Models for Compact Pulsing X-Ray Sources

Abstract

Cen X-3 is probably a neutron star, releasing the infall energy of accreted matter. Sufficient material for accretion will be provided by a conventional stellar wind from its more massive companion star. That star is not likely to rotate synchronously; therefore a ‘Roche lobe’ analysis of the eclipses is not valid. A ‘tidal lobe’ analysis allows the neutron star to have a mass of the order of one solar mass. Overflow of the ‘Roche lobe’ is neither necessary as a source of mass nor probable in view of the observed stellar line widths of the two identified X-ray companions.The mass flow onto the condensed star is very small in all cases. It is limited, for an object of m solar masses by the Eddington Limiting Luminosity to Ṁac < 10–7.4m(M⊙ yr−1), which limit applies even if the accreting object contacts or traverses its companion star.The observed 4.84 s rotation period of the Cen X-3 neutron star is very simply explained as the critical value where a centrifugal barrier regulates the rate of infall to the surface. The X-ray spectrum is understood as blackbody radiation coming from a well-defined area near each magnetic pole of the neutron star.