Abundances of Stars with Planets: Trends with Condensation Temperature

TL;DR

This study measures precise elemental abundances in stars with planets, revealing correlations with condensation temperature that suggest planetary material accretion and potential signatures of planet formation, influenced by Galactic chemical evolution.

Contribution

It provides detailed abundance measurements for ten planet-hosting stars and analyzes their trends with condensation temperature, highlighting possible planet formation signatures.

Findings

Stars with positive slopes have close-in giant planets.

Refractory element trends vary among stars, indicating different accretion histories.

Galactic chemical evolution may influence observed abundance patterns.

Abstract

Precise abundances of 18 elements have been derived for ten stars known to host giant planets from high signal-to-noise ratio, high-resolution echelle spectroscopy. Internal uncertainties in the derived abundances are typically <=0.05 dex. The stars in our sample have all been previously shown to have abundances that correlate with the condensation temperature (T_c) of the elements in the sense of increasing abundances with increasing T_c; these trends have been interpreted as evidence that the stars may have accreted H-depleted planetary material. Our newly derived abundances also correlate positively with T_c, although slopes of linear least-square fits to the [m/H]-T_c relations for all but two stars are smaller here than in previous studies. When considering the refractory elements (T_c > 900 K) only, which may be more sensitive to planet formation processes, the sample can be separated into a group with positive slopes (four stars) and a group with flat or negative slopes (six stars). The four stars with positive slopes have very close-in giant planets (three at 0.05 AU) and slopes that fall above the general Galactic chemical evolution trend. We suggest that these stars have accreted refractory-rich planet material but not to the extent that would increase significantly the overall stellar metallicity. The flat or negative slopes of the remaining six stars are consistent with recent suggestions of a planet formation signature, although we show that the trends may be the result of Galactic chemical evolution.