New binary parameters for the symbiotic recurrent nova T Coronae Borealis

The amplitude of the ellipsoidal variability, the mass function and the evolutionary limits on the component masses have been used to constrain the binary system parameters of T Coronae Borealis. Contrary to all previous studies, our analysis shows that the mass ratio of T CrB is q ≡ M _g/ M _h≈0.6, which implies a low-mass binary system, with the stellar masses M _g～0.7 M⊙ for the red giant and M _h～1.2 M⊙ for the hot companion. This result strongly supports the thermonuclear runaway model for this recurrent nova, and solves all controversies about the nature of the hot component and the physical causes of its eruptions.