Left: specific intensities for the sdO star and for the three irradiated zones on the M dwarf. Note, we use a logarithmic scale on the abscissa to better represent the centre-to-edge variations of the specific intensities, μ is the cosine of the polar angle (between the line of sight and the surface normal at a given point on the companion) that takes the value 1 in the disk centre and 0 on the edge. There is only a little difference between the substellar zone (No. 1) and the intermediate zone (No. 2), but the terminator zone (No. 3) is substantially fainter. Each zone shows a moderate brightening towards the limb. Right: effects of limb darkening on the phase profile. The three-zone Tlusty model only provides a marginally better fit than a flat surface intensity distribution of the companion.