Variation of the angular velocity as a function of the radius in solar units. The continuous lines refer to the spin-up case with an orbital period equal to 1.4 days. The dashed curves correspond to the spin-up case with an orbital period equal to 1.0 days. Different ages are plotted with different colors as indicated in the inset, for both the continuous and dashed lines. The curves for the periods equal to 1.0 and 1.4 days, corresponding to an age of 113 000 years, are the same and thus are superposed.