AGB stars evolution & nucleosynthesis

Asymptotic Giant Branch stars are the main nuclear production phase of low-and intermediate mass stars.The double-shell burning of He and H around the electron degenerate core drives a rich pattern of nucleosynthesis, including the slow neutron capture process, as well as the formation of neutron rich isotopes.This nucleosynthesis is now observationally accessible in extremely metal poor stars, in particular the carbon enhanced s-process rich stars in binaries.The most common approach to model AGB star evolution and nucleosynthesis is the one-dimensional, spherically symmetric stellar evolution approximation.The input physics (mass loss, convective and nonconvective mixing, nucleosynthesis) and their uncertainties are discussed.More recently, hydrodynamic simulations of He-shell flash convection are becoming available, providing the means for a detailed analysis of some of the uncertain aspects of one-dimensional models.The differences between stellar interior convection and shallow surface convection is discussed.We also report on new studies that investigate the sensitivity of mixing and element production to nuclear reaction rates.

Hali tarjima qilinmagan