Astronomy and Astrophysics – Astronomy
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994pasp..106..745h&link_type=abstract
Astronomical Society of the Pacific, Publications (ISSN 0004-6280), vol. 106, no. 701, p. 745-755
Astronomy and Astrophysics
Astronomy
33
Infrared Spectra, Planetary Nebulae, Stellar Envelopes, Stellar Evolution, Stellar Spectra, Ultraviolet Spectra, Visible Spectrum, Astronomical Spectroscopy, Echelle Gratings, High Resolution, Iue, Spectral Resolution, Spectrographs, Stellar Models, Stellar Winds, Variable Stars
Scientific paper
A detailed high-spectral-resolution study of the spectrum of IC 418 is made for the region 3650 to 10050 A, using the Hamilton echelle spectrograph of Lick Observatory, and of the UV spectral region with archival International Ultraviolet Explorer (IUE) data. From high-resolution images in both the near- and mid-infrared, Hora et al. (1993) showed that IC 418 probably has a compact shell interior to the detached, well-known, main shell emission. If one assumes a black body or Hubeny (or standard LTE) model atmosphere energy distribution, it does not appear possible to construct a fully satisfactory nebula model that will simultaneously represent the H-beta flux, the (O III) 5007/H-beta ratio, and the scale of this planetary nebula (PN). Fortunately, IUE and IR data supply information on ions in addition to those optically observed so that the chemical composition can be reasonably well established by summing over concentrations of observed ions. In spite of the fact that IC 418 is carbon rich in sense of having a C/O ratio exceeding the solar value, it is a 'metal-poor' object. Possibly it resembles IC 4997 but in a more advanced evolutionary phase. The central star is variable and has a strong wind.
Aller Lawrence H.
Feibelman Walter A.
Hyung Siek
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