Recio-Blanco A.Rojas-Arriagada A.De Laverny P.Mikolaitis S.Hill V.Zoccali M.Fernández-Trincado J.G.Robin A.C.Babusiaux C.Gilmore G.Randich S.Alfaro E.Allende Prieto C.Bragaglia A.Carraro G.Jofré P.Lardo C.Monaco L.Morbidelli L.Zaggia S.2024-05-242024-05-242017-07Astronomy and Astrophysics Volume 6021 June 2017 Article number L140004-6361https://repositorio.unab.cl/handle/ria/57035Indexación: ScopusWe take advantage of the Gaia-ESO Survey iDR4 bulge data to search for abundance anomalies that could shed light on the composite nature of the Milky Way bulge. The α-element (Mg, Si, and whenever available, Ca) abundances, and their trends with Fe abundances have been analysed for a total of 776 bulge stars. In addition, the aluminum abundances and their ratio to Fe and Mg have also been examined. Our analysis reveals the existence of low-α element abundance stars with respect to the standard bulge sequence in the [α/ Fe] versus [Fe/H] plane. Eighteen objects present deviations in [α/ Fe] ranging from 2.1 to 5.3σ with respect to the median standard value. Those stars do not show Mg-Al anti-correlation patterns. Incidentally, this sign of the existence of multiple stellar populations is reported firmly for the first time for the bulge globular cluster NGC 6522. The identified low-α abundance stars have chemical patterns that are compatible with those of the thin disc. Their link with massive dwarf galaxies accretion seems unlikely, as larger deviations in α abundance and Al would be expected. The vision of a bulge composite nature and a complex formation process is reinforced by our results. The approach used, which is a multi-method and model-driven analysis of high resolution data, seems crucial to reveal this complexity. © ESO, 2017.enGalaxy: abundancesGalaxy: bulgeGalaxy: stellar contentArtículoCC BY 4.0 DEED Atribución 4.0 Internacional10.1051/0004-6361/201630220