Evolutionary tracks on the gravitational mass–equatorial radius M−R_eq plane, assuming a thin-disk accretion model, superimposed on the mass-radius curves for constant rotation rates in the range between 0 and 1000 Hz. Two angular momentum transport efficiencies are considered. Solid lines correspond to perfect angular momentum transfer from the accretion disk to the star, dashed lines correspond to half of the accretion-disk angular momentum transferred. The initial masses for these tracks are 1.4 M_⊙ and 1.8 M_⊙. For more details see the text.