Pub Date : 2026-01-20DOI: 10.1016/j.jheap.2026.100560
Zhaodong Shi , Rui-Zhi Yang
The Westerlund 1 (Wd 1) is the most massive known young star cluster in the Galaxy, and an extended γ-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 γ-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 γ 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 γ-ray emission of HESS J1646-458, and consequently the γ-ray emission of HESS J1646-458 is likely to be of hadronic origin.
{"title":"On the hadronic origin of the very high energy γ-ray emission surrounding the young massive stellar cluster Westerlund 1","authors":"Zhaodong Shi , 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":"2026-01-20","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}
Pub Date : 2026-01-13DOI: 10.1016/j.jheap.2026.100558
Amit Samaddar, S.Surendra Singh
In this work, we investigate the late-time cosmic dynamics in the framework of non-linear f(R, Lm) gravity, adopting the functional form . To explore the dark energy behavior, we assume an oscillatory parametric equation of state, , 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 and to , 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 to , reproducing ΛCDM behavior at late times. The derived Universe ages (t0 ≈ 13.3 Gyr) agree well with CMB and stellar constraints, confirming that the proposed oscillatory f(R, Lm) model provides an observationally consistent and dynamically viable alternative to ΛCDM cosmology.
{"title":"Late-time cosmic dynamics in f(R, Lm) gravity with recent observations","authors":"Amit Samaddar, 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<sub>m</sub></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><sub>0</sub> ≈ 13.3 Gyr) agree well with CMB and stellar constraints, confirming that the proposed oscillatory <em>f</em>(<em>R, L<sub>m</sub></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":"2026-01-13","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}
Pub Date : 2026-01-12DOI: 10.1016/j.jheap.2026.100554
Jessica Santiago , Kerkyra Asvesta , Maria Giovanna Dainotti , Pisin Chen
We present a new analysis of cosmic dipole anisotropy using gamma-ray bursts (GRBs) as high-redshift standardizable candles. GRBs are ideal probes for testing the cosmological principle thanks to their high luminosity, wide redshift range, and nearly isotropic sky coverage. For the first time, we employ the luminosity—time (L-T) relation, known in the literature as the bidimensional X-ray Dainotti relation, corrected for redshift evolution, to standardize a sample of 176 long GRBs detected by Swift. We test for dipolar modulations in the GRB Hubble diagram using both the Dipole Fit Method and a new approach introduced here, the Anisotropic Residual Analysis Method. Both methods yield consistent results: a dipole amplitude of Ad ≃ 0.6 ± 0.2 pointing towards (RA, DEC) (equatorial coordinates). As shown in the Appendix, this corresponds to a boost velocity of the observer with respect to the GRB rest-frame in the antipodal direction from the dipole direction. Extensive isotropy tests and 20,000 Monte Carlo simulations confirm that the detected signal cannot be explained by chance alignments or by the angular distribution of the GRB sample. We also show how, by incorporating a dipole term, residual correlations are eliminated, showing that the dipole model provides a better fit than standard isotropic ΛCDM.
