A theoretical analysis of the light curves of Type I supernovae is presented. A low-mass helium star (helium mass of about 1.5 to 4 solar masses), formed by mass transfer in a binary or by extensive mass loss, undergoes core collapse to form a neutron star. The 'reflected' shock synthesizes and ejects about 0.3 solar mass of Ni-56. The low-mass mantle slows the Ni-56 but allows it to escape. The shock does not give a vigorous display in the visual wavelengths because the envelope is not sufficiently extended to do so. The decay of Ni-56 powers the peak of the light curve; exponential-tail phase is powered by kinetic energy from positron emission by Co-56. The Co-Fe 'core' lights a surrounding, rapidly expanding, He-rich nebula. During the tail phase, the luminosity in gamma-ray lines is about 20 times that observed in the visible, and should be detectable with gamma-ray spectrometers now operational.
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W. David Arnett (1979) studied this question.