Measurements of the spin period of Swift J1749.4−2807 in the RXTE data. The spin period is computed in each case by using a time window with a duration of between 200 s and 1000 s (depending on the source intensity) and fitting with a Gaussian function the peak in the Z²-statistics corresponding to the first overtone of the pulse. From these measurements, we derived the orbital parameters reported in Table 3. The corresponding orbital solution is represented in this figure with a dotted line.