The spectrum of NGC 7027

Kaler, J. B.; Aller, L. H.; Czyzak, S. J.

doi:10.1086/190379

Cited by 46 publications

(62 citation statements)

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“…6, both the H  Balmer decrement and the He  Pfund decrement yield a best fit at N e ∼ 10 5 cm −3 , in reasonable agreement with densities derived from CEL diagnostics. The result rules out the possibility that H  and He  lines arise from dense regions with an electron density in excess of 10 7 cm −3 as proposed by Kaler et al (1976). In principle the H  Paschen decrement and the He  Pickering decrement may also be used to probe electron density (Péquignot & Baluteau 1988).…”

Section: Cel Diagnosticsmentioning

confidence: 60%

“…Based on the excitation classification scheme proposed by Dopita & Meatheringham (1990) The complete spectral data from the UV to IR accumulated here allow us to calculate the energy-balance temperature (the Stoy temperature) of the CS of NGC 7027. The method was first introduced by Stoy (1933) and then advanced by Kaler et al (1976) and Preite-Martinez & Pottasch (1983). The method rests on the idea that the total flux of all CELs (which provide the major cooling rate of the nebula) relative to Hβ, is a measure of the average heating rate per photoionization incident (dominated by photoionization of hydrogen given its high abundance), and thus depends on the effective temperature of the central star.…”

Section: The Central Starmentioning

confidence: 99%

“…1 and Appendices A and B with their tables are only available in electronic form at http://www.edpsciences.org Also Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218. observations using photographic plates were presented by Bowen & Wyse (1939) and Wyse (1942). Combining photographic and spectrophotometric techniques, Kaler et al (1976) measured intensities of lines between 3132-8665 Å. They suggested that the nebula may contain a dense central ionized region with electron density of N e ∼ 10 7 cm −3 .…”

Section: Introductionmentioning

confidence: 99%

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Integrated spectrum of the planetary nebula NGC 7027

Zhang¹,

Liu²,

Luo³

et al. 2005

A&A

123

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We present deep optical spectra of the archetypal young planetary nebula (PN) NGC 7027, covering a wavelength range from 3310 to 9160 Å. The observations were carried out by uniformly scanning a long slit across the entire nebular surface, thus yielding average optical spectra for the whole nebula. A total of 937 emission features are detected. The extensive line list presented here should prove valuable for future spectroscopic analyses of emission line nebulae. The optical data, together with the archival IUE and ISO spectra, are used to probe the temperature and density structures and to determine the elemental abundances from lines produced by different excitation mechanisms. Electron temperatures have been derived from the hydrogen recombination Balmer jump (BJ), from ratios of He  optical recombination lines (ORLs) and from a variety of diagnostic ratios of collisionally excited lines (CELs). Electron densities have been determined from the intensities of high-order H  Balmer lines and of He  Pfund lines, as well as from a host of CEL diagnostic ratios. CEL and ORL diagnostics are found to yield compatible results. Adopting respectively electron temperatures of T e = 12 600 and 15 500 K for ions with ionization potentials lower or higher than 50 eV and a constant density of N e = 47 000 cm −3 , elemental abundances have been determined from a large number of CELs and ORLs. The C 2+ /H + , N 2+ /H + , O 2+ /H + and Ne 2+ /H + ionic abundance ratios derived from ORLs are found to be only slightly higher than the corresponding CEL values. We conclude that whatever mechanism is causing the BJ/CEL temperature discrepanies and the ORL/CEL abundance discrepancies that have been observed in many PNe, it has an insignificant effect on this bright young compact PN. The properties of the central star are also discussed. Based on the integrated spectrum and using the energy-balance method, we have derived an effective temperature of 219 000 K for the ionizing star. Finally, we report the first detection in the spectrum of this bright young PN of Raman-scattered O  features at 6830 and 7088 Å, pointing to the existence of abundant neutral hydrogen around the ionized regions.

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Section: Cel Diagnosticsmentioning

confidence: 60%

Section: The Central Starmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Integrated spectrum of the planetary nebula NGC 7027

Zhang¹,

Liu²,

Luo³

et al. 2005

A&A

123

View full text Add to dashboard Cite

show abstract

“…Nevertheless, in order to dredge up the faint lines that were at the lower limit of detectability in the earlier work (5,32), exposures up to nearly 3 hr were required. Measurable intensities can be found for many weak emission lines that were merely noted as "detected" on the earlier list.…”

Section: New Spectroscopic Possibilitiesmentioning

confidence: 99%