摘要
The recent discoveries of pulsed X-ray emission from three ultraluminous X-ray （ULX） sources have finally enabled us to recognize a subclass within the ULX class： the great pretenders, neutron stars （NSs） that appear to emit X-ray radiation at isotropic luminosities Lx = 7 × 10^39 erg s-1 _ 1 ×10^41 erg s-i only because their emissions are strongly beamed toward our direction and our sight lines are offset by only a few degrees from their magnetic-dipole axes. The three known pretenders appear to be stronger emitters than the presumed black holes of the ULX class, such as Holmberg II ＆ IX X-1, IC10 X-1 and NGC 300 X-1. For these three NSs, we have adopted a single reasonable assumption, that their brightest observed outbursts unfold at the Eddington rate, and we have calculated both their propeller states and their surface magnetic-field magnitudes. We find that the results are not at all different from those recently obtained for the Magellanic Be/X-ray pulsars： the three NSs reveal modest magnetic fields of about 0.3-0.4TG and beamed propeller-line X-ray luminosities of 1036 - 1037 erg s-1, substantially below the Eddington limit.
The recent discoveries of pulsed X-ray emission from three ultraluminous X-ray （ULX） sources have finally enabled us to recognize a subclass within the ULX class： the great pretenders, neutron stars （NSs） that appear to emit X-ray radiation at isotropic luminosities Lx = 7 × 10^39 erg s-1 _ 1 ×10^41 erg s-i only because their emissions are strongly beamed toward our direction and our sight lines are offset by only a few degrees from their magnetic-dipole axes. The three known pretenders appear to be stronger emitters than the presumed black holes of the ULX class, such as Holmberg II ＆ IX X-1, IC10 X-1 and NGC 300 X-1. For these three NSs, we have adopted a single reasonable assumption, that their brightest observed outbursts unfold at the Eddington rate, and we have calculated both their propeller states and their surface magnetic-field magnitudes. We find that the results are not at all different from those recently obtained for the Magellanic Be/X-ray pulsars： the three NSs reveal modest magnetic fields of about 0.3-0.4TG and beamed propeller-line X-ray luminosities of 1036 - 1037 erg s-1, substantially below the Eddington limit.
基金
DMC,SGTL and RC were supported by NASA grant NNX14-AF77G
DK was supported by a NASA ADAP grant
