A mixed helium-oxygen shell in some core-collapse supernova progenitors

摘要

We evolve models of rotating massive stars up to the stage of iron corecollapse using the MESA code and find a shell with a mixed composition ofprimarily helium and oxygen in some cases. In the parameter space of initialmasses of 13-40 Mo and initial rotation velocities of 0-450 km/s that weinvestigate, we find a mixed helium-oxygen shell with a significant mass onlyfor a small fraction of the models. While the shell is formed due to rotationalmixing, the pre-collapse rotation rate is not very high, as required for anenergetic collapse-induced thermonuclear explosion. Our results suggest thatthe collapse-induced thermonuclear explosion mechanism that was revisitedrecently can account for at most a small fraction of core-collapse supernovae.The presence of such a mixed helium-oxygen shell still might have someimplications for core-collapse supernovae, such as some nucleosynthesisprocesses when jets are present, or might result in peculiar sub-luminouscore-collapse supernovae.