A comprehensive study of the relations between the properties of planetary systems and the chemical compositions of their host stars

TL;DR

This study analyzes the chemical compositions of 561 Kepler host stars, revealing how elemental abundances influence planetary system properties and highlighting the role of alpha-elements in planet formation, with implications for understanding stellar and planetary evolution.

Contribution

It provides a detailed analysis of multiple elemental abundances in exoplanet host stars, linking stellar chemistry to planetary system characteristics and expanding knowledge beyond iron-centric metallicity.

Findings

Stars with only large or hot planets are enriched in certain elements.

Alpha-element enhancement may aid large planet formation in metal-poor stars.

The Sun shows refractory element depletion unrelated to planet formation.

Abstract

The giant planet-metallicity correlation revealed that planetary formation depends on the stellar properties. There is growing evidence that it is also valid for smaller hot planets, but it is not clear whether elements other than iron also influence the properties of planetary systems. To investigate this, we determined the abundances of 13 chemical elements (Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni and Cu) for a sample of 561 Kepler exoplanet-hosting stars using high-resolution Keck/HIRES spectra. We find that stars in systems having only large or hot planets are enriched in some elements relative to those having only small or warm planets, respectively, with this signature being related to the underlying stellar metallicity. This Kepler sample is composed of stars belonging to the Galactic low- and high-$\alpha$ sequences, corresponding to the chemical thin and thick disks. Our results reveal that stars enhanced in $\alpha$-elements may facilitate the formation of large planets in metal-poor environments although the iron abundance is still a limiting factor. We also investigated chemical abundances as a function of elemental condensation temperatures and found that there is a diversity of slopes regardless of the exoplanetary systems hosted by the star. We confirmed that the Sun is depleted in refractory elements relative to the solar twins in our sample, all of which host a diversity of exoplanets, suggesting that this depletion is caused by processes not related to planet formation.