Journal of High Energy Astrophysics最新文献

{"title":"Disentangling the origins of the NANOGrav signal: Early Universe models and ΔNeff bounds","authors":"Ido Ben-Dayan ,&nbsp;Utkarsh Kumar ,&nbsp;Amresh Verma","doi":"10.1016/j.jheap.2025.100510","DOIUrl":"10.1016/j.jheap.2025.100510","url":null,"abstract":"<div><div>We investigate whether an Early-Universe stochastic gravitational–wave background (SGWB) can account for the common-spectrum process reported by NANOGrav, while also being consistent with current and projected CMB measurements of extra radiation. We compute the contribution of effective number of relativistic species, <span><math><mi>Δ</mi><msub><mrow><mi>N</mi></mrow><mrow><mi>eff</mi></mrow></msub></math></span>, for a number of Early-Universe models proposed to explain the pulsar timing array (PTA) spectrum. We demonstrate that models predicting <span><math><mi>Δ</mi><msub><mrow><mi>N</mi></mrow><mrow><mi>eff</mi></mrow></msub></math></span> above the CMB limit would either be excluded or require a significant additional contribution from other sources to explain the NANOGrav signal while remaining consistent with the CMB constraints. We find that current NANOGrav 15-year dataset, sensitive up to 60 nHz, gives a negligible contribution to <span><math><mi>Δ</mi><msub><mrow><mi>N</mi></mrow><mrow><mi>eff</mi></mrow></msub></math></span> and remains well below the present and future CMB detection threshold. However, when we project future PTA capabilities reaching upto 1 μHz, even with our conservative estimate we find that Inflation, Scalar Induced Gravitational Waves (SIGW), and metastable cosmic strings can induce a <span><math><mi>Δ</mi><msub><mrow><mi>N</mi></mrow><mrow><mi>eff</mi></mrow></msub></math></span> large enough for <span><math><mo>&gt;</mo><mn>3.5</mn><mi>σ</mi></math></span> detection by the Simons Observatory.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100510"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571745","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":"Confronting dark energy in Harada's Conformal Killing Gravity with observational data","authors":"Mohsen Khodadi ,&nbsp;Gaetano Lambiase ,&nbsp;Javad T. Firouzjaee","doi":"10.1016/j.jheap.2025.100512","DOIUrl":"10.1016/j.jheap.2025.100512","url":null,"abstract":"<div><div>Based on a comprehensive analysis of recent observational data—a combination of DESI DR1, Planck CMB, and Pantheon+ SN Ia—this study critically evaluates the two dark energy (DE) proposals within Harada's Conformal Killing Gravity (CKG) model. The model at question predicts either a dominant phantom-type effective DE component with EoS <span><math><mi>ω</mi><mo>=</mo><mo>−</mo><mn>5</mn><mo>/</mo><mn>3</mn></math></span> or a hybrid scenario combining a cosmological constant (<span><math><mi>ω</mi><mo>=</mo><mo>−</mo><mn>1</mn></math></span>) with a subdominant <span><math><mi>ω</mi><mo>=</mo><mo>−</mo><mn>5</mn><mo>/</mo><mn>3</mn></math></span> fluid (around 5%) to address the Hubble tension (HT) and late-time acceleration. An analysis based on the Trans-Planckian Censorship Conjecture (TCC) demonstrates that the pure CKG fluid scenario <span><math><mi>ω</mi><mo>=</mo><mo>−</mo><mn>5</mn><mo>/</mo><mn>3</mn></math></span> is excluded, whereas the hybrid model remains only marginally compatible. Our Markov Chain Monte Carlo (MCMC) analysis constrains the effective DE density parameter to <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mtext>eff</mtext></mrow></msub><mo>=</mo><msubsup><mrow><mn>0.009</mn></mrow><mrow><mo>−</mo><mn>0.007</mn></mrow><mrow><mo>+</mo><mn>0.006</mn></mrow></msubsup></math></span> (68% CL), consistent with zero and ruling out the <span><math><mo>∼</mo><mn>5</mn><mtext>%</mtext></math></span> contribution required by Harada's CKG. The resulting Hubble expansion history <span><math><mi>H</mi><mo>(</mo><mi>z</mi><mo>)</mo></math></span> and effective EoS <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mtext>eff</mtext></mrow></msub><mo>(</mo><mi>z</mi><mo>)</mo></math></span> are indistinguishable from those of ΛCDM. Bayesian model comparison via the Akaike Information Criterion (AIC) shows no statistical preference for CKG over ΛCDM (<span><math><mi>Δ</mi><mtext>AIC</mtext><mo>=</mo><mo>+</mo><mn>2.6</mn></math></span>), disfavoring the additional complexity of the CKG model. The key output of this study is that both DE proposals in Harada's CKG are ruled out by current cosmological data, and HT remains unresolved.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100512"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571750","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":"Spectral–timing evolution of a black hole X-ray binary Swift J1727.8–1613: Linking disk reflection and type-C QPO frequency during the 2023 outburst","authors":"Manoj Ghising ,&nbsp;Nirpat Subba ,&nbsp;Mohammed Tobrej ,&nbsp;Binay Rai ,&nbsp;Bikash Chandra Paul","doi":"10.1016/j.jheap.2025.100513","DOIUrl":"10.1016/j.jheap.2025.100513","url":null,"abstract":"<div><div>We present a comprehensive spectral–timing analysis of a BHXB Swift J1727.8−1613 during its 2023 outburst, using five pointed <em>NuSTAR</em> observations sampling the luminous hard–intermediate state. Broadband 3–79 keV spectroscopy employs a physically motivated model