Spectroscopic analysis of four post-AGB candidates

TL;DR

This study conducts a detailed spectroscopic abundance analysis of four candidate post-AGB stars, revealing dust-rich circumstellar environments and complex chemical mixing processes affecting their surface compositions.

Contribution

It provides the first detailed abundance analysis of these four unexplored post-AGB candidates using high-resolution spectra and constructs their spectral energy distributions.

Findings

All stars show double-peaked IR SEDs indicating dusty circumstellar material.

CNO abundances suggest N production via CN cycling and third dredge-up mixing.

Depletion patterns vary, indicating multiple processes affecting surface abundances.

Abstract

We have done a detailed abundance analysis of four unexplored candidate post- Asymptotic Giant Branch(AGB) stars IRAS 13110 - 6629, IRAS 17579 - 3121, IRAS 18321 - 1401 and IRAS 18489 - 0629 using high resolution spectra. We have constructed Spectral Energy Distributions (SED) for these objects using the existing photometric data combined with infrared (IR) fluxes. For all sample stars, the SEDs exhibit double peaked energy distribution with well separated IR peaks showing the 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 produced by He burning by third dredge up although C/O ratio remains less that 1. A moderate 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 indicate the presence of other processes affecting the observed abundance pattern.