Pristine CNO Abundances from Magellanic Cloud B Stars. II. Fast Rotators in the Large Magellanic Cloud Cluster NGC 2004

We present spectroscopic abundance analyses of three main-sequence B stars inthe young Large Magellanic Cloud cluster NGC 2004. All three targets haveprojected rotational velocities around 130 km/s. Techniques are presented thatallow the derivation of stellar parameters and chemical abundances in spite ofthese high v sin i values. Together with previous analyses of stars in thiscluster, we find no evidence among the main-sequence stars for effects due torotational mixing up to v sin i around 130 km/s. Unless the equatorialrotational velocities are significantly larger than the v sin i values, thisfinding is probably in line with theoretical expectations. NGC 2004/B30, a starof uncertain evolutionary status located in the Blue Hertzsprung Gap, clearlyshows signs of mixing in its atmosphere. To verify the effects due torotational mixing will therefore require homogeneous analysis of statisticallysignificant samples of low-metallicity main-sequence B stars over a wide rangeof rotational velocities.Comment: 12 pages, 5 figures, 2 tables; accepted for publication in ApJ (vol. 633, p. 899