Gravitational torque in circumbinary discs: global radial oscillations

Understand

Circumbinary discs (CBDs) arise in many astrophysical settings, including young stellar binaries and supermassive black hole binaries.

• Their structure is mediated by gravitational torques exerted on the disc by the central binary.
• The spatial distribution of the binary torque density (so-called excitation torque density) in CBDs is known to feature global large-amplitude, quasi-periodic oscillations, which are often interpreted in terms of the local resonant Lindblad torques.
• Here we investigate the nature of these torque oscillations using 2D, inviscid hydrodynamic simulations and theoretical calculations.