Nucleosynthesis of low and intermediate-mass stars

Abstract

The asymptotic giant branch (AGB) is the last nuclear-burning phase for low and intermediate-mass stars with initial masses between about 0.8 to 8 solar masses. The AGB phase of evolution is very short, comprising less than 1 per cent of the main-sequence lifetime, nevertheless, it is on the AGB that the richest nucleosynthesis occurs for this mass range. The nucleosynthesis is driven by thermal instabilities of the helium-burning shell, the products of which are dredged to the stellar surface by recurrent mixing episodes. Hot bottom burning occurs in the most massive AGB stars, and this also alters the surface composition. I review the evolution and nucleosynthesis from the main sequence through to the tip of the AGB. The nucleosynthesis that occurs during the AGB is explored in detail, including a discussion of the effects of hot bottom burning. I finish with a brief review of the slow-neutron-capture process that produces elements heavier than iron.