{"title":"Measuring cosmic dipole with the GRB luminosity-time relation","authors":"Jessica Santiago , Kerkyra Asvesta , Maria Giovanna Dainotti , Pisin Chen","doi":"10.1016/j.jheap.2026.100554","DOIUrl":"10.1016/j.jheap.2026.100554","url":null,"abstract":"<div><div>We present a new analysis of cosmic dipole anisotropy using gamma-ray bursts (GRBs) as high-redshift standardizable candles. GRBs are ideal probes for testing the cosmological principle thanks to their high luminosity, wide redshift range, and nearly isotropic sky coverage. For the first time, we employ the luminosity—time (L-T) relation, known in the literature as the bidimensional X-ray Dainotti relation, corrected for redshift evolution, to standardize a sample of 176 long GRBs detected by <em>Swift</em>. We test for dipolar modulations in the GRB Hubble diagram using both the Dipole Fit Method and a new approach introduced here, the Anisotropic Residual Analysis Method. Both methods yield consistent results: a dipole amplitude of <em>A<sub>d</sub></em> ≃ 0.6 ± 0.2 pointing towards (RA, DEC) <span><math><mrow><mo>≈</mo><mo>(</mo><msup><mn>134</mn><mo>∘</mo></msup><mo>±</mo><msup><mn>30</mn><mo>∘</mo></msup><mo>,</mo><mo>−</mo><msup><mn>36</mn><mo>∘</mo></msup><mo>±</mo><msup><mn>21</mn><mo>∘</mo></msup><mo>)</mo></mrow></math></span> (equatorial coordinates). As shown in the Appendix, this corresponds to a boost velocity of the observer with respect to the GRB rest-frame in the antipodal direction from the dipole direction. Extensive isotropy tests and 20,000 Monte Carlo simulations confirm that the detected signal cannot be explained by chance alignments or by the angular distribution of the GRB sample. We also show how, by incorporating a dipole term, residual correlations are eliminated, showing that the dipole model provides a better fit than standard isotropic ΛCDM.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100554"},"PeriodicalIF":10.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146076894","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}
Pub Date : 2026-01-12DOI: 10.1016/j.jheap.2026.100556
Manish Yadav , Archana Dixit , M.S. Barak , Anirudh Pradhan
In this study, we investigate the oscillatory dark energy model wsinCDM based on the DESI BAO data together with OHD, Pantheon Plus, and SH0ES measurements. We examine how the DESI data influence the dark energy equation-of-state plane (w0, wa) within cosmological models that are free from Hubble tension and employ a Monte Carlo Markov Chain (MCMC) approach. Our findings indicate that although the parameter space still favors wa < 0 and , the cosmological constant remains consistent with the DESI+OHD+PP combination at the 2σ level. We also observe that the best-fit Hubble constant H0 is higher for the DESI+OHD+PP+SH0ES data combination, leading to a residual Hubble tension of less than 1σ to remain consistent with the SH0ES measurement. These results suggest that attempts to address the Hubble tension tend to reduce indication of DESI for the oscillatory dark energy model. Therefore, claims that the cosmological constant should be approached with greater caution, considering both the latest observational datasets and the existing cosmological tensions. We also obtained the present deceleration parameter and the effective equation-of-state value as and , respectively, for the DESI+OHD+PP+SH0ES dataset combination. Further analysis indicated a strong departure of w0 from at the 4σ level for the DR2+OHD+DES-5yr data combination. The inferred Ωm tended to shift toward higher values when supernova samples were included, indicating a systematic preference for larger Ωm in combinations involving supernova data.
{"title":"Dynamical oscillations in dark energy: Joint constraints on the wsinCDM model from DESI, OHD, and supernova samples","authors":"Manish Yadav , Archana Dixit , M.S. Barak , Anirudh Pradhan","doi":"10.1016/j.jheap.2026.100556","DOIUrl":"10.1016/j.jheap.2026.100556","url":null,"abstract":"<div><div>In this study, we investigate the oscillatory dark energy model <em>w</em><sub>sin</sub>CDM based on the DESI BAO data together with OHD, Pantheon Plus, and SH0ES measurements. We examine how the DESI data influence the dark energy equation-of-state plane (<em>w</em><sub>0</sub>, <em>w<sub>a</sub></em>) within cosmological models that are free from Hubble tension and employ a Monte Carlo Markov Chain (MCMC) approach. Our findings indicate that although the parameter space still favors <em>w<sub>a</sub></em> < 0 and <span><math><mrow><msub><mi>w</mi><mn>0</mn></msub><mo>></mo><mo>−</mo><mn>1</mn></mrow></math></span>, the