Accurate fundamental parameters and detailed abundance patterns from spectroscopy of 93 solar-type Kepler targets
Abstract
We present a detailed spectroscopic study of 93 solar-type stars that are targets of the NASA/Kepler mission and provide detailed chemical composition of each target. We find that the overall metallicity is well represented by Fe lines. Relative abundances of light elements (CNO) and α elements are generally higher for low-metallicity stars. Our spectroscopic analysis benefits from the accurately measured surface gravity from the asteroseismic analysis of the Kepler light curves. The accuracy on the log g parameter is better than 0.03 dex and is held fixed in the analysis. We compare our Teff determination with a recent colour calibration of VT-KS [TYCHO V magnitude minus Two Micron All Sky Survey (2MASS) KS magnitude] and find very good agreement and a scatter of only 80 K, showing that for other nearby Kepler targets, this index can be used. The asteroseismic log g values agree very well with the classical determination using Fe I-Fe II balance, although we find a small systematic offset of 0.08 dex (asteroseismic log g values are lower). The abundance patterns of metals, α elements and the light elements (CNO) show that a simple scaling by [Fe/H] is adequate to represent the metallicity of the stars, except for the stars with metallicity below -0.3, where α-enhancement becomes important. However, this is only important for a very small fraction of the Kepler sample. We therefore recommend that a simple scaling with [Fe/H] be employed in the asteroseismic analyses of large ensembles of solar-type stars.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- June 2012
- DOI:
- 10.1111/j.1365-2966.2012.20686.x
- arXiv:
- arXiv:1203.0611
- Bibcode:
- 2012MNRAS.423..122B
- Keywords:
-
- stars: abundances;
- stars: atmospheres;
- stars: fundamental parameters;
- stars: solar-type;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- MNRAS, in press, 12 pages