Search Publications
Some problems of the detection of the high energy gamma-radiation in space
Fradkin, M. I.; Ginzburg, V. L.; Kurnosova, L. V. +8 more
The flux of the diffuse gamma-radiation in the Galaxy was measured with the instruments on board of the satellites COS-B and Compton Gamma Ray Observatory (CGRO). It was shown that the spectrum of the diffuse gamma-rays N(E) in the energy range from very low energy (some tens keV) up to some GeV may be represented by the expression N(E) = AE^kdE, …
Pulsar studies with GRO-COMPTEL
Strong, A. W.; Schönfelder, V.; Kuiper, L. +9 more
Pulsar measurements performed by the experiment COMPTEL, aboard the Compton Gamma Ray Observatory, are described. The main results refer to the Crab and Vela pulsars whose pulse shape characteristics are given in some detail and light curves are compared with those above 50 MeV, as observed by the COS-B satellite. No other gamma-ray pulsars have b…
The variable energy-distribution of the gamma-ray emission from Geminga
Grenier, I. A.; Hermsen, W.; Hote, C.
The gamma-ray emission of Geminga during five COS-B observations has been analysed to derive its spectral properties between 50 MeV and 5 GeV. In all observations but one, the spectrum presents a turnover between 100 and 200 MeV, the source becoming very weak at the lowest gamma- ray energies. During the remaining observation, the spectrum is cons…
Gamma rays and interstellar gas in the Cepheus region: A new gamma-ray source?
Grenier, I. A.; Lebrun, F.
A recent CO survey of the Cepheus Flare region (100°<=1<=141°, 8°<=b<=22°) has allowed a detailed study of the diffuse gamma-ray emission and the gas content of this nearby region. The comparison of the HI and CO observations with the COS-B gamma-ray data yields estimates of the N(H2)/WCO ratio in this molecular complex and …
Highlights from the COS-B mission
Hermsen, W.
The European Space Agency's high-energy (E>50 MeV) gamma-ray observatory COS-B was operational from August 1975 to April 1982 and in that time made 65 observations of about 1 month duration and with a field-of-view of approximately 0.4 sr each. The high counting statistics achieved over the total mission allowed, for the first time, a detailed …
Gamma-ray constraints on the Galactic halo
Bloemen, J. B. G. M.
Some findings from recent COS-B analyses of the diffuse Galactic γ-ray emission are briefly summarized, with emphasis on their impact for our understanding of the Galactic cosmic-ray halo.
Two new results on PSR 0833-45: (1) optical data on its birthplace, and (2) possible polarization in its high energy gamma-ray emission
Bignami, G. F.
Two new and completely different results are presented, both related to the Vela pulsar PSR 0833-45. In Part I, recent ESO optical images of the pulsar and its starfield are compared to the discovery plates, and used to set stringent upper limits on its proper motion and thus on its birthplace. Consequences are briefly explored. Part 2 refers to a…
Gamma rays from accreting matter onto collapsed objects
Giovannelli, F.; Karakula, S.; Tkaczyk, W.
In the spherical accretion onto massive objects, the matter may be heated up to temperatures as high as 1012 °K. In such a hot plasma, the thermal bremsstrahlung (e-e and e-p) and π° decay from inelastic collisions of protons are the main γ-ray sources. We determined the γ -ray production spectra from the π° decay and from bremsstrahlun…
Studies of high-latitude gamma rays
Strong, A. W.
COS-B gamma-ray data (70-5000 MeV) in the latitude range 10°< b <90° are compared with the expected emission from cosmic-ray interactions with interstellar gas. An additional component is found to be necessary to explain the latitude dependence of the emission. Two possible origins for this component are discussed: a gamma-ray halo around th…
Rapid short-term pulse-period variations in Vela X-1 (4U 0900-40)
van der Klis, M.; Bonnet-Bidaud, J. M.
Results are presented of an analysis of 83 days of 2-12 keV X-ray observations of Vela X-1 (4U 0900-40) obtained during three separate pointings with the ESA COS-B satellite. The pulsation period is shown to undergo very rapid intrinsic changes, at a rate of up to P˙/P ~ 10-1 yr-1 during intervals of a few days. The lower val…