Related papers: Constraints on Models for TeV Gamma Rays from Gamm…
Recent observations of Sgr A$^*$ by Fermi and HESS have detected steady gamma-ray emission in the GeV and TeV bands. We present a new model to explain the GeV gamma-ray emission by inverse Compton scattering by nonthermal electrons supplied…
Many gamma-ray bursts (GRBs) have been observed from radio wavelengths, and a few at very-high energies (VHEs, > 100GeV). The HAWC gamma-ray observatory is well suited to study transient phenomena at VHEs due to its large field of view and…
A complete model for the origin of high-energy >~10^{14} eV) cosmic rays from gamma-ray bursts (GRBs) and implications of this hypothesis are described. Detection of high-energy neutrinos from GRBs provide an unambiguous test of the model.…
A fraction of gamma-ray bursts exhibit distinct spectral features in their prompt emission below few 10s of keV that exceed simple extrapolations of the low-energy power-law portion of the Band spectral model. This is also true for the…
We calculate the spectra expected from unsteady relativistic wind models of gamma-ray bursts, suitable for events of arbitrary duration. The spectral energy distribution of the burst is calculated over photon energies spanning from eV to…
With the arrival of powerful, ground-based gamma-ray detectors, we can now begin to seriously probe, via simultaneous X-ray/TeV observations, the origin of the gamma-ray emission in the blazars Mrk 421 and 501. If the synchrotron-Compton…
We present the spectral analysis of duration-integrated broadband spectra (in $\sim30 $keV$-200 $MeV) of 15 bright BATSE gamma-ray bursts (GRBs). Some GRB spectra are very hard, with their spectral peak energies being above the BATSE LAD…
Gamma-ray bursts (GRBs) are widely suggested as potential sources of ultrahigh-energy cosmic rays (UHECRs). The kinetic energy of the jets dissipates, leading to the production of an enormous amount of $\gamma$-ray photons and possibly also…
Gamma-ray Bursts (GRB) were discovered by satellite-based detectors as powerful sources of transient $\gamma$-ray emission. The Fermi satellite detected an increasing number of these events with its dedicated Gamma-ray Burst Monitor (GBM),…
The origin of sub-TeV gamma rays detected by Fermi-LAT from the Fermi bubbles at the Galactic center is still unknown. In a hadronic model, acceleration of protons and/or nuclei and their subsequent interactions with gas in the bubble…
The recent detection of TeV photons from two gamma-ray bursts (GRBs), GRB 190114C and GRB 180720B, has opened a new window for multi-messenger and multi-wavelength astrophysics of high-energy transients. We study the origin of…
The expected opacity of the intergalactic space limits the mean free path of TeV gamma rays to dozens of Megaparsecs. However, TeV photons from numerous more distant sources have been detected. This might be interpreted, in each particular…
We investigate the GeV emission from gamma-ray bursts (GRBs), using the results from the Energetic Gamma Ray Experimental Telescope (EGRET), and in view of the Gamma-ray Large Area Space Telescope (GLAST). Assuming that the conventional…
The gamma-ray burst (GRB) model for production of ultra-high-energy cosmic-rays (UHECRs) is based on the hypothesis that GRBs arise from the dissipation of the kinetic energy of relativistic fireballs at cosmological distances. Recent GRB…
The recent detection of delayed, low energy emission from Gamma-Ray Burst (GRB) sources confirmed the cosmological origin of the bursts and provided support for models where GRBs are produced by the dissipation of the kinetic energy of…
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…
We calculate the spectrum of blast wave models of gamma-ray burst sources, for various assumptions about the magnetic field density and the relativistic particle acceleration efficiency. For a range of physically plausible models we find…
Eleven bright gamma-ray bursts (GRBs) detected by BATSE have also been seen at much higher energies by EGRET, six at energies above 10 MeV. Such observations imply that these bursts are optically thin to photon-photon pair production at all…
The high energy emission from Gamma-ray Bursts has some interesting features, including the absence of the GeV excess in the prompt spectrum, the delayed onset of the GeV emission, and the longer duration of the GeV emission than the prompt…
Cosmological models that include suppression of the power spectrum of density fluctuations on small scales exhibit an exponential reduction of high-redshift, non-linear structures, including a reduction in the rate of gamma ray bursts…