  One ultraluminous X-ray source in M82 is identified as an accreting neutron
star recently (named as NuSTAR J095551+6940.8). It has a super-Eddington
luminosity and is spinning up. For an aged magnetar, it is more likely to be a
low magnetic field magnetar. An accreting low magnetic field magnetar may
explain both the super-Eddington luminosity and the rotational behavior of this
source. Considering the effect of beaming, the spin-up rate is understandable
using the traditional form of accretion torque. The transient nature, spectral
properties of M82 X-2 are discussed. The theoretical period range of accreting
magnetar is provided. Three observational appearances of accreting magnetars
are summarized.
