  Quiescent X-ray luminosities are presented in low mass X-ray binaries with
use of evolutionary calculations. The calculated luminosities are compared with
observed ones in terms of timeaveraged mass accretion rate. It is shown that
neutrino emission by strong pion condensation can explain quiescent X-ray
luminosity of SAX J1808.4-3658 and we do not need direct Urca processes
concerning nucleons and/or hyperons.
