Discovery of Two New Accreting Pulsating White Dwarf Stars

We report the discovery of two new accreting pulsating white dwarf stars among the cataclysmic variables of the Sloan Digital Sky Survey: SDSS J074531.91+453829.5 and SDSS J091945.10+085710.0. We observe high-amplitude nonsinusoidal variations of 4.5%-7% at a period close to 1230 s in the optical light curves of SDSS J074531.91+453829.5 and a low-amplitude variation of 0.7%-1.6% near 260 s in the light curves of SDSS J091945.10+085710.0. We infer that these optical variations are a consequence of nonradial g-mode pulsations in the accreting primary white dwarfs of these cataclysmic variables. However, we cannot rule out the remote possibility that the 260 s period could be the spin period of the accreting white dwarf SDSS J091945.10+085710.0. We also uncovered a nonvariable, SDSS J171145.08+301320.0, during our search; our two observing runs exclude any pulsation-related periodicities in the range 85-1400 s with an amplitude ≥0.5%. This discovery paper brings the total number of known accreting white dwarf pulsators to 11.