Kippenhahn diagram showing internal structure of the donor and accretor of the model with initial donor mass, mass ratio, and orbital period of 44.6 M_⊙, 0.5, and 7.9 d, respectively, as a function of the stellar age. The green hatched line shows the regions of the star that are unstable to convection. The purple cross-hatched line shows the extent of convective overshooting above the convective core. The yellow hatching denotes the regions of thermohaline mixing. Red shows the regions of semi-convective mixing. The black line gives the total mass of the star as a function of stellar age.