The puzzling story of flare inactive ultra fast rotating M dwarfs. II. Searching for radial velocity variations

ABSTRACT Observations made using TESS revealed a sample of low-mass stars which show a periodic modulation on a period 58 MJup and probability P(M2 < 90 MJup) = 50 per cent. There is no evidence for the companion in our spectra, strengthening the case for a brown dwarf companion. We also examine the folded TESS light curves of all our targets, finding at least two are eclipsing binaries and one which has been contaminated by a spatially nearby δ Sct star. We estimate that around 1/4 of our targets may have been contaminated by short period variable stars. However, the majority of our targets are consistent with being single, low mass stars whose variability is due to starspots. We outline the possible reasons why they are not flare active despite being such rapid rotators.