A homogeneous spectroscopic analysis of host stars of transiting planets

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.

Transiting exoplanets from the CoRoT space mission

“…In a larger study, Ammler-von Eiff et al (2009) included a consistent re-observation and analysis of 13 transiting hosts, as well as a re-analysis of about 40 other objects (including and CoRoT4b), come to similar conclusions as Santos et al (2004), i.e., that the presence of planets is a strongly rising function of metallicity. We note, however, that even in the data of Ammler-von Eiff et al (2009), about 20% of the stars are under-abundant. As pointed out by these authors, there is probably a difference in planetary structure that depends on the metallicity of the star and reflects different formation mechanisms.…”

Transiting exoplanets from the CoRoT space mission

“…We have discussed the consequences of this characterization and we presented evidence that this particular target provides important information about the knowledge of the interactions between the structure of stars, the formation of planets, and their joint evolution (Ikoma et al 2006;Ammler-von Eiff et al 2009;Meléndez et al 2009a;Nordlund 2009;Ramírez et al 2009;Lanza 2010).…”

SWEET-Cat: A catalogue of parameters for Stars With ExoplanETs

“…As before, most of these parameters have already been published in dedicated papers (e.g. Santos et al 2006;Ammler-von Eiff et al 2009, see also Mortier et al, in prep. ) or in planet discovery papers where the spectroscopic analysis was done by our team (see Santerne et al 2012, for a recent example).…”