9928(  1) - 04/04/03 10:20  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9928
                                                       Version: 1
                                                       Check-in Date: 04-Apr-2003
                                                                      10:20:32

1.Proposal Title:
New Insights into Betelgeuse's Inhomogeneous Wind
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2. Proposal For  3. Cycle
AR               11
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4. Investigators
                                                                                     Contact?
    PI: Graham Harper                     University of Colorado at Boulder
   CoI: Dr. Alexander Brown               University of Colorado at Boulder             N

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5. Abstract

Our understanding of the physical causes of mass loss from evolved late-type stars
has been stymied by the lack of observations that resolve the wind acceleration
region. Recently both multi-wavelength cm-radio and STIS UV observations of Alpha
Orionis (M2 Iab) have been obtained that probe these crucial spatial scales. Our
recent 2002 cm-radio VLA + Pie Town data show that the vast majority of the inner
wind is much cooler (1500 K) than the 5000-8000 K predicted from previous UV
observations. A volume of hot plasma must, however, be present to explain the UV
emission. An understanding of such inhomogeneous winds is a prerequisite to advances
in determining the nature of the mass loss process in M supergiants. Using VLA data
we made the first step towards a mean description of the complex atmosphere (Harper,
Brown & Lim 2001 ApJ 551, 1073), and now we propose to use STIS E230M spatial scans
of Alpha Ori to construct the first detailed thermodynamic multi-component model.
The 25x100 mas aperture scans provide the first opportunity to truly resolve the
wind acceleration region and probe the enigmatic hot plasma which is the site
additional heating. Using state-of-the-art analysis tools, we will empirically
determine, for the first time, the electron and hydrogen density as a function of
position (and velocity) and empirically determine the geometry and filling factor of
the hot plasma. This detailed model will allow us test the proposed mechanisms for
mass loss and heating.
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                                                9928(  1) - 04/04/03 10:20  - [  2]

            Summary Form for Proposal  9928

  Item                         Used in this proposal
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  Proposal Category            AR
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