A NEW LOOK AT CARBON ABUNDANCES IN PLANETARY-NEBULAE .2. BB 1, NGC, NGC 1535, NGC 2440, AND NGC 7027

This paper is the second in a series that reports on the outcome of a study of carbon abundances in a carefully chosen sample of planetary n ebulae representing a large range in progenitor mass and metallicity. We use the Final Archive IUE database containing consistently reduced IUE spectra to measure line strengths of C III] lambda 1909, along wit h numerous other UV lines for the planetary nebulae BB 1, NGC 650, NGC 1535, NGC 2440, and NGC 7027. Combining these measurements with optic al data from the literature, we determine values for the abundance rat ios He/H, O/H, C/O, N/O, and Ne/O for these five objects using a five- level program, but we fine-tune the results with corrections derived f rom detailed photoionization models constrained by the same set of emi ssion lines. All five objects show enhanced levels of C/O and N/O but depleted O/H with respect to the Sun.