The s-process in meteoritic interstellar grains, a continuos interaction between Nuclear Physics and Astrophysics

Details The s-process in meteoritic interstellar grains, a continuos interaction between Nuclear Physics and Astrophysics The s-process in meteoritic interstellar grains, a continuos interaction between Nuclear Physics and Astrophysics

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja....13716g&link_type=abstract

EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #13716

Astronomy and Astrophysics

Astrophysics

Scientific paper

The results of s-process nucleosynthesis calculations for Asymptotic Giant Branch stars (AGB) of different initial mass and different metallicity are discussed in the framework of stellar evolutionary models using an updated network of neutron capture cross sections. They are applied to the astrophysical interpretation of the stellar origin of meteoritic interstellar SiC grains of different populations. The neutron production is driven by the 13C(α,n)16O reaction taking place in radiative conditions during the interpulse periods in a tiny layer (13C pocket) at the top of the He- and C-rich region. A second neutron exposure is released by the reaction 22Ne(α,n)25Mg during recurrent convective thermal pulses. This neutron source is marginal in low mass AGB stars. However, it affects the final distribution of isotopes involved in branching in the s-flow. The s-enriched material is subsequently mixed with the envelope according to the efficiency of the third dredge up, and then ejected in the interstellar medium by stellar winds. Noble gases are most likely implanted in the already formed SiC grains in the protoplanetary phase. We provide strong constraints for the Ne-E(H), Kr-S and Xe-S meteoritic components as compared with stellar models. With decreasing the initial metallicity, from solar to around 1/10 solar, the s-process abundance distribution in AGB stars first feeds the Zr-peak, then the Zr-peak is partly bypassed in favor of the Ba-peak (at metallicities around one third solar), eventually the s-process distribution is peaked at the double-magic nucleus 208Pb, at the termination point of the s-path. The predicted s-process isotopic composition of all elements is strongly dependent on the metallicity, especially for isotopes involved in branchings in the s-flow. This has important impacts in discriminating the origin of subclasses Y and Z SiC grains with future NANOSIMS OR CHARISMA measurements.

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