The Newly Discovered Nova Super-Remnant Surrounding Recurrent Nova T Coronae Borealis: Will it Light Up During the Coming Eruption?

TL;DR

This study reports the discovery of a large, faint super-remnant nebula around T Coronae Borealis, a recurrent nova, and discusses its implications for future observations of the upcoming nova eruption.

Contribution

It provides the first detection of a super-remnant around T CrB and predicts the optical thinness of ejecta, influencing expectations for light echoes during the next eruption.

Findings

A ~30-parsec nebula detected around T CrB in Halpha, [NII], and [SII] images.

No detectable continuum or [OIII] emission from the super-remnant.

Predicted absence of fluorescent light echoes following the upcoming nova eruption.

Abstract

A century or less separates the thermonuclear-powered eruptions of recurrent novae in the hydrogen-rich envelopes of massive white dwarfs. The colliding ejecta of successive recurrent nova events are predicted to always generate very large (tens of parsecs) super-remnants; only two examples are currently known. T CrB offers an excellent opportunity to test this prediction. As it will almost certainly undergo its next, once-in ~80-year recurrent nova event between 2024 and 2026, we carried out very deep narrowband and continuum imaging to search for the predicted, piled-up ejecta of the past millenia. While nothing is detected in continuum or narrowband [OIII] images, a ~30-parsec-diameter, faint nebulosity surrounding T CrB is clearly present in deep Halpha, [NII] and [SII] narrowband Condor Array Telescope imagery. We predict that these newly detected nebulosities, as well as the recent ejecta that have not yet reached the super-remnant, are far too optically-thin to capture all but a tiny fraction of the photons emitted by RN flashes. We thus predict that fluorescent light echoes will NOT be detectable following the imminent nova flash of T CrB. Dust may be released by the T CrB red giant wind in pre-eruption outbursts, but we have no reliable estimates of its quantity or geometrical distribution. While we cannot predict the morphology or intensity of dust-induced continuum light echoes following the coming flash, we encourage multi-epoch Hubble Space Telescope optical imaging as well as James Webb Space Telescope infrared imaging of T CrB during the year after it erupts.