Dynamics of line-driven winds from disks in cataclysmic variables. II. Mass-loss rates and velocity laws

We analyze the dynamics of two-dimensional stationary, line-driven winds fr om accretion disks in cataclysmic variable (CV) stars by generalizing the f ormalism of Castor, Abbott, and Klein (CAK) for O stars. In Paper I, we sol ved the wind Euler equation, derived its two eigenvalues, and addressed the solution topology and wind geometry. Here, we focus on mass-loss rates and velocity laws of the wind. We find that disk winds, even in luminous nova- like variables, have low optical depth, even in the strongest driving lines . This suggests that thick-to-thin transitions in these lines occur in the wind. For disks with a realistic radial temperature law, the mass loss is d ominated by gas emanating from the inner decade in radius. The total mass-l oss rate associated with the wind from a disk of luminosity 10 L. is simila r to 10(-1)2 M. yr(-1), or 10(-4) of the mass accretion rate. This is 1 ord er of magnitude below the lower limit obtained from fitting P Cygni line pr ofiles using kinematical wind models when the Lyman continuum is suppressed . The difficulties associated with such small mass-loss rates for line-driv en winds from disks in CVs are principal and confirm our previous work on t his subject. We conjecture that this issue may be resolved by detailed non- LTE calculations of the CAK line force within the context of CV disk winds and/or by better accounting for the disk energy distribution and wind ioniz ation structure. We find that the wind velocity profile is well approximate d by the empirical law used in kinematical modeling. The acceleration lengt h scale is given by the footpoint radius of the wind streamline in the disk . This suggests an upper limit of similar to 10r(wd) to the acceleration sc ale, which is smaller by factor of a few as compared with values derived fr om line fitting.