Searching for the 1 mHz variability in the flickering of V4743 Sgr: A cataclysmic variable accreting at a high rate

Abstract

Aims. A few well studied cataclysmic variables (CVs) have shown discrete characteristic frequencies of fast variability; the most prominent ones are around log(f/Hz) ≃ −3. Because we still have only small number statistics, we obtained a new observation to test whether this is a general characteristic of CVs, especially if mass transfer occurs at a high rate typical for dwarf nova in outbursts, in the so called high state. Methods. We analysed optical Kepler data of the quiescent nova and intermediate polar V4743 Sgr. This system hosts a white dwarf accreting through a disc in the high state. We calculated the power density spectra and searched for break or characteristic frequencies. Our goal is to assess whether the milihertz frequency of the flickering is a general characteristic. Results. V4743 Sgr has a clear break frequency at log(f/Hz) ≃ −3. This detection increases the probability that the megahertz characteristic frequency is a general feature of CVs in the high state, from 69% to 91%. Furthermore, we propose the possibility that the variability is generated by a similar mechanism as in the nova-like system MV Lyr, which would make V4743 Sgr unique.