Journal of High Energy Astrophysics最新文献

{"title":"Probing generalized emergent dark energy with DESI DR2","authors":"Vipin Kumar Sharma ,&nbsp;Himanshu Chaudhary ,&nbsp;Sanved Kolekar","doi":"10.1016/j.jheap.2025.100518","DOIUrl":"10.1016/j.jheap.2025.100518","url":null,"abstract":"<div><div>As an update on the initial findings of DESI, the new results provide the first hint of potential deviations from a cosmological constant (<span><math><mrow><mi>ω</mi><mo>=</mo><mo>−</mo><mn>1</mn></mrow></math></span>), which, if confirmed with significance <span><math><mrow><mo>&gt;</mo><mo>(</mo><mn>2</mn><mo>−</mo><mn>4</mn><mo>)</mo><mi>σ</mi></mrow></math></span>, would challenge the validity of Λ within the ΛCDM model. We explore the Generalized Emergent Dark Energy (GEDE) model using recent BAO measurements from DESI DR2, Type Ia supernova compilations, and CMB distance priors. Employing nested sampling, we constrain the parameter Δ, which characterizes deviations from ΛCDM. Our analysis shows that with CMB+DESI DR2 alone, GEDE tends to prefer positive values of Δ. However, when different SNe Ia calibrations are included, the model favors negative values of Δ, corresponding to an earlier injection of dark energy. The Marginalized constraints on <em>ω</em>(<em>z</em>) further shows that GEDE sharply emerges but then asymptotes to <span><math><mrow><mi>ω</mi><mo>=</mo><mo>−</mo><mn>1</mn></mrow></math></span> without crossing it. At <em>z</em> ∼ 1 data, GEDE provides a better fit than ΛCDM, while at <em>z</em> ≲ 0.5 the data favor <span><math><mrow><mi>ω</mi><mo>&gt;</mo><mo>−</mo><mn>1</mn></mrow></math></span>, bringing the model deviate from ΛCDM. Bayesian model comparison shows weak support for GEDE with CMB+DESI DR2 (<span><math><mrow><mi>ln</mi><mi>B</mi><mi>F</mi><mo>=</mo><mn>1.96</mn></mrow></math></span>), moderate with PP (<span><math><mrow><mi>ln</mi><mi>B</mi><mi>F</mi><mo>=</mo><mn>2.65</mn></mrow></math></span>), weak-to-moderate with Union3 (<span><math><mrow><mi>ln</mi><mi>B</mi><mi>F</mi><mo>=</mo><mn>2.34</mn></mrow></math></span>), and weak with DES-SN5Y (<span><math><mrow><mi>ln</mi><mi>B</mi><mi>F</mi><mo>=</mo><mn>1.44</mn></mrow></math></span>). Overall, GEDE is consistent with current data and mildly favored when SNe Ia are included, making it a viable extension of ΛCDM that merits further investigation with future high precision measurements.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100518"},"PeriodicalIF":10.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748544","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":"Probing Horndeski gravity via Kerr black hole: Insights from thin accretion disks and shadows with EHT observations","authors":"Xiao-Xiong Zeng ,&nbsp;Chen-Yu Yang ,&nbsp;Muhammad Israr Aslam ,&nbsp;Rabia Saleem","doi":"10.1016/j.jheap.2025.100540","DOIUrl":"10.1016/j.jheap.2025.100540","url":null,"abstract":"<div><div>In this study, we have considered the Kerr-like black hole (BH) model in Horndeski gravity and analyse the visual characteristics of shadow images under two illumination models, such as a celestial light source and a thin accretion disk. To capture the BH shadow images, we utilize a recent fisheye camera model and ray-tracing procedures. In this view, we carefully addressed the influence of the spin parameter <em>a</em> and the hair parameter <em>h</em> on the BH shadow images. The results indicate that for smaller values of <em>h</em>, the BH shadow contours shift noticeably towards the right side of the screen, while for larger values of <em>h</em>, the nearly circular shadow gradually deforms into a possible flatness profile. For a celestial light source, the larger values of <em>h</em> lead to a reduction in the corresponding radius of the photon ring, while the space-dragging effect becomes more pronounced with increasing <em>a</em>. We further discuss the distinctive characteristics of images observed in both prograde and retrograde accretion disk scenarios. The results reveal that variations in <em>h</em> significantly affect both the inner shadow and the resulting Einstein ring. Subsequently, we also discussed the distinct features of red-shift configurations on the disk for both direct and lensed images, which are closely related to the accretion flow and the relevant parameters. We also attempt to use the recent observational data from M87* and Sgr <em>A</em>* and constraint the hair parameter <em>h</em>, the results are consistent and promising.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100540"},"PeriodicalIF":10.