Beyond the Iron Peak: r- and s-process Elemental Abundances in Stars with Planets

TL;DR

This study analyzes heavy element abundances in stars with planets, revealing chemical differences from non-host stars that are consistent with galactic chemical evolution, supporting a primordial origin of planetary host star traits.

Contribution

It provides one of the first detailed comparisons of neutron-capture element abundances in planetary host stars versus non-host stars, emphasizing primordial origins.

Findings

Host stars show higher heavy element abundances than non-host stars.

Abundance differences are consistent with galactic chemical evolution.

Chemical traits are primordial, not due to pollution during star or planet formation.

Abstract

We present elemental abundances of 118 stars (28 of which are known extrasolar planetary host stars) observed as part of the Anglo-Australian Planet Search. Abundances of O, Mg, Cr, Y, Zr, Ba, Nd and Eu (along with previously published abundances for C and Si) are presented. This study is one of the first to specifically examine planetary host stars for the heavy elements produced by neutron capture reactions. We find that the host stars are chemically different to both the standard solar abundance and non-host stars in all elements studied, with enrichments over non-host stars ranging from 0.06 dex (for O) to 0.11 dex (for Cr and Y). Such abundance trends are in agreement with other previous studies of field stars and lead us to conclude that the chemical anomalies observed in planetary host stars are the result of normal galactic chemical evolution processes. Based on this observation, we conclude that the observed chemical traits of planetary host stars are primordial in origin, coming from the original nebula and not from a ``pollution'' process occurring during or after formation and that planet formation occurs naturally with the evolution of stellar material.