Journal of High Energy Astrophysics最新文献

{"title":"Prospects for joint reconstruction of imaging air Cherenkov telescope array and extensive air shower array","authors":"Zhipeng Zhang ,&nbsp;Ruizhi Yang ,&nbsp;Shoushan Zhang ,&nbsp;LiQiao Yin ,&nbsp;Jiali Liu ,&nbsp;Yudong Wang ,&nbsp;Lingling Ma ,&nbsp;Zhen Cao","doi":"10.1016/j.jheap.2024.07.012","DOIUrl":"10.1016/j.jheap.2024.07.012","url":null,"abstract":"<div><p>In this paper, we proposed a joint reconstruction of <em>γ</em>-ray events using both extensive air array (EAS) and Imaging air Cherenkov Telescope array (IACT). We considered eight Cherenkov telescopes to be built on the LHAASO (Large High Altitude Air Shower Observatory) site and investigate the improvement in differential sensitivity when combining the information from both IACT and Moun detectors of LHAASO-KM2A. We found that due to the higher cosmic ray background rejection power and higher gamma ray retention ratio provided by muon detectors of LHAASO, such a joint reconstruction can significantly improve the sensitivity of IACTs, especially for extended sources and long exposure time. The sensitivity of the eight-telescopes array can be improved by <span><math><mn>25</mn><mtext>%</mtext><mo>−</mo><mn>60</mn><mtext>%</mtext></math></span> in different energy ranges using joint reconstructions with muon detectors.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 280-285"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142012009","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":"Charged gravastar model in Rastall theory of gravity","authors":"Debadri Bhattacharjee,&nbsp;Pradip Kumar Chattopadhyay","doi":"10.1016/j.jheap.2024.08.001","DOIUrl":"10.1016/j.jheap.2024.08.001","url":null,"abstract":"<div><p>Gravastars are considered as exotic compact objects, may be found at the end of gravitational collapse of massive stars, to resolve the complexities of black holes. In this paper, we analyse the role of charge on the possible formation of an isotropic spherically symmetric gravastar configuration in the framework of Rastall gravity. Gravastar contains three distinct layers <em>viz.</em> (i) Interior region characterised by the equation of state, <span><math><mi>p</mi><mo>=</mo><mo>−</mo><mi>ρ</mi></math></span>, which defines the repulsive outward pressure in the radial direction at all points on the thin shell, (ii) Thin shell contains an ultra-relativistic stiff fluid, which is denoted by the equation of state <span><math><mi>p</mi><mo>=</mo><mi>ρ</mi></math></span> following Zel'dovich's criteria for a cold baryonic universe, and can withstand the repulsive pressure exerted by the interior region, and (iii) Exterior region which is the vacuum space-time represented by the Reissner-Nordström solution. Following above specifications, we construct and analyse charged gravastar model in the framework of Rastall gravity, which represents several salient features. The basic physical attributes, <em>viz.</em> proper length, energy, entropy and equation of state parameter of the shell are investigated. In this model, it is interesting to note that for a large radius of the hypersurface (<em>R</em>), the equation of state parameter of the thin shell corresponds to a dark energy equation of state with <span><math><mi>W</mi><mo>(</mo><mi>R</mi><mo>)</mo><mo>→</mo><mo>−</mo><mn>1</mn></math></span>. However, for small value of <em>R</em>, <span><math><mi>W</mi><mo>(</mo><mi>R</mi><mo>)</mo><mo>→</mo><mn>0</mn></math></span>, defines dust shell. The stability of the model is ensured through the study of gravitational surface redshift and maximisation of shell entropy within the framework of Rastall theory of gravity.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 248-257"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948332","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 - I: Short time-scale variability within leptonic scenario","authors":"Bitan Ghosal ,&nbsp;Nilay Bhatt ,&nbsp;Subir Bhattacharyya ,&nbsp;Kuldeep Kumar Yadav","doi":"10.1016/j.jheap.2024.07.009","DOIUrl":"10.1016/j.jheap.2024.07.009","url":null,"abstract":"<div><p>Blazars are known for showing strong variability over different time-scales in all wavelengths. In this work, we present the study of characterising the short-term variability of blazar in presence of Kraichnan and Kolmogorov types of turbulence within the framework of time-dependent leptonic model. We considered the acceleration of relativistic electrons by both first and second order Fermi processes. The second order Fermi process involves the resonant interaction of the relativistic electrons with magnetohydrodynamics (MHD) turbulence. Along with the acceleration, the relativistic electrons lose energy through synchrotron and synchrotron self-Compton processes. Electrons also escape the acceleration/radiation zone diffusively. A short term variability in photon light curve i.e.'flare' like scenario was generated through an impulsive injection of fresh electrons in the acceleration zone. It is shown that the flare characteristics are different for the two cases of turbulence. We also point out that the evolution of the particle and photon spectra differ for these two turbulence scenarios during flare.