On tidal effects in accretion disks

The influence of tidal forces on accretion disks in close binary systems is examined by means of 2-D hydrodynamical modelling. It is found that tidal torques are capable of removing the angular momentum from the disk on a time scale significantly shorter than the accretion time scale. The efficiency of the torques remains high even in disks with radii as small as 10% of the separation between the components of the binary. It is suggested that the main effect of viscosity is to enable the angular momentum loss due to tidal torques rather than to redistribute the angular momentum within the disk. 22 refs., 8 figs., 2 tabs. (author)