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The multiple stellar populations (MPs) of $\sim$11-13 Gyr-old GlobularClusters (GCs) in our Galaxy are characterized by different content of severallight elements. These elements describe well-defined patterns like the C-N andthe Na-O anticorrelations and the He-N and Na-N correlations. The discovery ofthe MPs in Magellanic Cloud GCs opened up new paths for the investigation ofchemical anomalies in clusters with different age and physical properties. Inthis context, we used Hubble Space Telescope photometry to investigate the MPsand constrain their chemical composition of four $\sim$6-11 Gyr extragalacticGCs, namely NGC 121,NGC 339, NGC 416 and Lindsay 1 in the Small MagellanicCloud. The comparison of the stellar colors with synthetic spectra suggeststhat second-population stars of NGC 121, NGC 339, NGC 416 are slightly enhancedin helium by $\delta$Y = 0.009$\pm$0.006, 0.007$\pm$0.004 and 0.010$\pm$0.003,respectively, with respect to the first population, while we find nosignificant helium variation in Lindsay 1 ($\delta$Y = 0.000$\pm$0.004).Moreover, second-population stars of all the clusters are, on average, enhancedin nitrogen and depleted in carbon and oxygen, in close analogy with what weobserve in Galactic GCs.

Helium variation in four Small Magellanic Cloud GCs