Plots of the 610 sdB candidates’ variability indices. Au/Ai is the phase-folded models’ amplitude ratio between the u- and i-band filters for the dominant frequency, whereas sigvar is the significance of variability (also known as the reduced weighted χ²) computed from candidates’ fluxes in the q-band filter. The skewness and kurtosis (Friedrich et al. 1997) are obtained from the q-band fluxes, while the MAD and magnitude of variability (V), defined in Sect. 4, are derived from the q-band magnitudes.