Lecturer: Dr. Takashi Moriya Affiliation: University of Bonn Abstract: Pair-instability supernovae (PISNe) are thermonuclear explosions of very massive stars. The stellar core needs to be heavier than about 60 Msun for stars to be PISNe. Mass loss prevents massive stars from making large enough cores to be PISNe, and PISNe are presumed to exist in metal-free or metal-poor environment where radiation-driven mass loss is small. Stellar evolution models show that such PISN progenitors evolve to red supergiants (RSGs) shortly before their explosions. However, RSGs are suggested to be pulsationally unstable, and they can experience huge mass loss driven by the pulsation. We investigate the effect of the pulsation-driven mass loss on PISN progenitors. We find that hydrogen-rich layers of PISN progenitors are significantly reduced by the pulsation-driven mass loss, even if they are initially metal-free. Because the pulsation-driven mass-loss terminates when the hydrogen-rich envelope is lost, the core mass is not affected by the pulsation-driven mass loss and they still explode as PISNe. However, the large pulsation-driven mass loss can significantly alter observational properties of PISNe. Additional details of the upcoming Astrophysics' seminars can be found on the following link. ‏האירוע הזה כולל שיחת וידאו ב-Google Hangouts. הצטרף: https://hangouts.google.com/hangouts/_/mail.huji.ac.il/astrophysics?hceid=bWFpbC5odWppLmFjLmlsX2c0czhydDlpcmhwZzRvdGNybWIzZGFqcjdvQGdyb3VwLmNhbGVuZGFyLmdvb2dsZS5jb20.dltmu953iv13db2ai9mr8hd828&hs=121