Journal of High Energy Astrophysics最新文献

{"title":"Modeling self-bound binary compact object with a slow rotation effect and effect of electric field gradient on the mass-radius limit and moment of inertia","authors":"S.K. Maurya , Abdelghani Errehymy , Ksh. Newton Singh , M.K. Jasim , Kairat Myrzakulov , Zhanbala Umbetova","doi":"10.1016/j.jheap.2024.09.002","DOIUrl":"10.1016/j.jheap.2024.09.002","url":null,"abstract":"<div><p>In this paper, we investigate the effects of electric field gradients on the secondary component of GW190814 and other binary compact objects. Using general relativistic equations, we derive a model with three conditions and analyze its metric potentials, electric charge, energy density, stresses, and anisotropy parameter. The metric potentials in our analysis match the Schwarzschild exterior at the stellar surface, exhibiting smooth behavior without any central singularity. The electric charge increases from zero at the core to a maximum at the surface, indicating an outward electric force. The energy density, radial and tangential pressures, and anisotropy all demonstrate well-behaved trends. The model is found stable based on the Harrison-Zeldovich-Novikov criteria, adiabatic index, and causality. Investigating the electric charge influence, we find increased charge leads to decreasing pressures and lower central adiabatic index, suggesting the need to optimize charge for long-term stability. The analysis of mass-radius ratio and moment of inertia-mass demonstrates the model's ability to capture the equation of state (EOS) stiffness. Finally, from the <span><math><mi>M</mi><mo>−</mo><mi>R</mi></math></span> and <span><math><mi>I</mi><mo>−</mo><mi>M</mi></math></span> curves we have shown that the mass obtained for the slowly rotating star is higher than the non-rotating case due to the contribution from rotational energy <span><math><mfrac><mrow><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac><mspace></mspace><mi>I</mi><mspace></mspace><msup><mrow><mi>Ω</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> for all values of <span><math><msub><mrow><mi>E</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>. It is very surprising to find that the electric field per radial distance i.e. <span><math><mi>E</mi><mo>/</mo><mi>r</mi><mo>=</mo><msqrt><mrow><msub><mrow><mi>E</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msqrt></math></span> is maximum at a particular mass for a chosen radius, specifically for <em>r</em> (km), <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>N</mi><mi>R</mi></mrow></msub><mspace></mspace><mo>(</mo><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub><mo>)</mo></math></span>, and <span><math><msqrt><mrow><msubsup><mrow><mi>E</mi></mrow><mrow><mn>0</mn></mrow><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msubsup></mrow></msqrt><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup></math></span> (/km<sup>4</sup>). The electric field per unit radius also influences the EOS significantly with overall form <span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>=</mo><mi>a</mi><mi>ρ</mi><mo>−</mo><mi>b</mi><msup><mrow><mi>ρ</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>−</mo><mi>c</mi></math></span> for all <span><math><mi>a</mi><mo>,</mo><mspace></mspace><mi>b</mi><mo>,</mo><mspace></mspace><mi>c</mi><mo>></mo><mn>0</mn></math></span>. This means that the ","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"44 ","pages":"Pages 45-59"},"PeriodicalIF":10.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142162573","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":"Cosmological tests of the dark energy models in Finsler-Randers space-time","authors":"Z. Nekouee ,&nbsp;Himanshu Chaudhary ,&nbsp;S.K. Narasimhamurthy ,&nbsp;S.K.J. Pacif ,&nbsp;Manjunath Malligawad","doi":"10.1016/j.jheap.2024.08.006","DOIUrl":"10.1016/j.jheap.2024.08.006","url":null,"abstract":"<div><p>The Finsler-Randers space-time offers a novel perspective on cosmic dynamics, departing from the constraints of General Relativity. This paper thoroughly investigates two dark energy models resulting from the parametrization of <em>H</em> within this geometric framework. We have conducted some geometrical and physical analysis of the dark energy models in Finslerian geometry. First, we have derived the field equations governing the universe's evolution within the Finsler-Randers formalism, incorporating the presence of dark energy. Through this, we explore its implications on cosmological phenomena, including cosmic expansion, late-time behavior of the universe, cosmological