Rotation of the Hyades derived from Hipparcos data

Abstract

Data from the Hipparcos catalog are used to study the internal kinematics of the Hyades cluster. Cluster members whose proper motions and parallaxes are known with precisions not less than 5 mas/yr and 3 mas were used. The proper motions were reduced to the cluster center. A correlation between a component of the tangential velocity and the parallax provides evidence for possible rotation of the cluster. The total velocity gradient is 0.04±0.03 km s^-1 pc^-1. The rotation axis is located perpendicular to the direction to the Hyades apex on the celestial sphere.