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Using K2, we recently discovered a new type of periodic photometricvariability while analysing the light curves of members of Upper Sco (Stauffer\etal\ 2017). The 23 exemplars of this new variability type are all mid-Mdwarfs, with short rotation periods. Their phased light curves have one or morebroad flux dips or multiple arcuate structures which are not explicable byphotospheric spots or eclipses by solid bodies. Now, using TESS data, we havesearched for this type of variability in the other major sections of Sco-Cen,Upper Centaurus-Lupus (UCL) and Lower Centaurus-Crux (LCC). We identify 28stars with the same light curve morphologies. We find no obvious differencebetween the Upper Sco and the UCL/LCC representatives of this class in terms oftheir light curve morphologies, periods or variability amplitudes. The physicalmechanism behind this variability is unknown, but as a possible clue we showthat the rapidly rotating mid-M dwarfs in UCL/LCC have slightly differentcolors from the slowly rotating M dwarfs - they either have a blue excess (hotspots?) or a red excess (warm dust?).  One of the newly identified stars (TIC242407571) has a very striking lightcurve morphology. At about every 0.05 in phase are features that resembleicicles, The "icicles" arise because there is a second periodic system whosemain feature is a broad flux dip. Using a toy model, we show that the observedlight curve morphology results only if the ratio of the two periods and theflux dip width are carefully arranged.

the astronomical journal

Even More Rapidly Rotating Pre-Main Sequence M Dwarfs with Highly  Structured Light Curves: An Initial Survey in the Lower Centaurus-Crux and  Upper Centaurus-Lupus Associations