Multifilter observations of the complex periodic variations in eight pre-main sequence stars

Follow up time series photometry through various combinations of the BVRCIC filter set is presented for eight young stars. The complex periodic variability of seven of the stars was first discovered in TESS photometry, while one star was first observed by K2. The periods of the stars are short -0.2-0.4 d. Reddening, effective temperatures, and bolometric magnitudes are estimated by fitting spectral energy distributions. The new photometry typically covers several cycles of variability. In some cases, photometry was obtained in more than one observing season. All new light curves differ from those obtained from satellite missions, in some cases substantially so. Amplitudes are almost always larger, the shorter the effective wavelength of the filter, but the relationship can be weak or non-monotonic. Given that all but one of the stars are in associations older than 10 Myr, it seems unlikely that protoplanetary discs play an important role in the complex variability patterns. Modelling of the wavelength dependence of amplitudes in terms of dust absorption in debris discs is explored. The conclusion is that excesses of small grains as compared with the average Galactic composition would be required.