Fluorine Abundances in Galactic AGB Stars

TL;DR

This study measures fluorine in Galactic AGB stars using advanced models, finding lower F abundances than previous studies, aligning better with nucleosynthesis theories, but some stars still show unexpected high F levels.

Contribution

It provides updated fluorine abundance measurements in AGB stars using improved models and line lists, resolving previous discrepancies with theoretical predictions.

Findings

F abundances are lower than previous estimates.

New measurements agree with recent nucleosynthesis models.

Some stars still show higher F than models predict.

Abstract

An analysis of the fluorine abundance in Galactic AGB carbon stars (24 N-type, 5 SC-type and 5 J-type) is presented. This study uses the state- of-the-art carbon rich atmosphere models and improved atomic and molecular line lists in the 2.3 {\mu}m region. F abundances significantly lower are obtained in comparison to previous study in the literature. The main reason of this difference is due to molecular blends. In the case of carbon stars of SC-type, differences in the model atmospheres are also relevant. The new F enhancements are now in agreement with the most recent theoretical nucleosynthesis models in low- mass AGB stars, solving the long standing problem of F in Galactic AGB stars. Nevertheless, some SC-type carbon stars still show larger F abundances than predicted by stellar models. The possibility that these stars are of larger mass is briefly discussed.