Carbon abundance of stars in the LAMOST-Kepler field

TL;DR

This study investigates the relationship between stellar carbon abundance and exoplanet occurrence in the Kepler field, revealing correlations with metallicity and potential influences of Galactic chemical evolution.

Contribution

It provides the first large-scale analysis of carbon abundances in Kepler stars and their connection to planet hosting, using LAMOST spectral data.

Findings

GCE-consistent trend of [C/H] with metallicity

Higher [C/H] among giant planet hosts

Preference for giant planets around stars with sub-solar [C/Fe] and higher [Fe/H]

Abstract

The correlation between host star iron abundance and the exoplanet occurrence rate is well-established and arrived at in several studies. Similar correlations may be present for the most abundant elements, such as carbon and oxygen, which also control the dust chemistry of the protoplanetary disk. In this paper, using a large number of stars in the Kepler field observed by the LAMOST survey, it has been possible to estimate the planet occurrence rate with respect to the host star carbon abundance. Carbon abundances are derived using synthetic spectra fit of the CH G-band region in the LAMOST spectra. The carbon abundance trend with metallicity is consistent with the previous studies and follows the Galactic chemical evolution (GCE). Similar to [Fe/H], we find that the [C/H] values are higher among giant planet hosts. The trend between [C/Fe] and [Fe/H] in planet hosts and single stars is similar; however, there is a preference for giant planets around host stars with a sub-solar [C/Fe] ratio and higher [Fe/H]. Higher metallicity and sub-solar [C/Fe] values are found among younger stars as a result of GCE. Hence, based on the current sample, it is difficult to interpret the results as a consequence of GCE or due to planet formation.