2007A&A...473..257L

We present an analysis of high resolution spectra in the J band of five ultra cool dwarfs from M6 to L0. We make use of a new ab initio water vapour line list and existing line lists of FeH and CrH for modelling the observations. We find a good fit for the MnI 12899.76Å line. This feature is one of the few for which we have a reliable oscillator strength. Other atomic features are present but most of the observed features are FeH and H₂O lines. While we are uncertain about the quality of many of the atomic line parameters, the FeH and CrH line lists predict a number of features which are not apparent in our observed spectra. We infer that the main limiting factor in our spectral analysis is the FeH and CrH molecular spectra.