Journal of High Energy Astrophysics最新文献

{"title":"Comprehensive spectro-temporal studies of GX 17+2 using AstroSat observations","authors":"Neal Titus Thomas,&nbsp;S. Lavanya,&nbsp;S.B. Gudennavar,&nbsp;S.G. Bubbly","doi":"10.1016/j.jheap.2024.12.007","DOIUrl":"10.1016/j.jheap.2024.12.007","url":null,"abstract":"<div><div>We performed a comprehensive spectro-temporal study of the Z-type neutron star low-mass X-ray binary GX 17+2 using long term data from the <em>AstroSat</em>/Soft X-ray Telescope (SXT) and Large Area X-ray Proportional Counter (LAXPC). The hardness–intensity diagrams (HIDs) of the source revealed a positive correlation between the hardness and intensity, characteristic of soft spectral state. Additionally, the LAXPC-20 HID showed the presence of secular shifts in both hardness and intensity. Time-averaged spectral modelling in the 0.7 − 30.0 keV energy range indicated that the spectra could be well fitted with the model combination: <span>constant</span> × <span>edge</span> × <span>edge</span> × <span>tbabs</span> × <span>thcomp</span> × <span>bbodyrad</span>. This analysis yielded a blackbody radius (<span><math><msub><mrow><mi>R</mi></mrow><mrow><mi>b</mi><mi>b</mi></mrow></msub></math></span>) of ∼59 km, photon index (Γ) of ∼2.84 and electron temperature (<span><math><mi>k</mi><msub><mrow><mi>T</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span>) of ∼4.84 keV. Time-averaged temporal analysis revealed normal branch oscillations (NBOs) at ∼ 7 Hz in Observations 1 and 3, flaring branch oscillation (FBO) at ∼15 Hz in Observation 2, and horizontal branch oscillation (HBO) at ∼36 Hz in Observation 5. Flux resolved spectro-temporal analysis indicated that the source remained in the soft spectral state throughout all observations. A positive correlation was observed between <span><math><mi>k</mi><msub><mrow><mi>T</mi></mrow><mrow><mi>b</mi><mi>b</mi></mrow></msub></math></span>, <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>b</mi><mi>b</mi></mrow></msub></math></span> and <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>b</mi><mi>o</mi><mi>l</mi></mrow></msub></math></span>, whereas an anti-correlation was noted between <span><math><mi>k</mi><msub><mrow><mi>T</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> and <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>b</mi><mi>o</mi><mi>l</mi></mrow></msub></math></span>. The constant frequency of NBOs with an increase in <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>b</mi><mi>o</mi><mi>l</mi></mrow></msub></math></span> suggests that their origin lies in a region strongly influenced by the corona, as explained by the radiation-hydrodynamic model. The origin of FBOs may be attributed to the damped radiation-hydrodynamic mode of radial flow, while the origin of HBOs is supported by the beat-frequency model.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 250-261"},"PeriodicalIF":10.2,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102787","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":"Effect of baryon number density (n) on the maximum mass and stability of strange stars","authors":"Anusmita Nag,&nbsp;Debadri Bhattacharjee,&nbsp;Koushik Ballav Goswami,&nbsp;Pradip Kumar Chattopadhyay","doi":"10.1016/j.jheap.2024.12.005","DOIUrl":"10.1016/j.jheap.2024.12.005","url":null,"abstract":"<div><div>A new class of relativistic solutions of Einstein field equations for an anisotropic strange star admitting the Vaidya-Tikekar type metric potential in the framework of MIT bag model equation of state of the strange matter, <span><math><msub><mrow><mi>p</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>=</mo><mfrac><mrow><mn>1</mn></mrow><mrow><mn>3</mn></mrow></mfrac><mo>(</mo><mi>ρ</mi><mo>−</mo><mn>4</mn><mi>B</mi><mo>)</mo></math></span>, where <em>B</em> is termed as bag constant, is presented. In order to integrate the quark core hypothesis and provide an explanation for a physically feasible stellar model, we have examined the baryon number dependent <em>B</em> (<em>n</em>) via an extreme Wood-Saxon, like parameterisation. The energy per baryon <span><math><mo>(</mo><msub><mrow><mi>E</mi></mrow><mrow><mi>B</mi></mrow></msub><mo>)</mo></math></span> has been calculated to restrict <em>B</em> (<em>n</em>) within the stable