9517(  1) - 12/06/01 12:30  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9517
                                                       Version: 1
                                                       Check-in Date: 06-Dec-2001
                                                                      11:43:21

1.Proposal Title:
Compressional Heating of Accreting White Dwarfs and Classical Novae Ignition
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2. Proposal For  3. Cycle
AR               11
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4. Investigators
                                                                                     Contact?
    PI: Lars Bildsten                     University of California, Santa Barbara
   CoI: Mr. Dean Townsley                 University of California, Santa Barbara       N

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5. Abstract

We are proposing a broad theoretical study of the compressional (and nuclear)
heating of white dwarfs (WDs) accreting at rates relevant to cataclysmic variables
(CVs), where the fresh fuel is burned unstably in classical novae. Our work will
yield the internal WD luminosity as a function of the time averaged accretion rate,
<~ngle\dot M\rangle, WD mass and metallicity. We also include the recurrent heating
and cooling of the WD throughout the classical novae limit cycle in order to find
the WD core temperature and accumulated mass at ignition. Comparing these
theoretical masses to the observed ejected masses will tell us whether the WD mass
in CVs is secularly increasing or decreasing and whether CVs can actually be Type Ia
progenitors. Several Dwarf novae systems have been observed in quiescence with
HST/STIS, when the accretion rate is low and the WD photosphere can be directly
detected. Initial comparisons of our theoretical work to these observations is
encouraging and supports Sion's suggestion that gravitational energy release within
the WD rejuvenates an otherwise cold WD into a much hotter state. Our work has
immediate relevance to: (1) the STIS observations noted above and (2) HST searches
for quiescent, low <~ngle\dot M\rangle CVs in globular clusters (where the optical
and UV magnitudes are affected by the hot WD).
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                                                9517(  1) - 12/06/01 12:30  - [  2]

            Summary Form for Proposal  9517

  Item                         Used in this proposal
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  Proposal Category            AR
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