Variation of luminosity (black line), L, and polar radius (yellow line), R_p, normalised to the values of a non-rotating star as a function of critical velocity fraction, ω. The left panel shows models with masses 10M_⊙ and the right panel 20M_⊙. All models have burnt 3% by mass of their initial hydrogen (i.e. X_c = 0.7169). Each cross represents a value computed by a MESA model. Dashed lines show extrapolated values.