AAS 203rd Meeting, January 2004
Session 7 Star Formation
Poster, Monday, January 5, 2004, 9:20am-6:30pm, Grand Hall

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[7.15] How Does Low Metallicity Affect the Rotational Velocities of Very Massive Stars?

L. R. Penny, A. J. Sprague, G. Seago (College of Charleston), D. R. Gies (Georgia State University)

Are the rotational velocities of massive stars the same in all galaxies despite their metallicities? We lack the key measurements of projected rotational velocity, V sin i, to answer this important question. There is no study of the V sin i distribution for stars in any galaxy other than the Milky Way. Here we present preliminary V sin i values of these low metallicity, high mass stars from Space Telescope Imaging Spectrograph (STIS) and International Ultraviolet Explorer (IUE) UV observations of 21 Large Magellanic Cloud (LMC, ZLMC =0.007) and 23 Small Magellanic Cloud (SMC, ZSMC =0.002) O-type stars with well determined spectral classifications. Our methodology is based on a previous study of the projected rotational velocities of Galactic O-type stars using IUE Short Wavelength Prime (SWP) Camera high dispersion spectra. Our final results will be the first study of projected rotational velocities of O-type stars outside our own Galaxy. They are a critical first step in constraining several areas in the theoretical study of massive stars and their evolution, notably the predictions that massive stars in a low metallicity environment (1) may form with higher rotational velocities and (2) will have decreased angular momentum loss as the evolve. Support for proposal #09945 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.