Hertzsprung–Russell diagram with tracks of MESA models with initial masses of 20 M_⊙ and 60 M_⊙ and different initial rotation velocities. The black line represents the zero-age main sequence for stars with the composition described in Sect. 3, while the brown line represents the zero-age main sequence for helium stars. Thick solid lines indicate that a model is core hydrogen burning with X_c > 0.01; thin solid lines indicate core helium burning; dashed lines indicate that a model is in an in-between, shorter-lived phase. The observed apparently single Wolf–Rayet stars (Table 2) are displayed as gray circles. Those in a binary system are displayed as gray diamonds (Table 1). The numbers indicate the identifier of the star, e.g., SMC AB1.