The Evolution of Planet-Disk Systems That Are Mildly Inclined to the Orbit of a Binary Companion

TL;DR

This study investigates how giant planets and their protoplanetary disks evolve in binary star systems, revealing that mutual inclinations oscillate and tend to align over time due to secular effects and gas accretion.

Contribution

The paper combines analytic methods and hydrodynamic simulations to analyze the evolution of inclined planet-disk systems in binaries, highlighting the roles of secular resonance and disk mass.

Findings

Planet-disk systems generally do not remain coplanar unless the disk is very massive.

Secular oscillations cause the relative tilt to vary, with amplitudes linked to initial disk inclination.

Gas accretion onto the planet tends to realign the orbit with the disk over time.

Abstract

We determine the evolution of a giant planet-disk system that orbits a member of a binary star system and is mildly inclined with respect to the binary orbital plane. The planet orbit and disk are initially mutually coplanar. We analyze the evolution of the planet and the disk by analytic means and hydrodynamic simulations. We generally find that the planet and the disk do not remain coplanar unless the disk mass is very large or the gap that separates the planet from the disk is very small. The relative planet-disk tilt undergoes secular oscillations whose initial amplitudes are typically of order the initial disk tilt relative to the binary orbital plane for disk masses ~1% of the binary mass or less. The effects of a secular resonance and the disk tilt decay enhance the planet-disk misalignment. The secular resonance plays an important role for disk masses greater than the planet mass. At later times, the accretion of disk gas by the planet causes its orbit to evolve towards alignment, if the disk mass is sufficiently large. The results have several implications for the evolution of massive planets in binary systems.