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 217-226"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141850682","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":"Scalar's quasibound states in cosmological black hole background","authors":"David Senjaya","doi":"10.1016/j.jheap.2024.07.004","DOIUrl":"https://doi.org/10.1016/j.jheap.2024.07.004","url":null,"abstract":"<div><p>In this letter, we present in detail a novel exact solution of scalar quasibound states of a static spherically symmetric Schwarzschild de Sitter black hole. We investigate and work out the governing covariant scalar field wave equation, i.e., the Klein-Gordon equation and isolate the radial equation. In this letter, we show in detail, the derivation of the successfully obtained exact radial wave solutions which are expressed in terms of General Heun functions. Having the exact solutions in hand, the energy levels expression is obtained from special function's polynomial condition. In the last part, the Hawking radiation is investigated via the Damour-Ruffini method and the Hawking temperature is obtained from radiation distribution function.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 132-139"},"PeriodicalIF":10.2,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141596066","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":"Orbital motion and epicyclic oscillations around Bardeen black hole surrounded by perfect fluid dark matter","authors":"Yihu Feng ,&nbsp;Asifa Ashraf ,&nbsp;Saadia Mumtaz ,&nbsp;S.K. Maurya ,&nbsp;G. Mustafa ,&nbsp;Farruh Atamurotov","doi":"10.1016/j.jheap.2024.07.003","DOIUrl":"10.1016/j.jheap.2024.07.003","url":null,"abstract":"<div><p>We study the orbital and oscillatory motion of test particles moving around a rotating Bardeen black hole immersed in perfect fluid dark matter. We obtain the analytical solutions for the radial profiles of specific energy as well as the specific angular momentum of the equatorial stable circular orbits. Using the effective potential approach, we also discuss the stability of circular orbits. We compute the frequencies of radial and latitudinal harmonic oscillations as a function of mass, charge, and angular momentum of the black hole as well as the parameter describing the perfect fluid dark matter. The main characteristics of test particle quasi-periodic oscillations near stable circular orbits are examined in the equatorial plane. Furthermore, we study precessions of Periastron and Lense-Thirring. It is observed that the particle's motion around the black hole is strongly influenced by the model parameters.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 158-170"},"PeriodicalIF":10.2,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141630255","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":"Scattering of the UHECR at small pitch angle by damped plasma waves","authors":"M. Vukcevic","doi":"10.1016/j.jheap.2024.07.002","DOIUrl":"10.1016/j.jheap.2024.07.002","url":null,"abstract":"<div><p>In spite a lot of theoretical and experimental effort that has been achieved in ultra-high energy cosmic ray (UHECR) scattering research in last few decades, some questions remain unanswered, or partially answered. Two of them, that will be in the focus of this paper are: possible source of UHECRs and the acceleration mechanism of cosmic rays beyond PeV energies. Small pitch-angle scattering of UHECRs and possible confinement has been investigated using quasilinear theory in order to analytically calculate pitch-angle Fokker-Planck coefficient. CR particles resonantly interact with oblique low frequency damped waves. We show that the resonance function is broadened due to damping effects and this result is compared with the nonlinear broadening. Unlike the case of purely parallel (or antiparallel) propagating waves in slab turbulence, the presence of the compressive magnetic field component of oblique fast-mode waves allows the cosmic ray particles to resonantly interact with these waves through the n = 0 resonance, together with gyroresonance, which strongly influence the Hillas limit. The derived results can be used to compute the parallel mean free path for all forms of the turbulence spectrum; it has been applied on the transport and propagation of CRs close to ultra-high energies in the Galaxy. An accurate understanding of particle acceleration in astrophysical sources could help to interpret eventual transition from Galactic to extragalactic origin of cosmic rays, if any, and the shape of the UHECR spectrum at the highest energies.