A Survey of Disc Thickness and Viscosity in Circumbinary Accretion: Binary Evolution, Variability, and Disc Morphology

Understand

Much of the parameter space relevant to the evolution of astrophysical circumbinary accretion discs remains unexplored.

• We have carried out a suite of circumbinary disc simulations surveying both disc thickness and kinematic viscosity, using both constant-$\nu$ and constant-$\alpha$ prescriptions.
• We focus primarily on disc aspect ratios between $0.1$ and $0.033$, and on viscosities between $\nu=0.0005$ and $\nu=0.008$ (in units of binary semi-major axis and orbital frequency), and specialise to circular equal-mass binaries.
• Both factors strongly influence the evolution of the binary semi-major axis: at $\nu=0.0005,$ inspirals occur at aspect ratios $\lesssim0.059$, while at $\nu=0.004$ inspirals occur only at aspect ratios $\lesssim0.04$.