THE HIGH-STATE LOW-STATE TRANSITION IN V794 AQUILAE

We present a V-magnitude light curve of the cataclysmic binary V794 Aq uilae covering an 800 day time span. The system shows variations of up to 3 mag. In particular, there are two dips of similar to 1 mag which last for about 50 days, and are followed by a rapid recovery to the o riginal brightness, and a third dip of similar to 3 mag lasting about 100 days. These fluctuations are thought to be caused by the response of the accretion disk in the system to the cessation of mass transfer from the mass-losing secondary star. We present computations using a t ime-dependent accretion disk code to delineate a range of allowed beha vior for the accretion disk. To model the observed light curve, we req uire that the model parameters alpha(cold), and alpha(hot), which char acterize the degree of coupling of the viscous dissipation to the orbi tal shear in the low and high states of the accretion disk, be smaller than they have been inferred to be in the dwarf novae, and that the r atio alpha(hot)/alpha(cold) also be smaller. The fact that alpha seems to vary with the rate of mass transfer may provide support for the mo del of Vishniac and Diamond, in which the impact of the mass transfer stream onto the outer edge of the accretion disk excites internal wave s which transport angular momentum outward and provide the viscous dis sipation.