Related papers: Statistical Evidence for Three classes of Gamma-ra…
Context. The dissipation process responsible for the long gamma-ray burst (GRB) prompt emission and the kind of dynamics that drives the release of energy as a function of time are still key open issues. We recently found that the…
We use the BD2 sample of gamma-ray bursts (GRBs) based on 5.9 years of BATSE DISCLA data with a variety of models of the luminosity function to derive characteristic GRB luminosities, space densities and redshift distributions. Previously…
Two classes of gamma-ray bursts have been identified so far, characterized by durations shorter and longer than approximately 2 seconds. In 1998 two independent papers indicated the existence of the third class of the bursts roughly…
Analyzing light curves of a complete sample of bright Swift long gamma-ray bursts (LGRBs) of which the peak photon fluxes constructed with the bin width of 1 second in the Swift 15-350 keV energy band exceed 2.6 photons cm$^{-2}$s$^{-1}$,…
Gamma-ray bursts (GRBs) are divided into two classes according to their durations. We investigate if the softness of bursts plays a role in the conventional classification of the objects. We employ the BATSE (Burst and Transient Source…
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…
Identification of Gamma Ray Burst (GRB) progenitors based on the duration of their prompt emission ($T_{90}$) has faced several roadblocks recently. Long-duration GRBs (with $T_{90} > 2s$) have traditionally been thought to be originating…
We present here our results of the temporal and spectral analysis of a sample of 52 bright and hard gamma-ray bursts (GRBs) observed with the Fermi Gamma-ray Burst Monitor (GBM) during its first year of operation (July 2008-July 2009). Our…
Short-hard Gamma Ray Bursts (SGRBs) are currently thought to arise from gravitational wave driven coalescences of double neutron star systems forming either in the field or dynamically in globular clusters. For both channels we fit the peak…
We have performed a systematic study of Gamma-Ray Bursts (GRBs), which have various values in the peak energy of the ${\nu}F_{\nu}$ spectrum of the prompt emission, $E_{{\rm peak}}$, observed by \textsl{Swift}/BAT and \textsl{Fermi}/GBM,…
A sample of 427 gamma-ray bursts from a database (February 2002 - April 2008) of the RHESSI satellite is analyzed statistically. The spectral lags and peak-count rates, which have been calculated for the first time in this paper, are…
We compare the spectral properties of 227 Gamma Ray Bursts (GRBs) detected by the Fermi Gamma Ray Burst Monitor (GBM) up to February 2010 with those of bursts detected by the CGRO/BATSE instrument. Out of 227 Fermi GRBs, 166 have a measured…
In this paper we give a brief review of our recent studies on the long and short gamma-ray bursts (GRBs) detected Swift, in an effort to understand the puzzle of classifying GRBs. We consider that it is still an appealing conjecture that…
Popular models for the origin of gamma-ray bursts (GRBs) include short-lived massive stars as the progenitors of the fireballs. Hence the redshift distribution of GRBs should track the cosmic star formation rate of massive stars accurately.…
A sample of almost 400 Gamma-ray bursts (GRBs) detected by the RHESSI satellite is studied statistically. We focus on GRB duration and hardness ratio and use the statistical chi^2 test and the F-test to compare the number of GRB subgroups…
We report evidence from the 3B Catalogue that short (T_90 < 10 s) and long (T_90 > 10 s) GRB represent different populations and processes: Their spectral behavior is qualitatively different, with short bursts harder in the BATSE range, but…
The recent association of several short gamma-ray bursts (GRBs) with early type galaxies with low star formation rate demonstrates that short bursts arise from a different progenitor mechanism than long bursts. However, since the duration…
Knowledge of the bulk Lorentz factor $\Gamma_{0}$ of GRBs allows us to compute their comoving frame properties shedding light on their physics. Upon collisions with the circumburst matter, the fireball of a GRB starts to decelerate,…
The Burst and Transient Source Experiment (BATSE) classifies cosmological gamma-ray bursts (GRBs) into short (less than 2 s) and long (over 2 s) events, commonly attributed to mergers of compact objects and, respectively, peculiar…
Type I gamma-ray bursts (GRBs) are believed to originate from compact binary merger usually with duration less than 2 seconds for the main emission. However, recent observations of GRB 211211A and GRB 230307A indicate that some…