ESA-Gaia Multiplicity Study of Exoplanet Host Stars

The latest results of a survey are presented, which explores the data releases of the ESA-Gaia mission, in order to study the multiplicity of exoplanet host stars, located at distances closer than about 625 pc around the Sun. In total, 280 binaries, 27 hierarchical triples, and one quadruple stellar systems are detected among 1898 exoplanet host stars, whose multiplicity is investigated, yielding a multiplicity rate of at least 16%. The equidistance and the common proper motion of all detected companions and their exoplanet host stars are proven with their accurate Gaia astrometry. Companions with masses in the range between about 0.015 and 1.7 Msun are detected, which exhibit projected separations to the exoplanet host stars between about 30 and 10000 au. Beside many low-mass main sequence stars also 14 brown dwarfs are identified as companions of exoplanet host stars. In addition, 15 white dwarf companions are detected, whose true nature is revealed by their photometric properties. These degenerated companions and the exoplanet host stars form evolved stellar systems with exoplanets, which have survived (physically but also dynamically) the post main sequence evolution of the former primary stars in these systems.