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S-process in hot AGB star: A complex interplay between diffusive mixing and nuclear burning

par Goriely, Stéphane ;Siess, Lionel
Référence Astronomy & astrophysics, 421, 2, page (25-28)
Publication Publié, 2004

Article révisé par les pairs

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Résumé :

We present new qualitative results of the s-process nucleosynthesis in hot AGB stars resulting from diffusive convective overshooting. In this approach, protons from the convective envelope are injected into the adjacent 12C-rich layers, but depending on the thermodynamic conditions in the mixing zone, the nuclear proton lifetime can be comparable with (or even smaller than) the diffusion timescale. In such a case, the nucleosynthesis and diffusion equations must be coupled. Our simulations indicate that during this diffusive burning phase, the 14N-rich and 13C-rich layers overlap with drastic impact on the s-process distribution. Our study emphasizes the sensitivity of the s-process nucleosynthesis on the temperature of the partial mixing zone. We show that in this framework, a deep hot third dredge-up tends to inhibit the production of s-elements. We also provide a first qualitative estimate of the metallicity and mass dependence of the s-process efficiency in AGB stars and propose that this complex interplay could account for the large variety of the observed s-process efficiencies.