Journal of High Energy Astrophysics最新文献

{"title":"Probing spectral evolution and intrinsic variability of Mkn 421: A multi-epoch AstroSat study of X-ray spectra","authors":"Sikandar Akbar ,&nbsp;Zahir Shah ,&nbsp;Ranjeev Misra ,&nbsp;Naseer Iqbal ,&nbsp;Javaid Tantry","doi":"10.1016/j.jheap.2025.01.009","DOIUrl":"10.1016/j.jheap.2025.01.009","url":null,"abstract":"<div><div>Our study presents a time-resolved X-ray spectral analysis of Mkn<!--> <!-->421, using AstroSat observations taken during different epochs between 2016 and 2019. The variability of the source in X-rays is utilized to investigate the evolution of its spectral properties. Each observation period was divided into segments of about 10 ks, and we employed three forms of particle distributions like broken-power law (BPL), log-parabola (LP), and power-law with maximum electron energy (<span><math><mi>ξ</mi><mo>−</mo><mi>m</mi><mi>a</mi><mi>x</mi></math></span> model) undergoing synchrotron losses to fit the broad X-ray spectrum in each segment. We observed that all of these models provided good fit to the spectra. In case of broken-power law model, we investigated the relationship between normalized particle density at an energy less than the break energy and the index before the break. The results revealed an inverse correlation between the index and particle density with no time delay. Additionally, correlations between spectral parameters were used to determine the pivot energy. We observed that the pivot energy remained same across the observations. For <span><math><mi>ξ</mi><mo>−</mo><mi>m</mi><mi>a</mi><mi>x</mi></math></span> and LP model, we define analogous pivot energies and show that they also do not vary, indicating the model independent nature of the result. The constant pivot energy suggests that the source's variability arises from index variations and not due to changes in the normalization. Consequently, parameters such as magnetic field strength, doppler factor etc may not contribute to the source's variability. Instead, variations are primarily associated with the acceleration or escape timescales of emitted particles within the source.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 438-455"},"PeriodicalIF":10.2,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A white dwarf binary candidate discovered by LAMOST using dynamical method","authors":"Haifan Zhu ,&nbsp;Wei Wang ,&nbsp;Xue Li ,&nbsp;Jia-jia Li ,&nbsp;Pengfu Tian","doi":"10.1016/j.jheap.2025.01.015","DOIUrl":"10.1016/j.jheap.2025.01.015","url":null,"abstract":"<div><div>We present the discovery of a binary system containing a white dwarf candidate using data from the LAMOST. Our analysis of the radial velocity data allowed us to determine an orbital period of approximately 0.953 days and a mass function of 0.129 <span><math><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span>. Through spectral energy distribution (SED) fitting, we obtained the stellar parameters of the visible star. By combining these results with the mass function, we established a relationship between the mass of the invisible star and the system's inclination angle, along with the Roche lobe radius. We find that the mass of the invisible star is below the Chandrasekhar limit when the inclination angle exceeds <span><math><msup><mrow><mn>35</mn></mrow><mrow><mo>∘</mo></mrow></msup></math></span>. Given that systems with large variations in radial velocity typically have high inclination angles, we classify the invisible star as a white dwarf candidate. The Roche lobe radius exceeds the physical radius of the visible star, indicating that no mass transfer occurs, which results in a weak ellipsoidal modulation effect. Additionally, we obtained light curves from the TESS, ASAS-SN, and CRTS surveys. The light curves also exhibit a periodicity of approximately 0.95 days, with ellipsoidal modulation only in the 2019 TESS observations. Coupled with the strong <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>α</mi></mrow></msub></math></span> emission line observed in the LAMOST MRS spectrum, we infer that the surface of the visible star contains significant hot spots. This obscures the system's inherently weak ellipsoidal modulation, resulting in a manifestation of rotational variables. Furthermore, an analysis of the dynamical characteristics of this system indicates that it has a high inclination angle (&gt;60 degrees) and its orbital properties are consistent with those of typical thin disk stars, supporting the hypothesis that the invisible object is a white dwarf.