SN 1983V in NGC 1365 and the Nature of Stripped Envelope Core‐Collapse Supernovae

We present CCD photometry and low-resolution spectra of the spectroscopic Type Ic supernova SN 1983V in NGC 1365. Photometry in the B band spans nearly 250 days after maximum light, while the spectra cover the photospheric epoch, from 9 days before up to 38 days after B maximum. We also compile and discuss infrared photometry that has been published elsewhere. The photometric evolution of SN 1983V is analyzed in comparison with other Type Ic supernovae and with SN 1983N and SN 1993J. The spectroscopic evolution is described, line identifications are proposed, and evidence for H, He, and Si is discussed. The photometric evolution of SN 1983V suggests that it is a close relative of SN 1983N and SN 1993J, events for which it is supposed that the external layers comprising most of the He/H and H shells, respectively, were lost before the explosion. The mass-to-energy ratios of SN 1983V and SN 1993J are substantially different if estimated from the expansion velocities. However, the similarity of the B light curves suggests that if the masses and mass-to-energy ratios are not similar, then the mass of SN 1983V has to be large enough to compensate for the higher mass-to-energy ratio. The latter possibility contradicts the standard scenarios that describe these events and implies a precise fine-tuning of the masses and mass-to-energy ratios of the two supernovae. This contradiction, however, could be resolved if a significant fraction of the inner ejecta containing 56Ni does not follow the decrease in density expected for a spherically symmetric, homologous expansion.