Emission lines of [K V] in the optical spectra of gaseous nebulae
Keenan, F.P.; Aller, L.H.; Espey, B.R.; Exter, K.M.; Hyung, S.; Keenan, M.T.C.; Pollacco, D.L.; Ryans, R.S.I. (2002). Emission lines of [K V] in the optical spectra of gaseous nebulae. Proc. Natl. Acad. Sci. U.S.A. 99(7): 4152-4155. https://dx.doi.org/10.1073/pnas.062032299 In: Proceedings of the National Academy of Sciences of the United States of America. The Academy: Washington, D.C.. ISSN 0027-8424; e-ISSN 1091-6490, more |   |
| Authors | | Top | - Keenan, F.P.
- Aller, L.H.
- Espey, B.R.
- Exter, K.M., more
| - Hyung, S.
- Keenan, M.T.C.
- Pollacco, D.L.
- Ryans, R.S.I.
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| Abstract | Recent R-matrix calculations of electron impact excitation rates in K v are used to derive the nebular emission line ratio R = I(4122.6 Å)/I(4163.3 Å) as a function of electron density (Ne). This ratio is found to be very sensitive to changes in Ne over the density range 103 to 106 cm−3, but does not vary significantly with electron temperature, and hence in principle should provide an excellent optical Ne diagnostic for the high-excitation zones of nebulae. The observed value of R for the planetary nebula NGC 7027, measured from a spectrum obtained with the Hamilton Echelle spectrograph on the 3-m Shane Telescope, implies a density in excellent agreement with that derived from [Ne iv], formed in the same region of the nebula as [K v]. This observation provides observational support for the accuracy of the theoretical [K v] line ratios, and hence the atomic data on which they are based. However, the analysis of 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, reveals that the [K v] 4122.6 Å line in this object is badly blended with Fe ii 4122.6 Å. Hence, the [K v] diagnostic may not be used for astrophysical sources that show a strong Fe ii emission line spectrum. |
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