Observational HR diagram. Colour points represent the sources from the DR2 LPV catalogue that have positive ϵ(ϖ)∕ϖ < 0.1. The colour of the points is related to the G variability amplitude, measured by the 5–95% quantile range QR₅ of the cleaned G time-series, according to the colour scale on the right of the figure (the upper limit of the colour scale has been truncated to QR₅ = 1 mag for better visibility, all objects with QR₅ > 1 mag being plotted in red). The background grey points represent the sample of stars from the whole Gaia DR2 catalogue that have ϖ > 2 mas and ϵ(ϖ)∕ϖ < 0.1. The dotted line separates LPV candidates from YSO candidates (see text).