AIMS: We studied unique data of a nova-like system MV Lyr during transition
from the high to low state and vice versa taken by the Kepler space telescope.
We were interested in evolution of frequency components found previously by
Scaringi et al. in different data also obtained by Kepler. METHODS: We divided
the light curve into 10 day segments and investigated the corresponding power
density spectra. We searched for individual frequency components by fitting
with Lorentzian functions. Additionally, we investigated the variability using
averaged shot profiles calculated from the light curve divided into 10 equally
spaces subsamples. RESULTS: We found very complex changes of the power density
spectra. We focused our study onto three frequency components. Strong activity
increase is seen at low frequencies. Contrariwise, the high frequency part of
the spectrum strongly decreases in power with specific rise in characteristic
frequencies of the individual components. We discuss various scenarios of this
phenomenology as reprocessing of X-rays in a receding accretion disc or a
radiation from a more active region at the outer disc. Finally, we show that
various cataclysmic variables show similar characteristic frequencies in their
power density spectra. These are dependent on activity stage, making the
situation similar to X-ray binaries.Comment: accepted for publication to A&
