Non-LTE Spectral Analysis of Extremely Hot Post-AGB Stars: Constraints for Evolutionary Theory

TL;DR

This paper uses advanced Non-LTE spectral modeling of hot post-AGB stars to test stellar evolution theories, revealing evidence of nucleosynthesis processes like the s-process affecting elemental abundances.

Contribution

It provides new spectral analysis results of hot stars using comprehensive Non-LTE models, offering insights into AGB nucleosynthesis and stellar evolution.

Findings

Detection of Fe depletion indicating s-process activity

Identification of elemental abundance patterns in post-AGB stars

Validation of Non-LTE models for hot star atmospheres

Abstract

Spectral analysis by means of Non-LTE model-atmosphere techniques has arrived at a high level of sophistication: fully line-blanketed model atmospheres which consider opacities of all elements from H to Ni allow the reliable determination of photospheric parameters of hot, compact stars. Such models provide a crucial test of stellar evolutionary theory: recent abundance determinations of trace elements like, e.g., F, Ne, Mg, P, S, Ar, Fe, and Ni are suited to investigate on AGB nucleosynthesis. E.g., the strong Fe depletion found in hydrogen-deficient post-AGB stars is a clear indication of an efficient s-process on the AGB where Fe is transformed into Ni or even heavier trans iron-group elements. We present results of recent spectral analyses based on high-resolution UV observations of hot stars.