HEAD Division Meeting 1999, April 1999
Session 6. Deep Surveys
Poster, Monday, April 12, 1999, 8:30am-6:10pm, Gold Room

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[6.01] SMM Measurement of the Isotropic Cosmic Gamma-Ray Background

K. Watanabe (USRA/LHEA, NASA/GSFC), M. Leising (Clemson University), G. Share, R. Kinzer (NRL)

Given the Solar Maximum Mission Gamma-Ray Spectrometer's nine years of exposure and large field of view, its data contains a tremendously significant signal from the isotropic cosmic gamma-ray background (CGB) in the energy range 0.3 - 8.0 MeV. We have extracted this signal by modelling its modulation by the Earth s motion through its field of view, along with several other background components.

We can quantify the success of the technique and evaluate possible systematic errors because the true CGB should be constant in time and we have many independent measurements, and because all known other background components have narrow lines in them that should not be present in the CGB. We present the results of our measurement and place quantitative constraints on the 56{\rm Co} line emission from iron production in thermonuclear supernovae and on models of a matter-antimatter symmetric universe.


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