Elemental abundance differences in the massive planet-hosting wide binary HD 196067−68

Abstract

ABSTRACT It has been suggested that small chemical anomalies observed in planet-hosting wide binary systems could be due to planet signatures, where the role of the planetary mass is still unknown. We search for a possible planet signature by analysing the TC trends in the remarkable binary system HD 196067–HD 196068. At the moment, only HD 196067 is known to host a planet that is near the brown dwarf regime. We take advantage of the strong physical similarity between both stars, which is crucial to achieving the highest possible precision in stellar parameters and elemental chemical abundances. This system gives us a unique opportunity to explore whether a possible depletion of refractories in a binary system could be inhibited by the presence of a massive planet. We performed a line-by-line chemical differential study, employing the non-solar-scaled opacities, in order to reach the highest precision in the calculations. After differentially comparing both stars, HD 196067 displays a clear deficiency in refractory elements in the TC plane, a lower iron content (0.051 dex), and also a lower Li i content (0.14 dex) than its companion. In addition, the differential abundances reveal a TC trend. These targets represent the first cases of an abundance difference around a binary system hosting a super-Jupiter. Although we explored several scenarios to explain the chemical anomalies, none of them can be entirely ruled out. Additional monitoring of the system as well as studies of larger sample of wide binary systems hosting massive planets are needed to better understand the chemical abundance trend observed in HD 196067−68.