Time evolution of absorption RV (mean RV from the literature, and the Hα core RV for all the new spectra at our disposal), the V magnitude, and B − V, and U − B colour indices over the whole time interval covered by available observations. In the RV plot, black dots show the RVs from the literature, blue circles are from our high signal-to-noise (S/N) spectra, red ones from OND spectra, and green ones from the BeSS spectra. In panels with photometry, blue dots denote calibrated U​BV values, red the y magnitude of the Strömgren system, green the HIPPARCOSH_p magnitudes transformed to Johnson V, magenta the ASAS3 V magnitude, and brown the KWS V magnitude. We note the shorter time interval covered by the observed colour changes.