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Astron. Astrophys. 334, 153-158 (1998)

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Correlated nucleosynthesis of fluorine and s-process elements in asymptotic giant branch stars

N. Mowlavi 1, A. Jorissen * 2 and M. Arnould 2

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

Received 24 September 1997 / Accepted 2 January 1998

Abstract

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 [FORMULA] is, however, required to produce [FORMULA] and s-process elements at the observed levels through the operation of the [FORMULA] ([FORMULA],n) [FORMULA] neutron source. Our calculations allow to put strong constraints on this primary supply. They require a [FORMULA] mass fraction of at least 0.003, with little sensitivity to the stellar conditions. This value is about 30 times larger than the secondary [FORMULA] supply available at the end of the CNO cycle in solar-metallicity stars. The minimum [FORMULA] mass fractions required are found to vary between about [FORMULA] and 0.01, depending on the temperature at which the fluorine production occurs.

Key words: nucleosynthesis – stars: abundances – stars: AGB

* Research Associate, National Fund for Scientific Research (FNRS), Belgium

Send offprint requests to: N. Mowlavi

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© European Southern Observatory (ESO) 1998

Online publication: May 12, 1998

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