Related papers: Constraining the initial Lorentz factor of gamma-r…
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…
Explosions of massive stars are believed to be the source of a significant fraction of gamma-ray bursts (GRBs). If this is indeed the case, then the explosion blast wave propagates into a complex density structure, composed of a stellar…
Before the launch of the Fermi Gamma-ray Space Telescope there were only a handful of gamma-ray bursts (GRBs) detected at high energies (above 100 MeV), while several different suggestions have been made for possible high-energy emission…
In the external shock model, gamma-ray burst (GRB) emissions are produced by the energization and deceleration of a thin relativistic blast wave due to its interactions with the circumburst medium (CBM). We study the physical properties of…
Based on recent models of relativistic jet formation by thermal energy deposition around black hole-torus systems, the relation between the on- and off-axis appearance of short, hard gamma-ray bursts (GRBs) is discussed in terms of…
GRB 990123 was a long, complex gamma-ray burst accompanied by an extremely bright optical flash. We present the collective constraints on the bulk Lorentz factor for this burst based on estimates from burst kinematics, synchrotron spectral…
We numerically model the interaction between an expanding fireball and a stationary external medium whose density is either homogeneous or varies with distance as a power-law. The evolution is followed until most of the fireball kinetic…
The shock model has successfully explained the observed behaviors of afterglows from long gamma-ray bursts (GRBs). Here we use it to investigate the so-called early afterglows from short GRBs, which arises from blast waves that are not…
The jet photosphere has been proposed as the origin for the gamma-ray burst (GRB) prompt emission. In many such models, characteristic features in the spectra appear below the energy range of the $\textit{Fermi}$ GBM detectors, so joint…
We analyze the properties of a sample of long gamma-ray bursts (LGRBs) detected by the Fermi satellite that have a spectroscopic redshift and good follow-up coverage at both X-ray and optical/nIR wavelengths. The evolution of LGRB…
[Abridged] Very recently, relations between the peak energy of Gamma-Ray Burst burst spectra, the isotropic-equivalent energy of the burst, and the radiated energy of the burst have been found. In a way that is exactly analogous to the way…
Short gamma-ray bursts (GRBs) are believed to be produced by relativistic jets from mergers of neutron-stars (NS) or neutron-stars and black-holes (BH). If the Lorentz-factors $\Gamma$ of jets from compact-stellar-mergers follow a similar…
It has been suggested that the prompt emission in gamma-ray bursts (GRBs) could be described by radiation from the photosphere in a hot fireball. Such models must be tested by directly fitting them to data. In this work we use data from the…
Opacity effects in relativistic sources of high-energy gamma-rays, such as gamma-ray bursts (GRBs) or Blazars, can probe the Lorentz factor of the outflow and the distance of the emission site from the source, and thus help constrain the…
We study prompt optical emission from reverse shocks in the wind-type gamma-ray bursts. The emission is evaluated in both the thick and thin shell regimes. We discuss the angular time delay effect and the post-shock evolution of the…
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…
We investigate the properties of both the prompt and X-ray afterglows of gamma-ray bursts (GRBs) in the burst frame with a sample of 33 Swift GRBs. Assuming that the steep decay segment in the canonical X-ray afterglow lightcurves is due to…
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…
Aims: In this paper we study the main spectral and temporal properties of gamma-ray bursts (GRBs) observed by Fermi/GBM. We investigate these key properties of GRBs in the rest-frame of the progenitor and test for possible intra-parameter…
We analyze the prompt emission of GRB 100724B and GRB 160509A, two of the brightest Gamma-Ray Bursts (GRBs) observed by Fermi at $\lesssim{\rm MeV}$ energies but surprisingly faint at $\gtrsim100\;$MeV energies. Time-resolved spectroscopy…