9910(  1) - 04/04/03 10:12  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9910
                                                       Version: 1
                                                       Check-in Date: 04-Apr-2003
                                                                      10:11:58

1.Proposal Title:
Turbulent Variability of Disk Accretion in Cataclysmic Variables
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2. Proposal For  3. Cycle
AR               11
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4. Investigators
                                                                                     Contact?
    PI: Philip Armitage                   JILA
   CoI: Dr. Keith Horne                   University of St. Andrews                     N

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5. Abstract

HST observations of WZ Sagittae by Knigge et al. (2002) detect prominent
oscillations in the ultraviolet lightcurve following outburst. The oscillations
probably arise in or near the boundary layer between the accretion disk and the
white dwarf, and are a particularly clear example of the quasi- periodic variability
seen in many accreting systems. We propose to investigate theoretically the origin
and predicted properties of this variability. To do this we will run global
magnetohydrodynamic simulations of the inner accretion disk and boundary layer, from
which we will calculate predicted lightcurves using a range of assumptions as to how
energy is dissipated and radiated from the disk. The temporal power spectrum of the
predicted emission will be calculated and used as the primary point of comparison
with observations. If we are able to reproduce the observations successfully, the
investigation will provide a sound basis for using the observed variability of
cataclysmic variables in the UV to constrain the physical properties of the white
dwarf and inner accretion flow.
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                                                9910(  1) - 04/04/03 10:12  - [  2]

            Summary Form for Proposal  9910

  Item                         Used in this proposal
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  Proposal Category            AR
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