Galactic rotation derived from OB stars using hipparcos proper motions andradial velocities

We have examined the systematic velocity field of the solar neighborhood, b ased on Hipparcos (HIgh Precision PARallax COllecting Satellite) proper mot ions and ground-based radial velocities of about 240 O-B5 stars. The distan ces of these stars were derived from either Hipparcos parallaxes or the SKY MAP compilation of the spectroscopic: parallaxes. Using a first-order appro ximation: we obtained the galactic rotation at the solar vicinity of V-thet a = 255.52 +/- 8.33 km s(-1) assuming the galactocentric distance of the Su n, R. = 8.5 kpc. The slope of the galactic-rotation curve is given by (part ial derivative V-theta/partial derivative R)(R.) = -1.98+/-0.98 km s(-1) kp c(-1), and the rotation about the axis pointing to the galactic center is - R(-1)partial derivative V-z/partial derivative theta = 1.33 +/- 0.90 km s(- 1) kpc(-1) Our sample shows neither expansion nor contraction with respect to the Local Standard of Rest (LSR).