Spectral analysis of Kepler SPB and β Cephei candidate stars^⋆

¹ Thüringer Landessternwarte Tautenburg, 07778 Tautenburg, Germany
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² GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
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³ Instituto de Astrofísica de Andalucía (CSIC), Apartado 3004, 18080 Granada, Spain
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⁴ Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
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⁵ Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Belgium
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⁶ Georg-August-University, Göttingen, Germany
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⁷ Tavrian National University, Department of Astronomy, Simferopol, Ukraine
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⁸ Royal Observatory of Belgium
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Received: 16 September 2010
Accepted: 11 November 2010

Abstract

Context. For asteroseismic modelling, analysis of the high-accuracy light curves delivered by the Kepler satellite mission needs support by ground-based, multi-colour and spectroscopic observations.

Aims. We determine the fundamental parameters of SPB and β Cep candidate stars observed by the Kepler satellite mission and estimate the expected types of non-radial pulsators.

Methods. We compared newly obtained high-resolution spectra with synthetic spectra computed on a grid of stellar parameters assuming LTE, and checked for NLTE effects for the hottest stars. For comparison, we determined T_eff independently from fitting the spectral energy distribution of the stars obtained from the available photometry.

Results. We determine T_eff, log g, microturbulent velocity, vsini, metallicity, and elemental abundance for 14 of the 16 candidate stars. Two stars are spectroscopic binaries. No significant influence of NLTE effects on the results could be found. For hot stars, we find systematic deviations in the determined effective temperatures from those given in the Kepler Input Catalogue. The deviations are confirmed by the results obtained from ground-based photometry. Five stars show reduced metallicity, two stars are He-strong, one is He-weak, and one is Si-strong. Two of the stars could be β Cep/SPB hybrid pulsators, four SPB pulsators, and five more stars are located close to the borders of the SPB instability region.