Gaia DR2 hot Jupiter hosts and contact binaries

In this paper, we search for comoving, very wide companions with separations of 10^3^-10^4^AU for hot Jupiter hosts and main-sequence contact binaries in Gaia DR2, and compare the very wide companion fractions with their object-by-object-matched field star samples. We find that 11.9+/-2.5 per cent of hot Jupiter hosts and 14.1+/-1.0 per cent of contact binaries have companions at separations of 10^3^-10^4^AU.

While the very wide companion fraction of hot Jupiter hosts is a factor of 1.9+/-0.5 larger than their matched field star sample, it is consistent, within ~1{sigma}, with that of matched field stars if the matching is only with field stars without close companions (within ~50AU) as is the case for hot Jupiter hosts. The very wide companion fraction of contact binaries is a factor of 3.1+/-0.5 larger than their matched field star sample, suggesting that the formation and evolution of contact binaries are either tied to or correlated with the presence of wide companions.