| Abstract
| - A high-resolution and signal-to-noise ratio spectrum has been obtained for the protoplanetary nebula candidate HD 179821= IRAS 19114 + 0002 using the Academy of Sciences Astrophysical Observatory 6-m telescope and CCD detector. The spectroscopic indicators provide the atmospheric parameters Teff=6800 K and log g=1.3 (cgs), approximately equal to those for normal F5 supergiants. A standard local thermodynamic equilibrium (LTE) analysis by the model atmospheres method using these parameters shows that most of the iron-peak elements are at most only slightly deficient ([X] ≅ — 0.10 dex) relative to the normal red giant ε Vir, however, Sc and Ti are overabundant (~0.5 dex). The α-process elements are solar or slightly deficient, except Na, which is overabundant. Carbon and elements heavier than Ni are enhanced by + 0.7 dex on average compared with the standard star. The heliocentric radial velocity is found to be + 88.4 km s−1. The detached circumstellar shell, its radial velocity, and the likely overabundance of carbon and s-process elements suggest that HD 179821 is probably an evolved low-mass star in the evolutionary stage between the asymptotic giant branch (AGB) and planetary nebulae (PNe).
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