cosmological constant remains consistent with the DESI+OHD+PP combination at the 2<em>σ</em> level. We also observe that the best-fit Hubble constant <em>H</em><sub>0</sub> is higher for the DESI+OHD+PP+SH0ES data combination, leading to a residual Hubble tension of less than 1<em>σ</em> to remain consistent with the SH0ES measurement. These results suggest that attempts to address the Hubble tension tend to reduce indication of DESI for the oscillatory dark energy model. Therefore, claims that the cosmological constant should be approached with greater caution, considering both the latest observational datasets and the existing cosmological tensions. We also obtained the present deceleration parameter and the effective equation-of-state value as <span><math><mrow><msub><mi>q</mi><mn>0</mn></msub><mo>=</mo><mo>−</mo><mn>0.36</mn></mrow></math></span> and <span><math><mrow><msub><mi>w</mi><mtext>eff</mtext></msub><mo>=</mo><mo>−</mo><mn>0.57</mn></mrow></math></span>, respectively, for the DESI+OHD+PP+SH0ES dataset combination. Further analysis indicated a strong departure of <em>w</em><sub>0</sub> from <span><math><mrow><mi>w</mi><mo>=</mo><mo>−</mo><mn>1</mn></mrow></math></span> at the 4<em>σ</em> level for the DR2+OHD+DES-5yr data combination. The inferred Ω<sub><em>m</em></sub> tended to shift toward higher values when supernova samples were included, indicating a systematic preference for larger Ω<sub><em>m</em></sub> in combinations involving supernova data.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100556"},"PeriodicalIF":10.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146037530","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}
Pub Date : 2026-01-12DOI: 10.1016/j.jheap.2026.100548
Honghui Liu , Jiachen Jiang , Adam Ingram , Cosimo Bambi , Andrew C. Fabian , Ruben Farinelli , Renee Ludlam , Nathalie Degenaar , Jakub Podgorny , Andrea Santangelo , James F. Steiner , Andrew J. Young , Zuobin Zhang
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.
{"title":"Decoding Cygnus X-2: The critical role of reflection in IXPE data","authors":"Honghui Liu , Jiachen Jiang , Adam Ingram , Cosimo Bambi , Andrew C. Fabian , Ruben Farinelli , Renee Ludlam , Nathalie Degenaar , Jakub Podgorny , Andrea Santangelo , James F. Steiner , Andrew J. Young , 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":"2026-01-12","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}
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.
{"title":"Multifrequency evolution of the integrated pulse profile of radio pulsars by implementing the inverse compton mechanism","authors":"Tridib Roy , Mayuresh Surnis , Mageshwaran Tamilan , Monalisa Halder , 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":"2026-01-12","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}
Pub Date : 2026-01-10DOI: 10.1016/j.jheap.2026.100552
M. Reshma , C.S. Stalin , Amit Kumar Mandal , Abhijit Kayal , S.B. Gudennavar , Prajwel Joseph
Active galactic nuclei are known to exhibit flux variations across the entire electromagnetic spectrum. Among these, correlations between UV/optical and X-ray flux variations serve as a key diagnostics for understanding the physical connection between the accretion disk and the corona. In this work, we present the results of analysis of ultraviolet (UV) and X-ray flux variations in the narrow line Seyfert 1 galaxy Mrk 1044. Simultaneous observations in the far-UV band (FUV: 1300 - 1800 Å) and the X-ray band (0.5 - 7 keV) obtained during 31 August - 8 September 2018 with the Ultraviolet Imaging Telescope and the Soft X-ray Telescope onboard AstroSat were used for this study. Significant flux variability was detected in both FUV and X-ray bands. The fractional root mean square variability amplitude (Fvar) was found to be 0.036 ± 0.001 in the FUV band and 0.384 ± 0.004 in the X-ray band. To explore potential time lag between the two bands, cross-correlation analysis was performed using both the interpolated cross-correlation function (ICCF) and just another vehicle for estimating lags in nuclei (JAVELIN) methods. Results from both approaches are consistent within 2σ uncertainty, indicating that X-ray variations lead the FUV variations, with measured lags of 2.25 ± 0.05 days (ICCF) and days (JAVELIN). This is the first detection of a time delay between UV and X-ray variations in Mrk 1044. The observed UV lag supports the disk reprocessing scenario, wherein X-ray emission from the corona irradiates the accretion disk, driving the observed UV variability.