combining a cool truncated disk (<span>diskbb</span>), relativistic reflection (<span>relxill</span> in reflection-only mode), and Comptonized continuum (<span>nthComp</span>) to probe the inner accretion geometry around a rapidly spinning black hole (<span><math><msub><mrow><mi>a</mi></mrow><mrow><mo>⁎</mo></mrow></msub><mo>=</mo><mn>0.98</mn></math></span>) at moderate inclination. Simultaneous timing analysis reveals type-C quasi-periodic oscillations (QPOs) with novel coherence evolution: the quality factor (<em>Q</em>) exhibits a striking non-monotonic dependence on both QPO frequency and luminosity, peaking near <span><math><msub><mrow><mi>ν</mi></mrow><mrow><mi>QPO</mi></mrow></msub><mo>∼</mo><mn>1.2</mn></math></span> Hz and declining at both lower and higher frequencies. This turnover directly constrains Lense–Thirring precession geometry, implying optimal coherence at intermediate truncation radius. A tight photon-index–QPO-frequency correlation demonstrates that spectral softening and frequency rise are concurrent signatures of inward truncation-radius motion. The triadic luminosity evolution—rising disk and Compton, declining reflection—traces precession-driven geometry changes and corona beaming effects. Interpreting disk-normalization variability as apparent-area changes rather than physical radius swings provides new insight into disk-corona boundary layers. These quantitative results provide strong evidence for global Lense–Thirring precession regulation of both timing and spectral properties, establishing Swift J1727.8−1613 as a benchmark source for understanding accretion-geometry physics during black hole state transitions.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100513"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571749","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":"On perturbation induced minimal geometric decoupling in spacetime and its impact on mass-gap stability: Insights from the binary mergers GW190814, GW200210, and millisecond pulsars PSR J1614-2230 and PSR J0952-0607","authors":"Ksh. Newton Singh ,&nbsp;S.K. Maurya ,&nbsp;A. Errehymy ,&nbsp;Z. Umbetova ,&nbsp;K. Myrzakulov ,&nbsp;J. Rayimbaev","doi":"10.1016/j.jheap.2025.100501","DOIUrl":"10.1016/j.jheap.2025.100501","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This study investigates the internal composition and stability of mass-gap compact stars (CSTARs) formed from neutron star mergers or evolved massive pulsars, using the minimal geometric deformation (MGD) framework. Starting from a Buchdahl–Vaidya–Tikekar inspired metric ansatz, we derive exact, physically consistent unperturbed solutions describing static, spherically symmetric stars with energy densities monotonically decreasing from central values on the order of &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;15&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mrow&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;c&lt;/mi&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; to the surface at radius &lt;em&gt;R&lt;/em&gt;. To model realistic astrophysical effects such as gravitational waves or accretion, we introduce a perturbation function &lt;span&gt;&lt;math&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;r&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;sin&lt;/mi&gt;&lt;mo&gt;⁡&lt;/mo&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;ω&lt;/mi&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;r&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; characterized by amplitude &lt;em&gt;α&lt;/em&gt; and frequency &lt;em&gt;ω&lt;/em&gt;. Rather than assuming a fixed EOS, we adopt a well-defined ansatz for the metric component &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;r&lt;/mi&gt;&lt;mi&gt;r&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; (Eq. &lt;span&gt;&lt;span&gt;(21)&lt;/span&gt;&lt;/span&gt;), inducing pressure-density relations confirmed through radial profiles of pressure and density. We incorporate observational constraints from pulsars PSR J1614-2230 (&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mn&gt;1.97&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0.04&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0.0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&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;), PSR J0952-0607 (approximately &lt;span&gt;&lt;math&gt;&lt;mn&gt;2.35&lt;/mn&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&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 gravitational wave events GW190814 and GW200210, which suggest masses above &lt;span&gt;&lt;math&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&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;. Radius estimates such as &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mn&gt;13.70&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1.5&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;2.6&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mrow&gt;&lt;mi&gt;km&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; for PSR J0740+6620 provide additional bounds. As &lt;em&gt;α&lt;/em&gt; increases from 0 to 0.005, the EOS shifts sharply from linear to nonlinear. In contrast, increasing &lt;em&gt;ω&lt;/em&gt; up to &lt;span&gt;&lt;math&gt;&lt;mn&gt;0.06&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;km&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; with fixed &lt;span&gt;&lt;math&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0.001&lt;/mn&gt;&lt;/math&gt;&lt;/span&gt; causes only minor EOS deviations. The mass-radius (&lt;span&gt;&lt;math&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) relation is similarly affected: without perturbations (&lt;span&gt;&lt;math&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mi&gt;ω&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/math&gt;&lt;/span&gt;), the curve is smooth, reaching a maximum mass &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;max&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;≈&lt;/mo&gt;&lt;mn&gt;3.5&lt;","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100501"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145417674","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":"Measuring accretion disc properties in the transitional millisecond pulsar PSR J1023+0038 using XMM-Newton, NuSTAR, NICER and Chandra","authors":"Vishal Jadoliya ,&nbsp;Mayukh Pahari ,&nbsp;Sudip Bhattacharyya ,&nbsp;Shaswat Suresh Nair","doi":"10.1016/j.jheap.2025.100506","DOIUrl":"10.1016/j.jheap.2025.100506","url":null,"abstract":"<div><div>Whether the accretion disc in the X-ray high-mode of transitional millisecond pulsars (tMSP) reaches near the neutron star surface by penetrating the magnetosphere is a crucial question with many implications, including for continuous gravitational wave emission from the pulsar. We attempt to answer this question for the tMSP PSR J1023+0038 by segregating high-mode data and performing detailed spectral analysis using the <em>XMM-Newton</em> EPIC-PN+MOS1+MOS2 joint observations, <em>XMM-Newton</em>+<em>NuSTAR</em> joint observations, <em>NICER</em> and <em>Chandra</em> individual observations during different epochs. With the sum of longest exposures (∼202 ksec of high mode data from ∼364 ksec of total exposure), we performed a self-consistent spectral analysis and constrain the inner disc radius 16.8 ± 3.8 km with at least 3<em>σ</em> significance. Such a measurement is found consistent with best-fit spectral values of inner disc radius from other observatory like <em>NICER</em> and joint observations with <em>XMM-Newton</em> and <em>NuSTAR</em> within 3<em>σ</em> limits. We also detect a Fe emission line at 6.45 keV, for the first time from a tMSP, in the <em>Chandra</em> spectrum with 99% significance with an upper limit of the inner disc radius of 21 R_<em>g</em>, supporting independently the fact that inner disc extends into neutron stars magnetosphere during high mode. All results from our analysis imply that the accretion disc is significantly present and extended within the corotation radius of the neutron star in PSR J1023+0038 during the X-ray high-mode of the tMSP PSR J1023+0038. The measured range of inner disc radius is fully consistent with an independent analysis by <span><span>Bhattacharyya (2020)</span></span>, which suggests continuous gravitational wave emission from this neutron star, and the standard model of X-ray pulsations in accreting MSPs.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100506"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145519813","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 energy power-law tail in X-ray binaries spectrum and bulk Comptonization due to a conical outflow from a disk","authors":"Nagendra Kumar","doi":"10.1016/j.jheap.2025.100503","DOIUrl":"10.1016/j.jheap.2025.100503","url":null,"abstract":"<div><div>X-ray binaries (XRBs) often exhibit a high energy power-law tail (HEP-tail) and these tails can be generated by the bulk Comptonization (BMC) process with a free-fall bulk region onto the compact object. The radio emission (which is generated by a synchrotron-emitting outflowing electrons) is observed in all spectral state of XRBs. Interestingly, the variations of HEP-tail flux among different spectral states are similar to the variation of radio flux. We motivate to study the HEP-tail in BMC process with an outflowing medium. For this we consider a collimated and conical (of opening angle <span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>b</mi></mrow></msub></math></span> with axis perpendicular to the accretion disk) outflow geometry. We simulate the BMC spectrum by using a Monte Carlo scheme. We find that the emergent spectrum has power-law tail (of photon index <span><math><mi>Γ</mi><mo>&gt;</mo><mn>2</mn></math></span> and with high energy cut-off <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>c</mi></mrow></msub><mo>&gt;</mo><mn>200</mn></math></span> keV) only for <span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>b</mi></mrow></msub></math></span> greater than ∼30 degrees in conical outflow, while for a collimated or a conical outflow (<span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>b</mi></mrow></msub><mo>&lt;</mo><mn>30</mn></math></span> degrees) these HEP-tail can be only generated when it is also found in thermal Comptonized spectra (i.e., at sufficiently high Comptonizing medium temperature). These results are approximately consistent with analytically derived expressions. We describe the observed GRS 1915+105 spectrum for two classes <em>χ</em> and <em>γ</em> in conical outflow, for this the outflow speed is highly relativistic and the kinetic power of wind suggests that the HEP-tail can be generated at inner region of the accretion disk, like inner disk radio emission.