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Astron. Astrophys. 328, 598-601 (1997)

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Spectroscopy of the central stars of three evolved planetary nebulae *

W. Saurer 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, Universität Tübingen, Waldhäuser Straße 64, D-72076 Tübingen, Germany

Received 23 October 1996 / Accepted 18 November 1996

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 ([FORMULA] near 105 K) and comparison with post-AGB evolutionary tracks reveals that the masses range between 0.55 and 0.75 [FORMULA] ; 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: indi- vidual: PN G011.4+17.9, PN G308.2+07.7, PN G332.5- 16.9 – stars abundances – stars: fundamental parameters

* Based on observations collected at the European Southern Observatory, La Silla, Chile

Send offprint requests to: Walter.Saurer@uibk.ac.at

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© European Southern Observatory (ESO) 1997

Online publication: March 26, 1998

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