VERY-LOW MASS M-DWARFS - STARS OR BROWN DWARFS IN DISGUISE

We have used radial velocity and proper motion observations to determine the space motions of a sample of 25 low-luminosity M dwarfs. We find that the solar motion and velocity dispersions of these stars are similar to the kinematics of a sample of more luminous, earlier type M dwarfs. However, there is evidence to indicate that when objects selected by photometric criteria alone are considered, the kinematics are more characteristic of an similar to 3x10(8) year old population. This suggests that the faintest known stars may be younger on average than the local M dwarfs in the Galactic disk, indicating the possible presence of a number of brown dwarfs or transition objects in our sample of very low-mass objects.