Orbital Geometries of Exoplanet-Hosting Multi-Star Systems

The orbital geometries of exoplanets in multi-star systems offer a fossilized record of the systems’ dynamical histories. For many such systems, a combination of precise astrometric and radial velocity constraints has recently enabled joint orbital and spin-orbit constraints, offering new insights into the key mechanisms driving planetary systems’ dynamical evolution. We combine the archival set of stellar obliquity measurements with astrometric constraints from Gaia DR3 to examine the joint spin-orbit and orbit-orbit distributions of exoplanets in wide binary- and triple-star systems. We recover no clear correlation between spin-orbit and orbit-orbit misalignment within the observed sample of systems. We do, however, unveil an intriguing overabundance of fully aligned systems that are both spin-orbit and orbit-orbit aligned. We conclude by examining the conditions under which a joint spin-orbit and orbit-orbit alignment may result from tidal dissipation in the protoplanetary disk stage.