Journal of High Energy Astrophysics最新文献

{"title":"X-ray flux variability of Blazar Mrk 501 observed using NuSTAR","authors":"S.A. Ata ,&nbsp;Nasser M. Ahmed ,&nbsp;M.M. Beheary ,&nbsp;F.Y. Kamal","doi":"10.1016/j.jheap.2025.100417","DOIUrl":"10.1016/j.jheap.2025.100417","url":null,"abstract":"<div><div>We present a detailed spectral study of 12 X-ray NuSTAR observations of the BL Lac object Markarian (or Mrk) 501, spanning a period from 2013 to 2022. We extracted source spectra within an 80-arcseconds radius around the source center and background with a radius of 300-arcseconds. The X-ray flux variability of our sample was derived by extracting the Blazar Mrk 501 sample spectra and fitting them with six models in the XSPEC package; these models yielded similar results. The spectral models covered various physical processes, including thermal bremsstrahlung emission. In addition, we investigated the time variations of the model parameters. By comparing the fits from the six models, we found that the zpowerlw model is the best representation of the data in the low state, while the bremsstrahlung-zpowerlaw model best represents the data across all energy ranges. To verify the X-ray variability of our data, we fit their spectra, extracted using the same method from the same instrument, with the same model to estimate their X-ray luminosity and flux. To verify the variability of the estimated fluxes, we fitted them using the bremsstrahlung-zpowerlaw model and found clear variability over the 12 observations. The bremsstrahlung-zpowerlaw model was the best model fitting the data in the 3 – 50 keV band. The highest variability was found in observation 60002024006, with a flux variability of 39.72 × <span><math><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>11</mn></mrow></msup></math></span> (erg<!--> <!-->cm⁻² <!-->s⁻¹). While the lowest variability was found in observation 60466006002, with a flux variability of 1.34 × <span><math><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>11</mn></mrow></msup></math></span> (erg<!--> <!-->cm⁻² <!-->s⁻¹), making the flux variability range 38.38 × <span><math><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>11</mn></mrow></msup></math></span> (erg<!--> <!-->cm⁻² <!-->s⁻¹).</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100417"},"PeriodicalIF":10.2,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518342","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":"Development of source-dependent gamma-ray image parameters using Generative Adversarial Network (GAN) for the MACE telescope and its implications","authors":"Manas Pratim Das ,&nbsp;V.K. Dhar ,&nbsp;Anudeep Singh ,&nbsp;N. Bhatt ,&nbsp;K.K. Yadav","doi":"10.1016/j.jheap.2025.100416","DOIUrl":"10.1016/j.jheap.2025.100416","url":null,"abstract":"<div><div>In the field of Very High Energy (VHE) gamma-ray astronomy using the Imaging Atmospheric Cherenkov Technique (IACT), the main challenge is to elicit the faint gamma-ray signal from a huge deluge of Cosmic Ray (CR) signals. For this purpose, an extensive simulation database of <em>γ</em>-ray-induced extensive air shower (EAS) images across a wide energy range (30 GeV - a few 10 TeVs) must be generated. Moreover, different celestial <em>γ</em>-ray sources differ in flux and power-law spectral indices.</div><div>However, the position of the gamma-ray events in the image parameter hyperspace changes as per the gamma-ray source spectral profile. Hence, depending on the gamma-ray sources' spectral indices, the gamma domain cuts are subject to change. The gamma domain cuts proposed for a particular source (the Crab Nebula, for example) applied to a source of different spectral indices will inevitably result in an erroneous flux calculation of the source. The Generative Adversarial Network (GAN) is a potent unsupervised and generative Machine Learning (ML) tool to generate synthetic gamma-ray image parameters for sources with different spectral indices. This article will discuss the rationale behind developing a source-dependent database generation using the GAN and highlight its importance for the MACE telescope.