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 153-157"},"PeriodicalIF":10.2,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141623615","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":"Reconstructing f(Q) gravity from parameterization of the Hubble parameter and observational constraints","authors":"Anil Kumar Yadav ,&nbsp;S.R. Bhoyar ,&nbsp;M.C. Dhabe ,&nbsp;S.H. Shekh ,&nbsp;Nafis Ahmad","doi":"10.1016/j.jheap.2024.06.012","DOIUrl":"https://doi.org/10.1016/j.jheap.2024.06.012","url":null,"abstract":"&lt;div&gt;&lt;p&gt;In the present work our aim is to construct FRW cosmological models in the framework of &lt;span&gt;&lt;math&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; theory of gravity. We explore the accelerating behavior of the universe for particular form of &lt;span&gt;&lt;math&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; gravity model using a new simple parameterization of the Hubble parameter of the form&lt;span&gt;&lt;span&gt;&lt;span&gt;&lt;math&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msqrt&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msqrt&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mo&gt;[&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;]&lt;/mo&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt; We constraint on the associated free parameters present in &lt;span&gt;&lt;math&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; within 1&lt;em&gt;σ&lt;/em&gt;, 2&lt;em&gt;σ&lt;/em&gt; and 3&lt;em&gt;σ&lt;/em&gt; confidence limits by &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt;-minimization technique. We have found that all obtained values fall within the range as suggested by cosmological observations. By employing the best-fit values of the free parameters, we have determined the present values of the geometrical parameters and demonstrated the accelerating behavior of the Universe. We have discussed the physical behavior of the universe in our model through physical parameters like the energy density, pressure, equation of state parameter. Also, we have examined the kinematic variables of the universe in our model such as Hubble parameter, deceleration parameter, and age of the universe. In our model, the deceleration parameter &lt;span&gt;&lt;math&gt;&lt;mi&gt;q&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; indicates the universe's phase change from deceleration to acceleration. Moreover, the current value of the deceleration parameter is &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;q&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mn&gt;0.348&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0.0095&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0.0085&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;q&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mn&gt;0.351&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0.011&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0.010&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; with transition redshift value &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;t&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mn&gt;0.58&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0.015&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0.018&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;t&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mn&gt;0.59&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0.012&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 114-125"},"PeriodicalIF":10.2,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141596068","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":"IceCube results and perspective for neutrinos from LHAASO sources","authors":"Ke Fang,&nbsp;Francis Halzen","doi":"10.1016/j.jheap.2024.07.001","DOIUrl":"https://doi.org/10.1016/j.jheap.2024.07.001","url":null,"abstract":"<div><p>We briefly review the main results of the IceCube Neutrino Observatory one decade after the discovery of cosmic neutrinos. We emphasize the importance of multimessenger observations, most prominently for the discovery of neutrinos from our own Galaxy. We model the flux from the Galactic plane produced by Galactic cosmic rays interacting with the interstellar medium and discuss the perspectives of understanding the TeV-PeV emission of the Galactic plane by combining neutrino and gamma-ray observations. We draw attention to the interesting fact that the neutrino flux from the Galaxy is not a dominant feature of the neutrino sky, unlike the case in any other wavelength of light. Finally, we review the attempts to identify PeVatrons by confronting the neutrino and gamma-ray emission of Galactic sources, including those observed by LHAASO. We end with a discussion of searches for neutrinos from LHAASO's extragalactic transient source gamma-ray burst 221009A.