On The Secular Evolution of GG Tau A Circumbinary Disc: A Msialigned Disc Scenario

TL;DR

This paper proposes that the circumbinary disc around GG Tau A is misaligned and eccentric, explaining the observed large cavity and demonstrating through simulations that this configuration is stable over the system's lifetime.

Contribution

It introduces a misaligned, eccentric binary model for GG Tau A's disc and confirms its stability via secular evolution analysis.

Findings

A misaligned, eccentric binary fits the observed disc cavity.

SPH simulations support the stability of the misaligned configuration.

The system remains stable throughout the disc's lifetime.

Abstract

The binary system GG Tau A is observed to have a circumbinary disc with a dust ring located further out than expected, assuming a co-planar disc and a corresponding semi-major axis of 34 AU. Given the binary separation, this large cavity can be explained by relaxing the assumption of a co-planar disc and instead fit the observations with a mis-aligned circumbinary disc around an eccentric binary with a wider semi-major axis of 60 AU, consistent with fitting the proper motion data for the system. We run SPH simulations to check this possibility and indeed we find that a misalignment angle of 30 degrees and a binary eccentricity of 0.45 fit both the astrometric data and the disc cavity. However, such configuration could in principle be unstable to polar, rather that planar alignment. We investigate the secular evolution of this configuration and show that it is indeed stable throughout the disc lifetime.