Accreting magnetars: Linking ultraluminous X-ray pulsars and the slow pulsation X-ray pulsars

Abstract

Possible manifestations of accreting magnetars are discussed. It is shown that the four ultraluminous X-ray (ULX) pulsars can be understood in the accreting low magnetic field magnetar scenario. The NGC 300 ULX1 pulsar may have a higher dipole magnetic field than other sources. General constraint on their mass accretion rate confirmed their super-Eddington nature. Lower limits on their beaming factor are obtained. They do not seem to have strong beaming. The duty cycle of the ULX burst state can also be constrained by their timing observations. ULX pulsars may be in accretion equilibrium in the long run. During the outburst, they will spin-up, and run from the previous equilibrium state to the new equilibrium state. It is proposed that the slowest pulsation X-ray pulsar AX J1910.7+0917 may be an accreting magnetar with a low mass accretion rate. ULX pulsars, slow pulsation X-ray pulsars may all be accreting magnetars with different accretion rates. Seven possible signatures of an accreting magnetar are summarized.