A NEW CLASS OF NEUTRON STAR BINARIES AND ITS IMPLICATIONS

Recent discovery of 2M ⊙ neutron stars in white dwarf-neutron star binaries, PSR J1614-2230 and PSR J0348+0432, has given strong constraints on the maximum mass of neutron stars. On the other hand, all well-measured neutron star masses in double neutron star binaries are still less than 1.5M ⊙ . These observations suggest that the neutron star masses in binaries may depend on the evolution process of neutron star binaries. In addition, recent works on LMXB (low-mass X-ray binaries) provides us the possibility of estimating the masses and radii of accreting neutron stars in LMXBs. In this talk, we discuss the implications of recent neutron star observations to the neutron star equation of states and the related astrophysical problems. For the evolution of neutron star binaries, we also discuss the possibilities of super-Eddington accretion onto the primary neutron stars.