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 428-437"},"PeriodicalIF":10.2,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162960","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":"Gamma ray flares from active region within inhomogeneous AGN jet","authors":"A. Śmiałkowski,&nbsp;W. Bednarek","doi":"10.1016/j.jheap.2025.01.012","DOIUrl":"10.1016/j.jheap.2025.01.012","url":null,"abstract":"<div><div>Two stages of non-thermal emission from relativistic jets in active galaxies can be distinguished: a low level persistent emission and a high level variable emission. It has been recently proposed that both stages are produced in the inner (parsec scale) jet region where electrons are accelerated to TeV energies. We consider a scenario in which the low-level persistent emission originates in the extended, parsec-scale jet but the high level emission is produced by electrons accelerated in a localized region within the inner jet. Our aim is to calculate self-consistently the non-thermal emission expected from the AGN jet in different radiation stages. Then, we will be able to model different emission stages observed in blazars in terms of a single scenario. We modify the stationary, non-local, inhomogeneous AGN jet model for the stationary jet emission by introducing a small active region within the stationary jet, whose physical parameters differ significantly from those in the extended large-scale jet. We distinguish four different emission components which are due to the interaction of relativistic electrons in the active region with the radiation from the active region and radiation from the extended jet and also due to the electrons in the extended jet, which comptonize synchrotron radiation from the extended jet and the active region. Depending on the nature of the active region, we are able to explain the appearance of different types of emission levels in BL Lac type blazars, i.e. the high states observed only in the X-rays or only in the <em>γ</em>-rays. Moreover, we predict the existence of a new type of high emission state in BL Lacs, so called the orphan MeV-soft synchrotron state, in which the inverse Compton emission is mainly limited to the MeV energy range. Such type of blazars have not been observed up to now due to the limited sensitivity of telescopes in the MeV energy range.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 456-462"},"PeriodicalIF":10.2,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelling the energy dependent X-ray variability of Mrk 335","authors":"K. Akhila ,&nbsp;Ranjeev Misra ,&nbsp;Rathin Sarma ,&nbsp;Savithri H. Ezhikode ,&nbsp;K. Jeena","doi":"10.1016/j.jheap.2025.01.014","DOIUrl":"10.1016/j.jheap.2025.01.014","url":null,"abstract":"<div><div>We present a technique which predicts the energy dependent fractional r.m.s. for linear correlated variations of a pair of spectral parameters and apply it to an <em>XMM-Newton</em> observation of Mrk 335. The broadband X-ray spectrum can be interpreted as a patchy absorber partially covering the primary emission, a warm and hot coronal emission or a relativistically blurred reflection along with the primary emission. The fractional r.m.s. has a non-monotonic behaviour with energy for segments of lengths 3 and 6 ksecs. For each spectral model, we consider every pair of spectral parameters and fit the predicted r.m.s. with the observed ones, to get the pair which provides the best fit. We find that a variation in at least two parameters is required for all spectral interpretations. For both time segments, variations in the covering fraction of the absorber and the primary power law index gives the best result for the partial covering model, while a variation in the normalization and spectral index of the warm component gives the best fit in the two corona interpretation. For the reflection model, the best fit parameters are different for the two time segment lengths, and the results suggests that more than two parameters are required to explain the data. This, combined with the extreme values of emissivity index and reflection fraction parameters obtained from the spectral analysis, indicates that the blurred reflection model might not be a suitable explanation for the Mrk 335 spectrum. We discuss the results as well as the potential of the technique to be applied to other data sets of different AGN.