  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. Contrary to all previous studies, our analysis shows
that the mass ratio of T CrB q(M_giant/M_hot)=0.6, which implies a low mass
binary system, with the stellar masses M_giant=0.7 solar mass, and M_hot=1.2
solar mass. 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.
