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Astron. Astrophys. 351, 1036-1040 (1999)

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1. Introduction

The PN G218.9-10.7 (HDW5, HaWe7) was discovered by Hartl & Weinberger (1987) on the Palomar Observatory Sky Survey (POSS) as a low surface brightness Planetary Nebula (PN). The object has been included in some studies of PNe, e.g. Tylenda et al. 1991 (central star), Tylenda et al. 1992 (extinction), Acker et al. 1991 (size, H[FORMULA] flux). A summary and a list of observed emission lines is given by Acker et al. (1992). Hartl & Weinberger assumed the nebula to be a sphere with a blue star in the middle where only the sickle-shaped nebula is visible on both the red and blue POSS plates. Manchado et al. (1996), in the IAC Morphological Catalogue of Northern Galactic Planetary Nebulae, present an H[FORMULA] + [N II]. They also give an [O III] image which shows faint emission in the central part of the nebula and very faint roundish emission northeast. The latter, if verified, even if it is definitely absent in the POSS O-print, would be particularly interesting because at that position the H[FORMULA] image shows a sharp linear filament.

This paper presents optical spectroscopic observations and an H[FORMULA] + [N II] image of PN G218.9-10.7 aimed to clarify the nature of the object. We were motivated to make an H[FORMULA] + [N II] image deeper than mentioned by Manchado et al. (1996) to investigate the structure and to examine the morphology of the object. The plasma diagnostics which are unknown represent one of our objectives. In Sect. 2 the observations are described, the results and its discussion are given in Sect. 3.

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© European Southern Observatory (ESO) 1999

Online publication: November 16, 1999