The Kinematics of Semi-Regular Red Variables in the Solar Neighbourhood

Radial velocities for 67 northern M type SR variables observed at the Kottamia Observatory and for 53 similar southern stars observed at the Radcliffe Observatory are given. The kinematics of the SR variables are investigated on the basis of these and previously published radial velocities. There is no evidence for a dependence of mean kinematic property on period except that the variables with weak emission lines, in the period range 60140 days, have a higher velocity dispersion than the rest. This result is however strongly affected by the inclusion or omission of a few stars of high velocity in this group. Mean values of the components of the systematic motion and of the velocity dispersions and their standard errors (in km s ^–1 ) from 203 SR variables are, u = –20±4 v = –27±4 w = –12±5 α = 42±6 β = 42±6 γ = 34±9 The SR variables belong to the old disc population. There is no evidence for an outward expansion in the Galaxy of young objects relative to the SR variables. A logarithmic density gradient for old disc objects of $$\frac{\partial\,\text{log}\,v}{\partial\,\text{log}\,R}\,=\,-3\cdot7\pm 0\cdot9$$ is derived. Slightly amended systematic motion and velocity dispersion solutions for Me variables are also included.