Implications of Various Hadron Phases to Neutron Star Phenomena

Effects of various hadron phases on thermal and dynamical properties of neutron stars are studied in connection with astronomical phenomena. In particular, nucleon superfluidity and pion condensation are mainly considered. (1) It is shown that ALS solid core and rapid cooling in the presence of combined neutral and charged pion (π0πc)-condensed phase give the basis of an extended starquake model which explains both Vela and Crab pulsar glitches consistently. In this model, the neutron 1S0 and 3P2 superfluids having different couplings with the crust are related to the observed two relaxation times. (2) Extra neutrino emissivity under the π0πc-condensed phase is studied and each role of the π0 and πc condensates is clarified. By the use of this emissivity, cooling history of pion-condensed neutron stars are discussed. (3) First order phase transition from the πc-condensed phase to the π0πc one is shown to be essential to dynamical properties of pion-condensed neutron stars. Energy release associated with a mini-collapse is obtained in relation to the anomalous gamma-ray burst, where the dissipation mechanism in the pion-condensed phase is also discussed. (4) Characteristic features of hot and dense supernova matter are investigated and energy release of a hot neutron star at birth due to the first order phase transition to a cold pion-condensed neutron star is discussed in connection with the neutrino burst from the supernova SN1987A. Also the extent of spin-up due to the contraction during the early cooling stage is estimated. (5) Maximum rotation rates of neutron stars with and without pion condensates are obtained, and it is shown that they serve as a probe for the existence of pion condensation in neutron stars.