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White Dwarf Heating and Cooling in Dwarf Nova Outbursts
We calculate the time dependent thermal evolution of a white dwarf (WD) undergoing sudden accretion in a dwarf nova outburst, using both simulations and analytic estimates. Our cool result is that long after the outburst, the FRACTIONAL flux perturbation (NOT the absolute flux) about the quiescent flux decays as a power law with time. This is simply explained as adiabatic compression and subsequent cooling of the deep layers of the WD. We use this result to construct a simple fitting formula that yields estimates for both the quiescent flux and the total accreted column of material. We compare our work with the well-studied outburst of WZ Sge, finding that its cooling is well described by our model. Our power law result is a valuable tool for making quick estimates of the outburst properties. We show that fitting the late time lightcurve with this formula yields a predicted column within 20% of that estimated from our full numerical calculations. Related Links: Picture of an accretion disk in the high state "White Dwarf Heating and Subsequent Cooling in Dwarf Nova Outbursts," A. L. Piro, P. Arras, & L. Bildsten, 2005, Ap. J., 628, 401 |
