A New Interpretation for the Second Peak of T Coronae Borealis Outbursts: a Tilting Disk around a Very Massive White Dwarf

A new interpretation for the second peak of T Coronae Borealis (T CrB) outbursts is proposed based on a thermonuclear runaway (TNR) model. The system consists of a very massive white dwarf (WD) with a tilting accretion disk and a lobe-filling red-giant. The first peak of the visual light curve of T CrB outbursts is well reproduced by the TNR model on a WD close to the Chandrasekhar mass (MWD ∼> 1.35 M⊙), while the second peak is reproduced by the combination of the irradiated M-giant and the irradiated tilting disk. The derived fitting parameters are the WD mass MWD ∼ 1.35 M⊙, the M-giant companion mass MRG ∼ 0.7M⊙ (0.6 − 1.0M⊙ is acceptable), the inclination angle of the orbit i ∼ 70, and the tilting angle of the disk iprec ∼ 35 . These parameters are consistent with the recently derived binary parameters of T CrB. Subject headings: accretion disks — binaries: close — binaries: symbiotic — novae — stars: individual (T CrB)