APEC Seminar (Astronomy - Particle Physics - Experimental Physics - Cosmology)

Speaker: Heiko Moller (Darmstadt)
Title: Impact of Nuclear Reactions on the Fate of Intermediate-mass Stars
Date (JST): Thu, Nov 27, 2014, 15:45 - 16:45
Place: Seminar Room B
Abstract: Stars in the mass range of 8 to 12 solar masses represent the transition region between those that end their lives producing white dwarfs and those that undergo a core-collapse supernova and produce neutron stars.
The final phases of stellar evolution of these intermediate-mass stars are tightly connected to the behavior of nuclear reactions at high densities. Despite their importance, the stellar evolution of intermediate-mass stars has received little attention in the past. The pioneering work in this mass range was published by K.Nomoto in 1984 and 1987. Numerical and computational difficulties had hindered progress in the past, however two recent stellar evolution studies (S.Jones et al., 2013; K.Takahashi et al., 2013) revived the interest in intermediate-mass stars.
We investigate the super-AGB star progenitor models of S. Jones to determine their possible fate as electron capture supernova. Therefore, we explore the nuclear processes that are relevant for the modeling of these stars, starting with the appearance of electron capture reactions in the star. As 20O becomes abundant in the core, new reaction channels have to be considered that modify the neon-burning which now proceeds by the reactions 20Ne(gamma,alpha)16O, followed by 20O(alpha,gamma)Ne24. Once the star reaches a sufficiently high temperature, the fusion reactions of neutron-rich oxygen isotopes, O16+O20->S36* and O20+O20->S40*, may become important.