Left panel: evolution of the surface equatorial velocity as a function of time for 40 M_⊙ models. The colours indicate the ratio between the central and surface angular velocities. The orbital period for the binary model is 1.4 days, the secondary model has an initial mass equal to 26.7 M_⊙. Right panel: evolutionary tracks in the HRD for the same models as in the left panel. The colours indicate the N/C ratio at the surface normalised to the initial one (N/C_ini = 0.29 in mass fraction). In the binary systems, the stars initially have an angular velocity superior to the orbital velocity, and thus the tidal forces spin down the star (see Table A.1).