phase transition, and a few more. Also, we employ observational data such as Cosmic Chronometer, Supernovae, Gamma-Ray Bursts, Quasar, and baryon acoustic oscillations to constrain the parameters associated with dark energy in the Finsler-Randers universe. Comparing theoretical predictions with empirical observations, we assess the model viability and discern any deviations from the standard ΛCDM cosmology. Our findings offer intriguing insights into the nature of dark energy within this alternative gravitational framework, providing a deeper understanding of its role in shaping cosmic evolution. The implications of our results extend to fundamental cosmology, hinting at new avenues for research to unravel the mysteries surrounding dark energy and the geometric structure of the universe within non-standard gravitational theories.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"44 ","pages":"Pages 19-44"},"PeriodicalIF":10.2,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142162571","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":"Fine-grained photometric classification using multi-model fusion method with redshift estimation","authors":"Peng Cheng,&nbsp;Zhihui Liu,&nbsp;Fatemeh Zahra Zeraatgri,&nbsp;Liquan Mei","doi":"10.1016/j.jheap.2024.07.008","DOIUrl":"10.1016/j.jheap.2024.07.008","url":null,"abstract":"<div><p>The modern sky surveys accelerates astronomical data collection. We proposed a multi-model fusion method aimed at comprehensive and fine-grained astronomical source classification. This method incorporates a redshift estimation model using the mixture density network into a source classification model. Based on 1.2 million sources from the SDSS and the ALLWISE, we performed three-class experiments for stars, quasars, and galaxies, four-class experiments to further classify galaxies into normal and emission-line galaxies (NGs; ELGs), and seven-class experiments where ELG were refined into active galactic nuclei (AGNs), broad-line galaxies (BLs), star-forming galaxies (SFs), and starburst galaxies (SBs). In all experiments, our proposed method is superior to direct classification. In three- and four-class, we obtains 0.77% and 1.14% improvement in accuracy, demonstrating the effectiveness of adding redshift estimation. Meanwhile, three machine learning algorithms were stacked into one by us to finish fine-grained classification, which achieved an accuracy of 78.5%, with F1 scores of 99.2% for stars, 97% for quasars, 64.3% for NGs, 60.8% for AGNs, 68.3% for BLs, 87.2% for SBs, and 71.3% for SFs. The NMAD and <span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> for the redshift estimation part of our method are 0.18 and 0.916, while it has only 2.65% outliers. The method we proposed further mines the information contained in the photometry to achieve comprehensive and fine-grained classification, which will be beneficial for immediate analysis in large-scale surveys. Besides, this method can leverage feature importance to stimulate new insights for astronomers.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 198-208"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141839025","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":"Gravitational lensing of dark energy models and ΛCDM using observational data in loop quantum cosmology","authors":"Rownak Kundu ,&nbsp;Ujjal Debnath ,&nbsp;Himanshu Chaudhary ,&nbsp;G. Mustafa","doi":"10.1016/j.jheap.2024.07.013","DOIUrl":"10.1016/j.jheap.2024.07.013","url":null,"abstract":"<div><p>This paper investigates the accelerated cosmic expansion in the late Universe by examining two dark energy models, viscous modified Chaplygin gas (VsMCG) and variable modified Chaplygin gas (VMCG), within loop quantum cosmology alongside the ΛCDM model. The objective is to constrain cosmic parameters using the ΛCDM model and 30 of the latest <span><math><mi>H</mi><mo>(</mo><mi>z</mi><mo>)</mo></math></span> measurements from cosmic chronometers (CC), including Type Ia Supernovae, Gamma-Ray Bursts (GRB), Quasars, and 24 uncorrelated baryon acoustic oscillations (BAO) measurements across a redshift range from 0.106 to 2.33. The latest Hubble constant measurement from Riess in 2022 is included to enhance constraints. In the ΛCDM, VsMCG, and VMCG frameworks, best-fit parameters for the Hubble parameter (<span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>) and sound horizon (<span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span>) are obtained. The results highlight significant disparities between <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span> values