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Table 1

Summary of results on Na-O abundances along the HB in various clusters.

Cluster Red HB Blue HB

47 Tuc [Na/O] correlates with colour
(Gratton et al. 2013) (increases as B-V decreases)

NGC 1851 Mostly O-rich/Na-poor Na-rich/O-poor
(Gratton et al. 2012a) 1015% Na-rich, moderately O-poor (Na-O anticorrelation)
Mostly descendants from b-SGB Mostly descendants from f-SGB

NGC 2808 O-rich Moderately O-poor
(Gratton et al. 2011) Spread Na (correlated with colour) Moderately Na-rich

M 5 Na-poor, O-rich Na-O anticorrelation
(Gratton et al. 2013) Most stars with abundances
similar to RHB stars

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