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Astron. Astrophys. 327, 736-742 (1997)

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1. Introduction

The central stars of planetary nebulae (hereinafter PN) are believed to be the immediate precursors of white dwarfs, and the remnants cores of intermediate-mass stars which have lost most of their mass through stellar winds while on the AGB. Together with the white dwarf mass distribution (Weidemann 1990), the shape of the mass distribution of planetary nebulae nuclei (hereinafter PNN) provides constraints on the theory of stellar evolution, as well as on models of galactic evolution that are based on it.

Histograms of the distribution of PNN masses have been published by several authors (Schönberner 1981, Heap & Augensen 1987, Weidemann 1989, Tylenda et al. 1991, Zhang & Kwok 1993). They all agree that the distribution of central star masses is rather narrow, roughly concentrated around 0.60M [FORMULA], and exhibits a strong cutoff at 0.55M [FORMULA]. However, the exact value of the average PNN mass varies from one paper to another, and the proportion of PN with nuclei more massive than 0.7M [FORMULA] ranges from a few percent (Schönberner 1981) to 40% (Kaler et al. 1990). The problem of the studies mentioned above is that they make assumptions on the nebulae, which are not always explicit, thus making more difficult the discussion of the results.

In a previous work (Górny et al. 1997, hereinafter GST97), we have proposed a method to estimate PNN masses in which the assumptions were clearly stated. We applied it to a sample of PN for which we could assign a morphological class, in order to investigate any possible relation between the morphology and the central star masses. We now use the method for a larger sample of Galactic PN. The procedure and the observational data base are described in Sect. 2. The resulting distribution of PNN masses is presented and discussed in Sect. 3. Concluding remarks are given in Sect. 4.

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© European Southern Observatory (ESO) 1997

Online publication: April 6, 1998