Related papers: Massive protostars as gamma-ray sources
While star-forming galaxies could be major contributors to the cosmic GeV $\gamma$-ray background, they are expected to be MeV-dim because of the "pion bump" falling off below ~100 MeV. However, there are very few observations of galaxies…
Long-duration gamma-ray bursts are the manifestations of massive stellar death. Due to the immense energy release they are detectable from most of the observable universe. In this way they allow us to study the deaths of single (or binary)…
According to recent models, gamma-ray bursts apparently explode in a wide variety of ambient densities ranging from ~ 10^{-3} to 30 cm^{-3}. The lowest density environments seem, at first sight, to be incompatible with bursts in or near…
Massive Wolf-Rayet stars in a compact binary systems are characterised by very strong winds which collide creating a shock wave. If the wind nuclei accelerated at the shock can reach large enough energies, they suffer disintegration in…
Present knowledge indicates that gamma-ray bursts are linked with massive stars. They will become invaluable probes of the early universe and galaxy formation. In the future, it will be possible to use gamma-ray bursts for two purposes: 1)…
How and where cosmic rays are produced, and how they diffuse through various turbulent media, represent fundamental problems in astrophysics with far reaching implications, both in terms of our theoretical understanding of high-energy…
Merger and accretion shocks in clusters of galaxies can accelerate particles via first order Fermi process. Since this mechanism is believed to be intrinsically efficient, shocks are expected to be modified by the backreaction of the…
Non-thermal particles and high-energy radiation can play a role in the dynamical processes in star-forming regions and provide an important piece of the multiwavelength observational picture of their structure and components. Powerful…
Gamma-ray bursts are the strongest explosions in the Universe since the Big Bang, believed to be produced either in forming black holes at the end of massive star evolution or merging of compact objects. Spectral and timing properties of…
We examine and develop the model of gamma ray bursts origin proposed by Shaviv and Dar (astro-ph/9606032), according to which the strong gamma ray emission is produced by the interaction of the baryonic relativistic jet (outflow) with the…
We discuss some phenomenological aspects of $\gamma$-ray emitting jets. In particular, we present calculations of the $\gamma$-sphere and $\pi$-sphere for various target photon fields, and employ them to demonstrate how $\gamma$-ray…
(Abridged) We interpret gamma ray bursts as relativistic, electromagnetic explosions. Specifically, we propose that they are created when a rotating, relativistic, stellar-mass progenitor loses much of its rotational energy in the form of a…
Presently there are several classes of detected gamma-ray extragalatic sources. They are mostly associated to active galactic nuclei (AGN) and (at soft gamma rays) to gamma-ray bursts (GRB), but not only. Active galactic nuclei consist of…
Dense populations of stars surround the nuclear regions of galaxies. In this work, we study the interaction of a WR star with relativistic jets in active galactic nuclei. A bow-shaped double-shock structure will form as a consequence of the…
Gamma-ray blazars are among the most extreme astrophysical sources, harboring phenomena far more energetic than those attainable by terrestrial accelerators. These galaxies are understood to be active galactic nuclei that are powered by…
The non-thermal emission in the magnetospheres of presupernova collapsing stars with initial dipole magnetic fields and a certain initial energy distribution of the charged particles in a magnetosphere is considered. The analysis of…
Classical novae are cataclysmic binary star systems in which the matter of a companion star is accreted on a white dwarf (WD). Accumulation of hydrogen in a layer eventually causes a thermonuclear explosion on the surface of the WD,…
TeV Halos, extended regions of TeV gamma-ray emission around middle-aged pulsars, have recently been established as a new source class in gamma-ray astronomy. These halos have been attributed to relativistic electrons and positrons that…
Recently, we have proposed that the interaction between relativistic protons resulting from Fermi first order acceleration in the superbubble of a stellar OB association or in other nearby accelerator and ions residing in single stellar…
The high-energy radiation from short period binaries containing a massive star with a compact relativistic companion was detected from radio to TeV gamma rays. We show here that PeV regime protons can be efficiently accelerated in the…