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100416"},"PeriodicalIF":10.2,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144490061","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":"Two-component jet model for the afterglow emission of GRB 201216C and GRB 221009A and implications for jet structure of very-high-energy gamma-ray bursts","authors":"Yuri Sato ,&nbsp;Kohta Murase ,&nbsp;Yutaka Ohira ,&nbsp;Susumu Inoue ,&nbsp;Ryo Yamazaki","doi":"10.1016/j.jheap.2025.100415","DOIUrl":"10.1016/j.jheap.2025.100415","url":null,"abstract":"<div><div>In recent years, afterglow emission in the very-high-energy (VHE) band above 100 GeV has been clearly detected for at least five gamma-ray bursts (GRBs 180720B, 190114C, 190829A, 201216C and 221009A). For some of these VHE GRBs, we previously proposed a two-component jet model, consisting of two uniform jets with narrow and wide opening angles to explain their multiwavelength afterglows including VHE gamma rays. In this paper, we show that the VHE spectra and light curves of GRBs 201216C and 221009A can also be reasonably explained by our two-component jet model, based on two top-hat jets propagating into a constant-density circumburst medium. We find that for the five VHE GRBs, the collimation-corrected kinetic energies of the narrow and wide jets have typical values of <span><math><mn>5</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>49</mn></mrow></msup></math></span> erg and <span><math><mn>5</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>50</mn></mrow></msup></math></span> erg, respectively. We discuss the similarities and differences among the VHE GRBs, and the implications for the structure of their jets. In agreement with previous studies, the narrow jet of GRB 221009A has an atypically small opening angle, so that its intrinsic, collimation-corrected energy remains within a plausible range despite the unusually large isotropic-equivalent energy.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100415"},"PeriodicalIF":10.2,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321620","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":"Testing the quantum equivalence principle with gravitational waves","authors":"Saurya Das ,&nbsp;Mitja Fridman ,&nbsp;Gaetano Lambiase","doi":"10.1016/j.jheap.2025.100413","DOIUrl":"10.1016/j.jheap.2025.100413","url":null,"abstract":"<div><div>We study modifications of gravitational wave observables, such as the wave amplitude and frequency, which follow from the quantum equivalence principle, and are expressed in terms of the inertial, gravitational and rest masses of the LIGO/Virgo mirrors. We provide bounds on the violations of the quantum equivalence principle by comparing the results with the most resolved gravitational wave events observed by the LIGO/Virgo collaboration. The formalism is equally applicable to other future ground and space-based gravitational wave detectors.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100413"},"PeriodicalIF":10.2,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144270151","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":"Modelling self-gravitating systems in f(R,G) gravity with anisotropic pressure and Tolman-Kuchowicz background","authors":"M. Ilyas ,&nbsp;Zaib Un Nisa Shinwari","doi":"10.1016/j.jheap.2025.100414","DOIUrl":"10.1016/j.jheap.2025.100414","url":null,"abstract":"<div><div>The present study offers a comprehensive analysis of anisotropic matter distributions and various physical properties of compact stars within the framework of <span><math><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>G</mi><mo>)</mo></math></span>-gravity. To thoroughly explore these aspects, we focus on three specific compact stellar objects: Her X-1 (CS1), SAX J1808.4-3658 (CS2), and 4U 1820-30 (CS3). Using three distinct models of <span><math><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>G</mi><mo>)</mo></math></span>-gravity, we compute the relevant physical characteristics of these stars. For a systematic approach, the <span><math><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>G</mi><mo>)</mo></math></span>-gravity framework is decomposed into two components: <span><math><msub><mrow><mi>f</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> and <span><math><msub><mrow><mi>f</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mi>G</mi><mo>)</mo></math></span>. The <em>R</em>-dependent term, <span><math><msub><mrow><mi>f</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span>, is modelled following the Hu-Sawicki formalism, while the <em>G</em>-dependent term, <span><math><msub><mrow><mi>f</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mi>G</mi><mo>)</mo></math></span>, incorporates logarithmic and power-law formulations, leading to three viable gravitational models. We employ graphical analysis to examine the physical behaviour of these compact stars under the proposed modified gravity scenarios.