The Future of White Dwarf Asteroseismology Travis Metcalfe (NCAR) NGC 1514 – Crystal Ball Nebula

Kawaler & Dahlstrom (2000)

Elsworth & Thompson (2004)

( l =1, m=0)( l =2, m=0)( l =3, m=0)

Montgomery & Winget (1999)

Beyond Local Fitting Moore’s Law: Computing performance per unit cost doubles approximately every 18 months

Beyond Local Fitting Moore’s 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 didn’t run enough models Metcalfe & Nather (1999)

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) Metcalfe et al. (2005) Winget et al. (1994) EC (28400 K) CBS 114 (26200 K) GD 358 (24900 K) More Stars

Napiwotzki et al. (1999)Beauchamp et al. (1999) Parallel genetic algorithm optimizes 4 parameters to model each DBV star 0.45 < M * < 0.95 M sun < T eff < K < M env < M * < M He < M * Pure C core out to 0.95 fractional mass point More Models

Results: reasonable fits for M * and T eff ; 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) More Parameters

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

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)

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 Althaus et al. (2005) Grossman & Taam (1996)

More Dimensions “3D models are wrong in three dimensions.” – Ed Nather

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