Related papers: Multi-wavelength radiation models for low-luminosi…
We propose that a hierarchical shock model$\unicode{x2014}$including supernova remnant shocks, galactic wind termination shocks, and accretion shocks around cosmic filaments and galaxy clusters$\unicode{x2014}$can naturally explain the…
Gamma-ray bursts are produced by the dissipation of the kinetic energy of a highly relativistic fireball, via the formation of a collisionless shock. When this happens, Ultra High Energy Cosmic Rays up to 10^20 eV are produced. I show in…
Gamma-ray bursts (GRBs) and following afterglows are considered to be produced by dissipation of kinetic energy of a relativistic fireball and radiation process is widely believed as synchrotron radiation or inverse Compton scattering of…
In this paper, upper limits on the total luminosity of ultra-high-energy cosmic rays (UHECR) (E > $10^{18}$ eV) are determined for five individual sources. The upper limit on the integral flux of GeV-TeV gamma-rays of a given source is used…
Neutrinos with energies ranging from GeV to sub-TeV are expected to be produced in Gamma-Ray Bursts (GRBs) as a result of the dissipation of the jet kinetic energy through nuclear collisions occurring around or below the photosphere, where…
The dip model assumes that the ultra-high energy cosmic rays (UHECRs) above 10$^{18}$ eV consist exclusively of protons and is consistent with the spectrum and composition measure by HiRes. Here we present the range of cosmogenic neutrino…
The availability of simultaneous X-ray and Very High Energy (VHE) observations of blazars helps to identify the plausible radiative contributors to the VHE emission. Under leptonic scenario, the VHE emission from BL Lacs are attributed to…
We investigate ultra-fast outflows (UFOs) in active galactic nuclei (AGN) as potential sources of ultra-high-energy cosmic rays (UHECRs). We focus on cosmic-ray nuclei, an aspect not explored previously. These large-scale,…
The energetics, spectrum, and composition of cosmic rays with energies below about $10^{15}$ eV are fairly well explained by models involving supernova shocks. In contrast, no widely accepted theory exists for the origin of ultra-high…
The observation of very-high-energy (VHE, $\rm >10~GeV$) $\gamma$-ray emission from $\rm \gamma$-ray bursts (GRBs), especially in the prompt phase, will provide critical information for understanding many aspects of their nature including…
In a letter with the above title, published some time ago in PRL, Waxman made the interesting suggestion that cosmological gamma ray bursts (GRBs) are the source of the ultra high energy cosmic rays (UHECR). This has also been proposed…
Gamma-ray bursts (GRBs) are among the most luminous sources in the universe. The nature of their emission at TeV energies is one of the most relevant open issues related to these events. The temporal and spectral features inferred from the…
Gamma-ray bursts (GRBs) are considered as promising sources of ultra-high-energy cosmic rays (UHECRs) due to their large power output. Observing a neutrino flux from GRBs would offer evidence that GRBs are hadronic accelerators of UHECRs.…
The brightest long gamma-ray burst detected so far by the Swift-BAT and Fermi-GBM telescopes, GRB~221009A, provides an unprecedented opportunity for understanding the high-energy processes in extreme transient phenomena. We find that the…
Recent detections of gamma-ray bursts (GRBs) at TeV energies opened new prospects for investigating radiative environments and particle acceleration mechanisms under extreme conditions. In this paper, we study the afterglows of these GRBs -…
The Large High Altitude Air Shower Observatory (LHAASO) has recently reported five Galactic microquasars as Ultra-High-Energy (UHE) $\gamma$-ray emitters (> 100 TeV). Among these sources, the microquasar V4641 Sgr exhibits $\gamma$-ray…
Long GRB 190114C, identified on January 14th, 2019, was the first Gamma-ray Burst that substantially violated the defined 10 GeV energy limit of the Synchrotron model, with an observed emission between 0.2 - 1 TeV and a low redshift of z =…
The origin of ultra-high energy cosmic rays (UHECRs) is one of the most mystifying issues in astroparticle physics. It has been suggested that gamma-ray bursts (GRBs) are excellent acceleration sites for cosmic rays. The propagation of…
A significant fraction of the energy from the $\gamma$-ray burst (GRB) jets, after powering the keV-MeV emission, forms an ultra-relativistic shock propagating into the circumburst medium. The particles in the medium accelerate through the…
Fermi Gamma ray Space Telescope measurements of spectra, variability time scale, and maximum photon energy give lower limits to the apparent jet powers and, through gammagamma opacity arguments, the bulk Lorentz factors of relativistic…