X-ray secondary eclipse data shifted onto the scaled TESS light curve with best-fit secondary period, shown in the upper panel; blue data points refer to ROSAT data, green data points to XMM-Newton data, red curve is the best fit nightfall model to TESS; see text for details. Lower panel shows the same data as in upper panel, except that the periods between primary and secondary minima have been assumed to be identical. See text for details.