Non-equilibrium heating of white dwarfs during two-step neutronization and formation of small but finite core of the new phase is a main source of energy in these stars when the temperature is sufficiently small and Coulomb crystal becomes degenerate.
Existence of Chandrasekhar mass limit of white dwarfs Mch = 5.83 /μ2
z, μz = A/z, is connected with the prevalence of the relativistic degenerate electrons in pressure. When neutronization is taken into account, the maximal value of mass is smaller and is reached at finite density (Schatzman, 1958). The central density of the white dwarf with limiting mass is larger than threshold density of neutronization. Such star has a small, but finite core of new phase (Seidov, 1967). The neutronization threshold for the iron is equal to ρ = 1.15 109 g/cm3 The neutronization goes through two steps