Cool Stars 14 - Submitted Abstract # 61
This version created on 05 October 2006

Application of Profile Functions in Synthetic Spectra for Ultra Cool
Dwarfs


Christine M. S. Johnas, Hamburger Sternwarte, University of Hamburg
Peter H. Hauschildt, Hamburger Sternwarte, University of Hamburg
Andreas Schweitzer, Hamburger Sternwarte, University of Hamburg
Ansgar Reiners, Hamburger Sternwarte, University of Hamburg, Max-Planck Institute for Solar System Research

Shortly after finding the first brown dwarfs, it has been discovered
that the wings of alkali lines play a dominant role in the optical
spectra of ultra cool dwarfs.  Especially the far wings of NaI and KI
play an extraordinary role in the formation of the spectra.  Model
atmospheres are necessary in order to calculate synthetic spectra and
to derive reliable parameters and surface chemical composition for
such objects.  Using improved alkali resonance line profiles we
present a study on the abundance characteristic of the Li I absorption
doublet for brown dwarfs.  Furthermore, we have performed an analysis
of observations using the improved synthetic spectra.  For the
synthetic spectra, the general purpose stellar atmosphere code PHOENIX
(Hauschildt & Baron (1999)) is used.

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