ABSTRACT We collect data at well sampled frequencies from the radio to the γ–ray range for the following three complete–samples of blazars: the Slew Survey and the 1 Jy samples of BL Lacs and the 2 Jy sample of Flat Spectrum Radio–Loud Quasars (FSRQs). The fraction of objects detected in γ–rays (E > ∼ 100 MeV) is ∼ 17 %, 26 % and 40 % in the three samples respectively. Except for the Slew Surve...

Markarian 421 was the first extragalactic source to be detected with high statistical certainty at TeV energies. The Whipple Observatory gamma-ray telescope has been used to observe the Active Galactic Nucleus, Markarian 421 in 1996 and 1997. The rapid variability observed in TeV gamma rays in previous years is confirmed. Doubling times as short as 15 minutes are reported with flux levels reach...

The study of Galactic diffuse γ radiation combined with the knowledge of the distribution of the molecular hydrogen in the Galaxy offers a unique tool to probe the cosmic ray flux in the Galaxy. A methodology to study the level of the cosmic ray "sea" and to unveil target-accelerator systems in the Galaxy, which makes use of the data from the high resolution survey of the Galactic molecular clo...

Analysis of broad-band X/γ-ray spectra of NGC 4151 shows that the data are well modelled with an intrinsic spectrum due to thermal Comptonization with temperature ∼ 50 keV and X-ray spectral index α ∼ 0.4– 0.7. The variable X-ray spectrum pivots at ∼ 100 keV, which is consistent with the observed approximatly constant γ-ray spectrum. The observed UV/X-ray correlation can be explained by two spe...

There are now a half dozen young pulsars detected in high energy photons by the Compton GRO, showing a variety of emission efficiencies and pulse profiles. We present here a calculation of the pattern of high energy emission on the sky in a model which posits γ-ray production by charge depleted gaps in the outer magnetosphere. This model accounts for the radio to γ-ray pulse offsets of the know...

In this paper I investigate the γ-ray spectra of AGN by summing up the intensity and the power-law fit statistic of Quasars and OVV’s and BL Lac’s separately. The spectrum of the average AGN is softer than that of the extragalactic γ-ray background. It may be that BL Lac’s, of which the average has a harder spectrum than Quasars, make up the bulk of the extragalactic background. We also find cu...

Identifying γ-ray sources in the Galaxy is hampered by their poor localization, source confusion, and the large variety of potential emitters. Neutron stars and their environment offer various ways to power γ-ray sources: pulsed emission from the open magnetosphere and unpulsed γ rays from the wind nebula and from the cosmic rays accelerated in the supernova remnant. While the latter still awai...

The selection of the GLAST burst monitor (GBM) by NASA will allow the investigation of the relation between the keV and the MeV-GeV emission from γ-ray bursts. The GBM consists of 12 NaI and 2 BGO crystals allowing a continuous measurement of the energy spectra of γ-ray bursts from ∼ 5 keV to ∼ 30 MeV. One feature of the GBM is its high time resolution for time-resolved γ-ray spectroscopy. More...

The inner few hundred parsecs of our galaxy provide a laboratory for the study of the production and propagation of energetic particles. Very-high-energy γ-rays provide an effective probe of these processes and, especially when combined with data from other wave-bands, γ-rays observations are a powerful diagnostic tool. Within this central region, data from the H.E.S.S. instrument have revealed...

This work reports on the discovery of HESS J1514−591, a VHE γ-ray source found at the pulsar wind nebula (PWN) MSH 15−52 and its associated pulsar PSR B1509−58. The discovery was made with the High Energy Stereoscopic System (H.E.S.S.), which currently provides the most sensitive measurement in the energy range of about 0.2–100 TeV. This analysis is the first to include all H.E.S.S. data from o...