Spectral matching for abundances and clustering analysis of stars on the giant branches of {\omega} Centauri

TL;DR

This study combines photometry and spectroscopy to analyze stellar parameters and abundances in 221 giant stars of {} Centauri, using spectral matching and clustering to reveal chemical and evolutionary patterns.

Contribution

It introduces a spectral matching method combined with clustering analysis to classify stars and study their chemical abundances in {} Centauri.

Findings

Stars show expected C-N anticorrelation.

Most asymptotic giant branch stars are CN-weak.

CN-weak and CN-strong stars distribute differently on the CMD.

Abstract

We have determined stellar parameters and abundances for 221 giant branch stars in the globular cluster {\omega} Centauri. A combination of photometry and lower-resolution spectroscopy was used to determine temperature, gravity, metallicity, [C/Fe], [N/Fe] and [Ba/Fe]. These abundances agree well with those found by previous researchers and expand the analysed sample of the cluster. k-means clustering analysis was used to group the stars into four homogeneous groups based upon these abundances. These stars show the expected anticorrelation in [C/Fe] to [N/Fe]. We investigated the distribution of CN-weak/strong stars on the colour-magnitude diagram. Asymptotic giant branch stars, which were selected from their position on the colour-magnitude diagram, were almost all CN-weak. This is in contrast to the red giant branch where a large minority were CN-strong. The results were also compared with cluster formation and evolution models. Overall, this study shows that statistically significant elemental and evolutionary conclusions can be obtained from lower resolution spectroscopy.