Related papers: Quasi-thermal Comptonization and gamma-ray bursts
I discuss the interpretation of the prompt phase in gamma-ray bursts as being dominated by quasi-thermal emission, rather than by synchrotron emission. Such an interpretation gives a more natural explanation of (i) the observed variety of…
Linear polarization have been observed in both the prompt phase and afterglow of some bright gamma-ray bursts (GRBs). Polarization in the prompt phase spans a wide range, and may be as high as $\gtrsim 50\%$. In the afterglow phase,…
GS 1826-238 is a well-studied X-ray bursting neutron star in a low mass binary system. Thermal Comptonisation by a hot electron cloud is a widely accepted mechanism accounting for its high energy emission, while the nature of most of its…
We investigate a scenario of photons scattering by electrons within a relativistic outflow. The outflow is composed of discrete shells with different speeds. One shell emits radiation for a short duration. Some of this radiation is…
(Abbreviated) Particle-in-cell simulations of relativistic, weakly magnetized collisionless shocks show that particles can gain energy by repeatedly crossing the shock front. This requires scattering off self-generated small length-scale…
Measurements of the linear polarization of high-energy emission from pulsars, accreting black holes, and gamma-ray bursts (GRBs) provide an opportunity for constraining the emission mechanisms and geometries (e.g., of the accretion disk,…
For inner magnetospheric models of hard X-ray and gamma-ray emission in high-field pulsars and magnetars, resonant Compton upscattering is anticipated to be the most efficient process for generating continuum radiation. This is due in part…
We consider delayed, volumetric heating in a magnetized outflow that has broken out of a confining medium and expanded to a high Lorentz factor ($\Gamma \sim 10^2-10^3$) and low optical depth to scattering ($\tau_{\rm T} \sim…
We consider dissipative effects occurring in the optically thick inner parts of the relativistic outflows producing gamma-ray bursts and X-ray flashes, emphasizing specially the Comptonization of the thermal radiation flux that is advected…
(Abridged) We consider the interaction of a relativistically-moving shell, composed of thermal photons, a reversing magnetic field and a small admixture of charged particles, with a dense Wolf-Rayet wind. A thin outer layer of Wolf-Rayet…
Selected topics dealing with X-ray/soft gamma-ray emission from accreting black-hole sources are reviewed. The shape of soft gamma-ray spectra of Seyferts observed by OSSE can be well modelled by thermal Comptonization. A very strong…
Previous studies have considered synchrotron as the emission mechanism for prompt Gamma-Ray Bursts (GRBs). These works have shown that the electrons must cool on a timescale comparable to the dynamic time at the source in order to satisfy…
It is generally supposed that when the "compactness" $l \equiv L\sigma_T/(r m_e c^3)$ in photons above the pair-production threshold is large, few $\gamma$-rays can escape. We demonstrate that even when $l \gg 1$, if the high energy and low…
Data from the Swift satellite has enabled us for the first time to provide a complete picture of the gamma-ray burst emission mechanism and its relationship with the early afterglow emissions. We show that gamma-ray photons for two bursts,…
The energetic electromagnetic eruptions observed during the prompt phase of gamma-ray bursts are attributed to synchrotron emissions. The internal shocks moving through the ultrarelativistic jet, which is ejected by an imploding…
Accreting black holes in galactic X-ray sources are surrounded by hot plasma. The innermost part of these systems is likely a corona with different temperatures for ions and electrons. In the so-called low-hard state, hot electrons…
We use 1+1/2 dimensional particle-in-cell plasma simulations to study the interaction of a relativistic, strongly magnetized wind with an ambient medium. Such an interaction is a plausible mechanism which leads to generation of cosmological…
X-ray spectra of nonmagnetic cataclysmic variables (nmCVs) in the ~ 0.3$-$15 keV energy band have been described either by one or several optically thin thermal plasma components, or by cooling flow models. We tested if the spectral…
We discuss gamma-ray bursts that have very hard spectra, consistent with black-body radiation, throughout their duration. We find that the temperature decay during a pulse can be well described by a broken power-law in time, with an…
Recent analyses of multiwavelength light curves of gamma-ray bursts afterglows point to values of the magnetic turbulence well below the canonical $\sim1\,$\% of equipartition, in agreement with theoretical expectations of a…