Upper panel: correlation between the HXD₁, evaluated using the direct method, with the third power of the mean count rate of the BL (in units of 10⁶). Blue circles correspond to the interval I series, blue triangles to the interval III series; red filled squares correspond to the series in interval II. The solid thick violet line indicates the linear best fit. Black circles and the thin black line are data points for the CCF estimates of HXD and their best fit. Central panel: correlation between the mean HXDs with the mean count rate in the PDS band (units of 10⁵). Symbols are the same as in the upper panel. Lower panel: correlation between the mean HXD₁ with the recurrence time of bursts as evaluated in Paper I. The solid thick line is the linear best fit of blue points only. Black circled points mark the irregular data series.