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145884291","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 b-CPL dynamical dark energy model with recent cosmological data","authors":"M. Koussour ,&nbsp;O. Donmez ,&nbsp;S. Bekov ,&nbsp;A. Altaibayeva ,&nbsp;A. Saginbay ,&nbsp;S. Muminov ,&nbsp;J. Rayimbaev","doi":"10.1016/j.jheap.2025.100516","DOIUrl":"10.1016/j.jheap.2025.100516","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We introduce and constrain a new parameterization for the dark energy equation of state, the b-CPL model, defined as &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;ω&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;b&lt;/mi&gt;&lt;mtext&gt;-CPL&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;ω&lt;/mi&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/msub&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;ω&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt;&lt;mfrac&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mi&gt;b&lt;/mi&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, which extends the standard CPL framework by including a parameter &lt;em&gt;b&lt;/em&gt;. This additional degree of freedom provides enhanced flexibility to capture potential deviations from standard dynamical dark energy behavior, while reducing to CPL for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;b&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and to ΛCDM in specific limits. Notably, the b-CPL parameterization remains finite at future times, avoiding divergences. Using a combined dataset of cosmic chronometers, PantheonPlus Type Ia supernovae, and DESI baryon acoustic oscillations, we perform a Markov Chain Monte Carlo analysis to constrain the cosmological parameters for the b-CPL, CPL, and ΛCDM models. The b-CPL model yields a more negative present-day equation of state (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;ω&lt;/mi&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;msubsup&gt;&lt;mn&gt;12&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0.20&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0.31&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) and a higher matter density (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mstyle&gt;&lt;mi&gt;Ω&lt;/mi&gt;&lt;/mstyle&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/msubsup&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;msubsup&gt;&lt;mn&gt;332&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0.049&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0.065&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) compared to CPL and ΛCDM. Model selection statistics based on the reduced chi-square, AIC, and BIC indicate that b-CPL is strongly preferred, showing decisive evidence over ΛCDM (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mstyle&gt;&lt;mi&gt;Δ&lt;/mi&gt;&lt;/mstyle&gt;&lt;mtext&gt;AIC&lt;/mtext&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;41.83&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mstyle&gt;&lt;mi&gt;Δ&lt;/mi&gt;&lt;/mstyle&gt;&lt;mtext&gt;BIC&lt;/mtext&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;30.91&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) and significant improvement over CPL (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mstyle&gt;&lt;mi&gt;Δ&lt;/mi&gt;&lt;/mstyle&gt;&lt;mtext&gt;AIC&lt;/mtext&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;26.05&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mstyle&gt;&lt;mi&gt;Δ&lt;/mi&gt;&lt;/mstyle&gt;&lt;mtext&gt;BIC&lt;/mtext&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;9.66&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). Physically, the b-CPL model exhibits a mild redshift evolution of the EoS parameter and tends to remain in the phantom regime (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;ω&lt;/mi&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/msub&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) at present, although within 68 % confidence level, the quintessence region (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;ω&lt;/mi&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/msub&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) is still allowed. It predicts the strongest present-day acceleration (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;q&lt;/mi&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0.62&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0.27&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;), and ","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100516"},"PeriodicalIF":10.