  The variability of fast-rotating Oe/Be stars has been reported in detail in
recent years. However, much less known about the behaviour of fast-rotating OB
stars without known decretion disks, and hence it is difficult to identify the
commonalities and differences in the photometric variability of these two
populations, especially with regards to their pulsational properties and their
link with the presence of circumstellar material. Via an in-depth literature
search, we identified a set of fast-rotating (v sin(i)>200 km/s) early B-type
stars not known to have disks. TESS and Kepler light curves were built for 58
stars that appear isolated (no bright neighbour within 1 arcmin and no known
companion) to avoid contamination of the light curves. Frequency spectra were
calculated and then analysed to determine the noise level and the presence of
significant signals above the noise. Red noise is detected in all targets,
without obvious correlations between noise and stellar parameters. Long-term
changes are much less frequent than in Be stars, with only 12% of our targets
having the variability below 0.5/d dominating their frequency spectrum. In
contrast, strong frequency groups are detected in about a third of targets, as
in Be stars. These groups generally occur in pairs with harmonic frequencies,
as is usually seen in Be stars, but with the first group more often displaying
larger amplitudes. Finally, the most frequent variability is due to isolated
frequencies in the 0.5-6./d range (which is found in two-thirds of cases and
dominates the spectra in 42% of the sample). Higher-frequency signals (up to
40/d) are sometimes also detected but rarely (only 12% of stars) appear as the
strongest ones of the frequency spectra. Overall, fast-rotating B-type stars,
with or without disks, display similar photometric properties, except as
regards their longer-term behaviour.
