Type Ib Supernovae

Abstract

In this chapter presents supernovae of Type Ib (SN Ib), the distinguishing characteristic of which is presence of helium spectral lines in optical spectra. Hydrogen lines are absent or inconspicuous, indicating that most or all of the hydrogen envelope was lost prior to explosion. The light curves of typical SN Ib generally resemble those of other stripped-envelope supernovae (SN IIb; Chapter “Type IIb Supernovae”, and SN Ic; Chapter “Type Ic Supernovae”) except that the early peak observed in a few SN IIb has not been detected in SN Ib (or SN Ic). The spectra of SN Ib resemble those of SN IIb apart from the lack of conspicuous hydrogen lines even at early times. Spectropolarization reveals that SN Ib tend to be substantially asymmetric. Like those of SN IIb, most progenitors of SN Ib probably are stars of initial main-sequence mass in the range of 10–18 solar masses, the hydrogen envelopes of which were stripped owing to binary interactions. The archival detection of one progenitor star supports this picture. A minority of progenitors may, however, be massive Wolf-Rayet stars that lose their envelopes by means of winds. The chapter also discusses Type Ibn supernovae (SN Ibn); the distinguishing characteristic is the presence in early spectra of narrow emission lines of helium, indicative of helium-rich circumstellar matter.