ABUNDANCE ANALYSIS OF THE HOT POST-AGB STAR BARNARD-29

We present a model atmosphere analysis for the relatively bright (V si milar to 13) globular cluster post-AGB star, Barnard 29, using IUE and high resolution (0.06 Angstrom FWHM) optical spectra. The derived atm ospheric parameters are T-eff = 20000+/-1000K and log g =3.0+/-0.1 dex , which imply a current mass of similar to 0.55M.. The chemical compos ition provides important constraints on the post-AGB evolutionary stag e. We find an overall metal deficiency of 1.46+/-0.11 dex, which is co mpatible with the mean [Fe/H] obtained from previous M13 studies. The most interesting feature is the severe carbon deficiency of more than 2.0 dex which has also been observed in a number of high latitude B-ty pe low gravity stars. Hence the present results supports the recent cl assification of these objects as hat post-AGB stars. Relative to the o verall metallicity, the observed carbon deficiency of Barnard 29 coupl ed with a significant nitrogen overabundance indicates that this star has left the AGB before the third dredge-up has occurred. The implicat ions for AGB and post-AGB evolution are briefly discussed.