On the Relative Rates of Decay of the Optical and Soft X-Ray Fluxes in Dwarf Nova Outbursts

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Abstract
We present time-dependent computations utilizing the accretion disk limit cycle instability to model the decay of the flux in dwarf nova outbursts. In particular, we model the optical and 0.1 keV fluxes in an attempt to account for recent findings by Ponman et al. The e-folding decay times of ~3 days for the optical and ~1 day for the soft X-ray/EUV in an outburst of SS Cygni are naturally accounted for in the model by the action of the cooling front which enacts the transition between the high and low states in the accretion disk. The difference in timescales between V and EUV stems from the fact that, roughly speaking, the optical flux samples the surface area of the hot part of the accretion disk, whereas the EUV samples the mass of the hot part of the accretion disk.

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