Discovery of Iron in PG1159 Stars

TL;DR

This study detects FeX lines in the hottest PG1159 stars, revealing solar iron abundance contrary to previous beliefs of iron depletion, and compares these findings with solar and cooler PG1159 stars.

Contribution

The paper reports the first detection of FeX lines in very hot PG1159 stars, indicating solar iron abundance and challenging prior assumptions of iron depletion in these stars.

Findings

FeX lines detected in PG1159 stars with Teff=150,000-200,000 K

Solar iron abundance found in these hot PG1159 stars

FeVIII lines identified in cooler PG1159 stars, including PG1159-035

Abstract

The lack of FeVII lines in PG1159 stars had led to the conclusion that in some objects iron must be strongly depleted. We have now detected FeX lines in FUSE spectra of the very hottest PG1159 stars Teff=150,000 - 200,000 K; RXJ2117.1+3412, K1-16, NGC 246, Longmore 4). Surprisingly, we derive a solar iron abundance. It is conspicuous that they are among the most massive PG1159 stars (0.71-0.82 Msun), in contrast to those objects for which strongest Fe-deficiency was claimed (0.53-0.56 Msun). Based on new FeVIII line identifications in SOHO/SUMER UV spectra of the Sun, we were able to detect these lines in FUSE spectra of several "cooler" (Teff<150,000 K) objects, among them is the prototype PG1159-035. An abundance analysis is in progress.