This chapter provides a review of γ-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 observations, are summarized. The case for active galactic nuclei is analyzed with special emphasis, since they represent the largest population of high energy sour...

There is growing evidence that some variable high-energy γ−ray sources are associated with pulsar wind nebulae. We review the current status of X-ray and radio studies of the sources most likely to be significant emitters above 100 MeV. The assumption of the γ−radiation arising from synchrotron processes puts a lower limit on the magnetic field and suggests there may be significant doppler boos...

This Chapter provides a review of γ-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 observations, are summarized. The case for active galactic nuclei is analyzed with special emphasis, since they represent the largest population of high energy sour...

Since 2004, the MAGIC γ-ray telescope has newly discovered 6 TeV blazars. The total set of 13 MAGIC-detected active galactic nuclei includes well-studied objects at other wavelengths like Markarian 501 and the giant radio galaxy M 87, but also the distant the flat-spectrum radio quasar 3C 279, and the newly discovered TeV γ-ray emitter S5 0716+71. In addition, also long-term and multi-wavelengt...

The isotropic component of the γ-ray flux between 100MeV and 100EeV (10 eV) contains important information about the origin of highest energy cosmic rays and the extragalactic magnetic field (EGMF). Using numerical simulations of extragalactic cosmic and γ-ray propagation we show that an average fraction of ≃ 10% γ-rays in the total cosmic ray flux around 10EeV would imply both a non-accelerati...

The GALPROP model for cosmic-ray (CR) propagation produces explicit predictions for the angular distribution of Galactic diffuse γ-rays. We compare our current models with EGRET spectra for various regions of the sky. This allows a critical test of alternative hypotheses for the observed GeV excess. We show that a population of hard-spectrum γ-ray sources cannot be solely responsible for the ex...

We present the results of a new model calculation of the γ-ray background produced by unresolved blazars, using the second EGRET catalogue and taking account of flaring. These results are compared to the preliminary γ-ray background spectrum reported recently by the EGRET team. We find that blazars can account for the entire extragalactic γ-ray background observed by EGRET. In addition the EGRE...

Excited states of the nucleus Er have been studied by Coulomb excitation using the GASP γ-ray detector system at the Laboratori Nazionali di Legnaro. The ground-state band along with a low-lying K = 0 band and γ-vibrational band were populated during the experiment. Based on the measured γ-ray yields, a set of interband and intraband matrix elements has been extracted using the Coulomb excitati...

Supernova remnants interacting with molecular clouds are potentially exciting systems in which to detect evidence of cosmic ray acceleration. Prominent γ-ray emission is produced via the decay of neutral pions when cosmic rays encounter the nearby dense clouds. In many of the supernova remnants coincident with γ-ray sources, the presence of OH(1720 MHz) masers is used to identify interaction wi...