Related papers: Thermal Radiation from GRB Jets
Relativistic outflows in the form of jets are common in many astrophysical objects. By their very nature, jets have angle dependent velocity profiles, Gamma = Gamma(r, theta, phi), where Gamma is the outflow Lorentz factor. In this work we…
Early afterglow observations of gamma-ray bursts (GRBs) are valuable for exploring the properties of their jets and ambient medium. We report our photometric and spectroscopic observations of GRB 210104A and discuss its jet properties with…
A distinct thermal or quasi-thermal spectral component is occasionally observed in gamma-ray burst (GRB) prompt emission spectra. Taking GRB 090902B as a case study, we investigate its origin within a structured jet framework, in which the…
The 2-m robotic Liverpool Telescope (LT) reacted promptly to the high-redshift (z=4.048) gamma-ray burst GRB 060206. The afterglow was identified automatically and multicolor r'i'z' imaging was triggered without human intervention.…
We study the narrowest spectra expected from gamma-ray bursts. We present an analytical function for the spectrum that is emitted from the photosphere of a radiation-dominated flow that is under acceleration. This is the narrowest possible…
Collapsars may be a source for the long Gamma Ray Bursts (GRBs) in the BATSE catalog. Collapsars may radiate gamma rays anisotropically by beamed jet emission close to the observer's line of sight. These jets must penetrate the…
Some progenitor models of gamma-ray bursts (GRBs) (e.g., collapsars) may produce anisotropic jets in which the energy per unit solid angle is a power-law function of the angle ($\propto\theta^{-k}$). We calculate light curves and spectra…
Gamma-ray bursts (GRB) are generally believed to be efficient particle accelerators. In the presence of energetic protons in a GRB jet, interactions between these protons and intense radiation field of the GRB are supposed to induce…
It is known that the high energy $(> 100\,\text{MeV})$ emission of gamma-ray bursts is delayed with respect to the low energy emission. However, the dependence of light curves on energy has not been studied for the high energy bands. In…
Nuclear and Coulomb collisions in GRB jets create a hot electron-positron plasma. This collisional heating starts when the jet is still opaque and extends to the transparent region. The e+- plasma radiates its energy. As a result, a large…
Recent detections of GeV photons in a few GRBs by Fermi-LAT have led to strong constraints on the bulk Lorentz factor in GRB outflows. To avoid a large gamma gamma optical depth, minimum values of the Lorentz factor are estimated to be as…
We have studied the relativistic beamed outflow proposed to occur in the collapsar model of gamma-ray bursts. A jet forms as a consequence of an assumed energy deposition of $\sim 10^{50}- 10^{51}$ erg/s within a $30^{\circ}$ cone around…
We discuss results from a decade long program to study the fine-scale structure and the kinematics of relativistic AGN jets with the aim of better understanding the acceleration and collimation of the relativistic plasma forming AGN jets.…
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…
We present observations by the Fermi Gamma-Ray Space Telescope Gamma-Ray Burst Monitor (GBM) of the nearby (z=0.55) GRB 101219B. This burst is a long GRB, with an associated supernova and with a blackbody component detected in the early…
We present the results of a numerical investigation of the spectra and light curves of the emission from the photospheres of long-duration gamma-ray burst jets. We confirm that the photospheric emission has high efficiency and we show that…
Strong variability is a common characteristic of the prompt emission of gamma-ray bursts (GRB). This observed variability is widely attributed to an intermittency of the central engine, through formation of strong internal shocks in the…
We discuss jet dynamics for narrow and wide gamma-ray burst (GRB) afterglow jets and the observational implications of numerical simulations of relativistic jets in two dimensions. We confirm earlier numerical results that sideways…
In this work we numerically calculate the thermal radiation efficiency of the baryonic outflow. The possible outflow acceleration in the transparent stage, which lowers thermal radiation efficiency, has been taken into account. In the…
We show that the photospheres of "failed" Gamma-Ray Bursts (GRBs), whose bulk Lorentz factors are much lower than 100, can be outside of internal shocks. The resulting radiation from the photospheres is thermal and bright in UV/Soft X-ray…