Emission of Photoneutrinos and Pair Annihilation Neutrinos from Stars

Field-theoretic calculations of the cross sections for the photoneutrino process, $\gamma +e^{-}\to e^{-}+\nu +\overline{\nu }$, and the pair annihilation process, $e^{+}+e^{-}\to \nu +\overline{\nu }$, are performed in order to obtain the neutrino luminosity of very hot stars ($T_c\gtrsim 5\times {10}^8°$K). The energy loss rate which is obtained for the latter process is sufficient to determine the rate of evolution of the stellar core when $T_c\gtrsim 2\times {10}^9°$K.