Stellar [Fe/H] and the frequency of exo-Neptunes
Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal e-mail: firstname.lastname@example.org
2 Departamento de Matemática Aplicada, Faculdade de Ciências da Universidade do Porto, Portugal
3 Observatoire de Genève, 51 Ch. des Mailletes, 1290 Sauverny, Switzerland
4 University of Turku – Tuorla Astronomical Observatory, Väisäläntie 20, 21500 Piikkiö, Finland
5 Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
Accepted: 30 April 2008
To understand the formation and evolution of solar-type stars in the solar neighborhood, we need to measure their stellar parameters to high accuracy. We present a catalogue of accurate stellar parameters for 451 stars that represent the HARPS Guaranteed Time Observations (GTO) “high precision” sample. Spectroscopic stellar parameters were measured using high signal-to-noise () spectra acquired with the HARPS spectrograph. The spectroscopic analysis was completed assuming LTE with a grid of Kurucz atmosphere models and the recent ARES code for measuring line equivalent widths. We show that our results agree well with those ones presented in the literature (for stars in common). We present a useful calibration for the effective temperature as a function of the index color and [Fe/H]. We use our results to study the metallicity-planet correlation, namely for very low mass planets. The results presented here suggest that in contrast to their jovian couterparts, neptune-like planets do not form preferentially around metal-rich stars. The ratio of jupiter-to-neptunes is also an increasing function of stellar metallicity. These results are discussed in the context of the core-accretion model for planet formation.
Key words: methods: data analysis / techniques: spectroscopic / stars: fundamental parameters / stars: planetary systems / stars: planetary systems: formation / Galaxy: solar neighborhood
Based on observations collected at La Silla Observatory, ESO, Chile, with the HARPS spectrograph at the 3.6-m telescope (072.C-0488(E)).
© ESO, 2008