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145610151","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":"Probing cosmic isotropy with gamma-ray bursts: A dipole and quadrupole analysis of BATSE and Fermi GBM data","authors":"Debosi Mondal,&nbsp;Biswajit Pandey,&nbsp;Amit Mondal","doi":"10.1016/j.jheap.2026.100549","DOIUrl":"10.1016/j.jheap.2026.100549","url":null,"abstract":"<div><div>The cosmological principle, asserting large-scale homogeneity and isotropy, underpins the standard model of cosmology. Testing its validity using independent astronomical probes remains crucial for understanding the global structure of the Universe. We investigate the angular distribution of Gamma-Ray Bursts (GRBs) using two of the most comprehensive all-sky datasets available, the BATSE (CGRO) and Fermi GBM catalogs, to test the isotropy of the GRB sky at large angular scales. We perform spherical harmonic decomposition of the GRB sky maps and estimate the dipole and quadrupole amplitudes. Statistical significance is evaluated by comparing the observed multipole amplitudes against distributions derived from 500 Monte Carlo realizations of isotropic skies. Our results show that the observed dipole amplitudes for both BATSE and Fermi GBM datasets lie within the 1<em>σ</em> region of their respective null distributions. However, the quadrupole amplitude in the raw, uncorrected BATSE and Fermi GBM skies appears elevated at 3.7<em>σ</em> and 3.0<em>σ</em>, respectively. After incorporating the BATSE sky exposure function, this apparent quadrupole anisotropy vanishes, indicating that instrumental non-uniformities fully account for the signal in that case. Owing to the absence of a publicly available full-sky exposure model for Fermi GBM, the Fermi analysis is restricted to the raw sky distribution. Our method’s reliability is validated through controlled simulations, which show it can detect the injected dipoles in BATSE-sized isotropic skies. These findings reinforce the statistical isotropy of the GRB sky and underscore the importance of accurate exposure corrections in cosmological anisotropy analyses.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100549"},"PeriodicalIF":10.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145938336","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 the hadronic origin of the very high energy γ-ray emission surrounding the young massive stellar cluster Westerlund 1","authors":"Zhaodong Shi ,&nbsp;Rui-Zhi Yang","doi":"10.1016/j.jheap.2026.100560","DOIUrl":"10.1016/j.jheap.2026.100560","url":null,"abstract":"<div><div>The Westerlund 1 (Wd 1) is the most massive known young star cluster in the Galaxy, and an extended <em>γ</em>-ray source HESS J1646-458 surrounding it has been detected up to 80 TeV in the very high energy, implying that cosmic rays (CRs) are accelerated effectively in the region. However, the dominant radiation process contributing to the <em>γ</em>-ray emission is not well constrained. In the present work, we develop a model of CR acceleration at the termination shock in the superbubble inflated by the interaction of the cluster wind from the Wd 1 with the surrounding interstellar medium. We then calculate the flux and radial profile of <em>γ</em> rays produced by the inelastic collisions of the hadronic CRs with the ambient gas. Our results with reasonable parameters can explain well the spectrum and radial profile of the <em>γ</em>-ray emission of HESS J1646-458, and consequently the <em>γ</em>-ray emission of HESS J1646-458 is likely to be of hadronic origin.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100560"},"PeriodicalIF":10.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077366","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 black hole shadows in dunkl spacetime using CUDA numerical computations","authors":"Saad Eddine Baddis,&nbsp;Adil Belhaj,&nbsp;Hajar Belmahi,&nbsp;Maryem Jemri","doi":"10.1016/j.jheap.2025.100541","DOIUrl":"10.1016/j.jheap.2025.100541","url":null,"abstract":"<div><div>With the help of CUDA high-performance numerical codes exploited in machine learning, we investigate the shadow aspect of new rotating and charged black holes using the Dunkl derivative formalism. Precisely, we first establish the corresponding metric function encoding the involved physical properties including the optical character. Exploiting such accelerated simulations, we approach the horizon radius behaviors in order to determine the regions of the moduli space providing physical solutions. Applying the Hamilton-Jacobi mechanism, we assess the shadow aspect for non-rotating and rotating solutions. Using such an aspect, we evaluate the energy rate of emission. Developing a high-performance CUDA numerical code, we derive strict constraints on the Dunkl deformation parameters in order to establish a link with the shadow observations provided by the Event Horizon Telescope collaboration.