Rotation of Early B-type Stars in the Large Magellanic Cloud - The role of evolution and metallicity

Abstract

I present measurements of the projected rotational velocities of a sample of 100 early B-type main-sequence stars in the Large Magellanic Cloud. This is the first extragalactic study of the distribution of stellar rotational velocities. The sample is drawn from two sources: a sample derived from the vicinity of the main-sequence turnoff of young clusters (ages 1-3x10^7yrs), and a sample from the general field. I find the cluster population exhibits significantly more rapid rotation than that seen in the field. I have drawn analogous Galactic cluster and field samples from the literature. Comparison of these samples reveals the same effect. I propose the observed difference between cluster and field populations can be explained by a scenario of evolutionary enhancement of the surface angular momentum over the main-sequence lifetime. A comparison is made between the cluster and field populations of the LMC and the Galaxy in order to explore the effects of metallicity. This shows that the LMC stars are more rapid rotators than their Galactic counterparts.

15 pages, PASA accepted

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