  We report on the detection of the linear rms-flux relation in two accreting
white dwarf binary systems: V1504 Cyg and KIC 8751494. The rms-flux relation
relates the absolute root-mean-square (rms) variability of the light curve to
its mean flux. The light curves analysed were obtained with the Kepler
satellite at a 58.8 s cadence. The rms-flux relation was previously detected in
only one other cataclysmic variable, MV Lyr. This result reenforces the
ubiquity of the linear rms-flux relation as a characteristic property of
accretion-induced variability, since it has been observed in several black hole
binaries, neutron star binaries and active galactic nuclei. Moreover, its
detection in V1504 Cyg is the first time the rms-flux relation has been
detected in a dwarf nova-type CV during quiescence. This result, together with
previous studies, hence points towards a common physical origin of
accretion-induced variability, independent of the size, mass, or type of the
central accreting compact object.
