Evolutionary tracks of a rapidly rotating 30  M_⊙ star, and of both components of a 16  M_⊙+14  M_⊙ close binary, in the HR diagram (left) and in the sHR diagram (right). Dots are placed on the tracks such that the stars spend 10⁵  yr between two dots. For comparison, the same tracks shown in Figs. 1 and 2 are included (black dotted lines). The sHR diagram contains lines of constant gravity (dotted straight lines), and its right ordinate scale is only valid for an unchanged surface helium abundance of Y ≃ 0.26.