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B.E Reddy, B.J. Hrivnak (Valparaiso U.)
In this paper we present an analysis of both low- and high-resolution spectra of the proto-planetary nebula IRAS~06530-0213 (V=14.1). The analysis of low-resolution spectra shows that the star is an F5 supergiant, with C2, C3, and enhanced s-process lines. From high-resolution spectral line analysis, we derived the following atmospheric parameters: T\rm eff=6900~K, log g=1.0, and \xit=4.35 km s-1. The abundance analysis based on the LTE model atmospheres shows that IRAS~06530-0213 is metal-poor ([Fe/H]=-0.9), carbon-rich (C/O>2.0), and overabundant in heavy elements like Y, Zr, La, Ba ([s-process/Fe]=2.0). For comparison purposes, we analyzed the similar but previously studied proto-planetary nebula IRAS~07134+1005, based on new high-quality, high-resolution, and more complete spectra. The analysis yielded the following atmospheric parameters: T\rm eff=7000~K, log g=0.25, \xit=4.50 km s-1, and the following abundance results: [Fe/H]=-1.2, [C/Fe]=1.22, and [s-process/Fe]=1.5.
Similar to other known carbon-rich proto-planetary nebulae, we detected circumstellar molecular bands of C2 (Phillips) and CN (Red System) in the red part of the optical spectrum of IRAS~06530-0213. From these, we derive an expansion velocity for the circumstellar envelope of V\rm exp\approx13 km s-1. Thus the metallicity, radial velocity (Vr=51 km s-1), elemental abundances, and circumstellar molecular lines indicate that IRAS~06530-0213 is a low-mass, carbon-rich proto-planetary nebula, similar to IRAS~07134+1005.
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