Related papers: Gross Spectral Differences between Bright and Dim …
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…
It is usual, in gamma-ray burst (GRB) studies, to compare the average properties of bright and faint GRBs, with the assumption that brightness classes reflect distance classes. When brightness is intented to reflect the distance to the…
I discuss the spectral properties of short GRBs detected by BATSE and compare them with long events. The detailed modeling of short GRB spectra shows that their being (on average) harder than long events (as it has been found by comparing…
Two types of Gamma-ray bursts (GRBs) are observed: short duration hard spectrum GRBs and long duration soft spectrum GRBs. For many years long GRBs were the focus of intense research while the lack of observational data limited the study of…
The cosmological origin of $\gamma$-ray bursts (GRBs) is now commonly accepted and, according to several models for the central engine, GRB sources should also emit at the same time gravitational waves bursts (GWBs). We have performed two…
We conjecture that bright gamma-ray bursts (GRBs) are bright because they come from sources which are intrinsically over luminous and not because they come from nearby sources. We show that this hypothesis is supported by theoretical and…
Individual gamma ray bursts (GRBs) have very diverse time behavior - from a single pulse to a long complex sequence of chaotic pulses of different timescales. I studied light curves of GRBs using data from the CGRO's BATSE experiment and…
Due to their highly luminous nature, gamma-ray bursts (GRBs) are useful tools in studying the early Universe (up to z = 10). We consider whether the available subset of Swift high redshift GRBs are unusual when compared to analogous…
We investigated the rest frame spectral lags of two complete samples of bright long (50) and short (6) gamma-ray bursts (GRB) detected by Swift. We analysed the Swift/BAT data through a discrete cross-correlation function (CCF) fitted with…
We show that the time variability of a gamma-ray burst (GRB) appears to be correlated with the absolute luminosity of the burst: smooth bursts are intrinsically less luminous. This Cepheid-like relationship can be used to determine the…
Gamma Ray Bursts (GRBs) are among the most powerful sources in the Universe: they emit up to 10^54 erg in the hard X-ray band in few tens of seconds. The cosmological origin of GRBs has been confirmed by several spectroscopic measurements…
The majority of Swift gamma-ray bursts (GRBs) observed at z > 6 have prompt durations of T90 < 30s, which, at first sight, is surprising given that cosmological time-dilation means this corresponds to < 5s in their rest frames. We have…
We study time-resolved spectra of the prompt emission of Swift Gamma-ray bursts (GRB). Our goal is to see if previous BATSE claims of the existence of a large amount of spectra with the low energy photon indices harder than 2/3 are…
Two classes of gamma-ray bursts have been identified in the BATSE catalogs characterized by durations shorter and longer than about 2 seconds. There are, however, some indications for the existence of a third type of burst. Swift satellite…
We classify gamma-ray bursts (GRBs) according to their observed durations and physical properties of their spectra. We find that long/hard bursts (of duration T_90 > 2.5 s, and typical photon energy E_p > 0.8 MeV corresponding to BATSE's…
The isotropic distribution of gamma-ray bursts as observed with the Burst and Transient Experiment (BATSE) strongly suggests that the bursts are at cosmological distances. At such distances, the expansion of the universe should redshift the…
Gamma-ray bursts (GRBs) are highly variable and exhibit strong spectral evolution. In particular, the emission properties vary from pulse to pulse in multipulse bursts. Here we present a time-resolved Bayesian spectral analysis of a…
We compare the properties of optically dark GRBs, defined by the optical-to-X-ray spectral index beta_OX<0.5, and normal ones discovered by the Swift satellite before the year 2008 in a statistical way, using data collected from the…
In an effort to understand the puzzle of classifying gamma-ray bursts (GRBs), we perform a systematic study of {\it Swift} GRBs and investigate several short GRB issues. Though short GRBs have a short ($\lesssim2$ s) prompt duration as…
One of the most important discoveries in the observation of gamma-ray bursts (GRBs) is that the total energy emitted by a GRB in gamma-rays has a very narrow distribution around 10^51 erg, which has led people to claim that GRBs are…