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K.S. Noll (STScI), T.R. Geballe (Gemini), S.K. Leggett (JACH), M. Marley (NMSU), T. J. Henry (CfA)
We have obtained spectra of four brown dwarf candidates and several very low mass stars from 2.9 - 4.0 um using the UKIRT CGS4 spectrometer. We used the spectra to search for spectral absorption from the strong nu3 band of methane which is centered at 3.3 um. The nu3 band of CH4 is approximately two orders of magnitude stronger than the overtone and combination bands at 1.6 and 2.2 um observed in the cool brown dwarf Gl 229B (T ~ 950 K). The nu3 band is, therefore, a superior way to search for possible weak CH4 features in warmer brown dwarfs (T > 1500 K) where the abundance of methane is expected to be lower than in Gl 229B. The spectra of Kelu 1, DENIS-P J1058.7-1548, DENIS-P J1228.2-1547, and DENIS-P J0205.4-1159 do not show evidence of a deep absorption band like that found in Gl 229B although weaker absorption may be present. Improved data reduction and model spectra will be presented with limits on the column abundance of CH4 in each of these objects.