Presentation #107.11 in the session “Asynchronous Posters”.
Analysis of the orbital periods of planet-pairs in Kepler and RV multi-planet systems has demonstrated that the period-ratios of resonant planets are slightly off the exact commensurability. Many studies have tried to account for this resonant offset by placing the two planets in an exact resonance and introducing a secondary mechanism that would deviate their period-ratio from perfect commensurability. The latter prompted us to examine the validity of this mechanism by determining the period-ratios of planets after they are naturally captured in a resonance. We simulated the migration and subsequent resonance-capture of a large battery of two-planet systems and calculated their period-ratios for different values of the planets’ masses, strength of dissipative forces, and rate of migration. Results indicated that capture always occurs at a near commensurability and is never exact. The extent of the departure from perfect resonance depends on the planets’ mass-ratio and rate of their migration. Our study demonstrates that the observed deviation from perfect commensurability is a natural occurrence and does not require a secondary process. We present the details of our study and discuss their implications for the formation and orbital architecture of resonant, multi-planet systems.