Pre-outburst signal in the light curves of the recurrent novae RS Oph and T CrB

TL;DR

This study identifies a pre-outburst brightness decrease in recurrent novae RS Oph and T CrB, suggesting a common precursor signal linked to envelope formation around the white dwarf.

Contribution

It provides the first observational evidence of a pre-outburst optical signal in recurrent novae and estimates the properties of the forming envelope.

Findings

Pre-outburst brightness decrease observed in T CrB and RS Oph.

Estimated envelope size of 1000-2000 km around the white dwarf.

Envelope mass estimated between 5×10^{-8} and 6×10^{-7} solar masses.

Abstract

Pre-outburst signal (a decrease of the optical brightness) just before the outburst is clearly detected in the observations of the T CrB obtained before and during the 1946 outburst. A similar decrease is also visible in the light curve of RS Oph during the 2021 outburst. We suppose that this is due to formation of a thick, dense envelope around the white dwarf, and we estimate its size (1000 - 2000 km), mass (5.10$^{-8}$ - 6.10$^{-7}$ M$_\odot$) and average density (5 - 16 g cm$^{-3}$).