Much more remarkable in the figure is qualitative differences between the ONe core and the Fe cores. Among other things, the Fe cores emit a substantial amount of neutrinos from much earlier on than the ONe core. This is simply due to their higher temperatures as mentioned earlier. The electron-positron pairs are more abundant, producing neutrinos copiously. In fact, the ONe core is so cold until the electron capture on Mg is opened that electrons are strongly degenerate and, as a consequence, positrons are scarce, making the neutrino luminosity from the pair annihilation negligibly small. Unfortunately, the plasmon contribution is also tiny as long as the temperature is very low, since only a small amount of plasmons are thermally populated then. It is hence understandable that the neutrino luminosity becomes substantial in the ONe core only after the electron captures and the subsequent burnings of oxygen and silicon heat it up, which occur less than a second before collapse. Even after the formation of the NSE region (T 5 × 10 9 K) inside the core, the number luminosity of the ONe core is much smaller than those of the Fe cores. As a matter of fact, ∼ 10 53 neutrinos are emitted in the 15 M ⊙ model while in the 8.4 M ⊙ model the number of emitted neutrinos is only ∼ 10 51 . Note, however, that the luminosity increases very quickly in the last few hundred milliseconds in the ONe core and It is still increasing rapidly at the end of our calculation. At this point the central density is 10 11 g/cm 3 and no more **data** are available from the stellar evolution calculation. Unlike the Fe cores, the ONe core is rather slowly contracting even at this point, with the NSE region being expanding gradually. We hence expect the luminosity continues to rise further until neutrinos are trapped inside the core, which will be somewhat delayed, since the neutrinos considered here have smaller energies (∼ 5 MeV) than those produced by electron captures during collapse (∼ 10 MeV).