Spectroscopic Determination of Stellar Parameters and Oxygen Abundances for Hyades/Field G-K Dwarfs

Abstract

It has been occasionally suggested that Fe abundances of K dwarfs derived from Fe I and Fe II lines show considerable discrepancies and oxygen abundances determined from high-excitation O I 7771-5 triplet lines are appreciably overestimated (the problem becoming more serious towards lower Teff), which however has not yet been widely confirmed. With an aim to clarify this issue, we spectroscopically determined the atmospheric parameters of 148 G-K dwarfs (Hyades cluster stars and field stars) by assuming the classical Fe I/Fe II ionization equilibrium as usual, and determined their oxygen abundances by applying the non-LTE spectrum fitting analysis to O I 7771-5 lines. It turned out that the resulting parameters did not show any significant inconsistency with those determined by other methods (for example, the mean differences in Teff and log g from the well-determined solutions of Hyades dwarfs are mostly <~100K and <~0.1dex). Likewise, the oxygen abundances of Hyades stars are around [O/H]~+0.2dex (consistent with the metallicity of this cluster) without exhibiting any systematic Teff-dependence. Accordingly, we conclude that parameters can be spectroscopically evaluated to a sufficient precision in the conventional manner (based on the Saha-Boltzmann equation for Fe I/Fe II) and oxygen abundances can be reliably determined from the O I 7771-5 triplet for K dwarfs as far as stars of Teff>~4500K are concerned. We suspect that previously reported strongly Teff-dependent discrepancies may have stemmed mainly from overestimation of weak-line strengths and/or improper Teff scale.

Accepted for publication in Astronomical Journal, 38 pages (including 14 figures and 2 tables), with supplementary online material

References in corpus (5)

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• The GAPS Programme at TNG -- XXV. Stellar atmospheric parameters and chemical composition through GIARPS optical and near-infrared spectra
• Stellar Characterization and Radius Inflation of Hyades M Dwarf Stars From the APOGEE Survey
• Coronal X-Ray Emission from Nearby, Low-Mass, Exoplanet Host Stars Observed by the MUSCLES and Mega-MUSCLES HST Treasury Survey Projects
• Properties of the Hyades, the eclipsing binary HD27130, and the oscillating red giant $\epsilon$ Tau
• Rubidium abundances of galactic disk stars