Atmospheric parameters of 82 red giants in the Kepler field

Author(s)

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

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

Teff 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 cdsarc.u-strasbg.fr/viz-bin/qcat

Organisation(s)

Department of Astrophysics

External organisation(s)

Aarhus University, University of Heidelberg, Katholieke Universiteit Leuven, University of Birmingham, University of Amsterdam (UvA), The University of Sydney, University of Victoria, National Aeronautics & Space Administration (NASA)

Journal

Astronomy & Astrophysics

Volume

543

ISSN

0004-6361

DOI

https://doi.org/10.1051/0004-6361/201219237

Publication date

07-2012

Peer reviewed

Yes

Austrian Fields of Science 2012

103004 Astrophysics

Keywords

Portal url

https://ucrisportal.univie.ac.at/en/publications/2339eb3b-570a-441e-b7bd-323fe748c478