  A total of 597 radial-velocity observations for 112 stars in the ~1.6 Gyr old
open cluster NGC 7789 have been obtained since 1979 with the radial velocity
spectrometer at the Dominion Astrophysical Observatory. The mean cluster radial
velocity is -54.9 +/- 0.12 km/s and the dispersion is 0.86 km/s, from 50
constant-velocity stars selected as members from this radial-velocity study and
the proper motion study of McNamara and Solomon (1981). Twenty-five stars (32%)
among 78 members are possible radial-velocity variable stars, but no orbits are
determined because of the sparse sampling. Seventeen stars are radial-velocity
non-members, while membership estimates of six stars are uncertain.
  There is a hint that the observed velocity dispersion falls off at large
radius. This may due to the inclusion of long-period binaries preferentially in
the central area of the cluster. The known radial-velocity variables also seem
to be more concentrated toward the center than members with constant velocity.
Although this is significant at only the 85% level, when combined with similar
result of Raboud and Mermilliod (1994) for three other clusters, the data
strongly support the conclusion that mass segregation is being detected.