{"title":"Detection of time delay between UV and X-ray variability in Mrk 1044 using AstroSat observations","authors":"M. Reshma , C.S. Stalin , Amit Kumar Mandal , Abhijit Kayal , S.B. Gudennavar , Prajwel Joseph","doi":"10.1016/j.jheap.2026.100552","DOIUrl":"10.1016/j.jheap.2026.100552","url":null,"abstract":"<div><div>Active galactic nuclei are known to exhibit flux variations across the entire electromagnetic spectrum. Among these, correlations between UV/optical and X-ray flux variations serve as a key diagnostics for understanding the physical connection between the accretion disk and the corona. In this work, we present the results of analysis of ultraviolet (UV) and X-ray flux variations in the narrow line Seyfert 1 galaxy Mrk 1044. Simultaneous observations in the far-UV band (FUV: 1300 - 1800 Å) and the X-ray band (0.5 - 7 keV) obtained during 31 August - 8 September 2018 with the Ultraviolet Imaging Telescope and the Soft X-ray Telescope onboard <em>AstroSat</em> were used for this study. Significant flux variability was detected in both FUV and X-ray bands. The fractional root mean square variability amplitude (<em>F</em><sub>var</sub>) was found to be 0.036 ± 0.001 in the FUV band and 0.384 ± 0.004 in the X-ray band. To explore potential time lag between the two bands, cross-correlation analysis was performed using both the interpolated cross-correlation function (ICCF) and just another vehicle for estimating lags in nuclei (JAVELIN) methods. Results from both approaches are consistent within 2<em>σ</em> uncertainty, indicating that X-ray variations lead the FUV variations, with measured lags of 2.25 ± 0.05 days (ICCF) and <span><math><mrow><mn>2</mn><mo>.</mo><msubsup><mn>35</mn><mrow><mo>−</mo><mn>0.01</mn></mrow><mrow><mo>+</mo><mn>0.02</mn></mrow></msubsup></mrow></math></span> days (JAVELIN). This is the first detection of a time delay between UV and X-ray variations in Mrk 1044. The observed UV lag supports the disk reprocessing scenario, wherein X-ray emission from the corona irradiates the accretion disk, driving the observed UV variability.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100552"},"PeriodicalIF":10.5,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976509","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}
Pub Date : 2026-01-09DOI: 10.1016/j.jheap.2026.100553
N. Sadeghnezhad , R. Jalalzadeh , Z. Davari , B. Afshar
The cosmological implications of New Tsallis holographic dark energy (NTHDE) in Rastall theory have been studied. Using the data set that includes DESI BAO (DR2), PantheonPlus SNe Ia, H(z) measurements, and BBN and the MCMC analysis, the key cosmological and model-specific parameters are constrained. The result is compared with that of the ΛCDM model indicating that in addition to providing a viable dynamical dark energy framework, predictions for H(z) are slightly more consistent with intermediate-redshift observations. Generally, the model remains compatible with current data and offers testable deviations from ΛCDM for upcoming surveys. It is also seen that when the energy density of quantum fields in vacuum, exposed by NTHDE, is combined with the Rastall correction term to the general relativity, a plausible candidate for dynamical dark energy is obtained that mimic the current value of the dark energy density parameter reported in the ΛCDM model. The latter cannot be repeated by NTHDE alone. Although NTHDE is not always classically stable, dynamical stability analysis reveals a stable de-Sitter fate for the Cosmos. The study also confirms previous theoretical and observational constraints on the Rastall parameter obtained by focusing on the thermodynamics, early universe, pulsars, and the early-type galaxies.