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100503"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145466544","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":"Exploring year-timescale transient and long-term quasi-periodic oscillations in optical and gamma-ray light curves of blazars","authors":"Ajay Sharma ,&nbsp;Sakshi Chaudhary ,&nbsp;Aishwarya Sarath ,&nbsp;Debanjan Bose","doi":"10.1016/j.jheap.2025.100466","DOIUrl":"10.1016/j.jheap.2025.100466","url":null,"abstract":"<div><div>A comprehensive analysis of quasi-periodic oscillations (QPOs) in the multi-wavelength observations of blazars has been carried out. Utilizing 15 years of Fermi-LAT observations of seven blazars in our sample, we identify both long-term and transient QPOs in the gamma-ray light curves, with timescales ranging from a few months to years. These periodicities were detected using the Lomb-Scargle periodogram (LSP) and REDFIT techniques. To robustly evaluate the statistical significance of the quasi-periodic signals observed in the LSPs, 2<span><math><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>5</mn></mrow></msup></math></span> synthetic <em>γ</em>-ray light curves were generated for each source using a stochastic model known as the Damped Random Walk (DRW). These gamma-ray QPOs are further supported by the detection of optical QPOs exhibiting similar timescales. A cross-correlation analysis between <em>γ</em>-rays and optical emissions reveals a significant peak (<span><math><mo>&gt;</mo><mn>3</mn><mi>σ</mi></math></span>) at or close to zero-lag. To investigate the physical origin of the observed gamma-ray QPOs with different timescales, we explore several plausible scenarios, with particular emphasis on a relativistic jet hosted by one of the black holes in a supermassive binary black hole (SMBBH) system, accretion disc model, and helical motion of magnetized plasma blob within the jet. The transient gamma-ray QPOs of month-like timescales are interpreted within the framework of the helical motion of plasma blob in jet, while the long-duration QPOs with multi-year timescales are explained using the SMBBH scenario. The gamma-ray light curves were modeled by employing a Markov Chain Monte Carlo (MCMC) approach, allowing us to constrain key physical parameters such as the jet Lorentz factor (Γ) and the viewing angle between the observer's line of sight (<em>ψ</em>) relative to the spin axis of SMBH.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100466"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145098696","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":"Galaxy evolution in the local Universe: Group richness effects on mergers and non-mergers","authors":"Pius Privatus ,&nbsp;Umananda Dev Goswami","doi":"10.1016/j.jheap.2025.100468","DOIUrl":"10.1016/j.jheap.2025.100468","url":null,"abstract":"<div><div>In this study, we use the luminous volume-limited samples obtained from the twelfth release of Sloan Digital Sky Survey data and mergers from Galaxy Zoo Project to investigate the influence of group richness in shaping galaxy properties' distributions and their relationships in the local Universe by comparison of mergers and non-mergers. The galaxies were restricted into mass-limited subsamples of low-mass, intermediate-mass and high-mass, assigned into groups from poor to rich group systems, where the distributions of star formation rate (SFR), specific SFR (SSFR), spectral index <span><math><msub><mrow><mtext>D</mtext></mrow><mrow><mi>n</mi></mrow></msub></math></span> (4000) and <span><math><mi>u</mi><mo>−</mo><mi>r</mi></math></span> colour properties between mergers and non-mergers for all subsamples and their relations with stellar mass of galaxies are compared. The study revealed a significant difference in the distributions between mergers' and non-mergers' properties for low-mass galaxies, while for high-mass galaxies the difference is very weak. For the low-mass sample, mergers possess higher SFR, SSFR than non-mergers when the group richness is kept constant, while for high-mass poor group galaxies have higher SFR, SSFR than rich group galaxies when merging status is kept constant. Mergers resemble young stellar populations and are bluer than non-mergers for low-mass, while for high-mass, mergers and non-mergers have comparable SFR, SSFR, <span><math><msub><mrow><mtext>D</mtext></mrow><mrow><mi>n</mi></mrow></msub></math></span> (4000), and <span><math><mi>u</mi><mo>−</mo><mi>r</mi></math></span> colour. The study concludes that group richness and stellar mass influence the mergers' and non-mergers' properties' distributions, and their relationships.