The ultra luminous X-ray source NuSTAR J095551+6940.8: A magnetar in a high mass X-ray binary

K. Y. Ekşi, İ. C. Andaç, S. Çıkıntoğlu, A. A. Gençali, C. Güngör, F. Öztekin

Published 2014-10-20Version 1

The recent detection of pulsations from the ultra luminous X-ray source (ULX) NuSTAR J095551+6940.8 in M82 by Bachetti et al.\ indicates that the object is an accreting neutron star in a high mass X-ray binary (HMXB) system. The super-Eddington luminosity of the object implies that the magnetic field is sufficiently strong to suppress the scattering cross-section unless its beam is viewed at a favourable angle. We show that the torque equilibrium condition for the pulsar indicates the dipole magnetic field of the neutron star is $\sim 10^{14}$ G, two orders of magnitude higher than that estimated by Bachetti et al., and further point to the possibility that even stronger magnetic fields could well be in the higher multipoles. This supports the recent view that magnetars descent from HMXBs.