An Abundance Analysis of the New Carbon-Rich Proto-Planetary Nebula IRAS 06530$-$0213

Abstract

In this paper, we present a study of the proto-planetary nebula (PPN) IRAS 06530$-$0213 based on low- and high-resolution spectra. The low-resolution spectrum shows that star is an F5 supergiant with molecular C$_{2}$ and C$_{3}$ and enhanced s-process lines. From the high-resolution spectra, the following atmospheric parameters were determined: $T_{\rm eff}$ = 6900 K, log$g$ = 1.0 and $ξ_{\rm t}$ = 4.5. Abundance analysis shows that IRAS 06530$-$0213 is metal-poor ([Fe/H]=$-$0.9) and overabundant in carbon ([C/Fe]=1.3), nitrogen ([N/Fe]=1.0), and s-process elements ([s-process/Fe]=1.9), indicating AGB nucleosynthesis and deep convective mixing. From the analysis of circumstellar C$_{2}$ and CN molecular bands in the spectrum of IRAS 06530$-$0213, an envelope expansion velocity of V$_{\rm exp}$=~14$\pm1$ 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) was also analyzed and compared with previous results.