High-resolution spectroscopy of the extremely iron-poor post-AGB star CC Lyr

TL;DR

This study presents high-resolution spectroscopy of the extremely iron-poor post-AGB star CC Lyr, revealing its chemical composition, dust depletion effects, and atmospheric dynamics, with implications for stellar evolution and circumstellar environment.

Contribution

It provides the first detection of Sr and Ba in CC Lyr and analyzes the effects of dust depletion and pulsation on spectral features, advancing understanding of metal-poor post-AGB stars.

Findings

Confirmed extremely low metallicity ([Fe/H]<-3.5)

Detected first Sr and Ba in CC Lyr

Identified atmospheric pulsation effects on spectral lines

Abstract

High-resolution optical spectroscopy was conducted for the metal-poor post-AGB star CC Lyr to determine its chemical abundances and spectral line profiles. Our standard abundance analysis confirms its extremely low metallicity ([Fe/H]<-3.5) and a clear correlation between abundance ratios and the condensation temperature for 11 elements, indicating that dust depletion is the cause of the abundance anomaly of this object. The very low abundances of Sr and Ba, which are detected for the first time for this object, suggest that heavy neutron-capture elements are not significantly enhanced in this object by the s-process during its evolution through AGB phase. Radial velocity of this object and profiles of some atomic absorption lines show variations depending on pulsation phases, which could be formed by dynamics of the atmosphere rather than by binarity or contributions of circumstellar absorption. On the other hand, the H-alpha emission with double peaks shows no evident velocity shift, suggesting that the emission is originating from the circumstellar matter, presumably the rotating disk around the object.