Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes

TL;DR

This paper provides a high-precision catalog of stellar parameters for 451 stars from the HARPS GTO sample, analyzing their metallicity and its relation to the occurrence of exo-Neptunes, and offering calibration tools for stellar temperature.

Contribution

It presents a new, accurate spectroscopic stellar parameter catalog for 451 stars, including a calibration for effective temperature based on color and metallicity, and investigates the metallicity-planet correlation.

Findings

Neptune-like planets do not prefer metal-rich stars.

The ratio of Jupiter to Neptunes increases with stellar metallicity.

Results support the core-accretion model of planet formation.

Abstract

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 (S/N) 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 B-V 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.