研究了新萨利斯全息暗能量（NTHDE）在拉斯托尔理论中的宇宙学意义。利用包括DESI BAO （DR2）、PantheonPlus snia、H(z)测量和BBN以及MCMC分析在内的数据集，对关键的宇宙学和模型特定参数进行了约束。结果与ΛCDM模型的结果进行了比较，表明除了提供一个可行的动态暗能量框架外，对H(z)的预测与中间红移观测结果略微一致。一般来说，该模型与当前数据保持兼容，并为即将进行的调查提供ΛCDM的可测试偏差。当NTHDE暴露的真空中量子场的能量密度与广义相对论的Rastall修正项相结合时，可以得到一个模拟ΛCDM模型中报告的暗能量密度参数当前值的动态暗能量候选者。后者不能仅由NTHDE来重复。虽然NTHDE并不总是经典稳定的，但动态稳定性分析揭示了宇宙的稳定de-Sitter命运。该研究还证实了先前通过热力学、早期宇宙、脉冲星和早期型星系获得的拉斯托参数的理论和观测约束。
{"title":"Observational constraints on New Tsallis holographic energy in Rastall theory","authors":"N. Sadeghnezhad , R. Jalalzadeh , Z. Davari , B. Afshar","doi":"10.1016/j.jheap.2026.100553","DOIUrl":"10.1016/j.jheap.2026.100553","url":null,"abstract":"<div><div>The cosmological implications of New Tsallis holographic dark energy (NTHDE) in Rastall theory have been studied. Using the data set that includes DESI BAO (DR2), PantheonPlus SNe Ia, <em>H</em>(<em>z</em>) measurements, and BBN and the MCMC analysis, the key cosmological and model-specific parameters are constrained. The result is compared with that of the ΛCDM model indicating that in addition to providing a viable dynamical dark energy framework, predictions for <em>H</em>(<em>z</em>) are slightly more consistent with intermediate-redshift observations. Generally, the model remains compatible with current data and offers testable deviations from ΛCDM for upcoming surveys. It is also seen that when the energy density of quantum fields in vacuum, exposed by NTHDE, is combined with the Rastall correction term to the general relativity, a plausible candidate for dynamical dark energy is obtained that mimic the current value of the dark energy density parameter reported in the ΛCDM model. The latter cannot be repeated by NTHDE alone. Although NTHDE is not always classically stable, dynamical stability analysis reveals a stable de-Sitter fate for the Cosmos. The study also confirms previous theoretical and observational constraints on the Rastall parameter obtained by focusing on the thermodynamics, early universe, pulsars, and the early-type galaxies.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100553"},"PeriodicalIF":10.5,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077365","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}
Pub Date : 2026-01-08DOI: 10.1016/j.jheap.2026.100551
Muhammad Israr Aslam , Rabia Saleem , Chen-Yu Yang , Xiao-Xiong Zeng
Based on two distinct thick accretion flow disk models, such as a phenomenological RIAF-like model and an analytical Hou disk model, we investigate the impact of relevant parameters on the visual characteristics of the Schwarzschild black hole (BH) surrounded by perfect fluid dark matter (PFDM). We impose a general relativistic radiative transfer equation to determine the synchrotron emission from thermal electrons and generate horizon-scale images. In the RIAF-like model, we notice that the corresponding photon ring and central dark region are expanded with the aid of the PFDM parameter η, with brightness asymmetries originating at higher inclination angles and closely tied to flow dynamics and emission anisotropy. The fundamental difference between isotropic and anisotropic radiation is that anisotropy introduces vertical distortions in the higher-order images, resulting in an elliptical appearance. For the Hou disk model, the observed images produce narrower rings and dark interiors, while polarization patterns trace the brightness distribution and changes with the variations of the inclination angle and PFDM parameter η, which reflects the spacetime signature. All these results indicate that the observed intensity and polarization characteristics in the framework of thick disk models may serve as valuable probes of underlying spacetime geometry and the accretion-dynamics close to the horizon.
