  I solve analytically the viscous evolution of a self-irradiated accretion
disc, as seen during outbursts of soft X-ray transients. The solutions predict
steep power-law X-ray decays L_X \sim (1+ t/t_visc)^{-4}, changing to L_X \sim
(1-t/t'_visc)^4 at late times, where t_visc, t'_visc are viscous timescales.
These forms closely resemble the approximate exponential and linear decays
inferred by King and Ritter (1997) in these two regimes. The decays are much
steeper than for unirradiated discs because the viscosity is a function of the
central accretion rate rather than of local conditions in the disc.
