Kippenhahn diagram of the RSG remnant of 2.80 M_⊙ with a BH and NS companion after the CE phase. The evolution of the interior of the RSG remnants through MT to a BH and NS companion are shown in the panel a and panel b, respectively, as a function of the remaining time until central Si depletion (Si mass fraction <  10⁻³). The blue colours indicate the intensity of nuclear energy production. Convection, convective overshooting, semi-convection, and thermohaline mixing are marked with grey, purple, brown, and yellow hatched zones, respectively. The red and green dotted lines denote the C and O core boundaries.