Estimates of the X7 orbital period (P_orb) and the projected semi-axis of the orbit for a spin period of ∼2.73s in XMM2. The confidence contour, more similar to an atoll rather than a ‘banana’ shape, is indicative of the low significance of the spin period detection. However, a similar plot can be obtained for XMM1 as well, boosting the real significance of the signal. The colour bar indicates the Leahy power of the signal.