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100414"},"PeriodicalIF":10.2,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144307326","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":"Variability study of classical supergiant X-ray binary 4U 1907+09 using NuSTAR","authors":"Raj Kumar ,&nbsp;Sayantan Bhattacharya ,&nbsp;Sudip Bhattacharyya ,&nbsp;Subir Bhattacharyya","doi":"10.1016/j.jheap.2025.100412","DOIUrl":"10.1016/j.jheap.2025.100412","url":null,"abstract":"<div><div>We investigate the X-ray variability of the supergiant X-ray binary 4U 1907+09 using the new <em>NuSTAR</em> observation of 2024. Unlike the previous <em>NuSTAR</em> observations, the source shows significant flux variation during the current one. The light curve exhibits dips (off-state) and flares (on-state). The phase-coherent timing analysis during the on-state yields a pulse period of <span><math><mn>443.99</mn><mo>(</mo><mn>4</mn><mo>)</mo><mspace></mspace><mi>s</mi></math></span>, showing the pulsar's continued spin-down. The pulse profiles show an asymmetric double-peaked structure with a phase separation of 0.47 between the two peaks. A cyclotron resonance scattering feature (CRSF) is also detected at <span><math><mo>∼</mo><mn>17.6</mn><mspace></mspace><mrow><mi>keV</mi></mrow></math></span>, along with its harmonic at <span><math><mo>∼</mo><mn>38</mn><mspace></mspace><mrow><mi>keV</mi></mrow></math></span>, persisting across all flux states. Flux-resolved spectroscopy reveals that the CRSF energy remains constant despite a 25-fold change in flux. The spectral parameters, like photon index and e-fold energy, are out of phase with the pulse shape, whereas the cutoff energy is in phase with the pulse shape. The source's luminosity during the on-state is <span><math><mn>2.85</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>35</mn></mrow></msup><mspace></mspace><mrow><mi>erg</mi><mspace></mspace><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, consistent with a “pencil” beam radiation pattern expected at this flux level from a collisionless gas-mediated shock. These results offer further insights into the accretion dynamics and magnetic field geometry of this system.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100412"},"PeriodicalIF":10.2,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144255388","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 New Master Supernovae Ia sample and the investigation of the Hubble tension","authors":"M.G. Dainotti ,&nbsp;B. De Simone ,&nbsp;A. Garg ,&nbsp;K. Kohri ,&nbsp;A. Bashyal ,&nbsp;A. Aich ,&nbsp;A. Mondal ,&nbsp;S. Nagataki ,&nbsp;G. Montani ,&nbsp;T. Jareen ,&nbsp;V.M. Jabir ,&nbsp;S. Khanjani ,&nbsp;M. Bogdan ,&nbsp;N. Fraija ,&nbsp;A.C.C. do E.S. Pedreira ,&nbsp;R.H. Dejrah ,&nbsp;A. Singh ,&nbsp;M. Parakh ,&nbsp;R. Mandal ,&nbsp;K. Jarial ,&nbsp;H. Sarkar","doi":"10.1016/j.jheap.2025.100405","DOIUrl":"10.1016/j.jheap.2025.100405","url":null,"abstract":"<div><div>Modern cosmological research still thoroughly debates the discrepancy between local probes and the Cosmic Microwave Background observations in the Hubble constant (<span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>) measurements, ranging from 4 to 6<em>σ</em>. In the current study, we examine this tension using the Supernovae Ia (SNe Ia) data from the Pantheon, Pantheon+ (P+), Joint Lightcurve Analysis (JLA), and Dark Energy Survey, (DES) catalogs combined together into the so-called Master Sample. The sample contains 3714 SNe Ia, and is divided all of them into redshift-ordered bins. Three binning techniques are presented: the equi-population, the moving window (MW), and the equi-spacing in the <span><math><mi>log</mi><mo>⁡</mo><mo>−</mo><mi>z</mi></math></span>. We perform a Markov-Chain Monte Carlo analysis (MCMC) for each bin to determine the <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> value, estimating it within the standard flat ΛCDM and 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 models. These <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> values are then fitted with