Spin-Orbit Misalignments as a Tracer of Planet Migration

Over two decades after the discovery of the first hot Jupiters, it is still unclear which mechanism(s) cause the planets to migrate to the short-period orbits where we observe them today. A key tracer of these processes is the spin-orbit misalignment, the angle between the stellar spin and planetary orbital angular momentum vectors; different migration mechanisms predict different distributions of spin-orbit misalignments. Spin-orbit misalignments are typically measured through the Rossiter-McLaughlin effect or Doppler tomography, and several dozen hot Jupiters now have such measurements in the literature. This is a sufficient sample to begin to distinguish among the different migration pathways. I will present initial results of a comprehensive statistical analysis of the spin-orbit misalignments of hot Jupiters. I concentrate on those around hot (Teff>6250 K) stars, which are expected to have experienced minimal tidal damping, and so should still maintain their primordial spin-orbit misalignment distribution. This project includes new Doppler tomographic spin-orbit misalignment measurements to expand the sample, and a new survey to identify stellar companions to these stars which could have driven dynamical migration.

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