When will T Coronae Borealis next erupt as a nova? Constraints from recurrence, orbital phase, and accretion-state evolution
When will T Coronae Borealis next erupt as a nova? Constraints from recurrence, orbital phase, and accretion-state evolution
Songpeng Pei, Xiaowan Zhang, Renzhi Su, Ziwei Ou, Yongzhi Cai, Qiang Li, Yu Liu, Xiaoqin Ren, Taozhi Yang
AbstractT Coronae Borealis (T CrB) is the nearest symbiotic recurrent nova and is now intensively monitored for its next eruption. We combine three constraints on the eruption time: historical recurrence, orbital phase, and recent accretion-state evolution. Conditioning on no eruption by 2026 July 11, the three effective historical intervals give illustrative survival-conditioned probabilities of 30.2\% for the rest of 2026 and 56.9\% within the following year; these are empirical indicators, not physical prediction probabilities. The four adopted historical eruption phases do not select a unique ignition phase, but form two loose pairs near $φ\simeq0.44$ and $φ\simeq0.62$, used here only as monitoring windows. The 1946 pre-eruption dip is difficult to explain by either a pure accretion-rate decline or standard dust extinction, and may have involved both accretion restructuring and source-dependent obscuration. If the renewed 2026 decline is the true pre-1946 analogue, an eruption around 2026 December remains plausible. Conversely, if post-2024 brightness remains below the 2014--2023 high state, an accretion-deficit estimate gives an earliest lower limit near 2029 May. The data therefore support conditional monitoring windows, not a unique date. These are conditional diagnostic scenarios rather than competing point predictions; the eventual eruption epoch will test their underlying assumptions.