Variability plot showing the spread of luminosity (left y-axis) and count rate (right y-axis) for all OB or HV SSS or nova sources. The x-axis is labelled with the catalogue source number (No.). When the lowest count rate was derived from an upper limit of the light curve, the lower count rate is marked by a downward arrow. The blue diamonds mark the sources that are classified as OB sources in the catalogue. The black dots mark the sources that are associated to optical novae.