the following phenomenological function: <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mi>z</mi><mo>)</mo><mo>=</mo><msub><mrow><mover><mrow><mi>H</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub><mo>/</mo><msup><mrow><mo>(</mo><mn>1</mn><mo>+</mo><mi>z</mi><mo>)</mo></mrow><mrow><mi>α</mi></mrow></msup></math></span>, where <span><math><msub><mrow><mover><mrow><mi>H</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub></math></span> is a free parameter representing <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mi>z</mi><mo>)</mo></math></span> fitted in <span><math><mi>z</mi><mo>=</mo><mn>0</mn></math></span>, and <em>α</em> is the evolutionary parameter. Our results indicate a decreasing trend characterized by <span><math><mi>α</mi><mo>∼</mo><mn>0.01</mn></math></span>, whose consistency with zero ranges from 1<em>σ</em> in 5 cases to 1 case at 3 <em>σ</em> and 11 cases at <span><math><mo>&gt;</mo><mn>3</mn><mi>σ</mi></math></span> in several samples and configurations. Such a trend in the SNe Ia catalogs could be due to evolution with redshift for the astrophysical variables or unveiled selection biases. Alternatively, intrinsic physics, possibly the <span><math><mi>f</mi><mo>(</mo><mi>R</mi><mo>)</mo></math></span> theory of gravity, could be responsible for this trend.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100405"},"PeriodicalIF":10.2,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144223597","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":"Constraining dark energy evolution in f(Q,C) gravity using observational datasets and geometric diagnostics","authors":"Amit Samaddar,&nbsp;S. Surendra Singh","doi":"10.1016/j.jheap.2025.100404","DOIUrl":"10.1016/j.jheap.2025.100404","url":null,"abstract":"<div><div>We investigate the cosmological implications of <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>,</mo><mi>C</mi><mo>)</mo></math></span> gravity with <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>,</mo><mi>C</mi><mo>)</mo><mo>=</mo><mi>α</mi><mi>Q</mi><mo>+</mo><mi>β</mi><mi>C</mi></math></span>, where <em>Q</em> is the non-metricity scalar and <em>C</em> encapsulates cosmological expansion terms. Three parameterizations of the EoS for dark energy, <span><math><mi>ω</mi><mo>=</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>+</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub><mi>z</mi></math></span>, <span><math><mi>ω</mi><mo>=</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>+</mo><mfrac><mrow><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub><mi>z</mi><mo>(</mo><mn>1</mn><mo>+</mo><mi>z</mi><mo>)</mo></mrow><mrow><mn>1</mn><mo>+</mo><msup><mrow><mi>z</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac></math></span> and <span><math><mi>ω</mi><mo>=</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>+</mo><mfrac><mrow><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub><msup><mrow><mi>z</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow><mrow><mn>1</mn><mo>+</mo><msup><mrow><mi>z</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac></math></span> are tested using the Hubble, Hubble+BAO, and Hubble+BAO+Pantheon datasets to constrain model parameters. The resulting Hubble and deceleration parameters reveal a transition from deceleration to acceleration, supporting current cosmic acceleration observations. Analysis of the energy density and pressure confirms positive energy density and a negative pressure for dark energy, potentially driving the late-time acceleration. We examine energy conditions, showing compliance with NEC, WEC and DEC, while SEC remains negative, supporting an accelerated expansion. Statefinder diagnostics suggest that two of the EoS parameterizations lead to Quintessence-like behavior with a time-varying dark energy component, while the third closely approaches ΛCDM showing slight deviations consistent with recent observations. Sound speed analysis demonstrates the physical stability of all parameterizations. Overall, our findings support <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>,</mo><mi>C</mi><mo>)</mo></math></span> gravity as a viable framework for describing diverse dark energy dynamics, providing insights into the Universe's accelerated expansion.