Magnetic-buoyancy-induced mixing in AGB stars: Fluorine nucleosynthesis at different metallicities

D Vescovi, S Cristallo, S Palmerini, C Abia… - Astronomy & …, 2021 - aanda.org
D Vescovi, S Cristallo, S Palmerini, C Abia, M Busso
Astronomy & Astrophysics, 2021aanda.org
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 19 F 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 13 C neutron source (the so-called 13 C …
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.
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