2016MNRAS.459.1682F

We report the discovery of a tertiary component to the prominent and nearby (d=14 pc) visual binary α Fornacis. The new invisible component is part of a 4-d short-period Ba-Bb subsystem, whose K-type α For Ba primary shows a striking [Ba/Fe]=+0.26 dex overabundance, at variance with a close to solar [Ba/Fe]=+0.04 dex abundance for its distant visual companion α For A. For the even nearer (d=8 pc) multiple star ξ Ursae Majoris and its alike 4-d Ba-Bb subsystem, we similarly find [Ba/Fe]=+0.37 dex for its G-type ξ UMa Ba primary, compared to a significantly lower [Ba/Fe]=+0.12 dex for the visual companion ξ UMa A. In both cases, the differential barium enrichment is direct evidence for short-period white dwarf systems and the creation of blue straggler stars through mass transfer and wind accretion, for their close and distant companions, respectively. These findings also imply that conventional stellar age datings for both α For and ξ UMa are likely not reliable.