Cool Stars 14 - Submitted Abstract # 121
This version created on 05 October 2006

Low Metallicity Models of Ultracool Dwarfs and the L Type Subdwarf
Class


Andreas Schweitzer, Hamburger Sternwarte, University of Hamburg
Peter H. Hauschildt, Hamburger Sternwarte, University of Hamburg
Alexander C. Wawrzyn, Hamburger Sternwarte, University of Hamburg

Since the discovery of the first subdwarfs (sd) of spectral type L in
2003 by Burgasser et al.  and Lepine et al.  more ultracool subdwarfs
have been found and spectra in different wavelength regions have been
obtained.  Furthermore, even in the extreme subdwarf (esd) class, a
cooler and later object than known before (an esdM8) has been
discovered by Burgasser et al.  hinting that even the esd class may
contain ultracool members.  The physical nature of the L type
subdwarfs, however, is unclear.  Similar to M type subdwarfs the L
type subdwarfs are suspected to be low metallicity objects, Using our
latest models and line lists (esp.  CaH line lists), we present first
atmosphere models and synthetic spectra for cool metal poor dwarfs.
They will be used to determine physical parameters of these newly
discovered objects.  We will be able to determine the nature of the
spectral features that cause the obejcts to be classified as subdwarfs
and to estimate temperature and metallicity.

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