Analysis of Keck HIRES spectra of early L-type dwarfs

We present analyses of high- and medium-resolution spectra of early L dwarf s. We have used our latest set of model atmospheres to reproduce and analyz e the observed features. We can model the optical flux and atomic line prof iles with the best accuracy to date. The models used to reproduce the obser vations include dust condensation and dust opacities. Compared with previou s studies using older models, we find that our dust treatment is much impro ved. The derived parameters for the objects are well in the expected range for old, very low mass objects. This is also supported by the absence of Li in most of the objects. For the objects showing Li, we can be almost certa in they are brown dwarfs. However, a spectral analysis in general, and this one in particular, can only very roughly determine mass and age.