Abstract

The presence of a close binary companion can affect the evolution of a massive star through one or more episodes of mass transfer, or by merger in a common-envelope phase. Monte Carlo calculations indicate that ∼ 20 – 35% of all massive supernovae are affected by processes of this type. The duplicity of the progenitor may be revealed by the illumination, in the supernova event, of axially symmetric material that had previously been ejected during the mass-transfer phase or by the expulsion of a common envelope. Moreover, the properties of the progenitor star, the peak supernova luminosity, and other observable features of the supernova event can be affected by prior binary membership. Binary interactions may be the cause of much of the variability among Type II supernova light curves, and may result, in Type Ib or Ic events in cases where the entire hydrogen-rich envelope has been stripped from the progenitor. Many of the peculiarities of SN 1987A and SN 1993J may well have resulted from the prior duplicity of the progenitor.