Evolution and Yields of Extremely Metal‐poor Intermediate‐Mass Stars

Intermediate-mass stellar evolution tracks from the main sequence to the tip of the AGB for five initial masses (2-6 M ☉ ) and metallicity Z = 0.0001 have been computed. The detailed one-dimensional structure and evolution models include exponential overshooting, mass loss, and a detailed nucleosynthesis network with updated nuclear reaction rates. The network includes a two-particle heavy neutron sink for approximating neutron density in the He-shell flash. It is shown how the neutron-capture nucleosynthesis is important in models of very low metallicity for the formation of light neutron-heavy species, like sodium or the heavy neon and magnesium isotopes. The models have high resolution, as required for modeling the third dredge-up. All sequences have been followed from the pre-main sequence to the end of the AGB when all envelope mass is lost. Detailed structural and chemical model properties as well as yields are presented. This set of stellar models is based on standard assumptions and updated input physics. It can be confronted with observations of extremely metal-poor stars and may be used to assess the role of AGB stars in the origin of abundance anomalies of some globular cluster members of correspondingly low metallicity.