Is there a metallicity enhancement in planet hosting red giants?

TL;DR

This study investigates whether red giant stars hosting planets show metallicity enhancements similar to dwarf stars, using high-precision radial velocity data and spectral analysis to compare metallicities between RV-variable and RV-stable giants.

Contribution

It provides the first spectral metallicity analysis of a large sample of evolved giant stars in a planet search survey, comparing RV-variable and RV-stable stars.

Findings

RV-variable giants tend to have higher metallicities.

Metallicity dependence similar to that of dwarf stars is suggested.

Preliminary results support the planet-metallicity correlation in giants.

Abstract

The Penn State/Toru\'n Centre for Astronomy Search for Planets Around Evolved Stars is a high-precision radial velocity (RV) survey aiming at planets detection around giant stars. It is based on observations obtained with the 9.2 m Hobby-Eberly Telescope. As proper interpretation of high precision RV data for red giants requires complete spectral analysis of targets we perform spectral modeling of all stars included in the survey. Typically, rotation velocities and metallicities are determined in addition to stellar luminosities and temperatures what allows us to estimate stellar ages and masses. Here we present preliminary results of metallicity studies in our sample. We search a metallicity dependence similar to that for dwarfs by comparing our results for a sample of 22 giants earlier than K5 showing significant RV variations with a control sample of 58 relatively RV-stable stars.