A New Look at Carbon Abundances in Planetary Nebulae. I. PB 6, HU 2--1, K648, and H4--1

Abstract

We introduce and describe a new long-term project whose goal is to employ final archived lUE spectra to study carbon abundances in a sample of planetary nebulae representing a broad range in progenitor mass and metallicity In this paper we report on initial results for PB 6, Hu 2-1, K648, and H4-1. Our UV line strengths for H4-1 are the first such data to be published for this object. By combining our measured UV line strengths with optical line strengths found in the literature for each object, we have determined values for the abundance ratios He/H, 0/H, C/O, N/O, and Ne/O using a combined atomic level-balancing-photoionization model approach. Eventually, the abundances from this and subsequent studies will be analyzed using a newly improved stellar evolution code for intermediate-mass stars with the goal of determining carbon yields for stars of this mass range.