Gamma-ray spectroscopy of radionuclei from galactic nucleosynthesis

A variety of radionuclei are produced during stellar evolution, especially during explosive events such as novae and supernovae. The detection of gamma-ray line emission from the decay of these radionuclei was one of the prime objectives of the HEAO 3 high-resolution gamma-ray spectrometer. A number of exciting results have been obtained to date from the analysis of the HEAO 3 data and they are summarized here. The most important discovery was that of a narrow cosmic line at 1809 keV from the decay of approximately 3 Msolar of 26Al in the present interstellar medium. In addition, searches have been performed for galactic sources of 60Fe, 44Ti, and 22Na, all produced in explosive events. While no positive detections were made, interesting new limits have been obtained. The HEAO 3 data have also been searched for the extended source of 511 keV line emission which is expected to result from galactic nucleosynthesis.