from late-time observational measurements, reflecting the known <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span> tensions. The gravitational lensing optical depth of the two dark energy models is studied by plotting <span><math><mi>log</mi><mo>⁡</mo><mo>(</mo><mi>τ</mi><mo>(</mo><msub><mrow><mi>z</mi></mrow><mrow><mi>l</mi></mrow></msub><mo>)</mo><mo>/</mo><msubsup><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msubsup><msub><mrow><mi>τ</mi></mrow><mrow><mi>N</mi></mrow></msub><mo>)</mo></math></span> vs <span><math><msub><mrow><mi>z</mi></mrow><mrow><mi>l</mi></mrow></msub></math></span>. The probability of finding gravitational lenses (optical depth) in both models increases with lens redshift <span><math><msub><mrow><mi>z</mi></mrow><mrow><mi>l</mi></mrow></msub></math></span>. The change in optical depth behavior for different parameter constraints is graphically analyzed. A joint analysis of VsMCG and VMCG with ΛCDM is conducted. While the models diverge in the early Universe, they are indistinguishable at low redshift. Using the Akaike information criteria, the analysis indicates that neither dark energy model can be dismissed based on the latest observations.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 239-247"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948333","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":"Massive Dirac equation in static Bumblebee black hole space-times, detailed derivations and novel exact solutions","authors":"David Senjaya","doi":"10.1016/j.jheap.2024.08.004","DOIUrl":"10.1016/j.jheap.2024.08.004","url":null,"abstract":"<div><p>In this work, we construct and investigate the relativistic spin-<span><math><mfrac><mrow><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac></math></span> fermionic fields quantum dynamics in static spherically symmetric Bumblebee black hole background. The derivation of the Dirac equation in a general static spherically symmetric black hole space-time is carried out in detail via tetrad formalism. With the help of total angular momentum operator, the angular equation can be separated from the radial part where the solution is given in terms of the spinor harmonics. The radial Dirac equation has a well-known problem due to the presence of the square root terms appearing simultaneously with the rest mass that prevents us to find exact solutions. In this work, we present exact solutions of light mass fermion's wave function and energy levels bound in the static Bumblebee black hole. We discover the exact solutions of the massive Dirac's radial equation in terms of the Confluent Heun functions. Moreover, thanks to the well-known polynomial condition of the Confluent Heun functions, we also derive the energy quantization.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 286-292"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142084263","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":"Model-independent parameterization of H(z) and its implications for cosmic evolution","authors":"Yerlan Myrzakulov ,&nbsp;O. Donmez ,&nbsp;M. Koussour ,&nbsp;S. Muminov ,&nbsp;S. Bekchanov ,&nbsp;J. Rayimbaev","doi":"10.1016/j.jheap.2024.07.010","DOIUrl":"10.1016/j.jheap.2024.07.010","url":null,"abstract":"<div><p>We investigate the model-independent parameterization of <span><math><mi>H</mi><mo>(</mo><mi>z</mi><mo>)</mo></math></span> in spatially homogeneous and isotropic FLRW space-time using Cosmic Chronometers (31 data points) and Pantheon+SH0ES (1701 points) datasets. The best-fit values for the model parameters <span><math><mo>(</mo><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><msub><mrow><mi>A</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>A</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>,</mo><msub><mrow><mi>A</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>)</mo></math></span> are obtained through MCMC analysis. Our results show that the EoS parameter <em>ω</em> transitions from a matter-dominated era through quintessence to <span><math><mi>ω</mi><mo>=</mo><mo>−</mo><mn>1</mn></math></span>, indicating convergence to ΛCDM at late times. The current <em>ω</em> values suggest an accelerating universe. Moreover, the model's squared sound speed <span><math><msubsup><mrow><mi>v</mi></mrow><mrow><mi>s</mi></mrow><mrow><mn>2</mn></mrow></msubsup></math></span> evolves from negative to positive, indicating increasing stability. The deceleration parameter <em>q</em> shows a smooth transition from deceleration to acceleration, with transition redshift <span><math><msub><mrow><mi>z</mi></mrow><mrow><mi>t</mi></mrow></msub></math></span> between 0.5 and 0.8. Further, the energy conditions are satisfied, and SEC violation at <span><math><mi>z</mi><mo>=</mo><mn>0</mn></math></span> supports current acceleration. The <span><math><mi>ω</mi><mo>−</mo><msup><mrow><mi>ω</mi></mrow><mrow><mo>′</mo></mrow></msup></math></span> plane lies in the freezing region, and the <span><math><mi>r</mi><mo>−</mo><mi>s</mi></math></span> plane approaches the ΛCDM limit at late times.