The first stars: Evolution and nucleosynthesis

We have computed stellar models of metal-free (Z=0) intermediate mass stars (4-8 M-.). We have found, for the first time, that these stars do experien ce the thermal pulse phase and enrich the envelope with He, C, primary N an d some O and Li. Adopting an IMF obtained for Z=0 stars, we show that Pop. III intermediate mass stars could have contributed significantly to the ear ly nitrogen and carbon galactic enrichment. Furthermore, local contaminatio ns would be very relevant.