Abstract

Disks around binaries may be found in a variety of astrophysical contexts, including around young stellar binaries and supermassive black hole binaries. I will present the results of hydrodynamical simulations of circumbinary accretion disks, focusing on their long-term evolution over secular and viscous timescales. Carefully chosen initial conditions and boundary conditions are used to ensure that the disk reaches a quasi-steady state, in which the time-averaged mass accretion rate onto the binary matches the mass supply rate at the outer disk. I will discuss the excitation of disk eccentricity by the binary, and how the coherent precession of the eccentric disk depends on the binary and disk parameters. I will also discuss the detailed balance of angular momentum transport through the disk by advection, viscous stress, and gravitational torque, from which the time-averaged net angular momentum transfer rate to the binary is determined. The specific angular momentum characterizing the angular momentum transfer, which depends on the binary eccentricity in a non-monotonic manner, is usually positive, implying that the the binary separation may grow in time.