Hollow Accretion Columns on Neutron Stars and the Effects of Gravitational Light Bending

Abstract

This study investigatesthe beam patterns for radiation originating in a hollow column ona slowly rotating neutron star where the Schwarzschild metric isappropriate for calculating photon paths. The beam pattern of a hollowcolumn is the sum of contributions from the two emitting surfaceson the inside and the outside of the column, which combine into atwo-component beam pattern. The shapes of the inside beam pattern,the outside beam pattern, and the combined beam pattern are studiedfor radial cones of different height and width, for isotropic andbeamed emission, and for different values of mass and radius of theneutron star. It is argued that the hollow cone model provides aninterpretation of the pulse profiles of the X-ray pulsar Centaurus X-3.