TYPE Ib/c SUPERNOVAE AND THEIR RELATION TO BINARY STARS

The present understanding of type Ib/c supernovae and their connection to interacting binaries is reviewed. The problems of the classification and the lack of well-observed events exclude direct inference of progenitor characteristics. The absence of hydrogen lines in the observed spectrum, nevertheless, requires restricted evolutionary schemes to produce suitable progenitor stars for core collapse explosions with no hydrogen envelope. New relative statistics among the supernova types are presented which indicate that SN~Ib/c are on average brighter than SN~II, and with the dense sampling of supernova searches in nearby galaxies, a small intrinsic incidence of SN~Ib/c is determined. The small rates might be in conflict with the observed ratio of massive stars in binaries in the Galaxy.