The evolution of massive stars to explosion

Abstract

We review the possible evolutionary paths from massive stars to explosive endpoints as various types of supernovae associated with Population I and hence with massive stars: Type II-P, Type II-L, Type Ib, Type Ic, and the hybrid events SN 1987K and SN 1993J. We identify SN 1954A as another hybrid event from the evidence for both H and He in its spectrum with velocities nearly the same as SN 1983J. Evidence for ejected 56Ni mass of ∼ 0.07 M⊙ suggests that SN II-P underwent standard iron core collapse, not collapse of an O-Ne-Mg core nor thermonuclear explosion of a C-O core. Most SN II-P presumably arise in single stars or wide binaries of ∼ 10 - 20 M⊙. There may be indirect evidence for duplicity in some cases in the form of strong Ba II lines, such as characterized SN 1987A. SN II-L are recognizably distinct from typical SN II-P and must undergo a significantly different evolution. Despite indications that SN II-L have small envelopes that may be helium enriched, they are also distinct from events like SN 1993J that must have yet again a different evolution. The SN II-L that share a common luminosity seem to have ejected a small nickel mass and hence may come from stars with O-Ne-Mg cores. The amount of nickel ejected by the exceptionally bright events, SN 1980K and SN 1979C, remains controversial. SN Ib require the complete loss of the H envelope, either to a binary companion or to a wind. The few identified have relatively large ejecta masses. It is not clear what evolutionary processes distinguish SN Ib’s evolving in binary systems from hybrid events that retain some H in the envelope. SN Ic events are both H and He deficient. Binary models.that can account for transfer of an extended helium envelope from low mass helium cores, ∼ 2 to 4 M⊙, imply C-O core masses that are roughly consistent with that deduced from the ejecta mass plus a neutron star, ∼ 2 to 3 M⊙. It is possible that the hybrid events are the result of Roche lobe overflow and that the “pure” events, SN Ib or SN Ic, result from common envelope evolution.