Study of the Rapid Variability of a Dwarf Nova SS Cyg at Different Brightness Levels

Abstract

Observations of the dwarf nova SS Cyg were made in 2019–2021 at different brightness levels (\(V \sim 10{-} {{12}^{m}}\)) both at the brightness decay stage after the outburst maximum, and in the quite state between outbursts. Data were obtained in \({{R}_{c}}\) (\( \sim {\kern 1pt} 8650\) observations, 3 sets) and V (\( \sim {\kern 1pt} 50\,000\) points, 22 sets) bands. The value of the system’s orbital period obtained in 2019–2021 (\({{P}_{{{\text{orb}}}}}{{ = 0.27408(2)}^{d}}\)) used in this study is 0.4% less than the value obtained more than a quarter of a century ago (1983–1996). The time resolution between two successive measurements is 6–14 s depending on the equipment used. An extensive database of new observational data allowed us to perform a quantitative analysis of observations. Analysis of the data after taking into account orbital variability and other trends associated with changes in the system’s emission flux during the night showed the presence of cyclic fluctuations in brightness, usually 4–10 events per orbital cycle – flickering. For most series of observations, the Lafleur-Kinman method determined such a value of the oscillation period at which convolution of observations with it showed a single wave. The obtained values of the characteristic flickering times and their amplitudes show their dependence on the average brightness level of the system. With increasing luminosity of the system, both of these quantities decreased linearly. From the size ratios of the binary system components of SS Cyg, it was shown that the source of flickering is located in the interaction region of the gas flow with the near-disk halo: only this region in the SS Cyg system with parameters (\(q\), \(i\), \({{R}_{d}}\)), defined by the authors earlier, can be eclipsed at large radii disk, and is clearly visible in all other orbital phases of the system.