Absorption column density values across the orbital phase derived from multiple X-ray satellite observations adapted from Kretschmar et al. (2021). We refer to the main text for considerations when comparing absolute N_H values. Different symbols are used to show data taken in different binary orbits by the same mission. The mean hardness profile from our MAXI/GSC sample is visually scaled and superimposed. The hardness ratio correlates positively with N_H but lacks a direct one-to-one relationship, hence the need for an arbitrary scaling.