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Issue A&A
Volume 421, Number 2, July II 2004
Page(s) L25 - L28
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20040184



A&A 421, L25-L28 (2004)
DOI: 10.1051/0004-6361:20040184

Letter

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

S. Goriely and L. Siess

Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, CP 226, 1050 Brussels, Belgium

(Received 18 February 2004 / Accepted 25 May 2004 )

Abstract
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 $\rm {}^{12}\kern-0.8ptC$-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 $\rm {}^{14}\kern-0.8ptN$-rich and $\rm {}^{13}\kern-0.8ptC$-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.


Key words: nucleosynthesis -- s-process -- AGB stars

Offprint request: S. Goriely, sgoriely@astro.ulb.ac.be




© ESO 2004


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