Institut für Astronomie und Astrophysik

Abteilung Astronomie

Preprint 08/96

Spectroscopy of the central stars of three evolved planetary nebulae

W. Sauer(1), K. Werner(2), and R. Weinberger(1)

(1)Institut für Astronomie der Leopold-Franzens-Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria
(2)Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany

accepted by Astronomy & Astrophysics

Abstract. We present results of a spectroscopic project that aims at investigations of stars in the upper left part of the HRD. We observed the central stars of the three old planetary nebulae PN G011.4+17.9, PN G308.2+07.7, and PN G332.5-16.9. The spectra (echelle) were analysed by fitting the H and He II lines with theoretical profiles from a grid of non-LTE model atmospheres. The models are composed of H and He and disregard metal opacities. The three nuclei appear to be very hot (T_eff near 10^5 K) and comparison with post-AGB evolutionary tracks reveals that the masses range between 0.55 and 0.75 M_sun; the central star of PN G332.5-16.9 shows an enrichment in He and probably also in C and N.

Key words: white dwarfs - planetary nebulae: individual: PN G011.4+17.9, PN G308.2+07.7, PN G332.5-16.9 - Methods: data analysis - Line: profiles - Stars: abundances

Paper (161k gzip'ed Postscript including figures)

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Jürgen Barnstedt (barnstedt AT astro.uni-tuebingen.de) Last updated 04-Aug-1997