window, i.e., <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>B</mi></mrow></msub><mo>&lt;</mo><mn>930.4</mn><mspace></mspace><mi>M</mi><mi>e</mi><mi>V</mi></math></span> <span><math><mo>(</mo><mmultiscripts><mrow><mi>F</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>56</mn></mrow></mmultiscripts><mi>e</mi><mo>)</mo></math></span>. This study investigates the baryon number density (<em>n</em>) induced phase transition between hadrons and quarks inside a stellar configuration. Interestingly, the nature of the variation of <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>B</mi></mrow></msub></math></span> vs. <em>n</em>, shows that for <span><math><mi>n</mi><mo>≥</mo><mn>1.1</mn><mspace></mspace><mi>f</mi><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></math></span> the energy per baryon approaches a constant value. We choose <span><math><mi>n</mi><mo>=</mo><mn>0.6</mn><mspace></mspace><mi>f</mi><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></math></span>, <span><math><mi>B</mi><mo>=</mo><mn>66.32</mn><mspace></mspace><mi>M</mi><mi>e</mi><mi>V</mi><mo>/</mo><mi>f</mi><msup><mrow><mi>m</mi></mrow><mrow><mn>3</mn></mrow></msup></math></span> within the stipulated restrictions and consider 4U 1608-52 as a strange star candidate. We find that all the characteristic properties are well satisfied within the stellar interior for the choice of parameters. The numerical solution of the TOV equations yields a maximum mass of strange quark stars of <span><math><mn>2.01</mn><mspace></mspace><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span> and a corresponding radius of <span><math><mn>10.96</mn><mspace></mspace><mi>K</mi><mi>m</mi></math></span>. Proposed model meets the necessary energy conditions and also stability criteria, confirming its viability as a realistic stellar model within the parameter space used.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 231-240"},"PeriodicalIF":10.2,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102785","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":"Search for very high energy gamma-ray emission from a sample of high redshift blazars with MACE","authors":"A. Tolamatti ,&nbsp;A. Garg ,&nbsp;A. Pathania ,&nbsp;K.K. Singh ,&nbsp;C. Borwankar ,&nbsp;M. Khurana ,&nbsp;P. Chandra ,&nbsp;A. Shukla ,&nbsp;S. Godiyal ,&nbsp;S. Godambe ,&nbsp;J. Hariharan ,&nbsp;Keshavanand ,&nbsp;N. Mankuzhyil ,&nbsp;S. Norlha ,&nbsp;P. Pandey ,&nbsp;D. Sarkar ,&nbsp;R. Thubstan ,&nbsp;K. Venugopal ,&nbsp;Z.A. Dar ,&nbsp;S.V. Kotwal ,&nbsp;K.K. Yadav","doi":"10.1016/j.jheap.2024.12.006","DOIUrl":"10.1016/j.jheap.2024.12.006","url":null,"abstract":"<div><div>Blazars, a subclass of face-on jetted active galactic nuclei, are the most persistent and powerful sources of cosmic gamma-rays in the Universe. They represent a dominant population of gamma-ray sources, spread all over the sky with known and unknown redshifts up to z ∼ 6 (e.g. <span><span>Belladitta et al. (2020)</span></span>). Detection of more than 3500 blazars by the space-based <em>Fermi</em>-Large Area Telescope (LAT) in the high energy (HE, above 100 MeV) band reveals that a significant amount of power carried by the relativistic plasma jets in blazars is dissipated at gamma-ray energies. However, a small fraction of only less than 3% are detected at very high energies (VHE, above 30 GeV) by the ground-based Cherenkov telescopes. Therefore, their detection at the highest possible energies is extremely important to understand the blazar-phenomenon in the Universe. In this paper, we report observational results obtained from the recent monitoring of the six high redshift (<span><math><mi>z</mi><mspace></mspace><mo>&gt;</mo><mspace></mspace><mn>0.3</mn></math></span>) blazars with the Major Atmospheric Cherenkov Experiment (MACE) in the energy range above ∼ 80 GeV. No statistically significant detection of the sources is found. Thus, for the null detections, we estimate 99% confidence level upper limit on the integral flux for the individual sources and use the <em>Fermi</em>-LAT measurements to constrain their gamma-ray emission behavior.