A LITHIUM-TEST AND MODELING OF LITHIUM LINES IN LATE-TYPE M-DWARFS - TEIDE1

The results of numerical modeling of lithium lines in the spectra of l ate-type M dwarfs are discussed. ''Line-by-line'' and ''just-overlappi ng'' approximations are used to compute the molecular opacities. Synth etic spectra are computed near two lithium lines-a resonance line at l ambda 6708 and a subordinate line at lambda 8126-for a number of late- type M dwarfs using the model atmosphere grids of Allard and Hauschild t. The two molecular absorption models used yield very similar profile s for strong lithium lines that could in principle be observed in the spectra of brown dwarfs. ''Pseudoequivalent'' widths of lithium absorp tion lines are computed and compared with the equivalent widths in the spectrum of the brown dwarf candidate Teidel measured by Rebolo ef al . This comparison indicates that the Lithium abundance in Teidel's atm osphere is high: logN > 3.0 and logN = 2.9 for lambda 6708 and lambda 8126, respectively. This provides strong evidence for identification o f Teidel as a brown dwarf.