  We now have a good measurement of the cooling rate of G117-B15A. In the near
future, we will have equally well determined cooling rates for other pulsating
white dwarfs, including R548. The ability to measure their cooling rates offers
us a unique way to study weakly interacting particles that would contribute to
their cooling. Working toward that goal, we perform a careful
asteroseismological analysis of G117-B15A and R548. We study them side by side
because they have similar observed properties. We carry out a systematic, fine
grid search for best fit models to the observed period spectra of those stars.
We freely vary 4 parameters: the effective temperature, the stellar mass, the
helium layer mass, and the hydrogen layer mass. We identify and quantify a
number of uncertainties associated with our models. Based on the results of
that analysis and fits to the periods observed in R548 and G117-B15A, we
clearly define the regions of the 4 dimensional parameter space ocuppied by the
best fit models.
