Abstract
A new self-sustained model for long-term light-curve variations of the supersoft X-ray sources RX J0513.9-6951 and V Sge is proposed based on an optically thick wind model of mass-accreting white dwarfs (WDs). When the mass accretion rate to a WD exceeds the critical rate of ∼ 1×10-6M⊙yr-1, optically thick strong winds begin to blow from the WD so that a formation of common envelope is avoided. The WD can accrete and burn hydrogen-rich matter on the surface of the WD at the critical rate. The excess matter transferred to the WD above the critical rate is expelled by winds. This is called ``accretion wind evolution.'' This ejection process, however, occurs intermittently because the mass transfer is attenuated by strong winds: the strong winds collide with the secondary surface and strip off the surface layer of the secondary. Properly formulating the mass-stripping effect and the ensuing decay of mass-transfer rate, we are able to reproduce the transition between the optical high/X-ray-off and optical low/X-ray-on states of the supersoft X-ray sources RX J0513.9-6951 and V Sge. Thus these two objects are the first examples of accretion wind evolution, which is a key evolutionary process in a recently developed evolutionary path to Type Ia supernovae.
