Early-time spectra of type IC supernovae - Further evidence for the presence of hydrogen

Comparison of the early-time optical spectra of the Type II SN 1985L and the Type Ic SN 1987M confirms the previously suspected presence of Hα in SN 1987M. The Hα line has a P Cygni profile in both objects, but it is not as prominent as in the Type II SN 1987K, whose spectrum at late times became indistinguishable from that of SNs Ic. A spectrum of the Type Ic SN 1991A reveals a weak but nearly unmistakable Hα emission line; faint Hα emission may also be present in the Type Ic SN 1990aa