{"title":"Imprints of dark matter on the shadow and polarization images of a black hole illuminated by various thick disks","authors":"Muhammad Israr Aslam , Rabia Saleem , Chen-Yu Yang , Xiao-Xiong Zeng","doi":"10.1016/j.jheap.2026.100551","DOIUrl":"10.1016/j.jheap.2026.100551","url":null,"abstract":"<div><div>Based on two distinct thick accretion flow disk models, such as a phenomenological RIAF-like model and an analytical Hou disk model, we investigate the impact of relevant parameters on the visual characteristics of the Schwarzschild black hole (BH) surrounded by perfect fluid dark matter (PFDM). We impose a general relativistic radiative transfer equation to determine the synchrotron emission from thermal electrons and generate horizon-scale images. In the RIAF-like model, we notice that the corresponding photon ring and central dark region are expanded with the aid of the PFDM parameter <em>η</em>, with brightness asymmetries originating at higher inclination angles and closely tied to flow dynamics and emission anisotropy. The fundamental difference between isotropic and anisotropic radiation is that anisotropy introduces vertical distortions in the higher-order images, resulting in an elliptical appearance. For the Hou disk model, the observed images produce narrower rings and dark interiors, while polarization patterns trace the brightness distribution and changes with the variations of the inclination angle and PFDM parameter <em>η</em>, which reflects the spacetime signature. All these results indicate that the observed intensity and polarization characteristics in the framework of thick disk models may serve as valuable probes of underlying spacetime geometry and the accretion-dynamics close to the horizon.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100551"},"PeriodicalIF":10.5,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976520","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}
Pub Date : 2026-01-07DOI: 10.1016/j.jheap.2026.100550
A. Bukhari , G. Abbas , Tao Zhu
Accretion disks around compact astrophysical objects provide an essential framework for examining the nature of strong gravitational fields and exploring possible manifestations of quantum gravity. In this paper, we examine the structural and radiative features of a geometrically thin disk encircling a quantum–corrected Reissner–Nordström black hole (QCRN–BH), where the spacetime geometry is influenced by both the electric charge Q and the quantum correction parameter ω. Employing the geodesic equations and the analysis of the effective potential, we obtain the criteria for stable circular motion, locate the innermost stable circular orbit (ISCO), and evaluate the corresponding specific energy, angular momentum, and angular velocity of the disk matter. The results demonstrate that higher values of either Q or ω drive the ISCO toward smaller radii, reduce the energy per unit mass, and enhance the overall radiative efficiency. The modified distributions of the flux, temperature, and luminosity suggest that quantum effects increase the conversion of gravitational energy in the inner disk region. This work highlights, for the first time, the combined impact of Q and ω on disk dynamics, stability, and emission properties, providing phenomenological perspective for distinguishing quantum–corrected black holes from classical ones.
{"title":"Orbital structure and radiative behavior of accretion disks around quantum-corrected charged black holes","authors":"A. Bukhari , G. Abbas , Tao Zhu","doi":"10.1016/j.jheap.2026.100550","DOIUrl":"10.1016/j.jheap.2026.100550","url":null,"abstract":"<div><div>Accretion disks around compact astrophysical objects provide an essential framework for examining the nature of strong gravitational fields and exploring possible manifestations of quantum gravity. In this paper, we examine the structural and radiative features of a geometrically thin disk encircling a quantum–corrected Reissner–Nordström black hole (QCRN–BH), where the spacetime geometry is influenced by both the electric charge <em>Q</em> and the quantum correction parameter <em>ω</em>. Employing the geodesic equations and the analysis of the effective potential, we obtain the criteria for stable circular motion, locate the innermost stable circular orbit (ISCO), and evaluate the corresponding specific energy, angular momentum, and angular velocity of the disk matter. The results demonstrate that higher values of either <em>Q</em> or <em>ω</em> drive the ISCO toward smaller radii, reduce the energy per unit mass, and enhance the overall radiative efficiency. The modified distributions of the flux, temperature, and luminosity suggest that quantum effects increase the conversion of gravitational energy in the inner disk region. This work highlights, for the first time, the combined impact of <em>Q</em> and <em>ω</em> on disk dynamics, stability, and emission properties, providing phenomenological perspective for distinguishing quantum–corrected black holes from classical ones.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"51 ","pages":"Article 100550"},"PeriodicalIF":10.5,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976543","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}
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