Polar alignment of a protoplanetary disc around an eccentric binary II: Effect of binary and disc parameters

TL;DR

This study investigates how a low-mass circumbinary disc can align perpendicularly to an eccentric binary's orbit through hydrodynamic simulations, considering various system parameters and comparing with linear theory predictions.

Contribution

It demonstrates that polar alignment of low-mass discs is robust across a wide range of binary and disc parameters, extending previous findings.

Findings

Polar alignment occurs over a broad parameter space.

Alignment depends on viscosity, temperature, and binary eccentricity.

Results align with linear theory predictions.

Abstract

In a recent paper Martin & Lubow showed that a circumbinary disc around an eccentric binary can undergo damped nodal oscillations that lead to the polar (perpendicular) alignment of the disc relative to the binary orbit. The disc angular momentum vector aligns to the eccentricity vector of the binary. We explore the robustness of this mechanism for a low mass disc (0.001 of the binary mass) and its dependence on system parameters by means of hydrodynamic disc simulations. We describe how the evolution depends upon the disc viscosity, temperature, size, binary mass ratio, orbital eccentricity and inclination. We compare results with predictions of linear theory. We show that polar alignment of a low mass disc may occur over a wide range of binary-disc parameters. We discuss the application of our results to the formation of planetary systems around eccentric binary stars.