Presentation #309.04 in the session “Exoplanets and Systems: Orbital Dynamics 2”.
The K2-138 system consists of six planets, five of which have been suggested to be in a chain of 3:2 mean motion resonances since the planet pairs’ period ratios are all near 1.5, but such no study has as of yet studied the dynamics of the system. To confirm the existence of this chain and to take advantage of the mutual gravitational perturbations, we photodynamically fit the system using PhoDyMM. We find that the orbital parameters and planetary masses are consistent with previous studies, suggesting that four of the five planets require 1-2% H/He envelopes to satisfy their densities. We integrate forward numerous solutions from the resulting posteriors to confirm and characterize the resonant chain. By running N-body simulations via rebound, we also find that this system and its resonant chain are consistent with in situ formation.