An abundance analysis is presented for IRAS 18095+2704 ( V887 Her ) , a post-AGB star and proto-planetary nebula .
The analysis is based on high-resolution optical spectra from the McDonald Observatory and the Special Astrophysical Observatory .
Standard analysis using a classical Kurucz model atmosphere and the line analysis program MOOG provides the atmospheric parameters : T _ { eff } = 6500 K , \log g = +0.5 , and a microturbulent velocity \xi = 4.7 km s ^ { -1 } and [ Fe/H ] = -0.9 .
Extraction of these parameters is based on excitation of Fe i lines , ionization equilibrium between neutral and ions of Mg , Ca , Ti , Cr , and Fe , and the wings of hydrogen Paschen lines .
Elemental abundances are obtained for 22 elements and upper limits for an additional four elements .
These results show that the star ’ s atmosphere has not experienced a significant number of C- and s -process enriching thermal pulses .
Abundance anomalies as judged relative to the compositions of unevolved and less-evolved normal stars of a similar metallicity include Al , Y , and Zr deficiencies with respect to Fe of about 0.5 dex .
Judged by composition , the star resembles a RV Tauri variable that has been mildly affected by dust-gas separation reducing the abundances of the elements of highest condensation temperature .
This separation may occur in the stellar wind .
There are indications that the standard 1D LTE analysis is not entirely appropriate for IRAS 18095+2704 .
These include a supersonic macroturbulent velocity of 23 km s ^ { -1 } , emission in H \alpha and the failure of predicted profiles to fit observed profiles of H \beta and H \gamma .