Activity of the post-nova V1363 Cygni on long timescales

Abstract

Abstract V1363 Cyg is a cataclysmic variable (CV) and a post-nova. Our analysis of its long-term optical activity used the archival data from the AAVSO database and literature. We showed that the accretion disk of V1363 Cyg is exposed to the thermal-viscous instability (TVI) for at least part of the time. The time fraction spent in the high state or the outbursts dramatically changed on the timescale of decades. The highly variable brightness of V1363 Cyg displayed several episodes of a strong brightening (bumps in the light curve) from a cool disk in the TVI zone. This can be interpreted to mean their vastly discrepant decay rates show that only some of these bumps can be attributed to the dwarf nova outbursts without strong irradiation of the disk by the hot white dwarf. The Bailey relation of the decay rate, if ascribed to a DN outburst of V1363 Cyg, speaks in favor of its orbital period Porb being very long for a CV, about 20–40 h. A dominant cycle length of about 435 d was present in the brightness changes all the time, even when the disk was well inside the TVI zone. We interpret it as modulation of the companion’s mass outflow by differential rotation of the active region(s).