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 209-216"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141850006","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":"Cosmology in R2-gravity: Effects of a higher derivative scalar condensate background","authors":"Raj Kumar Das ,&nbsp;Aurindam Mondal ,&nbsp;Subir Ghosh ,&nbsp;Supriya Pan","doi":"10.1016/j.jheap.2024.07.011","DOIUrl":"10.1016/j.jheap.2024.07.011","url":null,"abstract":"<div><p>A well known extension of Einstein's General Relativity is the addition of an <span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>-term, which is free of ghost excitations and in the linearized framework, reduces to the conventional spin-2 graviton and an additional higher derivative scalar. According to <span><span>Chakraborty and Ghosh (2022)</span></span>, the above scalar sector can sustain a Time Crystal-like minimum energy state, with non-trivial time dependence. Exploiting previous result that the scalar can sustain modes with periodic time dependence in its lowest energy, we consider this condensate as a source and study the Friedmann-Lemaître-Robertson-Walker (FLRW) cosmology in this background. The effect of the <span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>-term is interpreted as a back reaction. A remarkable consequence of the condensate is that, irrespective of open or close geometry of the Universe, for an appropriate choice of parameter window, the condensate can induce a decelerating phase before the accelerated expansion starts and again, in some cases, it can help to avoid the singularity in the deceleration parameter (that is present in conventional FLRW Cosmology).</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 231-238"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141853927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probing the nova shock physics with future gamma-ray observations of the upcoming outburst from T Coronae Borealis","authors":"Jian-He Zheng ,&nbsp;Hai-Ming Zhang ,&nbsp;Ruo-Yu Liu ,&nbsp;Min Zha ,&nbsp;Xiang-Yu Wang","doi":"10.1016/j.jheap.2024.07.007","DOIUrl":"10.1016/j.jheap.2024.07.007","url":null,"abstract":"<div><p>Nova shocks behave like scaled-down supernova remnant shocks with a lifetime of only a few weeks or months, thereby providing a unique opportunity to study the dynamics of non-relativistic shocks as well as the shock acceleration physics. Recently, GeV and TeV gamma-ray emissions from an outburst of the recurrent nova RS Ophiuchi have been observed. The light curves of the gamma-ray emissions suggest that they arise from an external shock, which is formed as the nova ejecta interacts with the ambient medium. The shock is thought to transition from an adiabatic shock to a radiative one at later times, but no such later observations are available for RS Ophiuchi. In addition, the spectral evolution of the gamma-ray outburst of RS Ophiuchi was not well measured, and hence the related particle acceleration mechanisms are not well understood. T Coronae Borealis (T CrB) is another recurrent nova in Milky Way and its last outburst was nearly ten times optically brighter than RS Ophiuchi. Recently the optical light curve of T CrB displayed a state transition behavior before the eruption, and it has been predicted that T CrB will undergo an outburst in the near future. By performing a theoretical investigation, we find that Fermi-LAT could probably capture the transition of the shock from the adiabatic phase to the radiative phase at the GeV band if the ambient wind medium is dense with <span><math><msub><mrow><mi>A</mi></mrow><mrow><mo>⋆</mo></mrow></msub><mo>≥</mo><mn>1</mn></math></span>, thanks to a longer detectable time than that of RS Ophiuchi. Due to its higher brightness, we also find that imaging atmospheric Cherenkov telescopes (IACTs) such as MAGIC and VERITAS, and extensive air shower experiments such as LHAASO could detect the nova outburst and measure the gamma-ray spectrum in the very-high-energy (VHE, <span><math><mo>&gt;</mo><mn>0.1</mn><mspace></mspace><mrow><mi>TeV</mi></mrow></math></span>) band more precisely. This can be used to constrain the high-energy cutoff index in the accelerated proton spectrum and the acceleration efficiency, which will shed light on the particle acceleration physics in nova shocks.