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Published online by Cambridge University Press: 12 April 2016
Although the frequencies of the pulsating white dwarfs are extremely stable, the evolutionary cooling of these geometrically constrained objects should lead to an observable period change over a sufficiently long time base. Direct measurement of a period change rate for the cooler white dwarfs should provide fundamental data on the core composition of these stellar remnants, and hence their cooling time scales. Progress on attempts to measure the period change rates of two white dwarfs is reported.