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100404"},"PeriodicalIF":10.2,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144205145","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":"Solving an interacting quintessence model with a sound horizon initial condition and its observational constraints","authors":"Wenzhong Liu ,&nbsp;Yabo Wu ,&nbsp;Supriya Pan ,&nbsp;Weiqiang Yang","doi":"10.1016/j.jheap.2025.100403","DOIUrl":"10.1016/j.jheap.2025.100403","url":null,"abstract":"<div><div>Astronomical observations suggest that the current standard Λ-Cold Dark Matter model in modern cosmology has some discrepancies when fitting the data during the whole expansion history of the universe. To solve the Hubble constant (<span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>) tension, usually an unknown mechanism is considered that shifts the sound horizon at the decoupling era. On the other hand, dynamical dark energy models are also considered to resolve the problems of the cosmological constant, and the additional degrees of freedom require initial conditions for a solution. In this article we have considered a coupled quintessence dark energy model with a special focus on its early-time behaviour. In our solution the initial conditions are naturally decided by setting the value of the sound horizon at the recombination time, <span><math><msup><mrow><mi>θ</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>. We find that during this process, <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> could be derived and its value rises with the coupling strength of the interaction. We also performed the background and cosmic microwave background power spectrum analysis, and find that the existence of the interaction term affects the energy density during a narrow time interval range and shifts the early cosmic microwave background spectrum. We also constrained the parameter space of the underlying scenario using the Markov chain Monte Carlo analysis. We find that the best-fit values of <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>S</mi></mrow><mrow><mn>8</mn></mrow></msub></math></span> are improved slightly for the interacting model, but not enough to release the tensions.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"47 ","pages":"Article 100403"},"PeriodicalIF":10.2,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144189937","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":"BL Lacertae under the flare of 2024: Probing temporal and spectral dynamics","authors":"Joysankar Majumdar,&nbsp;Sakshi Maurya,&nbsp;Raj Prince","doi":"10.1016/j.jheap.2025.100402","DOIUrl":"10.1016/j.jheap.2025.100402","url":null,"abstract":"<div><div>In October 2024, the object BL Lacertae experienced the brightest flaring event in gamma-ray (&gt;100 MeV) with a historically bright <em>γ</em>-ray flux of ∼2.59 <span><math><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup></math></span> erg cm⁻² s⁻¹ with a detection of a 175.7 GeV photon with Fermi-LAT. This event was also followed by very high-energy <em>γ</em>-ray detection with LHAASO, VERITAS, and MAGIC. Soon after, Swift-XRT and Swift-UVOT follow-up confirmed the concurrent flare in X-ray, UV, and optical bands. A minimum flux doubling/halving time of 1.06 ± 0.26 hour with 4<em>σ</em> significance has been observed with the Fermi-LAT orbit binned light curve. No compelling correlation has been found between <em>γ</em>-ray spectral indices and fluxes. The log-normal <em>γ</em>-ray flux distribution during the flare confirms the multiplicative nature of the non-linear perturbation causing the flare. We applied a one-zone leptohadronic model to fit the broadband SED during the flaring period. The broadband SED modeling reveals that the sudden enhancement of the magnetic field and bulk factor might promote the flare. The SED modeling also suggested a more compact emission region, which may be described by a shorter variability time than the observed one. The hadronic part best fitted the high energy part of the spectrum, suggesting the jets of BL Lac could provide a promising environment to accelerate the cosmic ray particles, such as protons. The jets of BL Lacertae could also be the possible source of astrophysical neutrinos, as an upper limit on neutrinos has already been reported from IceCube.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100402"},"PeriodicalIF":10.2,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144223097","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}