  Due to a new global analysis method, it is now possible to measure the
internal composition of pulsating white dwarf stars, even with relatively
simple theoretical models. The precise internal mixture of carbon and oxygen is
the largest single source of uncertainty in ages derived from white dwarf
cosmochronometry, and contains information about the rate of the
astrophysically important, but experimentally uncertain, ^12C(alpha,gamma)^16O
nuclear reaction. Recent determinations of the internal composition and
structure of two helium-atmosphere variable (DBV) white dwarf stars, GD 358 and
CBS 114, initially led to conflicting implied rates for the
^12C(alpha,gamma)^16O reaction. If both stars were formed through single-star
evolution, then the initial analyses of their pulsation frequencies must have
differed in some systematic way. I present improved fits to the two sets of
pulsation data, resolving the tension between the initial results and leading
to a value for the ^12C(alpha,gamma)^16O reaction rate that is consistent with
recent laboratory measurements.
