Formation of binary millisecond pulsars with relatively high surface dipole magnetic fields

We have carried out numerical evolutionary calculations of binary systems to investigate the formation of binary millisecond pulsars (pulsars with white dwarf companions). We apply a "standard scenario" in which the binary pulsars are formed from low-mass and intermediate-mass X-ray binaries as well as an alternative scenario in which the neutron stars are formed by accretion-induced collapse (AIC) of white dwarfs. The mass transfer processes are carefully followed by taking into account a number of binary interactions. Assuming that the magnetic fields of the neutron stars decay due to the accretion, we calculate the pulsar surface dipole magnetic field strength at the end of the mass transfer as a function of the final orbital period. We find that while the observed data of the majority of pulsars are compatible with the derived relations, we fail to produce binary pulsars with relatively high magnetic fields and short orbital periods (such as PSR B0655+64). We conclude that those systems are most likely formed through common-envelope phase.