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Astron. Astrophys. 322, 975-981 (1997)

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The chemical structure of bipolar planetary nebulae *

I. IC 4406

Romano L.M. Corradi 1, Mario Perinotto 2, Hugo E. Schwarz 3 and Jean-François Claeskens 4

1 Instituto de Astrofisica de Canarias, c. Via Lactea S/N, E-38200 La Laguna, Tenerife, Spain
2 Dipartimento di Astronomia e Scienza dello Spazio, Università di Firenze, Largo E. Fermi 5, I-50125 Firenze, Italy
3 Nordic Optical Telescope, Apartado 474, E-38700 Sta. Cruz de La Palma, Spain
4 Institut d'Astrophysique, Université de Liège, 5 Avenue de Cointe, B-4000 Liège, Belgium

Received 14 May 1996 / Accepted 12 December 1996

Abstract

Long slit spectrophotometry of the bipolar planetary nebula IC 4406, in the range from 360 to 930 nm, has been used to study the chemical structure along its major axis. We find that:
- the He, O, N, Ne, and Ar abundances are constant, within errors, along the major axis of the nebula. Average values for He/H, O/H, N/H, Ne/H, and Ar/H are: 0.126, 5.6 [FORMULA] 10-4, 2.0 [FORMULA] 10-4, 1.7 [FORMULA] 10-4 and 3.2 [FORMULA] 10-6, respectively. The N and He abundances of IC 4406 are quite modest for objects in this morphological class.
- The computed abundances of sulphur indicate an increase of S/H towards the external parts of the nebula, which may likely reflect inaccuracies in the available ionization correction factors.

Within the accuracy of the present data and analysis method, IC 4406 appears therefore to be a chemically homogeneous object.

Key words: ISM: abundances – planetary nebulae: individual: IC 4406

* Based on observations made at the European Southern Observatory

Send offprint requests to: R. Corradi (rcorradi@iac.es)

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© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998

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