M Giants with IGRINS II. Chemical Evolution of Fluorine at High Metallicities

Abstract

The origin and evolution of fluorine in the Milky Way galaxy is still in debate. In particular, the increase of the [F/Fe] in metal-rich stars found from near-IR HF-lines is challenging to explain theoretically. We determine the fluorine abundances from 50 M giants in the solar neighbourhood spanning a broad range of metallicities (-0.9<[Fe/H]<0.25 dex). These stars are cool enough to have an array of HF lines in the K band. We observed the stars with the IGRINS and investigate each of ten HF molecular lines in detail. Based on a detailed line-by-line analysis of ten HF lines, we find that the R19, R18 and R16 lines should primarily be used for abundance analysis. The R15, R14 and R13 lines can also be used, but the trends based on these lines show increasing dependencies with the stellar parameters. The strongest HF lines, namely R12, R11, R9 and R7 should be avoided since the abundances from them show significant trends with the stellar parameters, and a high sensitivity to variations in the microturbulence, especially for coolest metal-rich stars. This leads to a huge scatter and high fluorine abundances for supersolar metallicity stars, not seen in the trends from the weaker lines for the same stars. When estimating the final mean fluorine abundance trend versus metallicity, we neglect the fluorine abundances from the four strongest lines (R7, R9, R11 and R12) for all stars and use only those derived from R16, R18, and R19 for the coolest metal-rich stars. We confirm the flat trend of [F/Fe] found in other studies in the metallicity range of -1.0<[Fe/H]<0.0. We also find a slight enhancement at supersolar metallicities (0<[Fe/H]<0.15) but we cannot confirm the upward trend seen at [Fe/H]>0.25. We need more observations of M giants at super solar metallicities with a spectrometer like IGRINS to confirm if the metal-rich fluorine abundance upturn is real or not.

11 pages, 6 figures, Accepted for publication in A&A

References in corpus (15)

• The NumPy array: a structure for efficient numerical computation
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Line lists for the A2PI-X2Sigma+ (red) and {B2Sigma+-X2Sigma} (violet) Systems of CN, 13C14N, and 12C15N, and Application to Astronomical Spectra
• The Chemical Evolution of Fluorine in the Bulge - High-resolution K-band spectra of giants in three fields
• Fluorine in the Solar neighborhood: No evidence for the neutrino process
• Fluorine in the solar neighborhood - is it all produced in AGB-stars?
• Fluorine in the solar neighborhood: modelling the Galactic thick and thin discs
• The Galactic Chemical Evolution of phosphorus observed with IGRINS
• Chemical Evolution of Ytterbium in the Galactic Disk
• Chemical Evolution of Fluorine in the Milky Way
• M giants with IGRINS I. Stellar parameters and $\alpha$-abundance trends of the solar neighborhood population
• Fluorine Abundances in the Galactic Nuclear Star Cluster
• Fluorine Abundances in the Globular Cluster M 4
• An Archive of Spectra from the Mayall Fourier Transform Spectrometer at Kitt Peak

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