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| Paper: |
Constraints on AGB Models from s-Process Nucleosynthesis |
| Volume: |
378, Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes |
| Page: |
119 |
| Authors: |
Cristallo, S.; Straniero, O.; Gallino, R. |
| Abstract: |
Thermally pulsing AGB stars with mass lower than about 3 M⊙ play a fundamental role in the Galactic enrichment of heavy elements, by means of their s-process nucleosynthesis. The main neutron source is the 13C(α,n)16O reaction, operating during the interpulse phase. The amount of 13C required to explain the activation of the s-process can be obtained if, at the epoch of the third dredge-up, some protons are diffused from the H–rich envelope into the underlying radiative He–rich (and 12C–rich) intershell zone, thus allowing the formation of the so-called 13C pocket, through proton captures on carbon nuclei. Spectroscopic measurements of element overabundances in AGB stars and precise determinations of isotopic compositions in meteoritic SiC grains provide strong constraints on the amount of 13C held in the pocket. They generally show good agreement with nucleosynthesis predictions obtained by assuming M(13C) = 3×10−6 M⊙, corresponding to the standard case defined by Gallino et al. (1998), even if a certain spread is often required. |
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