Related papers: Gamma-Ray Bursts as Hypernovae
We assume that internal shocks of Gamma Ray Bursts (GRBs) consist of multiple sub-jets with a collimation half-angle $\sim {\rm several }\times\gamma_i^{-1}$, where $\gamma_i$ is the Lorenz factor of each sub-jet. If by chance a sub-jet is…
We investigated the spectral evolution in the 2--700 keV energy band of Gamma-Ray Bursts (GRBs) detected by the Gamma-Ray Burst Monitor (GRBM) and localized with the Wide Field Cameras (WFCs) aboard the BeppoSAX satellite before May 1998.…
We review the fireball shock model of gamma-ray burst prompt and early afterglow emission in light of rapid follow-up measurements made and enabled by the multi-wavelength Swift satellite. These observations are leading to a reappraisal and…
Gamma-ray burst (GRB) afterglows are likely produced in the shock that is driven as the GRB jet interacts with the external medium. Long-duration GRBs are also associated with powerful supernovae (SNe). We consider the optical and radio…
The supranova model for Gamma-Ray Bursts (GRBs) is becoming increasingly more popular. In this scenario the GRB occurs weeks to years after a supernova explosion, and is located inside a pulsar wind bubble (PWB). Protons accelerated in the…
In order to constrain the broad-band spectral energy distribution of the afterglow of GRB 100621A, dedicated observations were performed in the optical/near-infrared with the 7-channel "Gamma-Ray Burst Optical and Near-infrared Detector"…
The afterglow emission has become the main stream of Gamma-Ray burst research since its discovery three years ago. With the distance-scale enigma solved, the study of the late-time GRB emission is now the most promising approach to disclose…
The Cannon-Ball model of Gamma-Ray Bursts and their afterglows--described in the text and in innumerable previous occasions--is extremely successful and predictive. In a few intrinsically bright GRBs, gamma-rays with energies in the TeV…
Gamma Ray Bursts (GRBs) are bright, brief flashes of high energy photons that have fascinated scientists for 30 years. They come in two classes: long (>2 s), softspectrum bursts and short, hard events. The major progress to date on…
We propose that the gravitational collapse of supermassive objects ($ M\ga 10^4 M_\odot$), either as relativistic star clusters or as single supermassive stars (which may result from stellar mergers in dense star clusters), could be a…
The contemporaneous detection of gravitational waves and gamma rays from the GW170817/GRB 170817A, followed by kilonova emission a day after, confirmed compact binary neutron-star mergers as progenitors of short-duration gamma-ray bursts…
A GRB afterglow has been commonly thought to be due to continuous deceleration of a postburst fireball. Many analytical models have made simplifications for deceleration dynamics of the fireball and its radiation property, although they are…
The optical light that is generated simultaneously with the x-rays and gamma-rays during a gamma-ray burst (GRB) provides clues about the nature of the explosions that occur as massive stars collapse to form black holes. We report on the…
Gamma-ray bursts are thought to be the outcome of a cataclysmic event leading to a relativistically expanding fireball, in which particles are accelerated at shocks and produce nonthermal radiation. We discuss the theoretical predictions of…
Forward shocks caused by the interaction between a relativistic blast wave and the circum-burst medium are thought to be responsible for the afterglow emission in Gamma-Ray Bursts (GRBs). We consider the hydrodynamics of a spherical…
We describe our attempt to determine if gamma-ray burst (GRB) and afterglow emissions could both arise in external shocks for simple GRBs--bursts consisting of just a few peaks in their lightcurves. We calculate peak flux and peak frequency…
Conversion from neutron stars to strange stars as a possible mechanism of cosmological gamma-ray bursts (GRBs) has been discussed in previous works, although the existence of strange stars is still an open question. On the basis of this…
Gamma-ray bursts (GRBs), which are bright flashes of gamma rays from extragalactic sources followed by fading afterglow emission, are associated with stellar core collapse events. We report the detection of very-high-energy (VHE) gamma rays…
The taxonomy of optical emission detected during the critical first few minutes after the onset of a gamma-ray burst (GRB) defines two broad classes: prompt optical emission correlated with prompt gamma-ray emission, and early optical…
There are hints that nearby Type Ia supernovae may be a little different than those at large redshift. Confidence in the conclusion that there is a cosmological constant and an accelerating Universe thus still requires the hard work of…