Tidal dissipation and the formation of Kepler near-resonant planets

TL;DR

This paper suggests that tidal dissipation played a key role in shaping the near-resonant configurations of Kepler multi-planet systems, especially for close-in planets, explaining their period ratios.

Contribution

It provides evidence that tidal dissipation can account for the near-resonant period ratios observed, especially highlighting the distance-dependent effects.

Findings

Close-in systems show different period ratio distributions than distant ones.

Tidal dissipation effects are stronger for close-in planets.

Distance-dependent distribution supports tidal dissipation as a formation mechanism.

Abstract

Multi-planetary 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 these near-resonant systems were initially in resonance and reached their current configuration through tidal dissipation. The argument that has been opposed to this scenario is that it only applies to the close-in systems and not to the farthest ones for which the tidal effect is too weak. Using the catalog of KOI of the Kepler mission, we show that the distributions of period ratio among the most close-in planetary systems and the farthest ones differ significantly. This distance dependent repartition is a strong argument in favor of the tidal dissipation scenario.