ρ_c–T_c diagram for the 20 M_⊙ models with different values for α_ov and no extra envelope mixing (log(D_env/cm² s⁻¹) = 0) (left panel). The right panel shows the same for α_ov = 0.2 and the different values for the envelope mixing, where D = log(D_env/cm² s⁻¹). In the left panel, the grey line shows the non-rotating model from Brinkman et al. (2021) with α_ov = 0.2. In the right panel, the rotating models with initial rotational velocities for 150 and 300 km/s are added as a comparison for the different treatment of envelope mixing. The blue line is the same model in both panels. The black dashed lines give a rough indication of the equations of state, that is, radiative, ideal gas, and non-relativistic electron pressure (NR electrons). The grey horizontal lines indicate a central temperature of T_c = 10⁹.