7 Conclusions

We have found a new post-AGB star HD 172481 for which abundance analysis had not been carried out before, however the referee pointed out in a rather late stage of revision, the then unpublished work by Reyniers & Van Winckel (2001) where an independent abundance analysis has been carried out. We have highlighted a comparison of results in Sect. 5.5 and found both analyses to be in fairly good agreement. We have done a more complete analysis of HD 158616. This star can be now considered a post-AGB star beyond any doubt. Among the post-AGB stars, the number of stars showing C/O $\sim$1 or greater and also enhancement of s-process elements are very few. There are clear indications of stars having experienced the third dredge-up. The stars HD 158616 and HD 172481 belong to this important class. C/O of HD 172481 might have been prevented from exceeding one by HBB. The same may be responsible for large Li abundance but other possibilities like binarity cannot be ruled out. A long-term light and radial velocity monitoring of this object is planned for the future.

We found a very likely hot post-AGB candidate in HD 172324 but will feel more confident of its status after important elements like N are included and a more comprehensive study is made. Continuous monitoring of its spectrum in the H$_\alpha$ region is required to detect activity possibly related to stellar pulsations.

HD 218753 and HD 331319 have passed the giant branch and are in the He-core and H-shell burning stages. HD 9167 and HD 173638 essentially show solar abundance. HD 725 and HD 9167 show large radial velocities, however their galactocentric orbits are on the galactic plane and mildly eccentric, thus they are most likely massive and young disk stars. However, their large radial velocity could also be due to pulsations and/or orbital motions.

In the proto-Planetary Nebula HDE 341627 the He lines show two velocity components possibly indicating velocity stratification. The emission lines appear to have weakened since 1993.

Acknowledgements

AAF acknowledges Commission 38 of the IAU for a travel grant and the Indian Institute of Astrophysics for hospitality and financial support. We thank David Yong for getting us two spectra of HD 172481. We are also indebted to Ms. T. Sivarani for her help in identifying the lines for HDE 341617. We are grateful to the referee, Dr. R. Gallino, for helpful discussions and suggestions. This project has been supported at different stages by grants from DGAPA-UNAM (IN113599) and CONACyT (Mexico) (E130.2060) and CNRS (France).