Intra-night Flickering of RS Ophiuchi: II. Exponentially Distributed Quasi-Period Modes

Linearized and flattened light curves (29 in B band and 29 in V band) of the recurent nova RS Oph, taken in 2008-2017 by 5 telescopes, are analyzed. The purposes are (i) characterizing of the flickering phenomenon by various ways and (ii) justification of the "resonance" distribution of the modes of the flickering quasi-periods, found in Paper I. The typical observing circumstances are: monitoring duration 60-150 min, number of CCD frames 50-200 and time step 0.5-1.5 min. Part 1 presents photometric diagrams, standard and range deviations of the light curves in dependence on the average flux, as well as the distributions of the skewness and kurtosis of the histograms of the light curves. The intra-night flickering contains local disk obscures/shots and global disk instabilities. It seems both processes alternate their superiority. The average skewness, 0.12 +/- 0.30, gives weak privilege to the local shots. The average kurtosis, -0.17 +/- 0.62, gives some privilege to the global instabilities. In contrast to the random process with bell-shaped distribution of the deviations, deficit of small and large deviations is obvious in about 1/2 of the cases. Presence of light variations, close to oscillations, give some priority to the global disk instabilities. In Part 2 every light curve is scanned digitally by a system of data windows with sizes Theta. Six fractal parameters are derived as average values for each Theta and regarded as functions on Theta in log-log coordinates. The average structure gradient, 0.48 +/- 0.16, also does not point out the prior process of the light variations. The mean value of the Hurst gradient, 0.22 +/- 0.06, giving fractal dimension 1.78 +/- 0.06, corresponds to auto-correlation at short time scale. The asymmetry function, introduced in this work, shows that the mean duration of the elementary shots is 3.6 +/- 0.8 min. It seems the relatively weak and short local shots dominate at time scales of a few minutes. Part 3 presents 97 quasi-periods and their distributions. The quasi-periods are detected by the local minima of the structure functions as 58 primary, 20 secondary, 10 tertiary and 13 very short. All quasi-periods are confirmed by the local maxima of the relevant auto-correlation function. The distribution of the quasi-periods shows 6 modes, at 8, 13, 21, 30, 48 and 73 min. The modes of the quasi-period P follow exponential (or power) function on the number of the mode M with standard deviation of 4.7%. The power dependence is P-M = 3.48x1.55(M). This function predicts modes also at 3.5, 5.3 and 115 min, which are not detected in this work. However, the characteristic duration of the elementary shot, 3.6 +/- 0.8 min, corresponds well to the predicted mode at 3.5 min. Because 1.55 approximate to 3/2, the modes of the quasi-periods like obey 3/2 resonance with unknown reason. The relative energy of the quasi-period (i.e. of the quasi-periodic structure, including the energy of its substructures) correlates with the logarithm of the quasi-period under a slope coefficients 0.02. Generally, the flickering light curves are too complicated and various, without a possible classification (at least in the present work). Unique systematic is only the resonance-like sequence of the quasi-period modes.