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Gamma ray bursts are excellent candidates to constrain physical models which break Lorentz symmetry. We consider deformed dispersion relations which break the boost invariance and lead to an energy-dependent speed of light. In these models,…
Gamma-ray bursts (GRBs) are brief flashes of gamma rays, considered to be the most energetic explosive phenomena in the Universe. The emission from GRBs comprises a short (typically tens of seconds) and bright prompt emission, followed by a…
Detailed information on the physical parameters in the sources of cosmological Gamma-Ray Bursts (GRBs) is obtained from few plausible assumptions consistent with observations. Model-independent requirements posed by these assumptions on the…
Gamma-ray bursts (GRBs) are cosmological explosions which carry valuable information from the distant past of the expanding universe. One of the greatest discoveries in modern cosmology is the finding of the accelerated expansion of the…
Synchrotron radiation and Compton scattering are widely accepted as the most likely emission mechanisms of some astrophysical phenomena, such as gamma-ray bursts (GRBs) and active galactic nuclei (AGNs). The measurement on polarization of…
Active galactic nuclei (AGNs) and gamma-ray bursts (GRBs) are powerful astrophysical events with relativistic jets. In this Letter the broadband spectral properties are compared between GRBs and the well-observed blazars. The distribution…
The deviation from the power-law decline of the optical flux observed in GRB 970228 and GRB 980326 has been used recently to argue in favor of the connection between GRBs and supernovae. We consider an alternative explanation for this…
$\gamma$-ray bursts (GRBs) have puzzled astronomers since their accidental discovery in the sixties. The BATSE detector on COMPTON-GRO satellite has been detecting GRBs for the last four years at a rate of one burst per day. Its findings…
The physical origin of the >0.1 GeV emission detected from Gamma-Ray Bursts (GRBs) by the Fermi satellite has not yet been completely understood. In this work we consider the GeV light curves of ten GRBs with measured redshift detected by…
Due to their cosmological distances high-energy astrophysical sources allow for unprecedented tests of fundamental physics. Gamma-ray bursts (GRBs) comprise among the most sensitive laboratories for exploring the violation of the central…
Gamma ray bursts (GRB) occur at random points in the sky at cosmological distances. The spectra evolve through X-ray, optical region to possibly radio frequency. Though there are some models, the origin and time evolution of GRB are not…
We present the results of the spectral analysis of a sample of short bright $\gamma$--ray bursts (GRB) detected by BATSE and compare them with the average and time resolved spectral properties of long bright bursts. While the spectral…
We consider a speculative model for gamma-ray bursts (GRB), which predicts that the total kinetic energy in the ejected matter is less than the total energy in the gamma rays. There is also secondary energy in X-rays, which are emitted…
We present an updated catalog of 113 X-ray flares detected by Swift in the ~33% of the X-ray afterglows of Gamma-Ray Bursts (GRB). 43 flares have a measured redshift. For the first time the analysis is performed in 4 different X-ray energy…
Gamma-Ray Bursts (GRBs) are the brightest objects observed. They are also the most relativistic objects known so far. GRBs occur when an ultrarelativisitic ejecta is slowed down by internal shocks within the flow. Relativistic particles…
There is no consensus on the emission mechanism of $\gamma$-ray bursts (GRBs). A synchrotron model can produce $\gamma$-ray spectra with the empirical Band function form, from a piece-wise two-power-law electron energy distribution (2EPLS).…
We have averaged bright BATSE bursts to uncover the average overall temporal and spectral evolution of gamma-ray bursts (GRBs). We align the temporal structure of each burst by setting its duration to a standard duration, which we call…
Gamma-Ray Bursts (GRBs) are thought to originate at cosmological distances from the most powerful explosions in the Universe. If GRBs are not beamed then the distribution of their number as a function of Gamma-ray flux implies that they…
The observations of the prompt emission of gamma ray bursts (GRB) by GLAST Burst Monitor (GBM), on board Fermi Gamma-ray Space Telescope, suggest the presence of a significant thermal spectral component, whose origin is not well understood.…
The principal paradigm for gamma-ray bursts suggest that the prompt transient gamma-ray signal arises from multiple shocks internal to the relativistic expansion. This paper illustrates some properties of diffusive acceleration at…