Confirming the Metal-Rich Nature of Stars with Giant Planets

TL;DR

This study confirms that stars with giant planets tend to be more metal-rich than stars without planets, highlighting metallicity as a key factor in giant planet formation and suggesting possible accretion effects.

Contribution

It provides a high-precision spectroscopic comparison between stars with and without planets, confirming the metallicity excess in planet-hosting stars using an unbiased sample.

Findings

Stars with giant planets are more metal-rich.

Metallicity influences giant planet formation.

Evidence suggests possible matter accretion in stellar outer zones.

Abstract

With the goal of confirming the metallicity ``excess'' observed in stars with planetary mass companions, we have conducted a high-precision spectroscopic study of a ``comparison'' sample of dwarfs included in the CORALIE extra-solar planet survey (Santos, Israelian, & Mayor 2001). The targets were chosen following two basic criteria: they make part of a limited volume and they do not present the signature of a planetary host companion. The spectroscopic analysis, done using the very same technique as previous works on the metallicity of stars with planets, permitted a direct and non-biased comparison of the samples. The results have revealed that metallicity plays an impressive role on the giant planet formation. The chemical composition of the molecular cloud is probably the key parameter to form giant planets. Some evidences exist, however, showing the possibility of accretion of matter in the stellar outer convective zone. These conclusions impose serious constraints on the planetary systems formation and evolution models.