THE ASTRONOMICAL JOURNAL    VOLUME 113, NUMBER 5, PAGE 1691          MAY 1997

          ULTRAVIOLET PHOTOMETRY OF STARS IN THE COMPACT CLUSTER R136
                         IN THE LARGE MAGELLANIC CLOUD

                               DEIDRE A. HUNTER

    Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, Arizona 86001

                               WILLIAM D. VACCA

     Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, Hawaii 96822

                PHILIP MASSEY, ROGER LYNDS, AND EARL J. O'NEIL

           National Optical Astronomy Observatories, P.O. Box 26732,
                             Tucson, Arizona 85726

    We present ultraviolet photometry of stars in the Large Magellanic
    Cloud star cluster R136. The data were obtained with the refurbished
    Wide Field/Planetary Camera on the Hubble Space Telescope through an
    ultraviolet filter centered at 1750 A (F170W). These data, combined
    with optical HST observations presented previously, are used to explore
    the hot, luminous stellar population within the cluster. The first
    question we wanted to address was whether the ultraviolet could place
    better constraints on differential reddening and the degree of
    coevality within the cluster than optical photometry alone. The stellar
    sequence in the color magnitude diagram using the F170W-F555W color is
    broader than it was in the optical and is broader than would be
    expected from photometric uncertainties. Although there could be a
    modest age spread among the massive stars, a large part of the
    intrinsic spread in the color-magnitude diagram is likely to be due to
    reddening differences. There is also some evidence that stars in the
    outer parts of the cluster are affected by a larger range in reddening
    than those in the smaller region of the cluster core. The second
    question we addressed is whether ultraviolet photometry in combination
    with optical photometry can distinguish the most massive stars more
    readily than is possible with the optical colors. The F170W-F555W color
    is better at separating B supergiants, of which there is only one in
    R136, from comparably bright O and Wolf-Rayet stars. However, spectral
    classifications of the stars within R136 will be necessary to properly
    identify stellar types of the rest of the stars and to disentangle age
    and reddening effects. (Copyright) 1997 American Astronomical Society.