Related papers: Gamma-ray burst interaction with the circumburst m…
We present hydrodynamical models of circumstellar medium (CSM) of long gamma-ray burst (GRB) progenitor candidates. These are massive stars that have lost a large amount of mass in the form of stellar wind during their evolution. There are…
The association of long gamma-ray bursts (GRBs) with Type Ib/c supernovae implies that they explode into the winds of their Wolf-Rayet progenitor stars. Although the evolution of some GRB afterglows is consistent with expansion into a free…
A long-duration gamma-ray burst (GRB) has been widely thought to arise from the collapse of a massive star, and it has been suggested that its ambient medium is a homogenous interstellar medium (ISM) or a stellar wind. There are two shocks…
Likely progenitors for the GRBs (gamma-ray bursts) are the mergers of compact objects or the explosions of massive stars. These two cases have distinctive environments for the GRB afterglow: the compact object explosions occur in the ISM…
The afterglow emission that follows gamma-ray bursts (GRBs) contains valuable information about the circumburst medium and, therefore, about the GRB progenitor. Theoretical studies of GRB blast waves, however, are often limited to simple…
The association of a supernova with a gamma-ray burst (GRB 030329) implies a massive star progenitor, which is expected to have an environment formed by pre-burst stellar winds. Although some sources are consistent with the expected wind…
Gamma-ray bursts with long durations are widely thought to arise from the collapse of massive stars, where the wind environment is unavoidable. It is also believed that $\gamma$-ray bursts come from jets. Considering these two points in…
Gamma-ray burst (GRB) afterglow observations have allowed us to significantly constrain the engines producing these energetic explosions. Te redshift and position information provided by these afterglows have already allowed us to limit the…
We consider models for gamma-ray bursts in which a collimated jet expands either into a homogeneous medium or into a stellar wind environment, and calculate the expected afterglow temporal behavior. We show that (i) following a break and a…
Recent observations suggest that long-duration gamma-ray bursts (GRBs) and their afterglows are produced by highly relativistic jets emitted in core-collapse explosions. The pre-explosive ambient medium provides a natural test for the most…
Long Gamma-Ray Bursts (GRBs) are produced by ultra-relativistic jets launched from core collapse of massive stars. Most massive stars form in binaries and/or in star clusters, which means that there may be a significant external photon…
In relativistic strongly magnetized winds outflowing from the fast-rotating compact progenitors of gamma-ray bursts (GRBs) there are three regions where powerful high-frequency emission may be generated: (i) the thermal photosphere, (ii)…
Gamma-ray bursts are flashes of high-energy radiation lasting from a fraction of a second to several hours. Military satellites made the first detections of GRBs in the late 1960s. The $\gamma$-ray emission forms from shocks in a…
Massive stars lose a large fraction of their original mass over the course of their evolution. These stellar winds shape the surrounding medium according to parameters that are the result of the characteristics of the stars, varying over…
Gamma-ray bursts (GRBs) are the most electromagnetically luminous cosmic explosions. They are powered by collimated streams of plasma (jets) ejected by a newborn stellar-mass black hole or neutron star at relativistic velocities (near the…
Gamma-ray bursts (GRB) are short and intense bursts of $\sim$100 keV$-$1MeV photons, usually followed by long-lasting decaying afterglow emission in a wide range of electromagnetic wavelengths from radio to X-ray and, sometimes, even to GeV…
By now there is substantial evidence that Gamma-Ray Bursts (GRBs) originate at cosmological distances from very powerful explosions. The interaction between a GRB and its surrounding environment has dramatic consequences on the environment…
Although observations of circumstellar shock interactions around supernovae are generally consistent with a 1/r**2 density profile wind surrounding the progenitor star, this is not true for GRB (gamma-ray burst) afterglows. However, GRB…
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…
Currently popular models for progenitors of gamma-ray bursts (GRBs) are the mergers of compact objects and the explosions of massive stars. These two cases have distinctive environments for GRBs: compact object mergers occur in the…