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100541"},"PeriodicalIF":10.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145884289","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":"Multifrequency evolution of the integrated pulse profile of radio pulsars by implementing the inverse compton mechanism","authors":"Tridib Roy ,&nbsp;Mayuresh Surnis ,&nbsp;Mageshwaran Tamilan ,&nbsp;Monalisa Halder ,&nbsp;Siddhartha Biswas","doi":"10.1016/j.jheap.2026.100557","DOIUrl":"10.1016/j.jheap.2026.100557","url":null,"abstract":"<div><div>The Main Aim of this paper is to explain the emergence of new components of pulsars at higher radio bands by implementing the Inverse Compton Scattering Mechanism. From pulsar radio observation, it is seen that a couple of pulsars reveal new emission components at higher radio frequencies, although they show single-component emission at lower frequencies. We develop a brief outline, fostering inverse Compton scattering (ICS) of the low-frequency radio photons as a vulnerable source of scattering, susceptible to explaining the evolution of new components of some radio pulsars at higher bands. We couple the conventional curvature radiation (CR) mechanism and ICS, and suggest that the spectral convolution of the flux component individually from CR and the modulated template due to the ICS scattered component can be combined to reproduce such signatures associated with the diverse morphology of the integrated pulse profile. We reproduce the beam frequency diagram, the geometrical variation of different parameters of the emission geometry, as well as the multi-frequency evolution from theory. We have suitably tuned the input parameter space and given the combination of parameters that can tune to a particular scattered frequency in tabulated form. We conclude that ICS may be a responsible process for describing the emergence of new components in higher radio emission bands.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100557"},"PeriodicalIF":10.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146037528","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":"Decoding Cygnus X-2: The critical role of reflection in IXPE data","authors":"Honghui Liu ,&nbsp;Jiachen Jiang ,&nbsp;Adam Ingram ,&nbsp;Cosimo Bambi ,&nbsp;Andrew C. Fabian ,&nbsp;Ruben Farinelli ,&nbsp;Renee Ludlam ,&nbsp;Nathalie Degenaar ,&nbsp;Jakub Podgorny ,&nbsp;Andrea Santangelo ,&nbsp;James F. Steiner ,&nbsp;Andrew J. Young ,&nbsp;Zuobin Zhang","doi":"10.1016/j.jheap.2026.100548","DOIUrl":"10.1016/j.jheap.2026.100548","url":null,"abstract":"<div><div>We present a spectro-polarimetric re-analysis of the first IXPE observation of Cygnus X-2 which we determine to be mainly in the normal branch, from quasi-simultaneous observations with NuSTAR, NICER, and INTEGRAL. We measure the hard X-ray polarization angle and find it to be consistent with the previously measured position angle of the radio jet. Leveraging NuSTAR’s detection of both the relativistic Fe K emission line and the Compton hump, we constrain the flux contribution of the reflected emission from the inner accretion disk to be 10% of the total X-ray flux in the IXPE energy band. Unlike previous studies that modeled only the Fe K emission line, we fit the full-band reflection spectrum using a fully relativistic disk model. A polarization degree of approximately 20% for the reflection component could explain the hard X-ray polarization data from IXPE. We also discuss the inferred disk inclination angle derived from our spectro-polarimetric modeling.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100548"},"PeriodicalIF":10.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976507","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":"Late-time cosmic dynamics in f(R, Lm) gravity with recent observations","authors":"Amit Samaddar,&nbsp;S.Surendra Singh","doi":"10.1016/j.jheap.2026.100558","DOIUrl":"10.1016/j.jheap.2026.100558","url":null,"abstract":"<div><div>In this work, we investigate the late-time cosmic dynamics in the framework of non-linear <em>f</em>(<em>R, L_m</em>) gravity, adopting the functional form <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><msub><mi>L</mi><mi>m</mi></msub><mo>)</mo></mrow><mo>=</mo><mfrac><mi>R</mi><mn>2</mn></mfrac><mo>+</mo><msubsup><mi>L</mi><mi>m</mi><mn>2</mn></msubsup></mrow></math></span>. To explore the dark energy behavior, we assume an oscillatory parametric equation of state, <span><math><mrow><mi>ω</mi><mrow><mo>(</mo><mi>z</mi><mo>)</mo></mrow><mo>=</mo><msub><mi>ω</mi><mn>0</mn></msub><mo>+</mo><mi>b</mi><mi>sin</mi><mrow><mo>[</mo><mi>log</mi><mrow><mo>(</mo><mn>1</mn><mo>+</mo><mi>z</mi><mo>)</mo></mrow><mo>]</mo></mrow></mrow></math></span>, which