Kinematics of OB Stars

Abstract

The kinematics of 1817 stars of class O-B5 are examined. The 1655 stars with distances up to 1 kpc are taken from the Hipparcos catalog and 162 stars with distances greater than 1 kpc from Westlin's study of OB stars. The Ogorodnikov-Milne model of Galactic kinematics, with Edmondson's second-order terms included, is used for the equations of condition and mixed total least squares-least squares (TLS-LS) is used for the reduction method. Reasonable values for the parameters of Galactic kinematics are obtained. In particular, Oort A and B constants yield a Galactic rotation of 258.7+/-34.29 km s^-1 if we take the distance of the Sun from the Galactic center as 8.5+/-1.1 kpc. Although lower than the higher values obtained by some other investigators and higher than the IAU's recommended 220+/-20 km s^-1, all the determinations fall with their stated mean errors. Thus, no evidence for a significant difference in the various determinations exists. Evidence does exist, however, to assert that the TLS-LS reduction model with second-order terms seems superior to ordinary least-squares with only first-order terms.