The Future of White Dwarf Asteroseismology

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The Future of White Dwarf Asteroseismology
Travis Metcalfe (NCAR)
NGC 1514 Crystal Ball Nebula
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Kawaler Dahlstrom (2000)
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Elsworth Thompson (2004)
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http//asteroseismology.org/
(l 1, m0)
(l 2, m0)
(l 3, m0)
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Montgomery Winget (1999)
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Beyond Local Fitting

• Moores Law Computing performance per unit cost
  doubles approximately every 18 months

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Beyond Local Fitting

• Moores Law Computing performance per unit cost
  doubles approximately every 18 months
• More is Better Law If you spend more time
  writing the paper than running the models, you
  didnt run enough models

Metcalfe Nather (1999)
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More Stars

• DBV stars are thought to evolve from H-deficient
  post-AGB stars (He/C/O)
• He diffuses to the surface over time, growing
  thicker as the star gets cooler
• From several DBVs with different temperatures we
  can calibrate the theory

Sullivan et al. (in prep)
EC 20058 (28400 K)
Metcalfe et al. (2005)
CBS 114 (26200 K)
Winget et al. (1994)
GD 358 (24900 K)
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More Models

• Parallel genetic algorithm optimizes 4 parameters
  to model each DBV star
• 0.45 lt M lt 0.95 Msun
• 20000 lt Teff lt 30000 K
• 10-4 lt Menv lt 10-2 M
• 10-7 lt MHe lt 10-5 M
• Pure C core out to 0.95 fractional mass point

Napiwotzki et al. (1999)
Beauchamp et al. (1999)
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More Parameters

• Results reasonable fits for M and Teff
  qualitative agreement with theory
• Extension add realistic adjustable C/O profile
  to model core structure
• Application to CBS 114 agrees with the expected
  nuclear burning history and diffusion theory

Metcalfe (2005)
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Beyond the Spherical Cow

• Global exploration of relatively simple models
  has some limitations
• How else might we use our continually expanding
  computational potential?
• Another approach build the best physical models,
  but limit the exploration

http//www.moonjam.com/
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More Physics

• Time-dependent diffusion calculations for
  evolution of H and He layers
• Chemical profile of O/Ne models from repeated
  C-burning shell flashes
• Self-consistent treatment of phase separation
  during C/O crystallization

Corsico et al. (2004)
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More History

• Complete evolution from ZAMS, through mass-loss
  on AGB, to WD regime
• 5 chemical time steps for each evolutionary step
  70,000 models in total
• Double-diffusive mixing- length theory for fluid
  with composition gradients

Grossman Taam (1996)
Althaus et al. (2005)
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More Dimensions
http//www.lcse.umn.edu/
3D models are wrong in three dimensions. Ed
Nather
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The Future

• We can use computers to generate millions of
  simple models for comparison with observations.
• With similar resources, we can calculate a few
  complete evolutionary tracks using relatively
  sophisticated physical models.
• As computers get faster, they will allow us to
  generate millions of complete evolutionary
  models, opening the door to new tests of
  fundamental physics in white dwarf stars.

IBM Bluegene/L system