allows smooth deviations from the cosmological constant. Using a joint MCMC analysis with the latest Hubble 31 chronometer data, DESI DR2 BAO measurements, and Type Ia supernova samples (Pantheon+, DES-SN5Y and Union 3), we obtain well-constrained parameters around <span><math><mrow><msub><mi>H</mi><mn>0</mn></msub><mo>≃</mo><mn>67.6</mn><mo>−</mo><mn>67.8</mn><mspace></mspace><mtext>km</mtext><mspace></mspace><msup><mtext>s</mtext><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mtext>Mpc</mtext><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span> and <span><math><mrow><msub><mi>ω</mi><mn>0</mn></msub><mo>≈</mo><mo>−</mo><mn>0.47</mn></mrow></math></span> to <span><math><mrow><mo>−</mo><mn>0.48</mn></mrow></math></span>, consistent with Planck 2018 and other current observations. The model exhibits a dynamically accelerating expansion driven by an oscillatory equation of state, satisfies the null and dominant energy conditions while violating the strong energy condition and yields present-day value <span><math><mrow><msub><mi>q</mi><mn>0</mn></msub><mo>≃</mo><mo>−</mo><mn>0.47</mn></mrow></math></span> to <span><math><mrow><mo>−</mo><mn>0.48</mn></mrow></math></span>, reproducing ΛCDM behavior at late times. The derived Universe ages (<em>t</em>₀ ≈ 13.3 Gyr) agree well with CMB and stellar constraints, confirming that the proposed oscillatory <em>f</em>(<em>R, L_m</em>) model provides an observationally consistent and dynamically viable alternative to ΛCDM cosmology.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100558"},"PeriodicalIF":10.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146037531","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":"Hamilton-Jacobi analysis of noncanonical inflation in f(R, T) gravity: Constraints from planck/ACT data, and theoretical bounds","authors":"Zohdieh Ossoulian,&nbsp;Tayeb Golanbari,&nbsp;Khaled Saaidi","doi":"10.1016/j.jheap.2025.100531","DOIUrl":"10.1016/j.jheap.2025.100531","url":null,"abstract":"<div><div>The latest CMB data from ACT DR6, in combination with Planck, DESI, and BICEP/Keck, indicate a slight upward shift in the scalar spectral index. This trend puts several previously favored inflationary models under tension. In this work, we study an inflationary scenario in the framework of <em>f</em>(<em>R, T</em>) gravity, where <em>R</em> is the Ricci scalar and <em>T</em> is the trace of the energy-momentum tensor, with a nonminimal coupling between matter and curvature. The inflaton is assumed to be a noncanonical scalar field with a generalized kinetic energy. To analyze the dynamics of inflation, we employ the Hamilton-Jacobi formalism, where the Hubble parameter is expressed as a function of the scalar field rather than the potential. Within this setup, we examine two functional forms of the Hubble parameter, a power-law and an exponential form, and derive key observables such as the scalar spectral index <em>n_s</em> and the tensor-to-scalar ratio <em>r</em>. Comparing the results with ACT DR6, we explore the parameter space of the model. We find that the power-law case fits the data well across a wide range of free parameters, while the exponential case requires a large number of e-folds to be consistent with observations. After inflation, we study reheating, where the dynamics of reheating and inflation are closely linked. Taking into account the overproduction of primordial gravitational waves constrained by the observational bound on Δ<em>N</em>_eff, we obtain a lower limit on the reheating temperature, which is especially restrictive for the stiff equation of state <em>ω</em>_re. This bound implies that the number of e-folds of inflation should generally not exceed <em>N</em> ≲ 64(65). The resulting energy spectrum of gravitational waves exhibits an enhanced amplitude, thereby bringing it within the observable range of upcoming detectors. We also check the consistency of the model with the Swampland conjectures and the Trans-Planckian Censorship Conjecture (TCC). Our results demonstrate that combining <em>f</em>(<em>R, T</em>) gravity with noncanonical field dynamics provides a rich and testable framework for the early universe. In addition, the Hamilton-Jacobi approach, by avoiding extra approximations, yields a clearer picture of inflation in modified gravity and opens new directions for addressing fundamental problems in high-energy cosmology.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100531"},"PeriodicalIF":10.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797474","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}