Kippenhahn-diagram for our 200  M_⊙ model with v_ZAMS ≃ 300 km s^-1. The black solid line gives the stellar mass as a function of time. Blue shading indicates thermonuclear energy generation (see colour bar to the right of the plot). Green hatched parts show convective regions, and convective core overshooting is indicated in red. Three different regimes can be distinguished according to the rate at which the mass of the convective core decreases (see text).