Elemental Abundances in PG1159 Stars

TL;DR

This study analyzes elemental abundances in PG1159 stars to understand nuclear processes in their progenitors, revealing both agreements and discrepancies with stellar evolution models, and confirming their link to [WC] stars.

Contribution

It provides a detailed comparison of observed and predicted elemental abundances, highlighting areas for improvement in AGB stellar evolution models.

Findings

Good agreement for He, C, N, O, Ne, F, Si, Ar

Discrepancies for P, S, Fe suggest model shortcomings

Supports PG1159 stars as progeny of [WC] stars

Abstract

The hydrogen-deficiency in extremely hot post-AGB stars of spectral class PG1159 is probably caused by a (very) late helium-shell flash or a AGB final thermal pulse that consumes the hydrogen envelope, exposing the usually-hidden intershell region. Thus, the photospheric elemental abundances of these stars allow to draw conclusions about details of nuclear burning and mixing processes in the precursor AGB stars. We compare predicted elemental abundances to those determined by quantitative spectral analyses performed with advanced non-LTE model atmospheres. A good qualitative and quantitative agreement is found for many species (He, C, N, O, Ne, F, Si, Ar) but discrepancies for others (P, S, Fe) point at shortcomings in stellar evolution models for AGB stars. PG1159 stars appear to be the direct progeny of [WC] stars.