  We examine a new paradigm to account for the exponential decay seen in the
light curves of some of the bright X-ray novae. These systems show an
exponential decay in soft X-rays with an e-folding time constant of ~30 d. We
investigate a scenario in which evaporation of matter into a corona is the
dominant mass removal mechanism from the accretion disk. We utilize the thermal
evaporative instability discovered by Shaviv and Wehrse. First we parametrize
local mass loss rates from the disk (fitted to vertical structure computations
of the optically thin structure using the photoionization code CLOUDY), and
then we utilize the scalings in our numerical time dependent model for the
decay. Both the ~30 d e-folding time scale for the decay and the secondary
maximum with its rapid rise time ~1-3 d which is seen in the X-ray nova light
curves can be produced by adjusting the strength of the evaporation.
