Gaia search for (sub)stellar companions of exoplanet hosts

Abstract

ABSTRACT We conduct a survey, which explores the data releases of the European Space Agency (ESA)–Gaia mission, in order to investigate the multiplicity of exoplanet hosts at distances of less than 625 pc around the Sun. With the accurate Gaia astrometry we are able to detect stellar and substellar companions of exoplanet hosts by proving the equidistance and common proper motion of these objects. Furthermore, by using the astro- and photometric data provided by the ESA–Gaia mission, we characterize the nature of the identified companions (substellar, stellar, main-sequence, or evolved), determine their properties (mass, effective temperature, and projected separation to the associated exoplanet host), and verify their orbital stability. In addition to main-sequence stars, the companions detected in this study include several brown and white dwarfs. So far in the course of our survey, the multiplicity of more than 2200 exoplanet hosts could be investigated, yielding a multiplicity rate of about 16 per cent (increased to about 19 per cent including published detections from other surveys). Finally, the derived physical properties of the companions were used to investigate the impact of the stellar multiplicity on the properties of the exoplanets and their hosts. In general, there are significant differences in the properties of these objects, dependent on the multiplicity status of their host system, e.g. higher masses of both planets and exoplanet hosts in multiple star systems. Furthermore, the masses and orbital eccentricities of multiple star planets significantly depend on the gravitational impact, induced by the companion star of the exoplanet host.