Resumption of mass accretion in RS Oph

TL;DR

This study documents the resumption of accretion in RS Oph after its 2006 outburst, evidenced by optical flickering and brightness decline, with implications for accretion rates and nova recurrence models.

Contribution

It provides observational evidence of accretion resumption post-outburst and estimates accretion rates, challenging existing thermonuclear runaway models for recurrence intervals.

Findings

Optical flickering resumed by day 241 post-outburst.

Detected brightness decline of 0.5 mag over two weeks.

Estimated accretion rates range from 10^{-10} to 10^{-9} Msun/yr.

Abstract

The latest outburst of the recurrent nova RS Oph occurred in 2006 February. Photometric data presented here show evidence of the resumption of optical flickering, indicating re-establishment of accretion by day 241 of the outburst. Magnitude variations of up to 0.32 mag in V-band and 0.14 mag in B on timescales of 600-7000 s are detected. Over the two week observational period we also detect a 0.5 mag decline in the mean brightness, from V~11.4 to V~11.9, and record B~12.9 mag. Limits on the mass accretion rate of ~10^{-10} to 10^{-9} Msun/yr are calculated, which span the range of accretion rates modeled for direct wind accretion and Roche lobe overflow mechanisms. The current accretion rates make it difficult for thermonuclear runaway models to explain the observed recurrence interval, and this implies average accretion rates are typically higher than seen immediately post-outburst.