Mean 9–13 keV pulse profiles of the four time intervals at different 35 d phases (see Table 1): Interval 1 in black (solid line), Interval 2 in green (dashed line), Interval 3 in red (dash dotted line) and Interval 4 in blue (dash dot dot dotted line). For general 35 d dependence see Staubert et al. (2010). As timing reference for pulse phase zero we use the “sharp-edge” at the trailing edge of the right shoulder of the main pulse which leads into an eclipse like minimum (Staubert et al. 2009b). Note that these pulse profiles are statistically so accurate that the uncertainties are smaller than the line width.