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Preprint 06/99

The iron abundance in hot central stars of planetary nebulae derived from IUE spectra

J.L. Deetjen, S. Dreizler, T. Rauch, and K. Werner

Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany

1999, Astronomy and Astrophysics, 348, 940-944

Abstract. We present the first attempt to determine the iron abundance in hot central stars of planetary nebulae. We perform an analysis with fully metal­line blanketed NLTE model atmo­ spheres for a sample of ten stars (Teff > 70.000K) for which high­resolution UV spectra are available from the IUE archive. In all cases lines of Fe VI or Fe VII can be identified. As a general trend, the iron abundance appears to be subsolar by 0.5 - 1 dex, however, the S/N of the IUE spectra is not sufficient to exclude a solar abundance in any specific case. Improved spectroscopy by either FUSE or HST is necessary to verify the possibility of a general iron deficiency in central stars. The sus­ pected deficiency may be the result of gravitational settling in the case of three high­gravity objects. For the other stars with low gravity and high luminosity dust fractionation during the previous AGB phase is a conceivable origin.

Key words: stars: abundances - stars: atmospheres - stars: evolution - stars: AGB and post-AGB - white dwarfs - Ultraviolet: stars

Paper (74k gzip'ed Postscript including figures)

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