UBVRI observations of the flickering of RS Ophiuchi at quiescence

We report observations of the flickering variability of the recurrent nova RS Oph at quiescence on the basis of simultaneous observations in five bands (UBVRI). RS Oph has a flickering source with (U−B)0=−0.62 ± 0.07, (B−V)0= 0.15 ± 0.10 and (V−R)0= 0.25 ± 0.05. We find for the flickering source a temperature Tfl≈ 9500 ± 500 K, and luminosity Lfl∼ 50–150 L⊙ (using a distance of d= 1.6 kpc). We also find that on a (U−B) versus (B−V) diagram, the flickering of the symbiotic stars differs from that of the cataclysmic variables. The possible source of the flickering is discussed. The data are available upon request from the authors.