Spectral Energy Distribution and Bolometric Luminosity of the Cool Brown Dwarf Gliese 229B

Infrared broadband photometry of the cool brown dwarf Gliese 229B extending in wavelength from 0.8 to 10.5 μm is reported. These results are derived from 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 for the data analysis. We describe these procedures in detail. The observed luminosity between 0.8 and 10.5 i m is (4.9±0.6)×10-6 Lsun. The observed spectral energy distribution is in overall agreement with a dust-free model spectrum by Tsuji et al. for Teff=900 K. If this model is used to derive the bolometric correction, the best estimate of the bolometric luminosity is 6.4×10-6 Lsun and 50% of this luminosity lies between 1 and 2.5 μm. Our best estimate of the effective temperature is 900 K. From the observed near-infrared spectrum and the spectral energy distribution, the brightness temperatures (TB) are estimated. The highest, TB=1640 K, is seen at the peak of the J band spectrum, while the lowest, TB≤600 K, is at 3.4 μm, which corresponds to the location of the fundamental methane band.