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 418-427"},"PeriodicalIF":10.2,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102962","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":"Insights into f(Q) gravity: Modeling through deceleration parameter","authors":"S.A. Narawade,&nbsp;B. Mishra","doi":"10.1016/j.jheap.2025.01.013","DOIUrl":"10.1016/j.jheap.2025.01.013","url":null,"abstract":"<div><div>In this paper, we have reconstructed <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> gravity cosmological models with the novel forms of the deceleration parameter. The parameters are constrained by incorporating the cosmological datasets from Hubble parameter, Type Ia Supernovae and Baryon Acoustic Oscillations. We have examined two parametrizations of the deceleration parameter and fit them into the models through Monte Carlo Markov Chain (MCMC) analysis, one with the power-law function and the other one with the logarithmic function. The Power-law model exhibits strong agreement with higher <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> values, aligning well with recent <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> measurements, whereas the logarithmic model achieves lower matter density constraints. Both the models successfully recover observationally consistent estimates for the Hubble constant <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> and matter density <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><msub><mrow><mi>m</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msub></math></span>, though with varying degrees of precision and alignment with the ΛCDM as a limit. These two models are used to reconstruct the <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> function for each case, yielding analytical expressions that closely align with the numerical solutions. Statistical comparisons using Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) reveal a competitive performance with the ΛCDM model and positioning these <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> models as promising alternatives to explain late time cosmic phenomena.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 409-417"},"PeriodicalIF":10.2,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102418","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":"Dark matter admixed neutron stars with a realistic nuclear equation of state from chiral nuclear interactions","authors":"Domenico Scordino ,&nbsp;Ignazio Bombaci","doi":"10.1016/j.jheap.2025.01.008","DOIUrl":"10.1016/j.jheap.2025.01.008","url":null,"abstract":"<div><div>We study the effects of dark matter on the structural properties of neutron stars. In particular we investigate how the presence of a dark matter component influences the mass-radius relation, the value of the maximum mass of a neutron star and other stellar properties. To model ordinary matter we use a state-of-the-art equation of state of <em>β</em>-stable nuclear matter obtained using the Brueckner-Hartree-Fock quantum many-body approach starting from two-body and three-body nuclear interactions derived from chiral effective field theory. The dark matter component of the star is modeled as a non-self-annihilating system of spin 1/2 fermions at zero temperature and its equation of state as an ideal relativistic Fermi gas. The equilibrium configurations of these dark matter admixed neutron stars (DANS) are calculated by solving a generalization of the Tolman-Oppenheimer-Volkoff equations to the case where the system consists of two perfect fluids interacting solely through gravity. We find that, depending on the dark matter particle mass <span><math><msub><mrow><mi>m</mi></mrow><mrow><mi>χ</mi></mrow></msub></math></span>, one can have somehow opposite effects on the stellar properties. In the case <span><math><msub><mrow><mi>m</mi></mrow><mrow><mi>χ</mi></mrow></msub><mo>=</mo><mn>1</mn><mspace></mspace><mtext>GeV</mtext></math></span>, the stellar gravitational maximum mass <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></math></span> decreases, whereas in the case <span><math><msub><mrow><mi>m</mi></mrow><mrow><mi>χ</mi></mrow></msub><mo>=</mo><mn>0.1</mn><mspace></mspace><mtext>GeV</mtext></math></span>, <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></math></span> increases with respect to the maximum mass of ordinary neutron