Related papers: Lorentz factor - Beaming Corrected Energy/Luminosi…
Gamma-ray burst are thought to be produced by highly relativistic outflows. Although upper and lower limits for the outflow initial Lorentz factor $\Gamma_0$ are available, observational efforts to derive a direct determination of…
We report observations of the early light curves of GRB 060418 and GRB 060607A, carried out with the pink robotic telescope REM. A clear peak is detected for both events, which is interpreted as the onset of the afterglow, that is the time…
The jet opening angle of gamma-ray bursts (GRBs) is an important parameter for determining the characteristics of the progenitor, and the information contained in the opening angle gives insight into the relativistic outflow and the total…
If gamma ray bursts are highly collimated, radiating into only a small fraction of the sky, the energy requirements of each event may be reduced by several (up to 4 - 6) orders of magnitude, and the event rate increased correspondingly. The…
GRB 160625B is an extremely-bright outburst with well-monitored afterglow emission. The geometry-corrected energy is high up to $\sim 5.2\times10^{52}$ erg or even $\sim 8\times 10^{52}$ erg, rendering it the most energetic GRB prompt…
X-ray flares were discovered in the afterglow phase of gamma-ray bursts (GRBs) by the {\em Swift} satellite a decade ago and known as a canonical component in GRB X-ray afterglows. In this paper, we constrain the Lorentz factors of GRB…
Gamma-ray Burst (GRB) collimation has been inferred with the observations of achromatic steepening in GRB light curves, known as jet breaks. Identifying a jet break from a GRB afterglow lightcurve allows a measurement of the jet opening…
Well-sampled optical lightcurves of 146 gamma-ray bursts (GRBs) are complied from the literature. Multiple optical emission components are extracted with power-law function fits to these lightcurves. We present a systematical analysis for…
A hyperaccreting stellar-mass black hole has been proposed as the candidate central engine of gamma-ray bursts (GRBs). The rich observations of GRBs by \textit{Fermi} and \textit{Swift} make it possible to constrain the central engine model…
The jet structure in gamma-ray burst (GRB) sources is still largely an open question. The leading models invoke either (i) a roughly uniform jet with sharp edges, or (ii) a jet with a narrow core and wide wings where the energy per solid…
We present a method to estimate the jet opening angles of long duration Gamma-Ray Bursts (GRBs) using the prompt gamma-ray energetics and an inversion of the Ghirlanda relation, which is a correlation between the time-integrated peak energy…
The shallow decay phase and flares in the afterglows of gamma-ray bursts (GRBs) is widely believed to be associated with the later activation of central engine. Some models of energy injection involve with a continuous energy flow since the…
It is generally supposed that a transition from the normal decay phase (decay slope $\sim -1$) to a steeper phase (decay slope $\sim -2$) could be suggested as a jet break. The jet opening angle $\theta_{\rm jet}$ is then calculated from…
Gamma-ray burst (GRB) emission is believed to originate in highly relativistic fireballs. Currently, only lower limits were securely set to the initial fireball Lorentz factor Gamma_0. We aim to provide a direct measure of Gamma_0. The…
We use a sample of 19 Gamma Ray Bursts (GRBs) that exhibit single-peaked optical light curves to test the standard fireball model by investigating the relationship between the time of the onset of the afterglow and the temporal rising…
We recently found that Gamma Ray Burst energies and luminosities, in their comoving frame, are remarkably similar. This, coupled with the clustering of energetics once corrected for the collimation factor, suggests the possibility that all…
The jet compositions, central engines, and progenitors of gamma-ray bursts (GRBs) remain open questions in GRB physics. Applying broadband observations, including GRB prompt emission and afterglow properties derived from {\em Fermi} and…
Direct multi-dimensional numerical simulation is the most reliable approach for calculating the fluid dynamics and observational signatures of relativistic jets in gamma-ray bursts (GRBs). We present a two-dimensional relativistic…
We present a model for relativistic jets which generates a particular angular distribution of Lorentz factor and energy per solid angle. We consider a fireball with specific internal energy E/M launched with bulk Lorentz factor \gamma_B.…
We investigate the jet propagation and breakout from the stellar progenitor for gamma-ray burst (GRB) collapsars by performing two-dimensional relativistic hydrodynamic simulations and analytical modeling. We find that the jet opening angle…