Timing analysis of 4U 1907+09. Top left, panel a: hardness ratio of the combined EPIC-pn, MOS1, MOS2 light curves (3–10 keV/0.5–3 keV). Top left, panel b: total rate in the 0.5–10 keV energy range. Bottom left, panel c: distance d_j from the average for each pulse profile as function of HR. Bottom left, panel d: distance d_j from the average for each pulse profile as function of the total rate. The numbers indicate the different intervals identified in panel b (see Eq. (1) for the definition of d_j). Right: plot of the best-fit parameters as a function of time obtained from the HR-resolved spectral analysis of the XMM-Newton observation of 4U 1907+09. The parameters reported in the different panels are those introduced in Table 2 and described in the text.