Ultraviolet spectra of planetary nebulae. I. The abundance of carbon in IC 418.
Harrington, J. P.; Lutz, J. H.; Seaton, M. J.; Stickland, D. J.
United States, United Kingdom, Spain
Abstract
IUE observations of IC 418 give fluxes in the lines C III λ1908, C II] λ2326, [O II] λ2470 and Mg II λ2800. Fluxes on the scale of F(Hβ) = 100 are obtained using a computed [O II] branching ratio F(λλ7320,30)/F(λ2470) and an observed ratio F(λλ7320, 30)/F(Hβ). The deduced carbon abundance is log {C} = 8.85 ± 0.2 compared with log {C} = 8.67 ± 0.1 for the Sun. A critical discussion is given on methods used previously to determine carbon abundances in planetary nebulae.