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.

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

References in corpus (24)

• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• An absolutely calibrated effective temperature scale from the InfraRed Flux Method
• S4N: A Spectroscopic Survey of Stars in the Solar Neighborhood
• Oxygen Abundances in Nearby FGK Stars and the Galactic Chemical Evolution of the Local Disk and Halo
• A Hipparcos study of the Hyades open cluster: Improved colour-absolute magnitude and Hertzsprung-Russell diagrams
• Abundances in the Local Region II: F, G and K Dwarfs and Subgiants
• An accurate and self-consistent chemical abundance catalogue for the APOGEE/Kepler sample
• Oxygen Line Formation in Late-F through Early-K Disk/Halo Stars: Infrared O I Triplet and [O I] Lines
• HIPPARCOS age-metallicity relation of the solar neighbourhood disc stars
• Consistent metallicity scale for cool dwarfs and giants. A benchmark test using the Hyades
• Magnesium isotope ratios in Hyades stars
• K dwarfs and the chemical evolution of the Solar cylinder
• The Distances to Open Clusters from Main-Sequence Fitting. I. New Models and a Comparison to the Properties of the Hyades Eclipsing Binary vB 22
• Oxygen from the Lambda 7774 High-Excitation Triplet in Open Cluster Dwarfs: Hyades
• High-Resolution Spectroscopy of Ursa Major Moving Group Stars
• Lithium, Carbon, and Oxygen Abundances of Hyades F-G Type Stars
• Red Giant evolution and specific problems
• Fe I and Fe II Abundances of Solar-Type Dwarfs in the Pleiades Open Cluster
• On the iron ionization balance of cool stars
• On the Iron Abundance Anomaly in K-dwarf and Hyades Stars
• Can surface oxygen abundances of red giants be explained by the canonical mixing theory?

Cited by in corpus (7)

• Astrometric Accelerations as Dynamical Beacons: Discovery and Characterization of HIP 21152 B, the First T-Dwarf Companion in the Hyades
• The GAPS Programme at TNG XXVIII -- A pair of hot-Neptunes orbiting the young star TOI-942
• 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