  Radial-velocities for the early-type stars in the Pleiades cluster have
always been challenging to measure because of the significant rotational
broadening of the spectral lines. The large scatter in published velocities has
led to claims that many are spectroscopic binaries, and in several cases
preliminary orbital solutions have been proposed. To investigate these claims,
we obtained and report here velocity measurements for 33 rapidly-rotating B, A,
and early F stars in the Pleiades region, improving significantly on the
precision of the historical velocities for most objects. With one or two
exceptions, we do not confirm any of the previous claims of variability, and we
also rule out all four of the previously published orbital solutions, for HD
22637, HD 23302, HD 23338, and HD 23410. We do find HD 22637 to be a binary,
but with a different period (71.8 days). HD 23338 is likely a binary as well,
with a preliminary 8.7 yr period also different from the one published.
Additionally, we report a 3635 day orbit for HD 24899, another new
spectroscopic binary in the cluster. From the 32 bona fide members in our
sample we determine a mean radial velocity for the Pleiades of 5.79 +/- 0.24
km/s, or 5.52 +/- 0.31 km/s when objects with known visual companions are
excluded. Adding these astrometric binaries to the new spectroscopic ones, we
find a lower limit to the binary fraction among the B and A stars of 37%. In
addition to the velocities, we measure v sin i for all stars, ranging between
69 and 317 km/s.
