Abundances of cool supergiants in the SMC young cluster NGC 330 ?

NGC 330 is the brightest SMC young cluster and contains many bright supergiants. This cluster has aroused special interest, since the earlier abundance determinations indicated an abundance lower by a factor ∼5 than in the SMC field young population. Taking advantage of our previous high resolution analysis of a sample of type K supergiants in the SMC field (Paper I and II), we analyse 6 cool supergiants in NGC 330, in order to compare in an homogeneous way, the metallicity and abundance ratios of various elements in NGC 330 and in the field of the SMC. The main results may be summarised as follows: • the deficiency of NGC 330 is found to be of [Fe/H] = −0.82±0.11 dex (mean and rms for 6 stars) whereas the field stars had a [Fe/H] = −0.69±0.10 dex (mean and rms for 6 stars). A slight difference may exist between the field and the cluster stars, but this difference is small. • the abundance pattern of the∼20 elements studied, is similar to that of the field supergiants, except for a few elements: oxygen’s star to star scatter is significantly larger in the cluster; the very heavy neutron capture process elements are less enhanced in the cluster. • lithium is detected in five stars and is low, indicating that the stars underwent dilution (mean value and rms for the 5 stars: log (Li) ' 0.1 ± 0.2 dex).