Observer’s view of a neutron star, illustrating the general relativistic effects on the visibility and flux of two accretion columns for an observer at infinite distance from the neutron star. Sky coordinates are parameterized through the impact parameters A and B, which correspond to the projected distance from the gravitational center in units of the Schwarzschild radius, r_s. The illustration corresponds to the two-pole geometry used in Sect. 3.2. Different apparent sizes of the accretion columns are due to strong light-bending effects.