HYDROGEN-POOR CIRCUMSTELLAR SHELLS FROM PULSATIONAL PAIR-INSTABILITY SUPERNOVAE WITH RAPIDLY ROTATING PROGENITORS

In certain mass ranges, massive stars can undergo a violent pulsation triggered by the electron/positron pair instability that ejects matter, but does not totally disrupt the star. After one or more of these pulsations, such stars are expected to undergo core-collapse to trigger a supernova (SN) explosion. The mass range susceptible to this pulsational phenomena may be as low as 50-70 M-circle dot if the progenitor is of very low metallicity and rotating sufficiently rapidly to undergo nearly homogeneous evolution. The mass, dynamics, and composition of the matter ejected in the pulsation are important aspects for determining the subsequent observational characteristics of the explosion. We examine the dynamics of a sample of stellar models and rotation rates and discuss the implications for the first stars, for LBV-like phenomena, and for superluminous SNe. We find that the shells ejected by pulsational pair-instability events with rapidly rotating progenitors (>30% the critical value) are hydrogen-poor and helium- and oxygen-rich.