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 241-249"},"PeriodicalIF":10.2,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102786","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":"Accretion onto a charged black hole in consistent 4D Einstein-Gauss-Bonnet gravity","authors":"Kourosh Nozari,&nbsp;Sara Saghafi,&nbsp;Mohammad Hassani","doi":"10.1016/j.jheap.2024.12.004","DOIUrl":"10.1016/j.jheap.2024.12.004","url":null,"abstract":"<div><div>In astrophysics, accretion is the process by which a massive object acquires matter. The infall leads to the extraction of gravitational energy. Accretion onto dark compact objects such as black holes, neutron stars, and white dwarfs is a crucial process in astrophysics as it turns gravitational energy into radiation. The accretion process is an effective technique to investigate the properties of other theories of gravity by examining the behavior of their solutions with compact objects. In this paper, we investigate the behavior of test particles around a charged four-dimensional Einstein–Gauss–Bonnet (4<em>D</em> EGB) black hole in order to understand their innermost stable circular orbit (ISCO) and energy flux, differential luminosity, and temperature of the accretion disk. Then, we examine particle oscillations around a central object via applying restoring forces to treat perturbations. Next, we explore the accretion of perfect fluid onto a charged 4<em>D</em> EGB black hole. We develop analytical formulas for four-velocity and proper energy density of the accreting fluid. The EGB parameter and the charge affect properties of the test particles by decreasing their ISCO radius and also decreasing their energy flux. Increasing the EGB parameter and the charge, near the central source reduces both the energy density and the radial component of the infalling fluid's four-velocity.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 214-230"},"PeriodicalIF":10.2,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162958","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 Hubble expansion in a Big Bang quantum cosmology","authors":"Maurice H.P.M. van Putten","doi":"10.1016/j.jheap.2024.12.002","DOIUrl":"10.1016/j.jheap.2024.12.002","url":null,"abstract":"<div><div>The Hubble expansion of the Universe is considered in the classical limit of a Big Bang quantum cosmology. In an IR-consistent coupling to the bare cosmological constant, we infer a dark energy as a relic of the Big Bang by loss of time-translation invariance on a Hubble time-scale. This dark energy is identified with the trace <em>J</em> of the Schouten tensor permitting an analytic solution <span><math><mi>H</mi><mo>(</mo><mi>z</mi><mo>)</mo></math></span>. Anchored by the <em>Baryonic Accoustic Oscillations</em>, <em>J</em>CDM predicts a Hubble constant <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>=</mo><msqrt><mrow><mn>6</mn><mo>/</mo><mn>5</mn></mrow></msqrt><mspace></mspace><msubsup><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow><mrow><mi>Λ</mi></mrow></msubsup></math></span> alleviating <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>-tension between the Local Distance Ladder and <span><math><msubsup><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow><mrow><mi>Λ</mi></mrow></msubsup></math></span> in ΛCDM, whose dark energy Λ is a constant. Emulated by <span><math><mi>w</mi><mo>(</mo><mi>a</mi><mo>)</mo><mi>Λ</mi></math></span>CDM, a CAMB analysis shows a <em>J</em>CDM fit to the <em>Planck</em> 2018 <span><math><msubsup><mrow><mi>C</mi></mrow><mrow><mi>l</mi></mrow><mrow><mi>T</mi><mi>T</mi></mrow></msubsup></math></span> power spectrum on par with ΛCDM with small positive curvature consistent with <em>Planck</em>-ΛCDM with no extra relativistic degrees of freedom. In late-time cosmology, <em>J</em>CDM is also consistent with the BAO recently measured by DESI. <em>J</em>CDM offers a novel framework to address <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>-tension, predicting background quantities consistent with the uncertainties in BAO measurements and early-Universe observations. It predicts a deceleration parameter <span><math><msub><mrow><mi>q</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>≃</mo><mo>−</mo><mn>1</mn></math></span>, that may be tested with upcoming low-redshift galaxy surveys.