are observed in the prompt emission of other long COM candidates. The observed evolution of gamma-ray pulses would imply that a relativistic jet is colliding with more slowly expanding material. This contrasts with the standard internal shock model for typical LGRBs, in which dissipation occurs at random locations within the jet itself. We tentatively propose a few simple toy models that may explain these properties and are able to reproduce the overall time profile.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"49 ","pages":"Article 100456"},"PeriodicalIF":10.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144988064","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":"Fermi-large area telescope detection of very high energy (>100 GeV) emission from misaligned jetted active galactic nuclei","authors":"Gunjan Tomar ,&nbsp;Vaidehi S. Paliya ,&nbsp;D.J. Saikia ,&nbsp;C.S. Stalin","doi":"10.1016/j.jheap.2025.100454","DOIUrl":"10.1016/j.jheap.2025.100454","url":null,"abstract":"<div><div>The detection of very-high-energy (VHE; &gt;100 GeV) <em>γ</em>-ray radiation from misaligned jetted Active Galactic Nuclei (AGN) challenges the emission models that primarily explain VHE emissions from beamed AGN, i.e., blazars. Using over 16 years of <em>Fermi</em>-Large Area Telescope (<em>Fermi</em>-LAT) Pass 8 data in the energy range 0.1−2 TeV, we systematically explore the VHE emission from a recently published sample of 160 radio galaxies. We identify 12 sources detected at <span><math><mo>&gt;</mo><mn>4</mn><mi>σ</mi></math></span> confidence level (test statistic or TS&gt;16), including nine with TS&gt;25 and two Fanaroff-Riley type II objects. This detected sample includes seven out of eight previously known VHE objects. Two radio galaxies are detected in the VHE band for the first time, and we identify three promising candidates with 16&lt;TS&lt;25. Additionally, 13 objects are identified as candidate VHE emitters with at least one VHE photon detected with the <em>Fermi</em>-LAT. These findings expand the sample of known VHE-emitting radio galaxies, whose multiwavelength follow-up observations can help provide insights into the emission mechanisms, jet physics, and the contribution of misaligned AGN to the extragalactic <em>γ</em>-ray background.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"49 ","pages":"Article 100454"},"PeriodicalIF":10.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144925421","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}