Publication Date:
2015-10-15
Description:
We study properties of luminous X-ray pulsars using a simplified model of the accretion column. The maximal possible luminosity is calculated as a function of the neutron star (NS) magnetic field and spin period. It is shown that the luminosity can reach values of the order of 10 40 erg s –1 for the magnetar-like magnetic field ( B 10 14 G) and long spin periods ( P 1.5 s). The relative narrowness of an area of feasible NS parameters which are able to provide higher luminosities leads to the conclusion that L ~= 10 40 erg s –1 is a good estimate for the limiting accretion luminosity of an NS. Because this luminosity coincides with the cut-off observed in the high-mass X-ray binaries luminosity function which otherwise does not show any features at lower luminosities, we can conclude that a substantial part of ultraluminous X-ray sources are accreting neutron stars in binary systems.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics