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We report the best evidence to date of a jet break in a short Gamma-Ray Burst (GRB) afterglow, using Chandra and Swift XRT observations of the X-ray afterglow of GRB 051221A. The combined X-ray light curve, which has three breaks, is…
It is believed that first-order phase transitions at or around the GUT scale will produce high-frequency gravitational radiation. This radiation is a consequence of the collisions and coalescence of multiple bubbles during the transition.…
We report on observations of correlated behavior between the prompt gamma-ray and optical emission from GRB 080319B, which (i) strongly suggest that they occurred within the same astrophysical source region and (ii) indicate that their…
Follow-up observations of large numbers of gamma-ray burst (GRB) afterglows, facilitated by the Swift satellite, have produced a large sample of spectral energy distributions and light curves, from which the basic micro- and macrophysical…
Using the 2.4m MDM and 8.4m Large Binocular Telescope, we observed nine GRB afterglows to systematically probe the late time behaviors of afterglows including jet breaks, flares, and supernova bumps. In particular, the LBT observations have…
We perform fully relativistic hydrodynamic simulations of the deceleration and lateral expansion of a relativistic jet as it expands into an ambient medium. The hydrodynamic calculations use a 2D adaptive mesh refinement (AMR) code, which…
The Fermi Large Area Telescope has revolutionised the $\gamma$-ray pulsar field, increasing the population to over 250 detected pulsars. The majority display spectra with exponential cutoffs in a narrow range around a few GeV. Models…
Gamma-ray bursts (GRBs) are produced during the propagation of ultra-relativistic jets. It is challenging to study the jet close to the central source, due to the high opacity of the medium. In this paper, we present numerical simulations…
Gamma ray bursts (GRB's) often feature subpulses that have a distinctively asymmetric profile -- they rise quickly and decay much more slowly, while their spectrum softens slightly with observer time. It is suggested that these subpulses…
Previous studies have found that the width of gamma-ray burst (GRB) pulse is energy dependent and that it decreases as a power-law function with increasing photon energy. In this work we have investigated the relation between the energy…
The jet opening angle of gamma-ray bursts (GRBs) is an important parameter for determining the characteristics of the progenitor, and the information contained in the opening angle gives insight into the relativistic outflow and the total…
BAT and XRT observations of two recent well-covered GRBs observed by Swift, GRB 050315 and GRB 050319, show clearly a prompt component joining the onset of the afterglow emission. By fitting a power law form to the gamma-ray spectrum, we…
We present a possible theoretical interpretation of the observed afterglow emission of long gamma-ray burst GRB 080710. While its prompt GRB emission properties are normal, the afterglow light curves in the optical and infrared bands are…
Gamma-ray bursts (GRBs) are powered by ultra-relativistic jets. The launching sites of these jets are surrounded by dense media, which the jets must cross before they can accelerate and release the high energy emission. Interaction with the…
GRB 090618 is a bright GRB with multiple pulses. It shows evidence of thermal emission in the initial pulses as well as in the early afterglow phase. As high resolution spectral data of \emph{Swift}/XRT is available for the early afterglow,…
Gamma-ray Burst (GRB) collimation has been inferred with the observations of achromatic steepening in GRB light curves, known as jet breaks. Identifying a jet break from a GRB afterglow lightcurve allows a measurement of the jet opening…
The gluon emission from an energetic heavy quark is suppressed in the forward direction below the angle $\Theta\lesssim m_Q/E$ for a quark of mass $m_Q$ and energy $E$ according to perturbative Quantum Chromodynamics (QCD) (``dead cone").…
Swift triggered on a precursor to the main burst of GRB 061121 (z=1.314), allowing observations to be made from the optical to gamma-ray bands. Many other telescopes, including Konus-Wind, XMM-Newton, ROTSE and the Faulkes Telescope North,…
Gamma-ray burst (GRB) 120729A was detected by Swift/BAT and Fermi/GBM, and then rapidly observed by Swift/XRT, Swift/UVOT, and ground-based telescopes. It had a single long and smooth \gamma-ray emission pulse, which extends continuously to…
We present a detailed analysis of GRB 151006A, the first GRB detected by Astrosat CZT Imager (CZTI). We study the long term spectral evolution by exploiting the capabilities of \emph{Fermi} and \emph{Swift} satellites at different phases,…