Kinematics of O-B5 giants

Abstract

To study the kinematics of O-B5 giant stars (luminosity class III), 290 non-Gould belt stars with proper motions taken from the Hipparcos catalogue are used, of which 107 have radial velocities taken from other sources. Semidefinite programming solves for the kinematical parameters and the coefficients of the velocity ellipsoid. The condition that both solutions must yield the same solar velocity is enforced. The results obtained are reasonable: solar velocity of 13.83 +/- 0.17 km s^-1 Oort's constants, in units of km s^-1 kpc^-1, A = 16.08 +/- 0.72 and B = -10.74 +/- 0.65, implying a rotational velocity of 228.0 +/- 21.4 km s^-1 if we take the distance to the Galactic Centre as 8.5 +/- 1.1 kpc; velocity dispersions, in units of km s^-1, of σ_x = 32.44 +/- 5.04, σ_y = 26.16 +/- 2.75, σ_z = 18.71 +/- 2.39 with a vertex deviation of -6.39°.