Contour plots for mag as a function of mass in M_⊙ and T_eff for CO (top), ONe (bottom) core compositions constructed according to Eq. (1) and theoretical models from Wood (1995), Holberg & Bergeron (2006) for the CO models, and Althaus et al. (2005, 2007) for the ONe models. The bar to the right indicates the colour coding for the magnitude differences, the line in the darkest region  mag delinating and the vertical lines the possible range of effective temperatures (30 000–50 000 K).