## Correlated nucleosynthesis of fluorine and s-process elements in asymptotic giant branch stars
^{1} Observatoire de Genève, CH-1290 Sauverny,
Switzerland^{2} Institut d'Astronomie et d'Astrophysique,
Université Libre de Bruxelles, C.P.226, Boulevard du Triomphe,
B-1050 Brüssel, Belgium
The production of fluorine and s-process elements in conditions simulating the helium-burning shell of asymptotic giant branch (AGB) stars is investigated from parametric one-zone nucleosynthesis calculations. Our calculations account for the correlation between the overabundances of these elements, as observed at the surface of S and C stars (Jorissen et al. 1992, A&A 261, 164). A primary supply of is, however, required to produce and s-process elements at the observed levels through the operation of the (,n) neutron source. Our calculations allow to put strong constraints on this primary supply. They require a mass fraction of at least 0.003, with little sensitivity to the stellar conditions. This value is about 30 times larger than the secondary supply available at the end of the CNO cycle in solar-metallicity stars. The minimum mass fractions required are found to vary between about and 0.01, depending on the temperature at which the fluorine production occurs.
* Research Associate, National Fund for Scientific Research (FNRS), Belgium
## Contents- 1. Introduction
- 2. Initial conditions, nuclear network and typical results
- 3. The nuclear transformations governing the
^{19}F production in neutron-rich He-burning layers - 4. Charts of
^{19}F and s-process yields - 5. Implications for AGB models
- 6. Conclusions
- Acknowledgements
- References
© European Southern Observatory (ESO) 1998 Online publication: May 12, 1998 |