Accretion and Magneto-Dipole Emission in Fast-Rotating Neutron Stars: New Spin-Equilibrium Lines

摘要

Although most of the proposed equations of state predict minimum spin periods well below one millisecond if more than about 0.3 solar masses are accreted onto a low magnetized neutron star through a Keplerian accretion disc, the spin periods of the recently discovered accreting millisecond pulsars all cluster in the quite narrow range between 1.7 and 5.4 ms; these spin periods are uncomfortably higher than the theoretical predictions. We propose and discuss here the possibility that emission due to a magneto-dipole rotator is relevant even during the accretion phase in fast-spinning neutron stars; this mechanism is able to explain the quite long spin periods observed in both low mass X-ray binaries and millisecond radio pulsars.