An Abundance Analysis of the New Carbon-rich Proto-Planetary Nebula IRAS 06530–0213

In this paper we present a study of the proto-planetary nebula (PPN) IRAS 06530-0213 based on low- and high-resolution spectra. The low-resolution spectrum shows that the star is an F5 supergiant with molecular C2 and C3 and enhanced s-process lines. From the high-resolution spectra, the following atmospheric parameters were determined: Teff = 6900 K, log g = 1.0, and ξt = 4.5. Abundance analysis shows that IRAS 06530-0213 is metal-poor ([Fe/H] = -0.9) and overabundant in carbon ([C/Fe] = 1.3), nitrogen ([N/Fe] = 1.0), and s-process elements ([s-process/Fe] = 1.9), indicating asymptotic giant branch (AGB) nucleosynthesis and deep convective mixing. From the analysis of circumstellar C2 and CN molecular bands in the spectrum of IRAS 06530-0213, an envelope expansion velocity of Vexp = 14 ± 1 km s-1 was determined, a typical value for post-AGB stars. Also typical of PPNs is the double-peaked spectral energy distribution. The properties of both the photosphere and circumstellar envelope suggest that IRAS 06530-0213 is unambiguously a low-mass, carbon-rich PPN. For comparison purposes, new, high-resolution spectra of the well-known PPN HD 56126 (IRAS 07134+1005) were also analyzed and compared with previous results.