stars. We also show that the presence of dark matter has indirect sizable effect on the proton fraction in the ordinary matter fluid and, in the case <span><math><msub><mrow><mi>m</mi></mrow><mrow><mi>χ</mi></mrow></msub><mo>=</mo><mn>1</mn><mspace></mspace><mtext>GeV</mtext></math></span>, results in a decrease of the threshold gravitational mass <span><math><msubsup><mrow><mi>M</mi></mrow><mrow><mi>t</mi><mi>o</mi><mi>t</mi></mrow><mrow><mi>d</mi><mi>u</mi><mi>r</mi><mi>c</mi><mi>a</mi></mrow></msubsup></math></span> for having direct URCA processes and fast stellar cooling. Finally we study the stability of dark matter admixed neutron stars with respect to radial perturbations.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 371-381"},"PeriodicalIF":10.2,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102417","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":"Analysis of Hawking evaporation, shadows, and thermodynamic geometry of black holes within the Einstein SU(N) non-linear sigma model","authors":"Shahid Chaudhary ,&nbsp;Muhammad Danish Sultan ,&nbsp;Asifa Ashraf ,&nbsp;Yousef Mohammad Alanazi ,&nbsp;Awatef Abidi ,&nbsp;Ali M. Mubaraki","doi":"10.1016/j.jheap.2025.01.010","DOIUrl":"10.1016/j.jheap.2025.01.010","url":null,"abstract":"<div><div>We explore the intriguing properties of black holes in the Einstein SU(N) non-linear sigma model with a focus on stability, thermodynamic geometry, the Hawking evaporation process, and shadow characteristics. Our study utilizes a novel generalized entropy framework which unify several established entropy models including Bekenstein, Barrow, Tsallis-Cirto, and Tsallis-Zamora entropies. By deriving expressions for specific heat capacity and Gibbs free energy, we unveil distinct stability regions and phase transitions. A key highlight of our investigation is the interplay between the flavor number and AdS length, which we show to profoundly influence black hole evaporation time via the Stefan-Boltzmann law. Numerical simulations reveal that higher flavor numbers shorten evaporation times and reduce the black hole's shadow radius, shedding light on the impact of SU(N) symmetry. Additionally, we employ Weinhold, Ruppeiner, and Quevedo thermodynamic geometries to compute scalar curvatures, visualizing microscopic interactions among black hole molecules. This comprehensive analysis bridges thermodynamic stability, quantum evaporation, and optical signatures, offering fresh perspectives on the rich dynamics of black holes in the Einstein SU(N) non-linear sigma model.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 463-475"},"PeriodicalIF":10.2,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The origin of very-high-energy gamma-rays from GRB 221009A: Implications for reverse shock proton synchrotron emission","authors":"B. Theodore Zhang ,&nbsp;Kohta Murase ,&nbsp;Kunihito Ioka ,&nbsp;Bing Zhang","doi":"10.1016/j.jheap.2025.01.007","DOIUrl":"10.1016/j.jheap.2025.01.007","url":null,"abstract":"<div><div>Recently, GRB 221009A, known as the brightest of all time (BOAT) GRB, has been observed across an astounding range of ∼18 orders of magnitude in energy, spanning from radio to very-high-energy (VHE) bands. Notably, the Large High Altitude Air Shower Observatory (LHAASO) recorded over 60000 photons with energies exceeding <span><math><mn>0.2</mn><mrow><mspace></mspace><mi>TeV</mi></mrow></math></span>, including the first-ever detection of photons above <span><math><mn>10</mn><mrow><mspace></mspace><mi>TeV</mi></mrow></math></span>. However, explaining the observed energy flux evolution in the VHE band alongside late-time multi-wavelength data poses a significant challenge. Our approach involves a two-component structured jet model, consisting of a narrow core dominated by magnetic energy and a wide jet component dominated by matter. We show that the combination of the forward shock electron synchrotron self-Compton emission from the two-component structured jet and reverse shock proton synchrotron emission from the wide jet could account for both the energy flux and spectral evolution in the VHE band, and the early TeV lightcurve may be influenced by prompt photons which could explain the initial steep rising phase. We notice the arrival time of the highest energy photon ∼ 13 TeV detected by LHAASO, especially a minor flare and spectral hardening occurring about ∼ 500 - 800 seconds after the trigger, is consistent with the emergence of the reverse shock proton synchrotron emission. These findings imply that the GRB reverse shock may serve as a potential accelerator of ultra-high-energy cosmic rays, a hypothesis that could be tested through future multimessenger observations.