HIRES radial velocity follow up for Kepler-1656

The system is consistent with an in situ dynamical origin of planet b followed by subsequent eccentric Kozai-Lidov perturbations that excite Kepler-1656b's eccentricity gently, i.e., without initiating tidal migration. Thus, despite its high eccentricity, we find no evidence that planet b is or has migrated through the high-eccentricity channel. Finally, we predict the outer orbit to be mutually inclined in a nearly perpendicular configuration with respect to the inner planet orbit based on the outcomes of our simulations and make observable predictions for the inner planet's spin-orbit angle.

Our methodology can be applied to other eccentric or tidally locked planets to constrain their origins, orbital configurations, and properties of a potential companion.