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 140-152"},"PeriodicalIF":10.2,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2214404824000569/pdfft?md5=068bf367644242663b4e28ca8a3a04a3&pid=1-s2.0-S2214404824000569-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141606805","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":"FLRW cosmology in Weyl type f(Q) gravity and observational constraints","authors":"G.K. Goswami ,&nbsp;Rita Rani ,&nbsp;J.K. Singh ,&nbsp;Anirudh Pradhan","doi":"10.1016/j.jheap.2024.06.011","DOIUrl":"https://doi.org/10.1016/j.jheap.2024.06.011","url":null,"abstract":"<div><p>Inspired by various works in a Weyl type <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> gravity to reduce some serious problems in General Relativity Theory (GR), we develop a model of the universe in a Weyl type <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> gravity which shows the transition from a decelerating state to an accelerating state of the universe at present when we consider a particular functional form of the <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> gravity as <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo><mo>=</mo><mo>(</mo><msup><mrow><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo><mo>(</mo><msub><mrow><mi>α</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>+</mo><msub><mrow><mi>α</mi></mrow><mrow><mn>2</mn></mrow></msub><mspace></mspace><mi>l</mi><mi>o</mi><mi>g</mi><mo>(</mo><msubsup><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msubsup><mi>Q</mi><mo>)</mo><mo>)</mo></math></span>. We numerically solve Weyl type <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> gravity field equations and obtain the numerical solutions to the Hubble parameter, deceleration parameter, distance modulus, and the apparent magnitudes of stellar objects using Ia Supernovae. Also, we obtain numerical solutions for the Weyl vector <em>w</em>, non-metricity scalar <em>Q</em>, and the Lagrangian multiplier <em>λ</em> appearing in the action of <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> gravity. We compare our model with the error bar plots of the observed Hubble dataset of 77 points, SNIa datasets of 580 points, and 1048 supernova Pantheon datasets of the apparent magnitudes, and the statistical analysis using Baryon Acoustic Oscillations (BAO). It is found that our results fit well with the observed values. The model envisages a unique feature: although the universe is filled with perfect fluid as dust whose pressure is zero, the Weyl vector dominance <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> creates acceleration.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 105-113"},"PeriodicalIF":10.2,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141596067","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":"Non-thermal emission from microquasar jets: The case of GRS 1915+105","authors":"Dmitry Khangulyan ,&nbsp;Valentí Bosch-Ramon ,&nbsp;Daniela Hadasch","doi":"10.1016/j.jheap.2024.06.006","DOIUrl":"https://doi.org/10.1016/j.jheap.2024.06.006","url":null,"abstract":"<div><p>Microquasars (μQs) represent a prominent population of Galactic sources, from which broadband non-thermal emission was detected. At present, the potential of μQs as sources of gamma-ray emission is poorly understood and constrained. In most cases, even the power of μQ jets remains largely uncertain, and this hinders the study of gamma-ray generation in these sources. Using observational data obtained in the radio band, we derive an estimate of the jet power in one of the most famous Galactic μQ, in GRS 1915+105. Compared to other studies of this subject, we additionally consider constraints related to the energy dissipated at internal shocks in the jet, the conditions at which are obtained using properties of the radio blobs detected in the jets. We show that even if one subtracts the rest-energy of matter in the jet, the jet power in this source should be very high, <span><math><msup><mrow><mn>10</mn></mrow><mrow><mn>39</mn></mrow></msup><mspace></mspace><mrow><mi>erg</mi><mspace></mspace><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, or even higher. The properties of the detected radio emission favor jets with a Gauss-strength magnetic field at parsec distances from the black hole. Such a strong magnetic field should suppress inverse Compton (IC) emission from relativistic electrons, at least from parsec-scale jet. On the other hand, this strong magnetic field makes μQ jets perfect proton accelerators. If present, protons should easily be accelerated in the ultra-high-energy regime. However, due to a diluted target, protons should not lose a notable fraction of their energy in the jet, injected into the interstellar medium at the jet termination. This should significantly enhance the density of cosmic rays in the vicinity of GRS 1915+105. This may manifest itself as an extended gamma-ray source or as several compact sources if the target gas has a highly inhomogeneous distribution. This analysis has direct implication for studying Galactic μQ with such gamma-ray observatories as LHAASO, CTA, and SWGA in the next decades.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 93-104"},"PeriodicalIF":10.2,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141596047","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}