• DOI:10.1093/mnras/stad735
• Corpus ID: 257427582

The B & V light curves for recurrent nova T CrB from 1842–2022, the unique pre- and post-eruption high-states, the complex period changes, and the upcoming eruption in 2025.5 ± 1.3

@article{Schaefer2023TheB,
  title={The B \& V light curves for recurrent nova T CrB from 1842–2022, the unique pre- and post-eruption high-states, the complex period changes, and the upcoming eruption in 2025.5 ± 1.3},
  author={Bradley E. Schaefer},
  journal={Monthly Notices of the Royal Astronomical Society},
  year={2023}
}

• B. Schaefer
• Published 9 March 2023
• Physics, Geology, Medicine
• Monthly Notices of the Royal Astronomical Society

T CrB is one of the most-famous and brightest novae known, and is a recurrent nova with prior eruptions in 1866 and 1946 that peak at V = 2.0. I have constructed light curves spanning 1842–2022 with 213,730 magnitudes, where the B and V magnitudes are fully corrected to the Johnson system. These light curves first reveal a unique complex high-state (with 20× higher accretion rate than the normal low-state) stretching from -10 to +9 years after eruption, punctuated with a deep pre-eruption dip (apparently from dust formation in a slow mass ejection) and a unique enigmatic secondary eruption (with 10 per cent of the energy of the primary eruption), with the light curves identical for the 1866 and 1946 eruptions. Starting in 2015, T CrB entered the high-state, like in 1936, so a third eruption in upcoming years has been widely anticipated. With the pre-1946 light curve as a template, I predict a date of 2025.5 ± 1.3 for the upcoming eruption, with the primary uncertainty arising from a possible lengthening of the pre-eruption high-state. I use the large-amplitude ellipsoidal modulation to track the orbital phase of the binary from 1867–2022. I measure that the orbital period increased abruptly by +0.185 ± 0.056 days across the 1946 eruption, the 1947–2022 years had a steady period decrease of (−8.9 ± 1.6) × 10−6 days-per-day, and the 1867–1946 years had a steady period change consistent with zero, at (+1.75 ± 4.5) × 10−6 days-per-day. These large period changes cannot be explained by any published mechanism.