Five groups of red giants with distinct chemical composition in the globular cluster NGC 2808

摘要: The chemical composition of multiple populations in the massive globular cluster (GC) NGC~2808 is addressed with homogeneous abundance re-analysis 140 red giant branch (RGB) stars. UVES spectra for 31 stars and GIRAFFE other giants were analysed same procedures used about 2500 23 GCs our FLAMES survey, deriving abundances Fe, O, Na, Mg, Si, Ca, Ti, Sc, Cr, Mn, Ni. Iron, elements from alpha-capture, Fe-group do not show intrinsic scatter. On scale metallicity [Fe/H]=-1.129+/-0.005+/-0.034$ (+/-statistical +/-systematic error) sigma=0.030 (31 stars). Main features related to proton-capture are retrieved, but improved statistics smaller associated internal errors allow uncover five distinct groups along Na-O anticorrelation. We observe large depletions anticorrelated enhancements Na also suggestive unusually high temperatures proton-captures. About 14% sample formed by solar or subsolar [Mg/Fe] ratios. Using [Na/Mg] ratios we confirm presence different composition, that called P1, P2, I1, I2, E order decreasing Mg increasing abundances. Statistical tests mean any pair cannot be extracted parent distribution. overlap recently detected UV photometry good perfect, confirming more components probably exist this complex GC.