Gamma-ray lines from type I supernovae

Analytic calculations are made of the time-dependent fluxes, shapes, median energies, and effective widths of the gamma-ray lines expected from the decay of nucleosynthetic Ni-56, Co-56, Fe-56, and Co-57 in current models of type I SNe. The attenuation and distortion of the line shapes due to Compton scattering and photoelectric absorption in the SN ejecta, line broadening from the expansion, and further distortion by the lookback effect from the differential light-travel time across the SN and by special relativistic effects are all taken into account. It is shown that several gamma-ray lines from such SNe should be measurable by detectors on the Gamma Ray Observatory and by the high-resolution spectrometer on the proposed Nuclear Astrophysics Explorer. The most intense and most detectable lines are the 0.847 and 1.238 MeV lines from Co-56 decay. Five other Co-56 decay lines, as well as the 0.158 MeV line from Ni-56 decay, should also be measurable. The models which can be tested by such observations are pointed out.