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| Paper: |
Abundance Patterns in S-type AGB Stars: Setting Constraints on
Nucleosynthesis and Stellar Evolution Models |
| Volume: |
445, Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants |
| Page: |
77 |
| Authors: |
Neyskens, P.; Van Eck, S.; Plez, B.; Goriely, S.; Siess, L.; Jorissen, A. |
| Abstract: |
During evolution on the AGB, stars of type S are the first to
experience s-process nucleosynthesis and the third dredge-up, and
therefore to exhibit s-process signatures in their atmospheres.
Their high mass-loss rates (10–7 to 10–6
M☉/year) make them major contributors to the AGB
nucleosynthesis yields at solar metallicity. Precise abundance
determinations in S stars are of the utmost importance for
constraining e.g. the third dredge-up luminosity and efficiency
(which has been only crudely parameterized in current nucleosynthetic
models so far). Here, dedicated S-star model atmospheres are used to
determine precise abundances of key s-process elements, and to set
constraints on nucleosynthesis and stellar evolution models. Special
interest is paid to technetium, an element with no stable isotopes.
Its detection is considered the best signature that the star effectively
populates the thermally-pulsing AGB phase of evolution. The derived
Tc/Zr abundances are compared, as a function of the derived [Zr/Fe]
overabundances, with AGB stellar model predictions. The [Zr/Fe]
overabundances are in good agreement with model predictions, while
the Tc/Zr abundances are slightly overpredicted. This discrepancy can
help to set better constraints on nucleosynthesis and stellar evolution
models of AGB stars. |
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