Alternation of the flickering morphology between the high and low state in MV Lyrae

Abstract

Aims. We studied unique data of the nova-like system MV Lyr taken by the Kepler space telescope during its transition from the high to low state and vice versa. We were interested in the evolution of frequency components found previously in different data also obtained by Kepler. Methods. We divided the light curve into ten-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 ten equally spaced subsamples. Results. We found very complex changes in the power density spectra. We focused our study onto three frequency components. A significant increase in activity is seen at low frequencies. Contrariwise, the high frequency part of the spectrum strongly decreases in power with a specific rise in characteristic frequencies of the individual components. We discuss various scenarios of this phenomenology such as the reprocessing of X-rays in a receding accretion disk or radiation from a more active region at the outer disk. 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.