2003ApJ...590.1049H

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 C₂and C₃and enhanced s-process lines. From the high-resolution spectra, the following atmospheric parameters were determined: T_eff=6900 K, logg=1.0, and ξ_t=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 C₂and CN molecular bands in the spectrum of IRAS 06530-0213, an envelope expansion velocity of V_exp=14±1 km/s 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.