Revised Fluxes for Gliese 229B

We have used the coronographic instrument CoCo with the IRTF's facility camera NSFCAM to obtain improved photometry at JHKL' of the giant planet/brown dwarf Gliese 229B. We have recalibrated the published spectra for this object, and re-calculated its luminosity. Our L' value, and our flux calibration of the spectra at JHK, are significantly different from those previously published. Our results show good agreement at all bands except H with evolutionary models by Burrows et al. which include grain condensation. The model comparison implies that Gliese 229B is likely to be a 0.5 Gyr-old 25 Jupiter-mass object with effective temperature around 900 K.