Flickering Returns as RS Oph Reestablishes Quiescent Conditions Following its 2021 Nova Outburst

Abstract

Abstract RS Oph has persistently displayed flickering at optical wavelengths when observed away from its repeating nova outbursts. During the 2006 eruption the flickering disappeared, and this repeated during the recent 2021 event. We have been monitoring RS Oph looking for the reappearance of flickering at B-band following the 2021 outburst. The flickering was still absent (σ(B) < 0.002 mag) on day +210 (counted from nova optical maximum), appeared at σ(B) = 0.008 mag on day +224, and raised to σ(B) = 0.029 mag on day +250. On following dates the amplitude remained large, although fluctuating. The recovery of B-band quiescence brightness by RS Oph begun around day +225 and was completed by day +260. The parallel patterns followed by the rise in system brightness and the reappearance of flickering confirm the central role played in RS Oph by the return to pre-outburst conditions of the accretion disk and the refilling by the RG wind of the immediate circumstellar space.