Title: Emission lines of [Cl II] in the optical spectra of gaseous nebulae
Authors: Keenan, FP ×
Aller, LH
Exter, Katrina
Hyung, S
Pollacco, DL #
Issue Date: Feb-2003
Publisher: Univ chicago press
Series Title: Astrophysical journal vol:584 issue:1 pages:385-389
Abstract: Recent R-matrix calculations of electron impact excitation rates among the 3s(2)3p(4) levels of Cl II are used to derive the nebular emission-line intensity ratios R-1=I(6161.8 Angstrom)/I(8578.7 Angstrom) and R-2=I(6161.8 Angstrom)/I(9123.6 Angstrom) as a function of electron temperature (T-e) and density (N-e). The ratios are found to be very sensitive to changes in T-e but not N-e for densities lower than 10(5) cm(-3). Hence, they should, in principle, provide excellent optical T-e diagnostics for planetary nebulae. The observed values of R-1 and R-2 for the planetary nebulae NGC 6741 and IC 5117, measured from spectra obtained with the Hamilton echelle spectrograph on the 3 m Shane Telescope, imply temperatures in excellent agreement with those derived from other diagnostic lines formed in the same region of the nebula as [Cl II]. This provides some observational support for the accuracy of the [Cl II] line ratio calculations and hence the atomic data on which they are based. The [Cl II] 8578.7 and 9123.6 Angstrom lines are identified for the first time (to our knowledge) in a high-resolution spectrum of the symbiotic star RR Telescopii, obtained with the University College London Echelle Spectrograph on the 3.9 m Anglo-Australian Telescope. However, the 6161.8 Angstrom feature is unfortunately too weak to be identified in the RR Telescopii observations, consistent with its predicted line strength.
ISSN: 0004-637X
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Non-KU Leuven Association publications
× corresponding author
# (joint) last author

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