Abundance analyses of the new R Coronae Borealis stars: ASAS-RCB-8 and ASAS-RCB-10

TL;DR

This study presents detailed abundance analyses of two newly discovered R Coronae Borealis stars, revealing their chemical compositions and placing them within the majority class, with notable differences in nitrogen, oxygen, and hydrogen content.

Contribution

It provides the first high-resolution spectral abundance analysis of the new RCB stars ASAS-RCB-8 and ASAS-RCB-10, expanding understanding of their chemical diversity.

Findings

ASAS-RCB-10 is one of the most nitrogen-poor majority RCBs.

ASAS-RCB-8 is hydrogen-poor, oxygen-poor, but nitrogen-rich.

Both stars belong to the majority class of RCBs.

Abstract

Abundance analyses of the two newly discovered R Coronae Borealis (RCB) stars ASAS-RCB-8 and ASAS-RCB-10 were conducted using high-resolution optical spectra and model atmospheres. Their chemical compositions place the pair among the majority class of RCBs. ASAS-RCB-10 is one of the most N-poor majority RCBs with an above average O abundance. Relative to ASAS-RCB-10, ASAS-RCB-8 is H poor by 1.6 dex, O-poor by 0.7 dex but N-rich by 0.8 dex suggesting a higher contamination by CNO-cycled material.