Upper panel: spectroscopic orbit of WASP-31, as illustrated by radial velocities from CORALIE (blue circles) and HARPS (red squares). The best-fitting Keplerian model, generated from the parameters of Table 4, is overplotted as a solid line. An RV taken at BJD = 2 455 168.8468, depicted in the plot by an open circle, fell during transit. As we did not treat the Rossiter-McLaughlin effect (e.g., Queloz et al. 2000a), we excluded this measurement from our combined analysis. Lower panel: a lack of correlation between bisector spans and radial velocities rules out a blended eclipsing binary or starspots as the cause of the photometric and spectroscopic variaitions. We adopted uncertainties on the bisector spans twice the size of those on the radial velocities. For both plots, the centre-of-mass velocity, γ = −124.92 m s^-1, was subtracted from the radial velocities and the Keplerian model.