[en] The various explanations proposed to explain the X-ray continuum observed in most active galactic nuclei are briefly presented. The radiation mechanisms are described with a special emphasis on Compton process and inverse Compton process

No abstract available

No abstract available

[en] The Caravane Collaboration's gamma-ray astronomy experiment aboard ESA's satellite COS-B has been recording celestial gamma rays in the energy range from about 50 MeV to several GeV since August 1975. These observations covers the whole range of galactic longitude, thus making it possible to present here the first complete detailed gamma-ray survey of the Milky Way with greatly improved statistical accuracy and significantly better energy measurement than in the previous survey. The present work concentrates on the spatial aspects of the gamma radiation, including localised sources

[en] Gamma - ray observations of PSR 1822 - 09 (P = 769ms) between 80 KeV and 6 MeV at balloon altitudes are reported which imply that the most important part of the energy emitted by this pulsar is in the MeV region. (U.K.)

[en] The ESA COS-B satellite has investigated the high energy gamma ray emission from the Cygnus region of the galaxy during November and December 1975. From the counts observed to originate within the vicinity of Cygnus X-3 a phase histogram has been derived using the approximately 4.8 hours period observed at X-ray and I.R. wavelengths. The phase analysis reveals no evidence for a modulation of the gamma ray emission at the time of the COS-B observation. A detailed investigation of the short-term variability of the source CG 195+4 is presented. This source is found to pulsate with a period of 59.19687 sec and a period derivative of 1.385x10^-9 with a multiple peak phase histogram, consistent with the SAS-2 results. The pulsed fraction above 100 MeV is 75+-25%. This preliminary study indicates also a harder pulsed energy spectrum than that of the Crab pulsar

[en] The aim of this paper is to provide a new value of the ratio N(H₂)/N(¹³CO) by making a comparison between the COS-B gamma-ray survey above 100 MeV and the CO survey of the Orion cloud complex

[en] Observations of the Crab pulsar (PSR 0531 + 21) in the energy range 0.2-6 MeV have been made with the balloon-borne Figaro II experiment. The gross appearance of the light curve is characterized by the well-known double-peak structure with a phase separation of 0.4. The data confirm that the second pulse is the dominant feature, and the interpulse region is more luminous than in other energy ranges. Above about 0.5 MeV, an extra structure was detected in the light curve, with two features at a phase lag of 0.4 as the main one. Phase-resolved spectroscopy indicates that the first peak spectrum is concave upward, and the second one is concave downward, while the averaged spectrum is well represented by a single power law with slope 2.2. The good timing accuracy of Figaro made it possible to measure a delay between gamma rays and radio waves of 300 + or - 70 microsec, that if produced by dispersion, implies a value of DM fitting very well the radio measurements 2 months before and after the observation. 29 refs

[en] We have made an analysis of the z-distribution of the pulsars in the second Molonglo Survey, in selected intervals of longitude. We find that this distribution is gaussian, with a mean height < z > of 380 pc assuming a mean electron density ne=0.025, and the local surface density of pulsars is found to be about 200 kpc^-2. The derived local birthrate of pulsars is then between 1.3 x 10^-5 and 11 x 10^-5 kpc^-2 yr^-1. This rate is consistent with determinations of the rate of supernova explosions, which is (0.8-7) x 10^-5 kpc^-2 yr^-1. (orig.)

[en] A new analysis of the UV background radiation measurements obtained with the ELZ instrument on board the D2B-Aura satellite is performed at high galactic latitudes (mod(b)>=30⁰) in two bandpasses centered at 1690 A and 2200 A. Correlations of the UV brightnesses with dust tracers are found; the scattering phase function of dust can be derived. Among regions exhibiting a UV flux in excess over the average correlation, an insight is given on the Eridanus region known as a hot spot in soft X-rays. (Auth.)