ON THE LI AND BE TESTS FOR BROWN DWARFS

We present the results of stellar evolution calculations which show qu antitatively how the measured abundances of lithium and beryllium in l ow-mass stellar objects can be used to discriminate between brown dwar fs and low-mass main-sequence stars. The evolution of boron, although less useful in this regard, is also studied. We define a transition ma ss range, below which at least 50% of the light element remains at the end of nuclear burning, and above which no more than 10% remains. We find that the transition mass range for Li burning is 0.059-0.062 M., while for Be the range is 0.075-0.077 M.. Using these results, we then examine the factors (e.g., age and luminosity) that affect our abilit y to identify low-luminosity objects as brown dwarfs. In particular, w e show that the lithium test would be well suited for brown dwarf cand idates located in nearby open clusters with ages in the range of 2 x 1 0(8)-5 x 10(8) yr.