The Magnetic Field of the Ultraluminous X-ray Pulsar M82 X-2

Nov 19, 2014
12 pages
e-Print:

Citations per year

20142016201820202020140
Abstract: (arXiv)
Pulsations were recently detected from the ultraluminous X-ray source X-2 in M82. The newly discovered pulsar has been described as a common neutron star with a 1 TG magnetic field that accretes above the Eddington rate and as a magnetar-like pulsar with a 100 TG magnetic field that is above the quantum limit. We show here that this X-ray source is not exotic in any sense. The standard equations of accretion along field lines predict that, for the measured spin period PSP_S and spinup rate PS˙\dot{P_S}, the isotropic X-ray luminosity LXL_X must be near the Eddington limit (i.e., LX3.5×1038L_{X}\approx 3.5\times 10^{38}~erg~s1^{-1}); and that the surface magnetic field BB, that does not depend on PSP_S, must be modest (i.e., B110B_*\approx 1-10 TG). The observed higher luminosity can be explained by a moderate amount of geometric beaming that occurs in our direction. Other ultraluminous X-ray sources may also turn out to be common pulsars with similar physical characteristics, but since the emission must occur at a favorable angle to the observer, we expect that very few such pulsars will be discovered in the future.
Note:
  • This paper has been withdrawn by the authors. New observations have led to a different calculation that will be presented in another paper