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 171-177"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141950095","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":"Addressing the rd tension using late-time observational measurements in a novel deceleration parametrization","authors":"Himanshu Chaudhary ,&nbsp;Ujjal Debnath ,&nbsp;S.K. Maurya ,&nbsp;G. Mustafa ,&nbsp;Farruh Atamurotov","doi":"10.1016/j.jheap.2024.08.003","DOIUrl":"10.1016/j.jheap.2024.08.003","url":null,"abstract":"<div><p>This paper introduces a novel cosmological model aimed at probing the accelerated expansion of the late Universe through a unique parametrization of the deceleration parameter. We aim to constrain key cosmic parameters by integrating recent measurements of the Hubble parameter obtained from various observational methods, including cosmic chronometers, Type Ia Supernovae, Gamma-Ray Bursts (GRB), Quasars, and Baryon Acoustic Oscillations (BAO) from recent galaxy surveys. With a redshift range spanning <span><math><mn>0.106</mn><mo>&lt;</mo><mi>z</mi><mo>&lt;</mo><mn>2.33</mn></math></span> and incorporating the latest Hubble constant measurement from Riess in 2022, our analysis yields optimal fit values for the Hubble parameter (<span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>) and sound horizon (<span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span>). Notably, we uncover an inconsistency in <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> values derived from late-time observational measurements, reflecting the well-known <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> tension. In terms of <span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span>, while there is close agreement between Joint analysis and Joint analysis with R22, discrepancies arise upon gradual inclusion of BAO and BAO with R22 datasets. Our model demonstrates excellent fit to observed data and aligns well with the standard ΛCDM paradigm at higher redshifts. However, its most intriguing aspect lies in predicting a super-accelerated expansion in the distant future, in contrast to the de Sitter phase predicted by ΛCDM. Additionally, unique behaviors in the jerk parameter hint at novel dynamics beyond traditional cosmological models. Statefinder and <span><math><msub><mrow><mi>O</mi></mrow><mrow><mi>m</mi></mrow></msub></math></span> Diagnostics tests were conducted, and comparison using the Akaike information criterion indicates neither model can be ruled out based on the latest observational measurements. These findings propose our cosmological model as a compelling alternative to ΛCDM, offering fresh insights into dark energy's nature and the cosmos' future.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 268-279"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141985695","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":"Impact of electron spectra on morphology of pulsar halos at ultra-high energies","authors":"Ying-Ying Guo ,&nbsp;Qiang Yuan","doi":"10.1016/j.jheap.2024.07.006","DOIUrl":"10.1016/j.jheap.2024.07.006","url":null,"abstract":"<div><p>The extended <em>γ</em>-ray halos around pulsars are unique probe of transportation of high-energy electrons (and positrons) in vicinities of such pulsars. Observations of morphologies of several such halos indicate that particles diffuse very slowly around pulsars, compared with that in the Milky Way halo. The energy-dependent morphologies are expected to be very important in studying the energy-dependence of the diffusion coefficient. In this work we point out that the spectrum of high-energy electrons takes effect in shaping the <em>γ</em>-ray morphologies at the ultra-high-energy bands, and thus results in a degeneracy between the electron spectrum and the energy-dependence of the diffusion coefficient. The reasons for such a degeneracy include both the Klein-Nishina effect of the inverse Compton scattering and the curvature (if any) of the electron spectrum. It thus necessary to take into account the spectral shape of electrons when deriving the energy-dependence of diffusion coefficient using ultra-high-energy <em>γ</em>-ray measurements of extended pulsar halos.</p></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"43 ","pages":"Pages 227-230"},"PeriodicalIF":10.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141838519","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}