We present the results of a spectroscopic study of the intermediate age (approximately 6.5 Gyr) massive cluster Kron 3 in the Small Magellanic Cloud. We measure CN and CH band strengths (at 3839 and 4300 Angstroms respectively) using VLT FORS2 spectra of 16 cluster members and find a sub-population of 5 stars enriched in nitrogen. We conclude that this is evidence for multiple populations in Kron 3, the fourth intermediate age cluster, after Lindsay 1, NGC 416 and NGC 339 (ages 6-8 Gyr), to display this phenomenon originally thought to be a unique characteristic of old globular clusters. At 6.5 Gyr this is one of the youngest clusters with multiple populations, indicating that the mechanism responsible for their onset must operate until a redshift of at least 0.75, much later than the peak of globular cluster formation at redshift ~3.
@article{arxiv.1801.09670,
title = {Kron 3: a fourth intermediate age cluster in the SMC with evidence of multiple populations},
author = {K. Hollyhead and C. Lardo and N. Kacharov and N. Bastian and M. Hilker and M. Rejkuba and A. Koch and E. K. Grebel and I. Georgiev},
journal= {arXiv preprint arXiv:1801.09670},
year = {2018}
}