SN 1983N and the Nature of Stripped Envelope--Core Collapse Supernovae

We present CCD photometric observations of SN 1983N obtained from images taken 290 and 340 days after maximum light. These points define a late time slope of 0.017 + 0.003 mag day ¹in the V band, nearly indistinguishable from that of SN 1993J at the same phase after second maximum. A comparative analysis of these two SNe shows that, although some puzzling differences exist, except for the outermost layers containing H in SN 1993J they were essentially similar, with the mass-to-energy ratio of SN 1993J probably larger. The similarity of the light curves of SN 1983N and SN 1993J has implications for the categorization of both Type Ib and Type II to Ib "transition" SNe. These two objects, together with SNe 1954A, 1987K, and 1983V, among others, seem to define a photometric group that cuts across the spectroscopic categories traditionally used to classify supernovae. The spectrum at maximum is insufficient to fully classify them.