Additional fluorine abundance determinations in evolved stars Abia Ladrón De Guevara, Carlos Antonio Cristallo, S. Cunha, K. Laverny, P. de Smith, V. V. Stars Abundances Carbon Nuclear reactions Nucleosynthesis 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. 2020-03-06T09:00:03Z 2020-03-06T09:00:03Z 2019 info:eu-repo/semantics/article Abia, C., Cristallo, S., Cunha, K., De Laverny, P., & Smith, V. V. (2019). Additional fluorine abundance determinations in evolved stars. Astronomy & Astrophysics, 625, A40. http://hdl.handle.net/10481/60064 10.1051/0004-6361/201935286 eng http://creativecommons.org/licenses/by-nc-nd/3.0/es/ info:eu-repo/semantics/openAccess Atribución-NoComercial-SinDerivadas 3.0 España EDP Sciences