@misc{10481/60064,
year = {2019},
url = {http://hdl.handle.net/10481/60064},
abstract = {We present new fluorine abundance measurements for a sample of carbon-rich asymptotic giant branch (AGB) stars and two other
metal-poor evolved stars of Ba/CH types. The abundances are derived from IR, K-band, high-resolution spectra obtained using
GEMINI-S/Phoenix and TNG/Giano-b. Our sample includes an extragalactic AGB carbon star belonging to the Sagittarius dSph
galaxy. The metallicity of our stars ranges from [Fe/H] = 0:0 down to -1:4 dex. The new measurements, together with those previously
derived in similar stars, show that normal (N-type) and SC-type AGB carbon stars of near solar metallicity present similar F
enhancements, discarding previous hints that suggested that SC-type stars have larger enhancements. These mild F enhancements are
compatible with current chemical-evolution models pointing out that AGB stars, although relevant, are not the main sources of this
element in the solar neighbourhood. Larger [F/Fe] ratios are found for lower-metallicity stars. This is confirmed by theory. We highlight
a tight relation between the [F/hsi] ratio and the average s-element enhancement [hsi/Fe] for stars with [Fe/H] > -0:5, which can
be explained by the current state-of-the-art low-mass AGB models assuming an extended 13C pocket. For stars with [Fe/H] < -0:5,
discrepancies between observations and model predictions still exist. We conclude that the mechanism of F production in AGB stars
needs further scrutiny and that simultaneous F and s-element measurements in a larger number of metal-poor AGB stars are needed to
better constrain the models.},
organization = {This work was partially supported by the Spanish grant
AYA2015-63588-P within the European Founds for Regional Development
(FEDER).},
publisher = {EDP Sciences},
keywords = {Stars},
keywords = {Abundances},
keywords = {Carbon},
keywords = {Nuclear reactions},
keywords = {Nucleosynthesis},
title = {Additional fluorine abundance determinations in evolved stars},
doi = {10.1051/0004-6361/201935286},
author = {Abia Ladrón De Guevara, Carlos Antonio and Cristallo, S. and Cunha, K. and Laverny, P. de and Smith, V. V.},
}