Other
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd..11e...4l&link_type=abstract
Pre-Solar Grains as Astrophysical Tools, 26th meeting of the IAU, Joint Discussion 11, 21 August 2006, Prague, Czech Republic, J
Other
Scientific paper
The signature of an origin in asymptotic giant branch (AGB) stars is shown by vast majority of the presolar grains recovered to date. These include more than 90% of SiC grains, those belonging to the mainstream, Y and Z populations, as well as most of the oxide and silicate grains belonging to populations I and II. The large amount of high-precision data obtained from the analysis of these grains allows us to set fresh constraints on theoretical models of AGB stars, in the case of elements whose abundances are completely determined by the nucleosynthesis occurring in these stars, and on Galactic chemical evolution (GCE) models, in the case of elements whose abundances record the initial composition of the parent stars of the grains. I will present some examples of the information that has been recently extracted by applying presolar grain data to AGB and GCE models. Recent analysis of the composition of several heavy elements in individual presolar SiC grains have produced new constraints on the most uncertain parameter in models of slow neutron captures (the s process) in AGB stars: the main neutron source,^13C. Interestingly, these findings are confirmed by an independent study comparing models of stellar population synthesis coupled to the s process to stellar observations. Another recent study has dealt, in particular, with the composition of presolar spinel grain OC2. This grain is a candidate to be the first discovered grain that originated in an AGB star of intermediate mass. In this case, its O composition sets constraints on the rate of the ^16O(p,γ)^ 17F reaction. Finally, a important effort has been made in order to couple high-precision data of the Si composition of SiC grains belonging to the mainstream, Z and Y populations to two different sets of detailed models of nucleosynthesis in AGB stars in order to reconstruct the GCE evolution of the Si isotopes. The resulting trend is different from that predicted by a previous GCE model. More recent GCE models have started to be applied to the problems arising from presolar grain analysis.
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