Stellar radii as a function of mass from standard stellar evolution models (Ekström et al. 2012). The slanted colored curves connect the radii of evolutionary models as a function of mass for a temperature as indicated by the label. The full drawn lines show models with rotational mixing of the core, and the dotted lines are from nonration-mixed cores. The thin black curves show the possible mass and radius solutions from the fit to the light curve when the semimajor axis is taken as the free parameter. The upper black curve corresponds to the relation between R₁ and M₁, and the lower black curves corresponds to that of R₂ on M₂. The thick parts of the black lines indicate the mass range we derived from the spectroscopic observations in Sect. 3.