Related papers: Polarization and light curve variability: the "pat…
The Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory observed GRB 021211 starting 105 s after the burst, among the earliest observations of an optical afterglow to date. Our well-sampled light curve, consisting of 18 points in…
Strong optical and radio flares often appear in the afterglow phase of Gamma-Ray Bursts (GRBs). It has been proposed that colliding ultra-relativistic shells can produce these flares. Such consecutive shells can be formed due to the…
Gamma ray burst (GRB) afterglow light curves have the potential to inform us about presently unobserved stages in the aftermath of a neutron star merger. Using numerical simulations of short GRB afterglows we obtain an approximate…
The dynamics of GRB jets during the afterglow phase is most reliably and accurately modelled using hydrodynamic simulations. All published simulations, however, have considered only a uniform external medium, while a stratified external…
(shortened) Context: GRB GRB 050509b, detected by the \emph{Swift} satellite, is the first case where an X-ray afterglow has been observed associated with a short gamma-ray burst (GRB). Within the fireshell model, the canonical GRB light…
We discuss the afterglows from the evolution of both spherical and anisotropic fireballs decelerating in an inhomogeneous external medium. We consider both the radiative and adiabatic evolution regimes, and analyze the physical conditions…
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,…
Models for gamma-ray burst afterglows envisage an hyper-relativistic fireball that is decelerated in the ambient medium around the explosion site. This interaction produces a shock wave which amplifies the magnetic field and accelerates…
We study an extensive sample of 87 GRBs for which there are well sampled and simultaneous optical and X-ray light-curves. We extract the cleanest possible signal of the afterglow component, and compare the temporal behaviors of the X-ray…
The afterglow of GRB 050401 presents several novel and interesting features : [1] An initially faster decay in optical band than in X-rays. [2] A break in the X-ray light curve after $\sim$ 0.06 day with an unusual slope after the break.…
We investigate the dynamics and afterglow light curves of gamma-ray burst (GRB) blast waves that encounter various density structures (such as bumps, voids, or steps) in the surrounding ambient medium. We present and explain the…
GRB afterglow jets have been notoriously difficult to resolve numerically using 2D hydrodynamical simulations due to high outflow Lorentz factors. By performing simulations in a boosted frame, it is possible to calculate light curves from…
Gamma-ray bursts (GRBs) associated with gravitational wave events are, and will likely continue to be, viewed at a larger inclination than GRBs without gravitational wave detections. As demonstrated by the afterglow of GW170817, this…
In recent years, surprise discoveries of pulsed emission from the Crab and Vela pulsars above 100 GeV have drawn renewed attention to this largely unexplored region of the energy range. In this paper, we discuss example light curves due to…
The detection of an afterglow, following a gamma-ray burst (GRB), can be described reasonably well by synchrotron emission from a relativistic spherical expanding blast wave, driven by an expanding fireball. We perform detailed calculations…
The ultra-relativistic outflows powering gamma-ray bursts (GRBs) acquire angular structure through their interaction with external material. They are often characterized by a compact, nearly uniform narrow core (with half-opening angle…
We present multi-color light-curves of the optical afterglow of GRB 000926. Beginning ~1.5 days after the burst, the light-curves of this GRB steepen measurably. The existence of such achromatic breaks are usually taken to be an important…
(Abridged) We report on observations of the optical and NIR afterglow of GRB020405. Ground-based optical observations started about 1 day after the GRB and spanned a period of ~10 days; archival HST data extended the coverage up to 70 days…
We report the earliest-ever detection of optical polarization from a GRB forward shock (GRB 141220A), measured $129.5-204.3\,$s after the burst using the multi-colour RINGO3 optical polarimeter on the 2-m fully autonomous robotic Liverpool…
Whether gamma-ray bursts are highly beamed or not is a very important question, since it has been pointed out that the beaming will lead to a sharp break in the afterglow light curves during the ultra-relativistic phase, with the breaking…