Top panel: light curves with a 25.5 s time resolution of all three observations as a function of orbital phase. Bottom panel: corresponding hardness ratios. All observations were in the low/hard state. Dips are strongest at ϕ_orb ~ 0.0, become weaker at ϕ_orb ~ 0.2 and ϕ_orb ~ 0.75, and completely fade at ϕ_orb ~ 0.5 (see also Paper II). Colors indicate the selected dipping stages (see right panel of Fig. 3 for the color denotation and Sect. 2.3 for details on the data selection).