Spectroscopic analysis of four post-AGB candidates

Abstract

We have done a detailed abundance analysis of four unexplored cand idate post- Asymptotic Giant Branch(AGB) stars IRAS 13110- 6629, IRAS 175 79 - 3121, IRAS 18321- 1401 and IRAS 18489- 0629 using high resolution spectra. W e have constructed Spectral Energy Distributions (SED) for these objects using the existing photometric data combined with infrared (IR) fluxes. For all sample stars, the S EDs exhibit double peaked energy distribution with well separated IR peaks showing th e presence of dusty circumstellar material. The CNO abundances indicate the production of N via CN cycling, but observed [C/Fe] indicates the mixing of carbon produce d by He burning by third dredge up although C/O ratio remains less that 1. A moderat e DG effect is clearly seen for IRAS 18489 - 0629 and IRAS 17579- 3121 while a large scatter observed in depletion plots for IRAS 18321- 1401 and IRAS 13110 - 6629 indicat e the presence of other processes affecting the observed abundance pattern.