Gas Accretion from a Circumbinary Disk to Protoplanetary Disks

Young circumbinary disks are expected to supply gas onto protoplanetary disks through accretion. Such mass supply has been studied based on new 2D numerical simulations in which a circular binary is surrounded by an isothermal Keplerian disk at the initial stage. The simulations show that the gas supply is variable due to oscillation of spiral waves in the circumbinary disk. The amplitude of the oscillation varies on the timescale of several tens rotation period. The gas supply rate is positively correlated with the amplitude of the oscillation. The gas is supplied through the L2 point to protoplanetary disks associated with the primary and secondary. The mass accretion rate tends to be higher for the primary disk although the secondary disk has a higher accretion rate in certain periods. The primary disk is perturbed so intensely by the impact of gas flow that the outer part is removed. Conversely, the secondary disk is quiet most of the time. Both the primary and secondary disks have travelling spiral waves which transfer angular momentum inside them. The mass supply from the circumbinary disk is higher when the temperature is higher. The inner edge of the circumbinary disk retreats gradually.