The “Super-Active” Accretion Phase of T CrB has Ended

Abstract

The symbiotic recurrent nova T CrB erupted for the second and last recorded time in 1946. Following the outburst, the accretion rate onto its WD has remained rather low with only occasional and minor flaring episodes, until in late 2014 it entered a “super-active” phase (SAP) that peaked in 2016 April: the flux radiated by Balmer lines increased by two orders of magnitude, accompanied by the appearance of strong He i, He ii, and many other emission lines. Following the sharp maximum, the intensity of the emission lines has been steadily decreasing, reaching back to pre-SAP levels by mid-2023. The end of SAP is also confirmed by the drop of B-band brightness to pre-SAP conditions and the simultaneous re-appearance of a large-amplitude flickering. This suggests that the accretion disk has emptied from the extra material that has driven the “super active” state and has completed its transfer onto the WD, setting the stage for a new and probably imminent nova eruption.