Celestial Diffuse Gamma Radiation above 30 MeV Observed by SAS-2
Abstract
The Small Astronomy Satellite (SAS) -2, launched on 1972 November 15, carried into orbit a 32-deck magnetic-core digitized spark chamber -ray telescope to study celestial ganima radiation in the energy range above 30 MeV. In the study of several regions with b" > 15', a finite, diffuse flux of -rays with a steep energy spectrum in the energy region from 35-200 MeV is observed. Representing the energy spectrum by a power law of the form dJ/dE = AE-a over this energy range, a is found to be 2.7 (+0A, -0.3), and the integral flux above 100 MeV is (2.8 +0.9, -0.7]) X 10- photons (cm2 sterad s)-1. Combining this result with existing lowenergy -ray data yields an energy spectrum which is not a simple power law in energy as in the X-ray region, but which instead demonstrates first an increase and then a decrease in slope, consistent within uncertainties with that predicted by cosmological theories, including the continuous production of high-energy -rays primarily from it mesons throughout the history of the Universe. Subject headings: cosmic background radiation - gamma rays
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1973
- DOI:
- 10.1086/181367
- Bibcode:
- 1973ApJ...186L..99F