THE FAINTEST STARS - INFRARED PHOTOMETRY, SPECTRA, AND BOLOMETRIC MAGNITUDES

We present infrared JHKLL' photometry (obtained with the IRTF telescope on Mauna Kea) for a selection of the latest stars known. We also present low resolution (lambda/DELTAlambda approximately 150-300) infrared spectra covering the range lambda almost-equal-to 1.0-2.5 mum (obtained with the UKIRT telescope, also on Mauna Kea). Because of the dry site at which these data were obtained we are able to correct for the presence of terrestrial H2O absorption and study the stellar H2O bands which dominate the atmospheres of these stars. We find that the L band fluxes of these stars are considerably depressed (relative to L' fluxes) by the presence of stellar H2O absorption in the 2.5-3.3 mum band. Strong H2O absorption is also seen in the 1.3-1.5, 1.8-2.1, and 2.3-3.0 mum bands of our spectra-we examine the amount of flux which is ''overcounted'' when these absorption bands are ignored and bolometric fluxes are calculated using broadband photometry alone. We find that a correction of only approximately 5%-10% is required to correct for the ''flux overcounting'' produced by using only broadband observations. The combined photometric and spectral data is used to evaluate bolometric corrections and bolometric magnitudes of a sample of late type M dwarfs which extends almost two magnitudes fainter than the faintest previously measured objects. Lastly, we examine some of the current problems associated with the effective temperature scale for very low mass stars.