Stellar groups. I. The Hyades and Sirius groups

The accurate proper motions of the FK3 and the available radial velocities have been used to establish the reality of an extended Hyades Group. The possible members of this group among the nearer stars are also discussed. The colour-luminosity array for the group is similar to that for two clusters, Hyades and Praesepe, included in it, except that stars of higher luminosity appear in the group at large than in clusters themselves. Also, 67 stars that appear to share the space motion of Sirius, here called the Sirius Group, present a colour-luminosity array that indicates, on the basis of the current theories of stellar evolution, that this group is probably younger than the Hyades Group.