Illustration (not to scale) of the computation in Sect. 4.1. The inhomogeneous wind induces a time-variable column density on the line of sight (solid line) as the constant X-ray flux point source (cross) orbits the star (in blue) at φ_orb = 0.21–0.25 (arc interval). The overdense regions are fiducially represented using radially fading spheroidal black dots and the inter-clump environment using a smoothly decaying spherical profile.