Chemical composition of post-AGB star candidates

TL;DR

This study provides detailed chemical abundance analyses of six post-AGB star candidates, revealing diverse evolutionary states and chemical signatures, including evolved stars, potential post-RGB objects, and young stars, with implications for stellar evolution understanding.

Contribution

First detailed optical spectroscopic abundance analysis of six post-AGB candidates, including identification of evolved, post-RGB, and young stellar objects in the sample.

Findings

IRAS 05338-3051 shows evolved star abundances similar to V453 Oph.

IRAS 18025-3906 is O-rich without s-process enrichment.

IRAS 18386-1253 exhibits refractory element depletion, possibly a post-RGB object.

Abstract

We present a high resolution detailed abundance analysis for a sample of six post-AGB candidate stars, five of them had not been studied spectroscopically in the optical region. All the analyzed objects are IRAS sources identified as possible post-AGB on the two-colours IRAS diagram. We find three objects with clear signs of evolved stars; IRAS 05338-3051 shows abundances similar to the RV Tauri V453 Oph; the lower-luminosity stars IRAS 18025 - 3906 is O-rich without s-process enrichment and IRAS 18386 - 1253 shows a moderate selective depletion of refractory elements generally seen in post-AGB stars, which show mid-IR excess; they may be evolved post-RGB objects, in which case these would be the first Galactic counterparts of post-RGB objects observed in the Large and Small Magellanic Clouds (Kamath et al. 2014, 2015). On the other hand, IRAS 02528 + 4350 seems to be a moderately metal-poor young object and IRAS 20259 + 4206 also seems to be a young object showing carbon deficiency; however, an analysis with better spectra might be in order to clarify its evolutionary state. Finally, our abundances calculations for the binary post-AGB star IRAS 17279 - 1119 are found in good agreement with those of De Smedt et al. (2016).