Other
Scientific paper
Dec 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...181.3401s&link_type=abstract
American Astronomical Society, 181st AAS Meeting, #34.01; Bulletin of the American Astronomical Society, Vol. 24, p.1172
Other
Scientific paper
I discuss our changed view of the gamma -ray sky as a result of measurements made by the gamma -ray spectrometer (GRS) on the Solar Maximum Mission satellite. This highly successful instrument was developed at UNH and MPE (Germany) to study solar flares and operated from 1980 February to 1989 November. The number of flares detected in nuclear gamma -rays swelled from 2 to ~ 100 and the number of nuclear lines detected increased from 3 to 13. Both solar neutrons and gamma -rays >10 MeV were detected for the first time and an ~ 154 d periodicity in the flare rate was discovered. The GRS's broad aperture ( ~ 130(deg) ) and excellent stability also permitted it to make significant celestial discoveries. Spectra accumulated from 177 cosmic gamma -ray bursts demonstrated convincingly that emission typically extends into the MeV energy range; one burst was observed from 20 keV to 80 MeV. No evidence has been found for narrow or moderately broadened emission lines >300 keV in any of the bursts. A study of the V/Vmax distribution was one of the first to reveal non-homogeneity in the source distribution. Perhaps the instrument's crowning achievement was discovery and monitoring of four lines from decay of (56) Co produced in SN1987A. Source transit techniques reveal that the 0.3 to 8.5 MeV spectrum in the direction of the Galactic center consists of a power-law continuum, a narrow line at 511 keV and positronium continuum from electron-positron annihilation, and a narrow line at 1.81 MeV from decay of (26) Al. There is no evidence for variability of this annihilation line, suggesting that it is primarily due to extended Galactic emission. There is also no evidence for transients that have been reported previously including broad line and continuum emission >=1 MeV from sources such as Cyg X-1, and lines above and below 511 keV from the Crab. Other significant line limits have been placed on (56) Co decay from SN1986G, (7) Be and (22) Na decays from novae, (44) Ti and (60) Fe decay from supernovae, neutron capture on H from compact sources, and C and O de-excitation from cosmic-ray interactions in the Galaxy. I discuss these measurements in the context of recent observations by the COMPTON Observatory.
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