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


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Ekşi K. Y. , Andaç İ. C. , Çıkıntoğlu S. , GENCALI A. A. , Güngör C. , OZTEKIN F.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol.448, no.1, 2015 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 448 Issue: 1
  • Publication Date: 2015
  • Doi Number: 10.1093/mnrasl/slu199
  • Title of Journal : MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
  • Keywords: X-rays: binaries, X-rays: individual: NuSTAR J095551+6940.8, SMALL-MAGELLANIC-CLOUD, SOFT GAMMA REPEATERS, NEUTRON-STARS, BLACK-HOLE, ACCRETING MAGNETARS, THOMSON SCATTERING, 4U 2206+54, SXP 1062, PULSARS, FIELD

Abstract

The recent detection of pulsations from the ultraluminous 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 that the dipole magnetic field of the neutron star is 6.7 x 10(13) 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 if the magnetic field decays an order of magnitude during the process of transition.