The recurrent nova RS Oph - simultaneous B and V band observations of the flickering variability

TL;DR

This study presents simultaneous B and V band observations of the flickering variability in the recurrent nova RS Oph, revealing correlations between brightness, flickering source size, and color, indicating active accretion processes.

Contribution

It provides detailed characterization of flickering properties in RS Oph during quiescence, including temperature, size, and color, with a novel correlation between brightness and flickering source radius.

Findings

Flickering amplitude ranges from 0.16 to 0.59 mag in B band.

A strong correlation exists between system brightness and flickering source radius.

Flickering temperature ranges from 7200 K to 18900 K.

Abstract

We performed 48.6 hours (in 28 nights) of simultaneous B and V band observations of the flickering variability of the recurrent nova RS Oph in quiescence. During the time of our observations the brightness of the system varied between 13.2 > B > 11.1 and the colour in the range 0.86 < B-V < 1.33 . We find that RS~Oph becomes more blue, as it becomes brighter, however the hot component becomes more red as it becomes brighter (assuming that the red giant is non-variable). During all the runs RS Oph exhibits flickering with amplitude 0.16 - 0.59 mag in B band. For the flickering source we find that it has colour -0.14 < B-V < 0.40, temperature in the range 7200 < T_fl < 18900, and average radius 1.1 < R_fl < 6.7 R_sun. We do not find a correlation between the temperature of the flickering and the brightness. However, we do find a strong correlation (correlation coefficient 0.81, significance 1.1x10^{-7} ) between B band magnitude and the average radius of the flickering source - as the brightness of the system increases the size of the flickering source also increases. The estimated temperature is similar to that of the bright spot of cataclysmic variables. The persistent presence of flickering indicates that the white dwarf is actively accreting material for the next outburst.