Related papers: The Gamma-Ray Background from Blazars: A New Look
The MAGIC collaboration has recently reported the detection of the strong gamma-ray blazar 3C279 during a 1-2 day flare. They have used their spectral observations to draw conclusions regarding upper limits on the opacity of the Universe to…
Since 2002, the number of detected blazars at E_\gamma > 100 GeV has more than doubled. I study all currently known BL Lac-type objects with published energy spectra. Their intrinsic energy spectra are reconstructed by removing…
Very high energy (VHE) gamma-rays from extragalactic sources, interacting by gamma-gamma collisions with diffuse intergalactic radiation fields, provide an alternative way to constrain the diffuse background light, completely independent of…
Astrophysical sources outside the Milky Way, such as active galactic nuclei and star-forming galaxies, leave their imprint on the gamma-ray sky as nearly isotropic emission referred to as the Extragalactic Gamma-Ray Background (EGB). While…
Recently, a new measurement of the auto- and cross-correlation angular power spectrum (APS) of the isotropic gamma-ray background was performed, based on 81 months of data of the Fermi Large-Area Telescope (LAT). Here, we fit, for the first…
Blazars emit a highly-variable non-thermal spectrum. It is usually assumed that the same non-thermal electrons are responsible for the IR-optical-UV emission (via synchrotron) and the gamma-ray emission (via inverse Compton). Hence, the…
A subset of the unidentified EGRET gamma-ray sources with no active galactic nucleus or other conspicuous counterpart appears to be concentrated at medium latitudes. Their long-term variability and their spatial distribution indicate that…
The Sun was recently predicted to be an extended source of gamma-ray emission, produced by inverse-Compton scattering of cosmic-ray electrons with the solar radiation. The emission was predicted to contribute to the diffuse extragalactic…
Structure formation in the universe can produce high energy gamma-rays from shock-accelerated electrons, and this process may be the origin of the extragalactic gamma-ray background (EGRB) as well as a part of the unidentified sources…
Cosmic gamma rays provide insight into some of the most dynamic processes in the Universe. At the dawn of a new generation of gamma-ray telescopes, this review summarizes results from the Energetic Gamma Ray Experiment Telescope (EGRET) on…
Blazars are radio-loud active galactic nuclei well known for their non thermal emission spanning a wide range of frequencies. The Roma-BZCAT is, to date, the most comprehensive list of these sources. We performed the cross-match of several…
The very high energy (VHE) gamma-ray spectral indices of blazars show strong correlation with the source redshift. Absence of any such correlation in low energy gamma rays and X-rays indicate the presence of Extragalactic Background Light…
We suggest that ultraluminous X-ray sources (ULXs) and some of the variable low latitude EGRET gamma-ray sources may be two different manifestations of the same underlying phenomena: high-mass microquasars with relativistic jets forming a…
We discuss the ability of the GLAST Large Area Telescope (LAT) to identify, resolve, and study the high energy gamma-ray sky. Compared to previous instruments the telescope will have greatly improved sensitivity and ability to localize…
The highest-energy blazars exhibit non-thermal radiation extending beyond 1 TeV with high luminosities and strong variabilities, indicating extreme particle acceleration in their relativistic jets. The gamma-ray spectra of blazars contain…
Blazars are a small fraction of all extragalactic sources but, unlike other objects, they are strong emitters across the entire electromagnetic spectrum. Recent data in the microwave region of the electromagnetic spectrum have become…
The Earth's high energy gamma-ray emission is caused by cosmic ray interactions with the atmosphere. The EGRET detector on-board the CGRO satellite is only the second experiment (after SAS-2) to provide a suitable dataset for the…
The extragalactic $\gamma$-ray background (EGB) arises from the accumulation of $\gamma$-ray emissions from resolved and unresolved extragalactic sources as well as diffuse processes. It is important to study the statistical properties of…
We report EGRET upper limits on the high-energy gamma-ray emission from clusters of galaxies. EGRET observations between 1991 and 2000 were analyzed at positions of 58 individual clusters from a flux-limited sample of nearby X-ray bright…
In a recent paper, Romero et al. (1999) have presented the results of a positional correlation analysis of the low-latitude unidentified gamma-ray sources in the Third EGRET catalog with complete lists of galactic objects like supernova…