Differential chemical abundance analysis of a 47 Tuc AGB star with respect to Arcturus

TL;DR

This paper performs a differential chemical abundance analysis of a 47 Tucanae AGB star relative to Arcturus, highlighting the importance of using a similar standard star to reduce systematic errors and clarifying Zr abundance discrepancies.

Contribution

It introduces a differential analysis method using a standard star with similar stellar parameters, improving accuracy in abundance measurements of AGB stars.

Findings

Zr abundance in Lee 2525 is +0.51 dex, aligning with s-process enrichment theories.

Y abundance is +0.53 dex, consistent with current nucleosynthesis models.

The study resolves previous discrepancies in Zr abundance measurements.

Abstract

This study resolves a discrepancy in the abundance of Zr in the 47 Tucanae asymptotic giant branch star Lee 2525. This star was observed using the echelle spectrograph on the 2.3 m telescope at Siding Spring Observatory. The analysis was undertaken by calibrating Lee 2525 with respect to the standard giant star Arcturus. This work emphasises the importance of using a standard star with stellar parameters comparable to the star under analysis rather than a calibration with respect to the Sun (Koch & McWilliam 2008). Systematic errors in the analysis process are then minimised due to the similarity in atmospheric structure between the standard and programme stars. The abundances derived for Lee 2525 were found to be in general agreement with the Brown & Wallerstein (1992) values except for Zr. In this study Zr has a similar enhancement ([Zr/Fe] = +0.51 dex) to another light s-process element, Y ([Y/Fe] = +0.53 dex), which reflects current theory regarding the enrichment of s-process elements by nuclear processes within AGB stars (Busso et al. 2001). This is contrary to the results of Brown & Wallerstein (1992) where Zr was under-abundant ([Zr/Fe] = +0.51 dex) and Y was over-abundant ([Y/Fe] = +0.50 dex) with respect to Fe.