Atmospheric parameters of 82 red giants in the Kepler field

July 2012 • 2012A&A...543A.160T

Authors • Thygesen, A. O. • Frandsen, S. • Bruntt, H. • Kallinger, T. • Andersen, M. F. • Elsworth, Y. P. • Hekker, S. • Karoff, C. • Stello, D. • Brogaard, K. • Burke, C. • Caldwell, D. A. • Christiansen, J. L.

Abstract • Context. Accurate fundamental parameters of stars are essential for the asteroseismic analysis of data from the NASA Kepler mission.
Aims: We aim at determining accurate atmospheric parameters and the abundance pattern for a sample of 82 red giants that are targets for the Kepler mission.
Methods: We have used high-resolution, high signal-to-noise spectra from three different spectrographs. We used the iterative spectral synthesis method VWA to derive the fundamental parameters from carefully selected high-quality iron lines. After determination of the fundamental parameters, abundances of 13 elements were measured using equivalent widths of the spectral lines.
Results: We identify discrepancies in log g and [Fe/H], compared to the parameters based on photometric indices in the Kepler Input Catalogue (larger than 2.0 dex for log g and [Fe/H] for individual stars). The T_eff found from spectroscopy and photometry shows good agreement within the uncertainties. We find good agreement between the spectroscopic log g and the log g derived from asteroseismology. Also, we see indications of a potential metallicity effect on the stellar oscillations.
Conclusions: We have determined the fundamental parameters and element abundances of 82 red giants. The large discrepancies between the spectroscopic log g and [Fe/H] and values in the Kepler Input Catalogue emphasize the need for further detailed spectroscopic follow-up of the Kepler targets in order to produce reliable results from the asteroseismic analysis.

Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.Reduced spectra are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/543/A160

Links

• PREPRINT http://arxiv.org/abs/1205.5642
• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/201219237/postscript
• ELECTR https://doi.org/10.1051%2F0004-6361%2F201219237
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2012A%26A...543A.160T
• PDF https://www.aanda.org/10.1051/0004-6361/201219237/pdf
• DATA http://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/543/A160
• DATA https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/543/A160
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2012A%26A...543A.160T
• DATA https://irsa.ipac.caltech.edu/bibdata/2012/T/2012A&A...543A.160T.html