The First Fluorine Abundance Determinations in Extragalactic AGB Carbon
  Stars
  Fluorine (19F) abundances (or upper limits) are derived in six extragalactic
AGB carbon stars from the HF(1-0) R9 line at 2.3358 mu in high resolution
spectra. The stars belong to the Local Group galaxies LMC, SMC and Carina dwarf
spheroidal, spanning more than a factor 50 in metallicity. This is the first
study to probe the behaviour of F with metallicity in intrinsic extragalactic
C-rich AGB stars. Fluorine could be measured only in four of the target stars,
showing a wide range in F-enhancements. Our F abundance measurements together
with those recently derived in Galactic AGB carbon stars show a correlation
with the observed carbon and s-element enhancements. The observed correlations
however, display a different dependence on the stellar metallicity with respect
to theoretical predictions in low mass, low metallicity AGB models. We briefly
discuss the possible reasons for this discrepancy. If our findings are
confirmed in a larger number of metal-poor AGBs, the issue of F production in
AGB stars will need to be revisited.