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 194-199"},"PeriodicalIF":10.2,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143098612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The interplay of WGC and WCCC via charged scalar field fluxes in the RPST framework","authors":"Mohammad Reza Alipour ,&nbsp;Jafar Sadeghi ,&nbsp;Saeed Noori Gashti ,&nbsp;Mohammad Ali S. Afshar","doi":"10.1016/j.jheap.2024.11.022","DOIUrl":"10.1016/j.jheap.2024.11.022","url":null,"abstract":"<div><div>In this paper, we investigate the weak cosmic censorship conjecture (WCCC) for the Reissner-Nordström (R-N) AdS black hole within the framework of restricted phase space thermodynamics (RPST). Additionally, we consider energy flux and the equivalence mass-energy principle to examine the weak gravity conjecture (WGC) alongside the weak cosmic censorship conjecture. The interaction of incoming and outgoing energy flux leads to changes in the black hole. We examine whether the second law of thermodynamics holds in this scenario. It is noted that, when absorption and superradiance reach equilibrium, and by using the thermodynamics of black holes in restricted phase space, if the black hole is in or near an extreme state with radiation and particle absorption, the weak cosmic censorship conjecture is upheld. Furthermore, by employing the equivalence mass-energy principle and second-order approximation near extremality, we find that when the black hole radiates and its central charge exceeds the scaled electric charge, the superradiance particles adhere to the weak gravity conjecture. This causes the black hole to move away from its extreme state. However, when particles that obey the weak gravity conjecture are attracted to a very small black hole, the black hole approaches its extremality state.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 160-167"},"PeriodicalIF":10.2,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143098607","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":"Some aspects of ModMax (A)dS black holes: Thermodynamics properties, heat engine, shadow, null geodesic and light trajectory","authors":"B. Eslam Panah ,&nbsp;N. Heidari","doi":"10.1016/j.jheap.2024.12.001","DOIUrl":"10.1016/j.jheap.2024.12.001","url":null,"abstract":"<div><div>In this paper, we focus on the extraction of electrically charged black holes in the presence of modified Maxwell nonlinear electrodynamics and the cosmological constant, known as ModMax-(A)dS black holes. These black holes are of particular interest due to the substantial influence of the nonlinear Maxwell field (ModMax) and the cosmological constant on their properties. After obtaining exact ModMax-(A)dS black hole solutions, we proceed to study their thermodynamic properties, including conserved and thermodynamic quantities, as well as the first law of thermodynamics in a non-extended phase space. The local and global stabilities of these black holes are then assessed. Local stability is evaluated by examining the heat capacity while determining global stability involves calculating the Helmholtz free energy. Then, we investigate the heat engine of ModMax (A)dS black holes, considering the effects of the ModMax parameter and the cosmological constant on all quantities. Moreover, we explore the imprint of ModMax (A)dS black hole parameters on the critical orbits and shadow radius size, the results are compared with EHT observational data of the Sagittarius A^⁎ black holes. Lastly, the null geodesics and light trajectory are discussed in the presence of the ModMax theory.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 181-193"},"PeriodicalIF":10.2,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143098611","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":"Power law cosmology in Gauss-Bonnet gravity with pragmatic analysis","authors":"Rita Rani ,&nbsp;Shaily ,&nbsp;G.K. Goswami ,&nbsp;J.K. Singh","doi":"10.1016/j.jheap.2024.11.021","DOIUrl":"10.1016/j.jheap.2024.11.021","url":null,"abstract":"<div><div>In this study, we present an approach <span><math><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>G</mi><mo>)</mo></math></span> gravity incorporating power law in <em>G</em>. To study the cosmic evolution of the universe given by the reconstruction of the Hubble parameter given by <span><math><mi>E</mi><mo>(</mo><mi>z</mi><mo>)</mo><mo>=</mo><msup><mrow><mo>(</mo><mn>1</mn><mo>+</mo><mfrac><mrow><mi>z</mi><mo>(</mo><mi>α</mi><mo>+</mo><msup><mrow><mo>(</mo><mn>1</mn><mo>+</mo><mi>z</mi><mo>)</mo></mrow><mrow><mi>β</mi></mrow></msup><mo>)</mo></mrow><mrow><mn>2</mn><mi>β</mi><mo>+</mo><mn>1</mn></mrow></mfrac><mo>)</mo></mrow><mrow><mfrac><mrow><mn>3</mn></mrow><mrow><mn>2</mn><mi>β</mi></mrow></mfrac></mrow></msup></math></span>. Subsequently, we use various