negligibly small and matter is ionized, but at the outer edge the flux is equal to the luminosity of the star, and matter completely recombines.

During the CRW phase the evolution of the density in the ejecta illustrates the homologous expansion (Fig. \[fig:crwdnt\]a). The behavior of the gas and radiation temperatures reflects two important facts (Fig. \[fig:crwdnt\]b). First, in the subphotospheric layers in an optically thick medium, under conditions very close to LTE, the radiation temperature is virtually equal to the gas temperature. Second, in the transparent layers, beyond the photosphere, the gas temperature turns out to be lower than the radiation temperature because of the weak interaction between matter and radiation and of the dominant role of adiabatic losses. From an inspection of the interior luminosity and the fraction of ionized hydrogen from $t=20$ days to $t=100$ days, the CRW characteristics described above are evident (Figs. \[fig:crwlxh\]a and \[fig:crwlxh\]b). Hence in this period the CRW occurs.

From $t=20$ days to $t=100$ days, the CRW propagates through a mass of $\approx 15.96 M_{\sun}$, while the outermost layers, those responsible for the luminosity during the first 18 days, contribute only about $0.13 M_{\sun}$. It is interesting that for this period the 