Tidal dissipation and the formation of Kepler near-resonant planets

ASD, IMCCE-CNRS UMR 8028, Observatoire de Paris, UPMC, 77 Av. Denfert-Rochereau, 75014 Paris, France
e-mail: delisle@imcce.fr

Received: 17 May 2014
Accepted: 25 September 2014

Abstract

Multiplanetary systems detected by the Kepler mission present an excess of planets close to first-order mean-motion resonances (2:1 and 3:2), but with a period ratio slightly higher than the resonant value. Several mechanisms have been proposed to explain this observation. Here we provide some clues that indicate that these near-resonant systems were initially in resonance and reached their current configuration through tidal dissipation. It has been argued that this only applies to the close-in systems and not to the farthest ones, for which the tidal effect is too weak. Using the KOI catalog of the Kepler mission, we show that the distributions of the period ratio among the most close-in and the farthest planetary systems differ significantly. This distance-dependent repartition is a strong argument in favor of the tidal dissipation scenario.