Comparisons of X-ray luminosities, bolometric luminosities, X-ray to bolometric luminosity ratios, and hardness ratios, taken by pairs. Green, red, blue, and black symbols correspond to known γ Cas objects, known magnetic objects (including Alfirk because of its magnetic secondary), non-γ Cas and non-magnetic O-type stars, and all other stars, respectively. Stars are used for known binaries (see Table 2), simple dots otherwise. As in Fig. 1, dubious cases are not shown and averages are used in case of multiple observations, the errors corresponding to the scatters around the means. For PZ Gem, both low-flux and high-flux cases are shown, as they differ significantly; they are connected so they can be easily spotted.