The observational properties of type 1b supernovae

All the available observations of the most probable SNe 1b are discussed, and a classification scheme is developed which is based only on optical spectroscopy and which defines the subclass 1b in a practical and rigorous manner. Two modern prototypes, the only SNe that have been observed to satisfy all the criteria, are chosen to represent SNe 1b. Other supernovae that have been classed as relatives or members of the subclass are briefly discussed.