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100468"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145098695","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":"Energetics of magnetized accretion-induced outflows around black holes: Description of a unified disk-jet connection","authors":"Shubhrangshu Ghosh ,&nbsp;Sudip Bhattacharyya","doi":"10.1016/j.jheap.2025.100469","DOIUrl":"10.1016/j.jheap.2025.100469","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We investigate the global energetics of the magnetized accretion-induced outflow in the context of a two-temperature accreting plasma around black holes (BHs), explicitly incorporating the effect of the ‘Ohmic heating’. We obtain substantially high electron temperature, with &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; even reaching &lt;span&gt;&lt;math&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; in the inner regions of the flow. The radiative cooling is primarily determined by the synchrotron loss which mostly dominates the inner accretion region, more so, in the context of flows towards super massive BHs (SMBHs). However, at a relatively high &lt;span&gt;&lt;math&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;˙&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;˙&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;Edd&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, bremsstrahlung emission dominates most of the accretion region. For stellar mass BHs, on the other hand, synchrotron dominates the cooling for a considerable portion of the inner and middle accretion region, with emission cooling rates significantly higher. Electron heating is primarily governed by turbulent Ohmic dissipation, with &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; primarily determined by the balance between Ohmic heating and synchrotron cooling. We obtain relatively high values of luminosity reaching &lt;span&gt;&lt;math&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;42&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mrow&gt;&lt;mi&gt;erg&lt;/mi&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and surpassing &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;35&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mrow&gt;&lt;mi&gt;erg&lt;/mi&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, from the inner accretion region, corresponding to &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;BH&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;8&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&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;, respectively, for moderately advective flows. Based on the estimates of the ratio of ‘mass flow rate into the jet’ to ‘mass inflow rate’ &lt;span&gt;&lt;math&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;˙&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;j&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;˙&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;, and comparing our theoretical finding with the ratio of radio-to-X-ray luminosities for several BH X-ray binaries (BHXRBs), we tentatively suggest that both steady and transient jets in BHXRBs could primarily be accretion powered, indicating a ","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100469"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145099039","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":"Effects of QCD-based equation of state on the structure and tidal deformability of compact stars in regularized 4D Einstein-Gauss-Bonnet gravity","authors":"Takol Tangphati ,&nbsp;Ayan Banerjee ,&nbsp;Anirudh Pradhan ,&nbsp;Javlon Rayimbaev","doi":"10.1016/j.jheap.2025.100493","DOIUrl":"10.1016/j.jheap.2025.100493","url":null,"abstract":"<div><div>We study quark star configurations in regularized four-dimensional Einstein-Gauss-Bonnet (4DEGB) gravity using a QCD-motivated equation of state with parameters <span><math><msub><mrow><mi>B</mi></mrow><mrow><mi>eff</mi></mrow></msub></math></span>, <span><math><msub><mrow><mi>a</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, and <span><math><msub><mrow><mi>a</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span>. The modified Tolman-Oppenheimer-Volkoff equations, incorporating 4DEGB corrections, are solved to examine mass-radius relations, tidal deformability, and stability across a range of <em>α</em>, <span><math><msub><mrow><mi>a</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, and <span><math><msub><mrow><mi>a</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span>. Positive <em>α</em> or larger <span><math><msub><mrow><mi>a</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> yields more massive, compact stars than in general relativity, with some configurations below the GR Buchdahl limit, potentially eliminating the mass gap with black holes. The dimensionless tidal deformability Λ decreases markedly with <em>α</em> and <span><math><msub><mrow><mi>a</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, while <span><math><msub><mrow><mi>a</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span> has only a minor effect. Models consistent with NICER, GW170817, and HESS J1731−347 constraints remain dynamically stable and causal. Our results demonstrate that the interplay between higher-curvature gravity and QCD microphysics can produce observationally viable deviations from general relativity, offering promising targets for future multimessenger constraints on dense matter and alternative gravity theories.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100493"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145269260","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}