  Observations made using TESS revealed a sample of low mass stars which show a
periodic modulation on a period $<0.2$~d. Surprisingly many of these Ultra Fast
Rotating (UFR) stars showed no evidence of flare activity which would be
expected from such rapidly rotating stars. We present results from a
spectroscopic survey of UFRs using the Nordic Optical Telescope to search for
radial velocity variations which could reveal evidence for binarity. Our sample
of 29 sources have a photometric period between 0.1-0.2d, cover spectral
classes of M0-4V, and show no evidence for flares. We detect only one source
with clear radial velocity shifts, with another two having Gaia RUWE values
which suggests they are binaries. Further observations reveal the former star
possibly contains a brown dwarf companion with a mass of M$_2$>58 M$_{\rm Jup}$
and probability P(M$_2$<90 M$_{\rm Jup}$) = 50\%. 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 $\delta$ 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.
