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Astron. Astrophys. 363, 767-778 (2000)

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Abundance in the planetary nebulae NGC 6537 and He2-111

S.R. Pottasch 1, D.A. Beintema 2 and W.A. Feibelman 3

1 Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen, The Netherlands
2 SRON Laboratory for Space Research, P.O. Box 800, 9700 AV Groningen, The Netherlands
3 Laboratory for Astronomy and Solar Physics, Code 681, Goddard Space Flight Center, MD, USA

Received 11 July 2000 / Accepted 26 September 2000


The ISO and IUE spectra of the bipolar planetary nebulae NGC 6537 and He2-111 are presented. These spectra are combined with the spectrum in the visual wavelength region from the nebulae to obtain a complete spectrum that is corrected for extinction. The chemical abundance of the nebulae is then determined and compared to previous determinations. The abundance of the two nebulae is quite similar. A comparison is then made with the abundance of two other bipolar planetary nebulae whose abundance is also determined with the help of ISO observations. It is shown that not all bipolar nebulae have similar abundance. NGC 6445 has a much lower nitrogen to oxygen ratio, similar to NGC 7027, but still not as low as the Orion nebula.

Key words: stars: abundances – stars: emission-line, Be – ISM: planetary nebulae: general – ISM: planetary nebulae: individual: NGC 6537 – ISM: planetary nebulae: individual: He2-111 – infrared: ISM: lines and bands

Send offprint requests to: pottasch@astro.rug.nl

© European Southern Observatory (ESO) 2000

Online publication: December 11, 2000