X-ray pulses from accretion columns: Contributions to the energy dependence of the pulse shape

We study the pulse profiles of medium-luminosity binary X-ray pulsars in the framework of a column model. The model includes relativistic effects in a Schwarzschild spacetime and the dipolar shape of the accretion funnel. It takes into account mechanisms that are expected to be of major importance for the energy dependence of the pulse shape: energy-dependent local beaming of radiation leaving the column, the luminous halo formed by illumination of the neutron star surface, and magnetic scattering in the upper accretion stream. Beam patterns and pulse profiles are calculated for different values of mass and radius of the neutron star and different local beaming functions. The results illustrate that the energy dependence of the pulse profiles is to a large degree determined by the energy-dependent relative importance of the halo and column contributions to the observed flux.