Secular Evolution of Planetary Systems in Binaries

TL;DR

This paper explores how the Kozai mechanism influences the long-term evolution of double-planet systems in binary star systems, revealing complex dynamical behaviors including synchronized eccentricity oscillations and orbital precession.

Contribution

It extends the understanding of secular planetary evolution by analyzing the effects of binary companions on multi-planet systems, highlighting phenomena like rigid orbital rotation.

Findings

Outer planet propagates perturbations to inner planet

Orbital eccentricities oscillate synchronously

Outer planet precesses faster than Kozai prediction

Abstract

The orbital eccentricity of a single planet around a component of a stellar binary system with a sufficiently large mutual inclination angle is known to oscillate on a secular timescale through the Kozai mechanism. We have investigated the effects of the Kozai mechanism on double-planet systems in binaries. The evolutionary sequence of a pair of planets under the influence of a binary companion is fairly complex. Various dynamical outcomes are seen in numerical simulations. One interesting outcome is the rigid rotation of the planetary orbits in which the planetary orbital planes secularly precess in concert, while the orbital eccentricities oscillate synchronously. In such cases the outer planet acts as a propagator of the perturbation from the binary companion to the inner planet and drives the inner planetary orbit to precess at a rate faster than what is predicted by the Kozai mechanism.