A homogeneous spectroscopic analysis of host stars of transiting planets ^*,**,***

¹ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
² Centro de Astronomia e Astrofísica da Universidade de Lisboa, Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal
³ Departamento de Matemática Aplicada, Faculdade de Ciências da Universidade do Porto, Portugal
⁴ Centro de Física Computacional, Universidade de Coimbra, Coimbra, Portugal
⁵ Observatório Astronómico e Departamento de Matemática, Universidade de Coimbra, Coimbra, Portugal
⁶ Observatoire de la Côte d'Azur, Laboratoire Cassiopée, CNRS UMR 6202, BP 4229, 06304 Nice Cedex 4, France
⁷ Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
⁸ Observatoire de Genève, Université de Genève, 51 Ch. des Mailletes, 1290 Sauverny, Switzerland
⁹ European Southern Observatory, Casilla 19001, Santiago 19, Chile

Received: 21 April 2009
Accepted: 1 August 2009

Abstract

Context. The analysis of transiting extra-solar planets provides an enormous amount of information about the formation and evolution of planetary systems. A precise knowledge of the host stars is necessary to derive the planetary properties accurately. The properties of the host stars, especially their chemical composition, are also of interest in their own right.

Aims. Information about planet formation is inferred by, among others, correlations between different parameters such as the orbital period and the metallicity of the host stars. The stellar properties studied should be derived as homogeneously as possible. The present work provides new, uniformly derived parameters for 13 host stars of transiting planets.

Methods. Effective temperature, surface gravity, microturbulence parameter, and iron abundance were derived from spectra of both high signal-to-noise ratio and high resolution by assuming iron excitation and ionization equilibria.

Results. For some stars, the new parameters differ from previous determinations, which is indicative of changes in the planetary radii. A systematic offset in the abundance scale with respect to previous assessments is found for the TrES and HAT objects. Our abundance measurements are remarkably robust in terms of the uncertainties in surface gravities. The iron abundances measured in the present work are supplemented by all previous determinations using the same analysis technique. The distribution of iron abundance then agrees well with the known metal-rich distribution of planet host stars. To facilitate future studies, the spectroscopic results of the current work are supplemented by the findings for other host stars of transiting planets, for a total dataset of 50 objects.