Panel S1 (a): evolution of the surface abundances in mass fraction as a function of the actual mass of the star for the nonrotating single star S1 with 30 M_⊙. Different evolutionary phases are indicated in the upper part of the figure. Panel S1 (b): evolution of abundance ratios in number as a function of the actual mass of the star S1. Panels S2 (a) and S2 (b): same as panels S1 (a) and S1 (b) but for the rotating model S2. Panels B1 (a) and B1 (b): same as the panels S1 (a) and S1 (b) but for the primary star in model B1 with initial P_orb = 6.0 days. Panels B3 (a) and B3 (b): same as the panels S1 (a) and S1 (b) for the primary star in model B3 with initial P_orb = 1000.0 days.