A NEW POPULATION OF BROWN DWARFS

In this paper we report the first results from a survey for low-mass s tars and brown dwarfs, based on a photographic stack of around 100 Sch midt plates. This survey extends photographic searches by about 2 mag, and covers an area of 25 deg(2). Some 30 faint objects with large R - I colours were selected for further study, and were found to have ver y strong molecular absorption in their spectra, but only moderately re d infrared colours. Five of these stars were selected for a parallax p rogramme; three of these were found to be at a distance of around 45 p c, implying a very low luminosity. On the basis of their luminosity al one it is clear that these stars are field brown dwarfs, and we discus s their likely evolutionary status in the context of current models of low-mass stellar evolution.