Is drag luminosity effective in recurrent novae?

We have studied the efficiency of frictional processes in common envelope phase at outbursts of three recurrent novae T Pyx, U Sco, and RS Oph, by using steady-state wind models. The drag luminosity is found to depend strongly on the envelope mass. It may play an important role for a relatively massive envelope of ∼10^-4 M_⊙ or more. For recurrent novae, however, acceleration due to the drag force is not important to eject the envelope mass because of its small envelope mass (∼10^-7-10^-5 M_⊙), in other words, its low density. Since the drag luminosity can be neglected at the extended phase of nova outburst, the light curves of these recurrent novae are determined only by the wind-driven mass loss as shown by Kato (1990).