9945(  1) - 04/04/03 10:30  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9945
                                                       Version: 1
                                                       Check-in Date: 04-Apr-2003
                                                                      10:30:37

1.Proposal Title:
Projected Rotational Velocities of O-type Stars at Low Metallicity
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2. Proposal For  3. Cycle
AR               11
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4. Investigators
                                                                                     Contact?
    PI: Laura Penny                       College of Charleston
   CoI: Dr. Douglas Gies                  Georgia State University Research             N
                                          Foundation

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5. Abstract

Are the rotational velocities of massive stars the same in all galaxies? We lack the
key measurements of projected rotational velocity, Vsin i, to answer this important
question. There is no study of the Vsin i distribution for stars in any galaxy other
than the Milky Way. We propose to determine the Vsin i values of these lower
metallicity, high mass stars from UV observations of 21 Large Magellanic Cloud (LMC)
and 23 Small Magellanic Cloud (SMC) 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 the International Ultraviolet
Explorer (IUE) Short Wavelength Prime (SWP) camera high dispersion spectra. This
previous study resulted in a catalog of Vsin i values for 177 O stars based on the
Conti & Ebbets (1977) system. Our proposed project would produce Vsin i values on
the same system so that all three metallicity enviroments could be compared without
biases that might be present due to individual atmospheric models being fit to
differing visual absorption features. Our project would be the first study of
projected rotational velocities of O-type stars outside our own Galaxy and is
crucially needed to constrain 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 they evolve.
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                                                9945(  1) - 04/04/03 10:30  - [  2]

            Summary Form for Proposal  9945

  Item                         Used in this proposal
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  Proposal Category            AR
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