Spectrum of the high-excitation planetary nebula NGC 6741 (33-2 1).

Abstract

Image tube observations carried out at the Lick and Mount Wilson Observatories were combined with IUE and infrared observations to study the spectra of the high-excitation planetary nebula NGC 6741. Plasma diagnostics were carried out and ion concentrations were calculated for ions from He I to Ca4(+). The ion densities and plasma diagnostics data were compared with theoretical nebular models to interpret the spectra and to obtain ionization correction factors. It is shown that the exciting star in NGC 6741 has an effective temperature near 160,000 K. The predicted abundance ratios for the lines at 5876/4686 A, 3426/3868 A, and 3727/5007 A conformed well to the observations. The derived logarithmic abundances in NGC 6741 are given in a table.