Tidal Resonance of Kepler Exoplanets

ARE THE KEPLER NEAR-RESONANCE PLANET PAIRS DUE TO TIDAL DISSIPATION?

Authors:

1. Man Hoi Lee (a)
2. D. Fabrycky (b,c,e)
3. D. N. C. Lin (c,d)

Affiliations:

a. Department of Earth Sciences and Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong

b. Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637, USA

c. UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USA

d. Kavli Institute for Astronomy and Astrophysics and School of Physics, Peking University, China

e. Hubble Fellow.

Abstract:

The multiple-planet systems discovered by the Kepler mission show an excess of planet pairs with period ratios just wide of exact commensurability for first-order resonances like 2:1 and 3:2. In principle, these planet pairs could have both resonance angles associated with the resonance librating if the orbital eccentricities are sufficiently small, because the width of first-order resonances diverges in the limit of vanishingly small eccentricity. We consider a widely held scenario in which pairs of planets were captured into first-order resonances by migration due to planet-disk interactions, and subsequently became detached from the resonances, due to tidal dissipation in the planets. In the context of this scenario, we find a constraint on the ratio of the planet's tidal dissipation function and Love number that implies that some of the Kepler planets are likely solid. However, tides are not strong enough to move many of the planet pairs to the observed separations, suggesting that additional dissipative processes are at play.