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

Differences in the elemental abundances of planethosting stars in binary systemscan give important clues and constraints about planetformation 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 planetwhile no planethas yet been detected around HD 80607. We determined stellar parameters as well as abundancesfor 23 elementsfor 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 formedfrom material with the same chemical composition, it is difficult to understand how giant planetformation could produce the present-day photospheric abundancesof the elementswe measure. We can not exclude the possibility that HD 80606 might have accreted about 2.5 to 5 $M_{\rm Earth}$ materialonto its surface, possibly from a planet destabilisedby the known highly-eccentric giant.