Light curve (red: +; blue: ×, vertically offset by 0.15 mag) of η Cen after pre-whitening for the 1.5562 c/d Štefl frequency (without this pre-whitening, the structure of the light curve is extremely similar). Overplotted are fits with the frequency, 0.034 c/d, which corresponds to the difference between the 1.732 c/d and 1.767 c/d variations. Note the apparent outburst around day −160 (a second one may have occurred at day −245) and the enhanced scatter near extrema and especially minima. The phase of the blue variability may be slightly different from the red one. In view of the additional ephemeral variations, this is not considered to be significantly established.