Detailed chemical compositions of the wide binary HD 80606/80607: revised stellar properties and constraints on planet formation

TL;DR

This study conducts a high-precision differential elemental abundance analysis of the wide binary HD 80606/80607, revealing very similar compositions and exploring implications for planet formation and stellar surface enrichment.

Contribution

It provides the first high-precision comparison of elemental abundances in this binary, constraining the effects of planet formation on stellar surface compositions.

Findings

HD 80606 is marginally more metal-rich than HD 80607.

No correlation between abundance differences and condensation temperature.

HD 80606 may have accreted 2.5 to 5 Earth masses of material.

Abstract

Differences in the elemental abundances of planet hosting stars in binary systems can give important clues and constraints about planet formation and evolution. In this study we performed a high-precision, differential elemental abundance analysis of a wide binary system, HD 80606/80607, based on high-resolution, high signal-to-noise ratio Keck/HIRES spectra. HD 80606 is known to host a four Jupiter mass giant planet while no planet has yet been detected around HD 80607. We determined stellar parameters as well as abundances for 23 elements for these two stars with extremely high precision. Our main results are: (i) we confirmed that the two components share very similar chemical compositions, but HD 80606 is marginally more metal-rich than HD 80607 with an average difference of +0.013 $\pm$ 0.002 dex ($\sigma$ = 0.009 dex) and (ii) there is no obvious trend between abundance differences and condensation temperature. Assuming this binary formed from material with the same chemical composition, it is difficult to understand how giant planet formation could produce the present-day photospheric abundances of the elements we measure. We can not exclude the possibility that HD 80606 might have accreted about 2.5 to 5 $M_{\rm Earth}$ material onto its surface, possibly from a planet destabilised by the known highly-eccentric giant.