The complex stellar system M 22: confirming abundance variations with high precision differential measurements

• DOI: 10.1093/mnras/stac2254
• Publication Date: 2022-08-14T01:48:11Z
• Authors: M McKenzie; D Yong; A F Marino; S Monty; E Wang; A I Karakas; A P Milone; M V Legnardi; I U Roederer; S Martell; D Horta
• Keywords: techniques: spectroscopic; stars: abundances; stars: Population II; globular clusters: general; globular clusters: individual: NGC 6656; 0103 physical sciences; 01 natural sciences

ABSTRACT M 22 (NGC 6656) is a chemically complex globular cluster-like system reported to harbour heavy element abundance variations. However, the extent of these variations and origin this cluster still debated. In work, we investigate chemical in-homogeneity using differential line-by-line analysis high-quality (R = 110 000, S/N 300 per pixel at 514 nm) VLT/UVES spectra six carefully chosen red giant branch stars. By achieving uncertainties as low ∼0.01 dex (∼2 cent), high precision data validates results previous studies reveals in Fe, Na, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Y, Zr, La, Ce, Nd, Sm, Eu. Additionally, can confirm that hosts two stellar populations with spread least 0.24 [Fe/H] an average s-process 0.65 dex. addition global across cluster, also find non-negligible within each populations, more metal-poor population hosting larger spreads elements heavier than Fe metal-rich. We address works do not identify anomalous abundances relate our findings current dynamical understanding cluster. Given results, suggest either nuclear star product merged clusters, or original building block Milky Way.