... cluster

Based on observations collected at the ESO Very Large Telescope (program 075.D-0736(A)).

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...

Appendix A is only available in electronic form at http://www.aanda.org

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... supergiants

Historically, the index f denotes stars with strong N III 4634-4641 Å and He II 4686 Å emission, while the symbol "+'' refers to stars showing Si IV 4089-4116 Å in emission.

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... references

The solar abundances have been recently revised for the lightest elements (Asplund et al. 2004), but not for the heaviest. Hence, we prefer to stick to the old values.

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...(N)

Note that the maximum value of X(N) is independent of the rotation rate of the star.

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