Abstract
To study the kinematics of the G giant stars (luminosity class III) use is made of proper motions and parallaxes taken from van Leeuwen's new reduction of the Hipparcos catalog. 3,075 stars, of which 658 have radial velocities, were used in the final study. The solution gives: solar velocity of 16.72±0.41 km s-1; Oort's constant's, in units of km s-1 kpc-1, A = 14.05±3.28 and B = -9.30±2.87, implying a rotational velocity of 198.48±26.95 km s-1 if we take the distance to the Galactic center as 8.2±1.1 kpc; velocity dispersions, in units of km s-1, of: σx = 51.78±0.55, σy = 42.81±0.32, σ_{z = 28.45±0.22 with a vertex deviation of 3.°88±6.°62. A comparison of the velocity dispersions with those given by other spectral types shows that Parenago's discontinuity also exists for the giant stars.
