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With its rapid-response capability and multiwavelength complement of instruments, the Swift satellite has transformed our physical understanding of gamma-ray bursts (GRBs). Providing high-quality observations of hundreds of bursts, and…
When a massive star explodes as a Gamma Ray Burst information about this explosion is retained in the properties of the prompt and afterglow emission. We report on new relationships between the prompt and X-ray afterglow emission of…
Gamma-ray burst (GRB) afterglows are likely produced in the shock that is driven as the GRB jet interacts with the external medium. Long-duration GRBs are also associated with powerful supernovae (SNe). We consider the optical and radio…
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 successful launch and operation of NASA's Swift Gamma-Ray Burst Explorer open a new era for the multi-wavelength study of the very early afterglow phase of gamma-ray bursts (GRBs). GRB early afterglow information is essential to explore…
Starting from April 2007, a search for solar daily variation of the muon intensity ($E_\mu >0.2$ GeV) at sea level and using two directional muon telescopes is in progress. In this survey, several ground level enhancements (GLEs) on the…
Cusps of superconducting strings can serve as GRB engines. A powerful beamed pulse of electromagnetic radiation from a cusp produces a jet of accelerated particles, whose propagation is terminated by the shock responsible for GRB. A single…
The long gamma-ray burst GRB 060714 was observed to exhibit a series of five X-ray flares beginning ~70 s after the burst trigger T0 and continuing until T0 + ~200 s. The first two flares were detected by the Burst Alert Telescope (BAT) on…
Gamma-ray bursts (GRBs) are short and intense emission of soft gamma-rays, which have fascinated astronomers and astrophysicists since their unexpected discovery in 1960s. The X-ray/optical/radio afterglow observations confirm the…
The follow-up of $\gamma$-ray bursts (GRBs) by the X-ray telescope (XRT, 0.3-10 keV) on board the Neil Gehrels Swift Observatory led to the discovery of a shallow decay phase (the so-called plateau) of the X-ray emission in a good fraction…
We describe our attempt to determine if gamma-ray burst (GRB) and afterglow emissions could both arise in external shocks for simple GRBs--bursts consisting of just a few peaks in their lightcurves. We calculate peak flux and peak frequency…
Extended emission is a mystery in short gamma-ray bursts (SGRBs). By making time resolved spectral analyses of brightest nine events observed by ${\it Swift}$ XRT, we obviously classify the early X-ray emission of SGRBs into two types. One…
Prompt {\gamma}-ray emissions from gamma-ray bursts (GRBs) exhibit a vast range of extremely complex temporal structures with a typical variability time-scale significantly short - as fast as milliseconds. This work aims to investigate the…
In relativistic strongly magnetized winds outflowing from the fast-rotating compact progenitors of gamma-ray bursts (GRBs) there are three regions where powerful high-frequency emission may be generated: (i) the thermal photosphere, (ii)…
The flare activity that is observed in GRBs soon after the prompt emission with the XRT (0.3-10 KeV) instrument on board of the Swift satellite is leading to important clues in relation to the physical characteristics of the mechanism…
We report the discovery of a correlation among three prompt emission properties of GRBs. These are the isotropic peak luminosity L_iso, the peak energy of the time-integrated prompt emission spectrum E_pk, and the ``high signal" timescale…
We consider the properties of a hyperaccretion model for gamma-ray bursts (GRBs) at the late time when the mass supply rate is expected to decrease with time. We point out that the region in the vicinity of the accretor and the accretor…
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…
We present optical and near-infrared (NIR) photometry of 28 gamma-ray bursts (GRBs) detected by the \textit{Swift} satellite and rapidly observed by the Reionization and Transients Infrared/Optical (RATIR) camera. We compare the optical…
Gamma-ray Bursts (GRBs) are relativistic cosmological beacons of transient high energy radiation whose afterglows span the electromagnetic spectrum. Theoretical expectations of correlated neutrino and/or gravitational wave (GW) emission…