Infrared broadband photometry of the cool brown dwarf Gliese 229B extending in wavelength from 0.8 to 10.5 mu m is reported. These results are derived fron both new data and reanalyzed, previously published data. Existing spectral data reported have been rereduced and recalibrated. The close proximity of the bright Gliese 229A to the dim Gliese 229B required the use of special techniques for the observations and also fur the data analysis. We describe these procedures in detail. The observed luminosity between 0.8 and 10.5 mu m is (4.9+/-0.6)x10(-6) L. The observed spectral energy distribution is in overall agreement with a dust-free model spectrum by Tsuji et al. for T(eff)approximate to 900 K. If this model is used to derive the bolometric correction, the best estimate of the bolometric luminosity is 6.4x10(-6) L. and 50% of this luminosity lies between 1 and 2.5 mu m. Our best estimate of the effective temperature is 900 K. From the observed near-infrared spectrum and the spectral energy distribution, the brightness temperatures (T-B) are estimated. The highest. T-B=1640 K, is seen al the peak of the J band spectrum, while the lowest, T-B less than or equal to 600 K, is at 3.4 mu m, which corresponds to the location of the fundamental methane band. (C) 1996 American Astronomical Society.
