Related papers: Quiescence and late time activity in collapsars du…

The duration of a gamma-ray burst (GRB) is a key indicator of its physics origin, with long bursts perhaps associated with the collapse of massive stars and short bursts with mergers of neutron stars.However, there is substantial overlap in…

When massive stars exhaust their fuel they collapse and often produce the extraordinarily bright explosions known as core-collapse supernovae. On occasion, this stellar collapse also powers an even more brilliant relativistic explosion…

Low luminosity gamma-ray bursts (ll-GRBs) constitute a sub-class of gamma-ray bursts (GRBs) that plays a central role in the GRB-supernova connection. While ll-GRBs differ from typical long GRBs (LGRBs) in many aspects, they also share some…

Gamma-ray bursts (GRBs) have been phenomenologically classified into long and short populations based on the observed bimodal distribution of duration. Multi-wavelength and multi-messenger observations in recent years have revealed that in…

We observe strong correlations between the temporal properties of gamma ray bursts (GRBs) and their apparent peak brightness. The strongest effect (with a significance level of 10^{-6}) is the difference between the brightness distributions…

The strong dependence of the neutrino annihilation mechanism on the mass accretion rate makes it difficult to explain the LGRBs with duration in excess of 100 seconds as well as the precursors separated from the main gamma-ray pulse by few…

Collapsars are the likely progenitors of Long Gamma-Ray Burst (lGRBs). lGRBs have been observed to last for thousands to tens of thousands of seconds, thus making unlikely the neutrino-driven engine as the main mechanism for driving the…

Some of the mysterious temporal properties of Fast Radio Bursts (FRB) may be explained if they are produced by dynamically triaxial magnetars. If the bursts are narrowly collimated along open field lines, then observed repeating FRB are…

We propose that repeated photoexcitation/ionization of high Z atoms of highly relativistic flows by star light in dense stellar regions followed by emission of decay/recombination photons, which are beamed and boosted to gamma ray energies…

Gamma ray burst (GRB) time series is a non-stationary time series with all its statistical properties varying with time. Considering that each GRB is a different manifestation of the same stochastic process we studied the time dependent as…

A gamma-ray burst (GRB) releases an amount of energy similar to that of a supernova explosion, which combined with its rapid variability suggests an origin related to neutron stars or black holes. Since these compact stellar remnants form…

The plateau in the duration distribution of long Gamma-Ray Bursts (LGRBs) provides a direct observational evidence for the Collapsar model. The plateau reflects the fact that the observed duration satisfies: $T_{90} = t_{e}-t_{b}$ where…

Long-duration gamma-ray bursts are the manifestations of massive stellar death. Due to the immense energy release they are detectable from most of the observable universe. In this way they allow us to study the deaths of single (or binary)…

We study the scenario where the gamma-ray bursts (GRBs) arise from core-collapse of very massive stars in star-forming regions in the starburst galaxies at high redshift. The bimodial structure of the gamma-ray bursts point to their…

Gamma ray bursts are the most luminous physical phenomena in the universe, consisting of flashes of gamma rays that last from seconds to hours. There have been attempts to observe gamma ray bursts, for example, from population III stars of…

We have analyzed publicly available RXTE/PCAs archival data of GRS 1915+105 during its burst/flaring state. The burst cycle ranges from 30 to 1300 s. These bursts are different from the type I and type II classical bursts seen in Low Mass…

Transiently accreting neutron stars in quiescence (Lx<10^34 erg/s) have been observed to vary in intensity by factors of few, over timescales of days to years. If the quiescent luminosity is powered by a hot NS core, the core cooling…

Ultra-long Gamma-Ray Bursts are a class of high energy transients lasting several hours. Their exact nature is still elusive, and several models have been proposed to explain them. Because of the limited coverage of wide field gamma-ray…

The various possibilities for the progenitors of gamma-ray bursts (GRBs) manifest in differing observable properties. Through deep spectroscopic and high-resolution imaging observations of some GRB hosts, I demonstrate that well-localized…

The chief distinction between ordinary supernovae and long-soft gamma-ray bursts (GRBs) is the degree of differential rotation in the inner several solar masses when a massive star dies, and GRBs are rare mainly because of the difficulty…