Carbon and Oxygen in Nearby Stars: Keys to Protoplanetary Disk Chemistry

TL;DR

This study provides a large catalog of carbon and oxygen abundances in nearby stars, revealing their relation to planet formation and identifying potential carbon-rich exoplanet hosts, with implications for disk chemistry and stellar populations.

Contribution

It offers the largest dataset of stellar C and O abundances, self-consistently measures C/O ratios, and identifies stars with potential carbon-dominated planets, advancing understanding of protoplanetary disk chemistry.

Findings

Planet-hosting stars are enriched in C and O.

Identified 46 stars with C/O ≥ 1.00 as potential carbon planet hosts.

Measured sub-solar C/O ratio in WASP-12, challenging previous assumptions.

Abstract

We present carbon and oxygen abundances for 941 FGK stars-the largest such catalog to date. We find that planet-bearing systems are enriched in these elements. We self-consistently measure C/O, which is thought to play a key role in planet formation. We identify 46 stars with C/O \geq 1.00 as potential hosts of carbon-dominated exoplanets. We measure a downward trend in [O/Fe] versus [Fe/H] and find distinct trends in the thin and thick disks, supporting the work of Bensby et al. Finally, we measure sub-solar C/O = 0.40+0.11 - 0.07, for WASP-12, a surprising result as this star is host to a transiting hot Jupiter whose dayside atmosphere was recently reported to have C/O \geq 1 by Madhusudhan et al. Our measurements are based on 15,000 high signal-to-noise spectra taken with the Keck 1 telescope as part of the California Planet Search. We derive abundances from the [O I] and C I absorption lines at {\lambda} = 6300 and 6587 {\AA} using the SME spectral synthesizer.