Viscous circumbinary protoplanetary discs -- I. Structure of the inner cavity

TL;DR

This study uses extensive numerical simulations to analyze the structure of inner cavities in viscous circumbinary protoplanetary discs, revealing how binary interactions influence disc morphology and identifying limitations in current models.

Contribution

It provides a comprehensive parameter space exploration of disc viscosities and binary eccentricities, offering new insights into cavity sizes and their relation to binary dynamics.

Findings

Larger cavities than previously modeled are possible within certain parameters.

The eccentricity of HD 142527's disc suggests binary influence but cannot be fully explained by current models.

Simulation data constrains binary eccentricity and viscosity based on observed disc features.

Abstract

Many of the most intriguing features, including spirals and cavities, in the current disc observations are found in binary systems like GG Tau, HD 142527 or HD 100453. Such features are evidence of the dynamic interaction between binary stars and the viscous disc. Understanding these dynamic interactions and how they result in the structure and growth of asymmetric circumbinary discs is a difficult problem, for which there is no complete analytical solution, that predicts the shape of the observed disc accurately. We use numeric simulation to evolve circumbinary discs with varying disc viscosities and investigate the size and shape of the inner cavities in such protoplanetary discs. We have simulated over 140 locally isothermal 2D grid-based disc models for > 3e4 binary orbits each and mapped out the parameter space relevant for protoplanetary discs. With this, it becomes possible to create parametrised profiles for individual discs to compare to observation and find limits to their binary eccentricity or internal viscosity from the simulation data. In the long-term simulations larger cavity sizes than previously considered are possible within the parameter space (< 6 binary separations). As an example, we find that the eccentricity of the disc around HD 142527 suggests the impact of the binary dynamics on the disc. However, even considering the larger cavity sizes, the large size of the cavity in HD 142527 remains unexplained by the simulations considering the most recent orbital constraints.