Magnetic field decay and the origin of neutron star binaries

The origin of magnetized neutron stars in binaries and the 1.55 ms pulsar is examined in terms of the magnetic field decay model for radio pulsars with a decay time scale of order 5 x 10 to the 6th yr over 7-10 e-foldings. Observational data of pulsing X-ray sources, nonpulsing X-ray sources, and binary radio pulsars are analyzed. Evolutionary scenarios for Her X-1, MXB 1730-335, 4U 1626-67, GX 1 + 4, 1E 2259 + 59, and long-period binary pulsars are described. The data reveal that: magnetic field strengths for accretion-powered X-ray pulsars in massive binaries and rotation-powered radio pulsars in short-period binaries support the formation of these neutron stars by core collapse following the Fe photodisintegration phase of a He-core remnant that resulted from mass transfer; however, the magnetic field strengths for neutron stars, low-mass X-ray binaries, and in wide radio pulsar binaries are explained if the magnetized neutron stars were formed less than 10 to the 8th years ago by accretion-induced collapse of a massive white dwarf. It is noted that with these two formation models all observations of the magnetic fields of neutron star in binaries are consistent with one single-field decay time scale consistent with one single-field decay time scale down to a surface field strength of less than or equal to 3 x 10 to the 9th G. 108 references.