Soft (left) and hard (right) fluxes, after correction for the interstellar absorption and in units 10^-12 erg cm^-2 s^-1, relative to the separation between the components in HD 166734 (in units of a). Swift and XMM-Newton observations are shown by magenta crosses and black filled circles, respectively. The best-fit relations are shown by dotted lines (in green when taking errors into account, so XMM-Newton data are driving the fit; in blue when all points have the same weight).