Pre-supernova models at very low metallicity

Abstract

A series of fast rotating models at very low metallicity (Z=1e-8) was computed in order to explain the surface abundances observed at the surface of CEMP stars, in particular for nitrogen. The main results are the following: - Strong mixing occurs during He--burning and leads to important primary nitrogen production. - Important mass loss takes place in the RSG stage for the most massive models. The 85 solar mass model loses about three quarter of its initial mass, becomes a WO star and could produce a GRB. - The CNO elements of HE1327-2326 could have been produced in massive rotating stars and ejected by their stellar winds.

5 pages, 3 figures, Contribution to "Nuclei in the Cosmos IX", June 25-30 2006, CERN, Geneva, to appear in Proceedings of Science