DENIS-P J1228.2−1547—A New Benchmark Brown Dwarf

Abstract
We present optical spectroscopy of three brown dwarf candidates identified in the first 1% of the DENIS sky survey. Low-resolution spectra from 6430 to 9150 Å show these objects to have similar spectra to the brown dwarf candidate GD 165B. High-resolution spectroscopy shows that one of the objects—DENIS-P J1228.2-1547—has a strong 2.3 ± 0.05 Å equivalent width absorption line of Li I λ6708 and is therefore a brown dwarf with mass below 0.065 M, and age 1.5 Gyr. DENIS-P J1228.2-1547 can now be considered a prototype for brown dwarfs closer to the hydrogen-burning limit than Gl 229B.