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The ionization structure of planetary nebulae. 3: NGC 7009Spectrophotometric observations of emission line intensities were made in 8 positions in the planetary nebula NGC 7009. For the 6 brightest positions, the coverage is from 1400 A to 10,000 A. Standard equations used to correct for the existence of elements in other than the optical observable ionization stages give results over a wide range of ionization that are consistent and agree with abundances calculated using ultraviolet lines. This result is particularly gratifying for N because previously the standard formula gave inconsistent abundances in NGC 7009. The major outstanding problem is that the lambda 4267 CII line implies a C(2+) abundance as much as 12 times greater than that determined from the UV lines. This discrepancy is greatest nearest the central star, as is the case in the planetary nebula NGC 6720. The logarithmic abundances (relative to H=12.00) are: He=11.07, 0=8.68, N=8.10, Ne=8.16, C=8.18, Ar=6.36, and S=7.12. The average of the Ne, Ar, and S abundances agrees to within 5% of that for NGC 6720, but the O, N, nd C abundances average 1.9 times lower in NGC 7009, suggesting that here may have been mixing of processed material in the planetary precursor in NGC 6720.
Document ID
19830007996
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Barker, T. (Wheaton Coll. Norton, MA, United States)
Date Acquired
September 4, 2013
Publication Date
January 1, 1982
Subject Category
Astrophysics
Report/Patent Number
NAS 1.26:169712
NASA-CR-169712
Accession Number
83N16267
Funding Number(s)
CONTRACT_GRANT: NSG-5376
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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