of positions, proper motions, parallaxes, and radial velocities from Gaia DR2 and information on membership from . The coordinates are given in the solar system bary-centric Galactic Cartesian coordinate system where the $X$-axis points to the Galactic centre, the $Y$-axis in the direction of Galactic rotation, and $Z$-axis to the Galactic north pole. The corresponding velocity coordinates are $U, V, W$. We found mean values $$\begin{array}{lcl}
\vec{R_c}  =  (X_c,Y_c,Z_c) & = & (-141.75 , -69.35, 100.45)\,{\rm pc}, \\
\vec{V_c}  =  (U_c,V_c,W_c) & = & ( -43.17, -20.62, -9.60)\,{\rm km\,s^{-1}}.\label{COPO}
\end{array}$$ These mean values are based upon 136 stars from with measured radial velocities. The standard errors of the mean in a position coordinate are 0.25 pc, and those of a velocity coordinate are 0.08 km s$^{-1}$.

Preparatory work {#prep}
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From the Gaia DR2 dataset we extracted all entries with a parallax greater than 2.4 mas, which gave 43,038,142 objects. For the further processing, we followed the procedures described in , Sect. 4.3 and Appendix C, Figs. C.1 and C.2, to obtain a stellar sample cleaned from possible artefacts with one small, but important change. Instead of the “unit weight error"-cut (UWE) we followed the new approach presented by Lindegren 