We revisit the constraints on primordial black holes (PBHs) in mass range ${10}^{13}\text{ }\text{ }\mathrm{g}--{10}^{18}\text{ }\mathrm{g}$ by comparing 100 keV--5 GeV gamma-ray background with isotropic flux from PBH Hawking radiation (HR). investigate three effects that may update abundance; (i) reliably calculating secondary spectra of HR for energy below 5 GeV, (ii) contributions to measured Galactic and annihilation due evaporated positrons, (iii) inclusion astrophysical sources. The...

Context. The intrinsic TeV emission of some BL Lacs are characterized by a hard spectrum (the hard-TeV spectrum) after correcting for the extragalactic background light. spectra pose challenge to conventional one-zone models, including leptonic model, photohadronic proton synchrotron etc. Aims. In this work, we study if hadronuclear (pp) model can be used interpret without introducing extreme parameters. Methods. We give analytical calculations there is parameter space and charge neutrality...

The first measurements from the CIBER experiment of extragalactic background light (EBL) in near-infrared (NIR) band exhibit a higher intensity than those inferred through $\ensuremath{\gamma}$-ray observations. Recent theoretical-EBL intensities are typically consistent with very high energy (VHE) Yet, it is possible that excess NIR radiation new component EBL and not tension TeV spectra distant blazars, since hypothetical axionlike particle (ALP) may lead to reduced opacity Universe for...

The present work considers a plane shock front propagating along cylindrical jet. Electrons experience diffusive acceleration around the front, and subsequently drift away into downstream flow, in which they emit most of their energy. Assuming proper boundary condition at interface between zone zone, we solve transport equation for electrons flow where combined effects escape, synchrotron inverse Compton cooling Thomson regime are taken account. Using electron spectrum obtained this manner...

We describe the theory of Fermi-type acceleration, including first-order Fermi acceleration at a parallel shock front and second-order in test particle limit. Including turbulent derivation general Fokker–Planck equation, we take into account basic particle-transport equation with spatially homogeneous isotropic distribution. In cases some special physical processes, construct equations, compile analytical or semi-analytical solutions 11 different cases. Even though, traditionally, one...

Axionlike particles (ALPs) are predicted in some well-motivated theories beyond the Standard Model. The TeV gamma-rays from active galactic nuclei (AGN) suffer attenuation by pair production interactions with cosmic background light (EBL/CMB) during its travel to earth. can be circumvented through photon-ALP conversions AGN and Galaxy magnetic-field, a flux enhancement is expected arise observed spectrum. In this work, we study potential of gamma-ray spectrum for energy up above 100 probe...

Neutrino annihilation process on a hyperaccreting disk is one of the leading models to explain generation relativistic jets gamma-ray bursts (GRBs). However, there still uncertainty regarding NAE neutron star-accretion disc (NS-disc) system because complicated microphysics processes and effects strong magnetic field. In this paper, we investigate by assuming that prompt jet GRB 070110 driven neutrino pair in NS-disc system. Our calculation shows $η_{ν\barν}> 1.2 \times 10^{-3}$ under...

Heartbeat star systems have been reported to exhibit two distinct different orbital dynamic evolution processes: apsidal precession (e.g., KIC 4544587) and decay 3766353). While experiencing similar tidal interactions, these binary display dynamical behaviors, which is a puzzling phenomenon. In this work, we deduced theoretical relation between the timescale of stellar pulsation Ppul periods Porb heartbeat stars based on resonance criteria representing local low-energy configuration. The...

We analyzed 199 GRBs detected by Fermi-LAT during the years 2008-2019. found 67 photons at energies >=10 GeV, which come from 34 GRBs. Out of these GRBs, detects significant (TS>=4) afterglow 0.1-200 GeV 25 present time-integrated spectra The a fraction (9/25) revealed harder component above an energy break 0.3-2 GeV. While shock synchrotron may account for lower end, high is naturally explained self-Compton (SSC) emission. perform broadband model fit to X-ray-LAT emission GRB 131231A....

We study the direct radiation excited by oscillating axion (or axion-like particle) dark matter in a homogenous magnetic field and its detection scheme. concretely derive analytical expression of axion-induced radiated power for cylindrical uniform field. In long wave limit, is proportional to square B-field volume mass $m_a$, whereas it oscillate as approaching short limit peak powers are side area $m_a^{-2}$. The maximum locates at $m_a\sim\frac{3π}{4R}$ fixed radius $R$. Based on this...

We study the direct radiation excited by oscillating axion (or axion-like particle) dark matter in a homogenous magnetic field and its detection scheme. concretely derive analytical expression of axion-induced radiated power for cylindrical uniform field. In long wave limit, is proportional to square B-field volume mass $m_a$, whereas it oscillate as approaching short limit peak powers are side area $m_a^{-2}$. The maximum locates at $m_a\sim\frac{3\pi}{4R}$ fixed radius $R$. Based on this...

Context. The very high-energy (VHE; ≥100 GeV) component from at least two gamma-ray bursts (GRBs), that is, GRB 180720B and 190114C, has been detected in the afterglow phase. It is widely discussed GeV to TeV emission originated a synchrotron self-Compton (SSC) process. VHE may cause an upturn spectral ends Fermi -Large Area Telescope ( -LAT) observing band. Aims. We aim find out whether additional commonly exists afterglows of -LAT GRBs. This study will help us better understand how common...