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Astron. Astrophys. 362, 730-736 (2000)


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Emission lines of O III in the optical and ultraviolet spectra of planetary nebulae

F.L. Crawford 1, F.P. Keenan 1, K.M. Aggarwal 1, A.W. Wickstead 2, L.H. Aller 3 and W.A. Feibelman 4

1 The Queen's University of Belfast, Department of Pure and Applied Physics, Belfast BT7 1NN, Northern Ireland, UK (fergal.crawford@qub.ac.uk; f.keenan@qub.ac.uk; k.aggarwal@qub.ac.uk)
2 The Queen's University of Belfast, Department of Pure Mathematics, Belfast BT7 1NN, Northern Ireland, UK (a.wickstead@qub.ac.uk)
3 University of California, Los Angeles, CA 90024, USA (aller@bonnie.astro.ucla.edu)
4 NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA (feibelman@iue.gsfc.nasa.gov)

Received 20 June 2000 / Accepted 8 September 2000

Abstract

Recent R -matrix calculations of electron impact excitation rates in OIII are used to calculate electron temperature and density-dependent emission line ratios

[EQUATION]

for a range of electron temperatures ([FORMULA] K) and densities ([FORMULA] cm-3) applicable to gaseous nebulae. The ratio-ratio diagrams ([FORMULA], [FORMULA]) and ([FORMULA], [FORMULA]) should, in principle, allow the simultaneous determination of [FORMULA] and [FORMULA] from measurements of the OIII features in a spectrum. Plasma parameters derived for a sample of mid- to high-excitation planetary nebulae from ([FORMULA], [FORMULA]) and ([FORMULA], [FORMULA]) measurements, produced using a combination of ultraviolet spectra obtained with the International Ultraviolet Explorer (IUE ) and optical data from a number of observing runs, are found to show excellent internal consistency. They also show, in general, good agreement with the values of [FORMULA] and [FORMULA] estimated from other line ratios in the nebulae, therefore providing observational support for the accuracy of the theoretical ratios and hence the atomic data adopted in their derivation.

Key words: atomic data – ISM: planetary nebulae: general

Send offprint requests to: F.L. Crawford

© European Southern Observatory (ESO) 2000

Online publication: October 24, 2000

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