Evolution of massive AGB stars

Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, CP 226, 1050 Brussels, Belgium

Abstract

The evolution of stars in the mass range 7–12 M_๏ is characterized by the off-center ignition of carbon in condition of partially degeneracy followed by the propagation of a convectively bound flame and the formation of a neon-oxygen core. In this chapter, we review the evolutionary features of these peculiar stars and pay a special attention to the thermally pulsing super-AGB phase and associated nucleosynthesis. The evolution toward electron capture supernovae for the most massive members of this class is briefly mentioned. In light of new computations, we also discuss the question of M_up, the critical mass above which carbon ignites as well as M_n, the minimum mass for the formation of a neutron star and analyze the dependence of these transition masses on metallicity.