Thermal structures of accreting neutron stars with neutrino losses due   to strong pion condensations
  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. 
Yasuhide Matsuo, Masa-aki Hashimoto, Koutarou Hayashida, Helei Liu,   Tsuneo Noda, Masayuki Y. Fujimoto
astro-ph.HE