7990(  1) - 04/16/98 14:09  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      7990
                                                       Version: 1
                                                       Check-in Date: 16-Apr-1998
                                                                      14:06:40

1.Proposal Title:
UV Photometry and Variability Analysis of NGC 6712: Probing Close Binaries
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2. Proposal For  3. Cycle
AR               7
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4. Investigators
                                                                                     Contact?
    PI: Bruce Margon                      University of Washington
   CoI: Eric Deutsch                      University of Washington                      N

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5. Abstract

Under Cycle 5 GO proposal 6121, 10 orbits of observations of the luminous, bursting
low-mass X-ray binary X1850-087 in the Galactic globular cluster NGC 6712 were
obtained by other investigators with WFPC2, principally in the ultraviolet. The
resulting light curve analysis of this one object, the goal of that proposal, has
been published. However, this dataset, which includes 4.5 hr of integration spanning
13.5 hr of time in a single ultraviolet filter, contains a wealth of information in
addition to the light curve of the primary target star. We propose to analyze this
dataset with two goals in mind. First we will create a deep (U-B) color- magnitude
diagram of this globular cluster, to compare with the same diagrams we have created
for three other globular clusters which harbor luminous X-ray sources. Our analysis
of these other clusters have revealed objects with similar ultraviolet-excess colors
as the low-mass X-ray binary optical counterparts, but of unknown nature. Second, we
will examine the dataset for other cluster variable objects, including eclipsing and
contact binaries, cataclysmic variables, SX Phoenicis stars, and RR Lyraes. This
long series of existing ultraviolet observations of NGC 6712 still holds important
information key to our understanding of the ultraviolet behavior of exotic objects
in globular clusters.
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  Data Distribution

  Media:           ELECTRONIC
  Blocking Factor: 10
  Ship To:         PI_Address
  Ship Via:
  Email:
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                                                7990(  1) - 04/16/98 14:09  - [  2]

            Summary Form for Proposal  7990

  Item                         Used in this proposal
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  Proposal Category            AR
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