Equilibria in the secular, non-coplanar two-planet problem

TL;DR

This paper studies the long-term behavior of a star with two inclined planets, identifying new stable configurations and classifying solutions based on angular momentum, with applications to various three-body systems.

Contribution

It introduces new equilibria in the secular dynamics of inclined two-planet systems and provides a comprehensive classification of these solutions.

Findings

Identified new stable equilibria in inclined two-planet systems.

Classified families of solutions based on angular momentum.

Applied results to the HD 12661 planetary system.

Abstract

We investigate the secular dynamics of a planetary system composed of the parent star and two massive planets in mutually inclined orbits. The dynamics are investigated in wide ranges of semi-major axes ratios (0.1-0.667), and planetary masses ratios (0.25-2) as well as in the whole permitted ranges of the energy and total angular momentum. The secular model is constructed by semi-analytic averaging of the three-body system. We focus on equilibria of the secular Hamiltonian (periodic solutions of the full system), and we analyze their stability. We attempt to classify families of these solutions in terms of the angular momentum integral. We identified new equilibria, yet unknown in the literature. Our results are general and may be applied to a wide class of three-body systems, including configurations with a star and brown dwarfs and sub-stellar objects. We also describe some technical aspects of the semi-numerical averaging. The HD 12661 planetary system is investigated as an example configuration.