Mira kinematics from Hipparcos data: a Galactic bar to beyond the Solar circle

The space motions of Mira variables are derived from radial velocities, Hip parcos proper motions and a period-luminosity relation. The previously know n dependence of Mira kinematics on the period of pulsation is confirmed and refined. In addition, it is found that Miras with periods in the range 145 -200 d in the general Solar neighbourhood have a net radial outward motion from the Galactic Centre of 75 +/- 18 km s(-1). This, together with a lag b ehind the circular velocity of Galactic rotation of 98 +/- 19 km s(-1), is interpreted as evidence for an elongation of their orbits, with their major axes aligned at an angle of similar to 17 degrees with the Sun-Galactic Ce ntre line, towards positive Galactic longitudes. This concentration seems t o be a continuation to the Solar circle and beyond of the bar-like structur e of the Galactic bulge, with the orbits of some local Miras probably penet rating into the bulge. These conclusions are not sensitive to the distance scale adopted. A further analysis is given of the short-period (SP) red gro up of Miras discussed in companion papers in this series. In Appendix A the mean radial velocities and other data for 842 oxygen-rich Mira-like variab les are tabulated. These velocities were derived from published optical and radio observations.