Volume 652, August 2021
|Number of page(s)||7|
|Section||Stellar structure and evolution|
|Published online||17 August 2021|
Magnetic-buoyancy-induced mixing in AGB stars: Fluorine nucleosynthesis at different metallicities
Goethe University Frankfurt, Max-von-Laue-Strasse 1, Frankfurt am Main 60438, Germany
2 INFN, Section of Perugia, Via A. Pascoli snc, 06123 Perugia, Italy
3 INAF, Observatory of Abruzzo, Via Mentore Maggini snc, 64100 Teramo, Italy
4 Department of Physics and Geology, University of Perugia, Via A. Pascoli snc, 06123 Perugia, Italy
5 University of Granada, Departamento de Fisica Teorica y del Cosmos, 18071 Granada, Spain
Accepted: 15 June 2021
Asymptotic giant branch (AGB) stars are considered to be among the most significant contributors to the fluorine budget in our Galaxy. While observations and theory agree at close-to-solar metallicity, stellar models at lower metallicities overestimate the fluorine production with respect to that of heavy elements. We present 19F nucleosynthesis results for a set of AGB models with different masses and metallicities in which magnetic buoyancy acts as the driving process for the formation of the 13C neutron source (the so-called 13C pocket). We find that 19F is mainly produced as a result of nucleosynthesis involving secondary 14N during convective thermal pulses, with a negligible contribution from the 14N present in the 13C pocket region. A large 19F production is thus prevented, resulting in lower fluorine surface abundances. As a consequence, AGB stellar models with mixing induced by magnetic buoyancy at the base of the convective envelope agree well with available fluorine spectroscopic measurements at low and close-to-solar metallicity.
Key words: stars: abundances / stars: AGB and post-AGB / stars: magnetic field / magnetohydrodynamics (MHD) / stars: carbon / nuclear reactions, nucleosynthesis, abundances
© ESO 2021
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