NGC 7789: An Open Cluster Case Study

TL;DR

This study analyzes high-resolution spectra of giants in NGC 7789 to compare elemental abundances using different linelists, revealing a lower magnesium abundance and significant barium enhancement, contributing to understanding of cluster chemical composition.

Contribution

It introduces a comparative analysis of elemental abundances using GES and Arcturus linelists in NGC 7789, highlighting differences in derived parameters and confirming Ba enhancement in young clusters.

Findings

[Fe/H] = 0.03 +/- 0.07 dex, consistent with literature

Lower [Mg/Fe] than previously reported

High [Ba/Fe] = +0.48 +/- 0.08 indicating Ba enhancement

Abstract

We have obtained high-resolution spectra of 32 giants in the open cluster NGC 7789 using the Wisconsin-Indiana-Yale-NOAO Hydra spectrograph. We explore differences in atmospheric parameters and elemental abundances caused by the use of the linelist developed for the Gaia-ESO Survey (GES) compared to one based on Arcturus used in our previous work. [Fe/H] values decrease when using the GES linelist instead of the Arcturus-based linelist; these differences are probably driven by systematically lower (~ -0.1 dex) GES surface gravities. Using the GES linelist we determine abundances for 10 elements - Fe, Mg, Si, Ca, Ti, Na, Ni, Zr, Ba, and La. We find the cluster's average metallicity [Fe/H] = 0.03 +/- 0.07 dex, in good agreement with literature values, and a lower [Mg/Fe] abundance than has been reported before for this cluster (0.11 +/- 0.05 dex). We also find the neutron-capture element barium to be highly enhanced - [Ba/Fe] = +0.48 +/- 0.08 - and disparate from cluster measurements of neutron-capture elements La and Zr (-0.08 +/- 0.05 and 0.08 +/- 0.08, respectively). This is in accordance with recent discoveries of supersolar Ba enhancement in young clusters along with more modest enhancement of other neutron-capture elements formed in similar environments.