Disruption of Planetary Orbits Through Evection Resonance with an External Companion: Circumbinary Planets and Multiplanet Systems

TL;DR

This paper develops an analytic theory to understand how evection resonance can excite planetary eccentricities or cause disruptions in circumbinary and multiplanet systems due to external stellar companions.

Contribution

It provides the first comprehensive analytic framework for predicting resonance effects on planetary systems influenced by distant companions.

Findings

Inward migration can lead to eccentricity growth via evection resonance.

Planets around shrinking binaries may not survive due to resonant eccentricity excitation.

Significant eccentricity excitation requires specific parameter conditions and slow planetary migration.

Abstract

Planets around binary stars and those in multiplanet systems may experience resonant eccentricity excitation and disruption due to perturbations from a distant stellar companion. This "evection resonance" occurs when the apsidal precession frequency of the planet, driven by the quadrupole associated with the inner binary or the other planets, matches the orbital frequency of the external companion. We develop an analytic theory to study the effects of evection resonance on circumbinary planets and multiplanet systems. We derive the general conditions for effective eccentricity excitation or resonance capture of the planet as the system undergoes long-term evolution. Applying to circumbinary planets, we show that inward planet migration may lead to eccentricity growth due to evection resonance with an external perturber, and planets around shrinking binaries may not survive the resonant eccentricity growth. On the other hand, significant eccentricity excitation in multiplanet systems occurs in limited parameter space of planet and binary semimajor axes, and requires the planetary migration to be sufficiently slow.