New solution to viscous evolution of accretion disks in binary systems

The analytical investigation of time-dependent accretion in disks is carried out. We consider a time-dependent disk in a binary system at outburst which has a fixed tidally-truncated outer radius. The standard model (Shakura-Sunyaev) of the disk is considered. The vertical structure of the disk is accurately described in two regimes of opacity: Thomson and free-free. The fully analytical solutions are obtained, characterized by powerlaw variations of accretion rate with time. The solutions supply asymptotic description of the disk evolution in flaring sources in the periods after outbursts while the disk is fully ionized. The X-ray flux of multicolor (black-body) α-disk is obtained as varying quasi-exponentially. The application to X-ray novae is briefly discussed concerning the observed faster-than-power decays of X-ray light curves. The case of time-dependent advective disk when the exponential variations of accretion rate can occur is discussed.