Average 2–25 keV PCA power spectrum for observations on July 30, after shifting the centroid of the lower peak to 722 Hz. The lower half of the spectrum has 4 Hz frequency bins, while the upper half is rebinned to 16 Hz bins for display purposes in order to enhance the broad, faint 1050 Hz peak. The inset shows the fitted QPO separation as a function of the mean lower QPO frequency (see text). The horizontal error bars represent the standard deviation of frequencies in the chosen band.