Ultraluminous X-ray pulsar: Accreting magnetar?

Magnetars are a special kind of neutron stars. There may also be accreting magnetars. From the studies of isolated magnetars, it is known that a neutron star with a strong dipole field only is not a magnetar. Super-slow X-ray pulsars may just be accreting high magnetic-field neutron stars. The ultra-luminous X-ray pulsar NuSTAR J095551+6940.8 may be an accreting magnetar. It may be an accreting low magnetic field magnetar with multipole field of 10(14) G and dipole field of 10(12) G. This point of view is consistent with the study of isolated magnetars. An ultra-luminous X-ray pulsar phase during binary evolution may result in massive millisecond pulsars. ((c) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)