The WC10 central stars CPD - 56° 8032 and He 2-113 - III. Wind electron temperatures and abundances

Orsola De Marco*, P. J. Storey, M. J. Barlow

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

We present a direct spectroscopic measurement of the wind electron temperatures and a determination of the stellar wind abundances of the WC10 central stars of planetary nebulae CPD-56° 8032 and He 2-113, for which high-resolution (0.15-Å) UCLES echelle spectra have been obtained using the 3.9-m Anglo-Australian Telescope. The intensities of dielectronic recombination lines, originating from autoionizing resonance states situated in the C2+ + e- continuum, are sensitive to the electron temperature through the populations of these states, which are close to their LTE values. The high-resolution spectra allow the intensities of fine-structure components of the dielectronic multiplets to be measured. New atomic data for the autoionization and radiative transition probabilities of the resonance states are presented, and used to derive wind electron temperatures in the two stars of 21 300 K for CPD -56°8032 and 16 400 K for He 2-113. One of the dielectronic lines is shown to have an autoionization width in agreement with the theoretical predictions. Wind abundances of carbon with respect to helium are determined from bound-bound recombination lines, and are found to be C/He = 0.44 for CPD-56° 8032 and C/He = 0.29 for He 2-113 (by number). The oxygen abundances are determined to be O/He = 0.24 for CPD-56° 8032 and 0.26 for He 2-113. The effect of optical depth on the temperature and abundance determinations is investigated by means of a Sobolev escape-probability model. We conclude that the optically thicker recombination lines can still be used for abundance determinations, provided that their upper levels are far from LTE.

Original languageEnglish
Pages (from-to)999-1014
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume297
Issue number4
Publication statusPublished - 11 Jul 1998
Externally publishedYes

Keywords

  • Atomic data
  • Planetary nebulae: general
  • Stars: AGB and post-AGB
  • Stars: individual: CPD-56° 8032
  • Stars: individual: He 2-113
  • Stars: Wolf-Rayet

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