2006BaltA..15..395K

Using the echelle spectrograph of the 6 m telescope, we obtained moderate resolution spectra of the post-AGB star CGCS6857 associated with an IR-source IRAS20000+3239 having an IR-feature at 21 µm in emission. In the optical spectrum we revealed bands of C₂ and CN molecules, but no C₃. The model atmospheric parameters adopted are: effective temperature T_eff=5000±200 K, logarithmic gravity logg=0.0 ±0.3 and microturbulent velocity ξ_t=9.0±1.0 km/s. We obtained low metallicity [Fe/H]=-1.4, a C/O abundance ratio close to 1 together with large overabundances of the s-process elements Y, Zr, Ba, La, Ce, Pr and Sm, with an average value [El/Fe] = +1.4. The heliocentric radial velocity from metallic lines is equal to v_ rad_(met) = -15±2 km/s.