The masses of faint White Dwarfs measured thanks to their orbital acceleration

Barium stars are main-sequence or red-giant stars that accreted heavy-metal-rich material from a former Asymptotic Giant Branch (AGB) companion in a binary system. The orbital properties of Barium stars are important to constrain interaction mechanisms in binary systems with giant stars, and their chemical abundances are tracers of AGB nucleosynthesis processes. These former AGB companions are now dim and, in most cases, not directly detectable white dwarfs. Their masses, however, contain important information about the formation of Barium stars and are a necessary input parameter if we want to use binary evolution or AGB nucleosynthesis models to better understand the history of these systems. The observational constraints concerning the orbital and stellar properties of Barium stars have increased in the past years thanks to long-period binary monitoring programs and to the accurate distances provided by the Gaia mission. However, important uncertainties remained concerning their faint white dwarf companions. In this contribution, I will show that, even though Gaia alone is not good enough to characterize these long-period binaries yet, the proper-motion acceleration measured between Hipparcos and Gaia is a very powerful constraint. By combining radial-velocity data with Hipparcos and Gaia astrometry, we measured the orbital inclinations of about 60 Barium star systems and obtained the absolute masses of their, otherwise hidden, white dwarf companions. Via initial-final mass relationships, we can then get direct information about the AGB stars that polluted Barium stars and learn about AGB nucleosynthesis processes and about the mass-transfer mechanisms at place in evolved binary systems.A paper with these results should get to the ArXiV before the end of the year, and future publications applying the same methodology to more complex targets will be submitted soon. Stay tuned