A puzzling periodicity in the pulsating DA white dwarf G 117-B15A
We present time-resolved optical spectrophotometry of the pulsatinghydrogen atmosphere (DA) white dwarf G 117-B15A. We find threeperiodicities in the pulsation spectrum (215 s, 272 s, and 304 s) all ofwhich have been found in earlier studies. By comparing the fractionalwavelength dependence of the pulsation amplitudes (chromatic amplitudes)with models, we confirm a previous report that the stronge