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 392-408"},"PeriodicalIF":10.2,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102416","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 embedded wormhole solutions and thermodynamics in extended teleparallel gravity","authors":"Allah Ditta ,&nbsp;G. Mustafa ,&nbsp;Asif Mahmood","doi":"10.1016/j.jheap.2025.01.006","DOIUrl":"10.1016/j.jheap.2025.01.006","url":null,"abstract":"<div><div>This work investigates the wormhole thermodynamics in teleparallel Rastall gravity using the Karmarkar condition. We apply the first law of wormhole thermodynamics to evaluate the total energy of the wormhole system. In addition, we analyze the stability and equilibrium and thermal stability by investigating the thermodynamic features of wormholes, such as Hawking temperature, wormhole temperature, average wormhole pressure, work energy, total energy, energy flux, and specific heat. We conclude that all the thermodynamic features ensure the thermal stability and equilibrium of the wormhole.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 350-358"},"PeriodicalIF":10.2,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"NuSTAR view of the X-ray transients Swift J174805.3-244637 and IGR J17511-3057","authors":"Aditya S. Mondal ,&nbsp;Mahasweta Bhattacharya ,&nbsp;Mayukh Pahari ,&nbsp;Biplab Raychaudhuri ,&nbsp;Rohit Ghosh ,&nbsp;Gulab C. Dewangan","doi":"10.1016/j.jheap.2025.01.005","DOIUrl":"10.1016/j.jheap.2025.01.005","url":null,"abstract":"<div><div>We report on the <em>NuSTAR</em> observations of the neutron star low-mass X-ray binary Swift J174805.3-244637 (hereafter Swift J17480) and the accreting millisecond X-ray pulsar IGR J17511-3057 performed on March 4, 2023, and April 8, 2015, respectively. We describe the continuum emission of Swift J17480 with a combination of two soft thermal components and an additional hard X-ray emission described by a power-law. We suggest that the spectral properties of Swift J17480 are consistent with a soft spectral state. The source IGR J17511-3057 exhibits a hard spectrum characterized by a Comptonized emission from the corona. The X-ray spectrum of both sources shows evidence of disc reflection. For the first time, we employ the self-consistent reflection models (<span>relxill</span> and <span>relxillNS</span>) to fit the reflection features in the <em>NuSTAR</em> spectrum. From the best-fit spectral model, we find an inner disc radius (<span><math><msub><mrow><mi>R</mi></mrow><mrow><mi>i</mi><mi>n</mi></mrow></msub></math></span>) is precisely constrained to <span><math><mo>(</mo><mn>1.99</mn><mo>−</mo><mn>2.68</mn><mo>)</mo><mspace></mspace><msub><mrow><mi>R</mi></mrow><mrow><mi>I</mi><mi>S</mi><mi>C</mi><mi>O</mi></mrow></msub></math></span> and inclination to <span><math><mn>30</mn><mo>±</mo><mn>1</mn><mi>°</mi></math></span> for Swift J17480. We determine an inner disc radius of <span><math><mo>≲</mo><mn>1.3</mn><mspace></mspace><msub><mrow><mi>R</mi></mrow><mrow><mi>I</mi><mi>S</mi><mi>C</mi><mi>O</mi></mrow></msub></math></span> and inclination of <span><math><mn>44</mn><mo>±</mo><mn>3</mn><mi>°</mi></math></span> for IGR J17511-3057. A low inclination angle of the system is required for both sources. For the source IGR J17511-3057, spinning at 4.1 ms, the value of co-rotation radius (<span><math><msub><mrow><mi>R</mi></mrow><mrow><mi>c</mi><mi>o</mi></mrow></msub></math></span>) is estimated to be ∼42 km (<span><math><mn>3.6</mn><mspace></mspace><msub><mrow><mi>R</mi></mrow><mrow><mi>I</mi><mi>S</mi><mi>C</mi><mi>O</mi></mrow></msub><mo>)</mo></math></span>, consistent with the position of inner disc radius as <span><math><msub><mrow><mi>R</mi></mrow><mrow><mi>i</mi><mi>n</mi></mrow></msub><mo>≲</mo><msub><mrow><mi>R</mi></mrow><mrow><mi>c</mi><mi>o</mi></mrow></msub></math></span>. We further place an upper limit on the magnetic field strength of the sources, considering the disc is truncated at the magnetospheric radius.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 359-370"},"PeriodicalIF":10.2,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102772","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}