Related papers: Indications for a cascade component in {\gamma}-ra…
Supernova remnants have long been suggested as a class of potential counterparts to unidentified gamma-ray sources. The mechanisms by which such gamma-rays can arise may include emission from a pulsar associated with a remnant, or a variety…
We develop a general expression for the gamma-gamma absorption coefficient for gamma-rays propagating in an arbitrary direction at an arbitrary point in space above an X-ray emitting accretion disk. The X-ray intensity is assumed to vary as…
This paper analyzes astrophysical scenarios that may be detected at the upper end of the energy range of the Gamma Ray Large Area Space Telescope (GLAST), as a result of cosmic-ray (CR) diffusion in the interstellar medium (ISM). Hadronic…
Blazars are the most violent steady/recurrent sources of high-energy gamma-ray emission in the known Universe. They are prominent emitters of electromagnetic radiation throughout the entire electromagnetic spectrum. The observable radiation…
The extragalactic analogs of the microquasars, the quasars, are strong gamma-ray emitters at GeV energies. It is expected that microquasars are also gamma-ray sources, because of the analogy with quasars and because theoretical models…
Flux distribution is an important tool to understand the variability processes in active galactic nuclei. We now have available a great deal of observational evidences pointing towards the presence of log-normal components in the high…
We study the possible detection of and properties of very high-energy (VHE) gamma-ray emission (in the energy band above 100 GeV) from high redshift sources. We report on the detection of VHE gamma-ray flux from blazars with redshifts…
We discuss the contribution of the blazar population to the extragalactic background radiation across the electromagnetic (e.m.) spectrum with particular reference to the microwave, hard-X-ray and gamma-ray bands. Our estimates are based on…
This Chapter provides a review of $\gamma$-ray sources lying at high Galactic latitudes. Their statistical properties and variability status, as well as studies involving cross correlations with lower frequency catalogs and multiwavelength…
I present a review of the main phenomenological properties at high energies related to massive gamma-ray binaries and I discuss some aspects of pulsar models for these objects.
We summarize the spectral characteristics of a sample of 22 bright gamma-ray bursts detected with the gamma-ray burst sensors aboard the satellite Ginga. This instrument employed a proportional and scintillation counter to provide…
We apply the IC e$^\pm$ pair cascade model in order to investigate the possible $\gamma$-ray emission features from another compact massive binary of the microquasar type, Cyg X-1. We conclude that the observational constraints at lower…
We present new theoretical estimates of the relative contributions of unresolved blazars and star-forming galaxies to the extragalactic gamma-ray background (EGB) and discuss constraints on the contributions from alternative mechanisms such…
The energy spectra of TeV gamma-rays from blazars, after being corrected for intergalatic absorption in the Extragalactic Background Light (EBL), appear unusually hard, a fact that poses challenges to the conventional models of particle…
The MAGIC telescope observed the region around the distant blazar 3C 66A for 54.2 h in 2007 August-December. The observations resulted in the discovery of a gamma-ray source at energies above 150 GeV centered at celestial coordinates…
Energy spectra of gamma-ray blazars may contain an imprint from the cosmic infrared background radiation due to gamma-ray absorption (pair-production) by soft photons constituting the extragalactic background light (EBL). The signature of…
In this study, we systematically studied the X-ray to GeV gamma-ray spectra of 61 {\it Fermi} Large Area Telescope (LAT) detected radio galaxies. We found an anticorrelation between peak frequency and peak luminosity in the high-energy…
Context. Most of the studies on extragalactic {\gamma}-ray propagation performed up to now only accounted for primary gamma-ray absorption and adiabatic losses ("absorption-only model"). However, there is growing evidence that this model is…
The observational progress in the $\gamma$-ray astronomy in the last few years has led to the discovery of more than a thousand sources at GeV energies and more than a hundred sources at TeV energies. A few different classes of compact…
The relevance of gamma-ray astronomy to the search for the origin of the galactic and, to a lesser extent, the ultra-high-energy cosmic rays has long been recognised. The current renaissance in the TeV gamma-ray field has resulted in a…