Related papers: Opacity Build-up in Impulsive Relativistic Sources
We propose that the internal energy of the GRB blast waves, thought to be stored in the form of relativistic protons co-moving with the blast wave, is converted explosively (i.e. on light crossing time scales) into relativistic electrons of…
The prompt emission of gamma-ray bursts (hereafter GRBs) probably comes from a highly relativistic wind which converts its kinetic energy into radiation via the formation of shocks within the wind itself. Such "internal shocks" can occur if…
Blazars, a subset of powerful active galactic nuclei, feature relativistic jets that shine in a broadband electromagnetic radiation, e. g. from radio to TeV emission. Here I present the results of the studies that explore gamma-ray and…
The observations of gamma-ray bursts (GRBs) such as 980425, 031203 and 060218, with luminosities much lower than those of other classic bursts, lead to the definition of a new class of GRBs -- low-luminosity GRBs. The nature of the outflow…
The interaction of TeV photons from blazars with the extragalactic background light produces a relativistic beam of electron-positron pairs streaming through the intergalactic medium (IGM). The fate of the beam energy is uncertain. By means…
The gamma-rays from gamma-ray bursts (GRBs) are believed to be produced by internal shocks driven by small timescale, ~1 ms, variation in the GRB outflows, and a pair-production spectral cutoff is generally expected around the GeV range.…
Gamma-ray bursts (GRBs) are powered by ultra-relativistic jets. Usually a minimum value of the Lorentz factor of the relativistic bulk motion is obtained based on the argument that the observed high energy photons ($\gg {\rm MeV}$) can…
Gamma-ray burst are thought to be produced by highly relativistic outflows. Although upper and lower limits for the outflow initial Lorentz factor $\Gamma_0$ are available, observational efforts to derive a direct determination of…
We develop a numerical formalism for calculating the distribution with energy of the (internal) pairs formed in a relativistic source from unscattered MeV--TeV photons. For GRB afterglows, this formalism is more suitable if the relativistic…
This paper examines the mechanism of internal shocks in opaque relativistic outflows, in particular in cosmological gamma-ray bursts. The shocks produce neutrino emission and affect the observed photospheric radiation from the explosion.…
A correlation is presented between the pulse lag and the jet-break time for seven BATSE gamma-ray bursts with known redshifts. This is, to our best knowledge, the first known direct tight correlation between a property of the gamma-ray…
We present detailed calculations of the prompt spectrum of gamma-ray bursts (GRBs) predicted within the fireball model framework, where emission is due to internal shocks in an expanding relativistic wind. Our time dependent numerical model…
The detection of the delayed emission in X-ray, optical and radio band, i.e. the afterglow of $\gamma$-ray bursts (GRBs), suggestes that the sources of GRBs are likely to be at cosmological distances. Here we explore the interaction of a…
Propagation of photons in relativistically expanding plasma outflows, characterized by steady Lorentz factor Gamma is considered. Photons that are injected in regions of high optical depth are advected with the flow until they escape at the…
For a sample of Swift and Fermi GRBs, we show that the minimum variability timescale and the spectral lag of the prompt emission is related to the bulk Lorentz factor in a complex manner: For small $\Gamma$'s, the variability timescale…
Blazars are strongly variable sources that occasionally show spectacular flares visible in various energy bands. These flares are often, but not always, correlated. In a number of cases the peaks of optical flares are found to be somewhat…
The transient emission produced behind internal shocks that are driven by overtaking collisions of a magnetized, relativistic outflow is considered. A self-consistent model capable of describing the structure and dynamics of the shocks and…
Well-sampled optical lightcurves of 146 gamma-ray bursts (GRBs) are compiled from the literature. By empirical fitting we identify eight possible emission components and summarize the results in a "synthetic" lightcurve. Both optical flare…
We present an interpretation of the phenomenological relations between the spectral peak, isotropic luminosity and duration of long gamma ray bursts that have been discovered by Amati et al., Ghirlanda et al., Firmani et al., and Liang &…
Assuming that the early optical emission is dominated by the external reverse shock (RS) in the standard model of gamma-ray bursts (GRBs), we intend to constrain RS models with the initial Lorentz factor $\Gamma_0$ of the outflows based on…