Fast stochastic variability study of two SU UMa systems V1504 Cyg and V344 Lyr observed by Kepler satellite

TL;DR

This study analyzes Kepler data of two SU UMa dwarf novae, V1504 Cyg and V344 Lyr, revealing their stochastic variability patterns and the influence of accretion disc dynamics during different activity stages.

Contribution

It provides the first detailed characterization of fast stochastic variability and break frequencies in these systems, linking variability features to accretion disc structure and activity stages.

Findings

Both systems show similar variability behavior during outburst and quiescence.

A stable low break frequency suggests disc-wide origin of variability.

High frequency components indicate inner disc rebuilding after quiescence.

Abstract

We analysed Kepler data of two similar dwarf novae V344 Lyr and V1504 Cyg in order to study optical fast stochastic variability (flickering) by searching for characteristic break frequencies in their power density spectra. Two different stages of activity were analysed separately, i.e. regular outbursts and quiescence. Both systems show similar behaviour during both activity stages. The quiescent power density spectra show a dominant low break frequency which is also present during outburst with a more or less stable value in V344 Lyr while it is slightly higher in V1504 Cyg. The origin of this variability is probably the whole accretion disc. Both outburst power density spectra show additional high frequency components which we interpret as generated by the rebuilt inner disc that was truncated during quiescence. Moreover, V344 Lyr shows the typical linear rms-flux relation which is strongly deformed by a possible negative superhump variability.