recent observational datasets of OHD, Pantheon, and BAO to estimate the model parameters <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><mspace></mspace><mi>α</mi></math></span>, and <em>β</em> applying the Markov Chain Monte Carlo (MCMC) technique in the emcee package to establish the validity of the model. In our findings, we observe that our model shows consistency with standard ΛCDM, transits from deceleration to acceleration, and enters the quintessence region in late times. The cosmological model satisfies necessary energy constraints, simultaneously violating the strong energy condition (SEC), indicating a repulsive nature and consistent with accelerated expansion. The cosmic evolution of the Hawking temperature and the total entropy for the various observational datasets also show the validity of the model. Thus, our established model demonstrates sufficient potential for explicitly describing cosmological models.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 168-180"},"PeriodicalIF":10.2,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143098610","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":"Quasinormal modes and greybody bounds of black holes endowed with modified Chaplygin gas","authors":"Y. Sekhmani ,&nbsp;D.J. Gogoi ,&nbsp;S.K. Maurya ,&nbsp;K. Boshkayev ,&nbsp;M.K. Jasim","doi":"10.1016/j.jheap.2024.11.020","DOIUrl":"10.1016/j.jheap.2024.11.020","url":null,"abstract":"<div><div>This paper investigates the quasinormal modes and greybody factors of black holes with modified Chaplygin gas. Applying the WKB approximation method, we analyze the impact of model parameters <em>A</em>, <em>β</em>, <em>B</em>, and <em>γ</em> on the oscillation frequency and damping rate of gravitational waves. Parameters <em>A</em> and <em>β</em> initially decrease these measures before a gradual increase, while <em>B</em> significantly influences them with a distinct critical point behaviour, and <em>γ</em> causes a gradual increase. Additionally, we explore greybody factor bounds analytically, revealing that smaller multipole moments <em>l</em> yield higher bounds, increasing <em>A</em> decreases bounds slowly, <em>B</em> significantly increases them, <em>β</em> decreases them, and <em>γ</em> has a minimal impact. These findings enhance our insight of the dynamics of black holes with modified Chaplygin gas, particularly their quasinormal modes and greybody factors.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 200-213"},"PeriodicalIF":10.2,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164035","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":"Effect of turbulence on blazar variability - II: Stochastic variability within leptonic scenario","authors":"Bitan Ghosal ,&nbsp;Nilay Bhatt ,&nbsp;Subir Bhattacharyya ,&nbsp;Kuldeep Kumar Yadav","doi":"10.1016/j.jheap.2024.11.019","DOIUrl":"10.1016/j.jheap.2024.11.019","url":null,"abstract":"<div><div>Understanding the origin of the long-term stochastic variability of blazars in different wavebands is a decade-long problem. In this work, we investigate the stochastic variability of blazar emission within the framework of a time-dependent one-zone leptonic model. This model considers the acceleration of the relativistic electrons present in the blazar jet by both the Fermi first order and second order acceleration process, along with radiative energy loss of the same electrons and diffusive escape of those electrons from the acceleration/emission zone. The effect of second order Fermi acceleration is incorporated in the present model through momentum diffusion coefficient considering random scattering of the relativistic electrons by magneto-hydrodynamic (MHD) turbulence. We simulate the variability in the multi-wavelength photon light curves by introducing stochastic variation in the electron injection. Then estimated the power spectral density, probability density function and rms-flux relation to quantify the variability. Here, we show that for different types of stochastic injection process, the nature of the variability changes. The variability properties also depend on the nature of the MHD turbulence present in the system.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"45 ","pages":"Pages 146-159"},"PeriodicalIF":10.2,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143098609","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}