Left: residual BRITE photometry of ζ Ori during three distinct epochs after all significant periodic variability was removed through iterative prewhitening. The same color-coding as in Fig. 2 has been applied. Right: corresponding Lomb-Scargle periodograms of the residual lightcurves, represented with the same scale as in Fig. 2. The flux residuals contain some remaining variability, which is not significant in the Lomb-Scargle periodogram.