Gaia Barium Dwarfs and Their Ostensibly Ordinary Counterparts

Abstract The recently identified Gaia population of main-sequence–white dwarf (MS+WD) binaries at separations of ∼1 au, often with moderate eccentricities, is not readily reproduced by binary population synthesis models. Barium (Ba) stars represent a closely related population whose enrichment in s -process elements both confirms the presence of a WD companion and attests to past binary interaction. It also indicates that mass transfer occurred at least during the late- and post–asymptotic giant branch (AGB) phases of the WD progenitor, when s -process elements are dredged up. In this work, we further explore the connection between the astrometrically identified Gaia MS+WD binaries and the classical Ba star…