Evolution of log(T_eff/K) (top panel), Γ_e and Γ_{e, switch} (middle panel, solid and dashed lines) as a function of stellar age for a star with M = 30 M_⊙, Ω/Ω_c = 0.6, at Z = 0.002. The color of the solid line indicates the burning stage: blue for hydrogen burning, orange for helium burning. The bottom panel shows η and η_switch as a function of Γ_e at the times indicated by the vertical dotted lines in the top and middle panels. The lines’ color goes from blue to red increasing the time. The point where η = η_switch is marked and represents the threshold for thick winds activation Γ_{e, switch}.