Space-time diagrams, or Kippenhahn diagrams, of the 15 M_⊙ model for GENEC (left) and MESA (right). The grey zones show convective regions. The plot background shade displays the total energy input, the nuclear energy subtracted by the loss of thermal neutrinos in log scale. Blue represents negative energy contributions and red positive contributions. On the right axis is shown the central abundance of a given selection of species to help identify the various burning phases. The black dashed line delimits the total mass of the model.