Hertzsprung-Russell diagram: evolutionary tracks of Clés models for the primary star of M_init = 17 M_⊙ (green), 18 M_⊙ (light blue), 19 M_⊙ (dark blue), 20 M_⊙ (pink), and 21 M_⊙ (orange), and D_T = 0 cm² s⁻¹ (solid line), 2 × 10⁶ cm² s⁻¹ (dashed line), 6 × 10⁶ cm² s⁻¹ (dotted-dashed line), and 10 × 10⁶ cm² s⁻¹ (dotted line). All models have α_ov = 0.30 and ξ = 1. The dots over-plotted on the corresponding tracks correspond to the models for which k_2, 1 is equal to , while the open circles correspond to the models for which k_2, 1 is equal to . The filled and open squares over-plotted on the tracks having an initial mass of 19 M_⊙ correspond to the models for which the mass equals the observational value within the error bars. The observational value is represented by the red point, and its error bars are represented by the dark red parallelogram.