Abundances of 439 stars in Omega Centauri

Our analysis reveals the presence of four distinct Fe populations, with the main peak occurring at a low metallicity, consistent with previous literature findings. We observe a discrete and pronounced Mg-Al anticorrelation, which exhibits variations in shape and extension as a function of metallicity.

Specifically, this anticorrelation is present in stars with metallicities lower than approximately -1.3dex, while it becomes less evident or absent for higher [Fe/H] values. Additionally, we detect (anti)correlations between Mg and Si, and between Al and Si, whose extensions also vary with metallicity, similar to the Mg-Al anticorrelation. These results suggest that the MgAl cycle plays a crucial role in the formation of multiple populations in Omega Centauri, with the presence of all (anti)correlations at metallicities lower than -1.3dex, providing evidence for the burning of Mg at very high temperatures (>10^8^K), at least in the metal-poor regime.