Evolution of the temperature (upper left panel), electron fraction (upper right panel), and radioactive energy deposition (lower left panel) in the oxygen core (blue), in the inner and outer (yellow and green) helium envelope, and in the hydrogen envelope (red) for the optimal model (M17-s-s-XH-low). In the lower right panel, we show the evolution of the (Rosseland mean) continuum photosphere (black) and the outer borders of the carbon-oxygen core (blue) and the inner and outer (green and yellow) helium envelope.