H. Jönsson¹, N. Ryde¹, G. M. Harper², M. J. Richter³ and K. H. Hinkle⁴

¹Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, SE-221 00 Lund, Sweden
²School of Physics, Trinity College, Dublin 2, Ireland
³Physics Department, University of California, Davis, CA 95616, USA
⁴National Optical Astronomy Observatory, P.O. Box 26732, Tucson, AZ 85726, USA

The origin of “cosmic” fluorine is uncertain, but there are three proposed production sites/mechanisms for the origin: asymptotic giant branch (AGB) stars, ν nucleosynthesis in Type II supernovae, and/or the winds of Wolf-Rayet stars. The relative importance of these production sites has not been established even for the solar neighborhood, leading to uncertainties in stellar evolution models of these stars as well as uncertainties in the chemical evolution models of stellar populations. We determine the fluorine and oxygen abundances in seven bright, nearby giants with well determined stellar parameters. We use the 2.3 μm vibrational-rotational HF line and explore a pure rotational HF line at 12.2 μm. The latter has never been used before for an abundance analysis. To be able to do this, we have calculated a line list for pure rotational HF lines. We find that the abundances derived from the two diagnostics agree. Our derived abundances are well reproduced by chemical evolution models including only fluorine production in AGB stars and, therefore, we draw the conclusion that this might be the main production site of fluorine in the solar neighborhood. Furthermore, we highlight the advantages of using the 12 μm HF lines to determine the possible contribution of the ν process to the fluorine budget at low metallicities where the difference between models including and excluding this process is dramatic.

Reference
Jönsson H, Ryde N, Harper GM, Richter MJ and Hinkle KH (2014) Fluorine in the Solar Neighborhood: Is It All Produced in Asymptotic Giant Branch Stars? The Astrophysical Journal Letters 789:L41.
[doi:10.1088/2041-8205/789/2/L41]

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