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| Paper: |
Nonlinear Analysis of Pulsating White Dwarf Lightcurves |
| Volume: |
493, 19th European Workshop on White Dwarfs |
| Page: |
187 |
| Authors: |
Provencal, J. L.; Montgomery, M. H.; Shipman, H.; WET Team |
| Abstract: |
Convection remains one of the largest sources of theoretical uncertainty in our understanding of
stellar physics. For example, Bergeron (1995) show that basic parameters such as flux, line
profiles, energy distribution, color indices, and equivalent widths are extremely sensitive to
the assumed convective parameterization. This is compelling, since we use our knowledge of these
basic parameters to calibrate white dwarf cooling sequences, provide detailed estimates for the
ages of individual white dwarfs, and determine the age of the Galactic disk. The Whole Earth
Telescope (WET) is engaged in a long term project to empirically calibrate the physical
properties of convection in pulsating white dwarfs by combining asteroseismology and
analysis of nonlinear light curves. Nonsinusoidal distortions, in the form of narrow peaks and
wider valleys, are observed in many pulsating white dwarf light curves. These are a reflection
of the local depth of the convection zone, a value which varies during a pulsation cycle.
Applying asteroseismology and convective light curve fitting to a wide sample of pulsating
white dwarfs provides an empirical map of how the convective response time (the convection
zone “depth”) varies as a function of effective temperature, and this can be compared with
theoretical models, both MLT and hydrodynamic. This project has resulted in a large database of
white dwarf lightcurves and pulsation frequencies. We present current results for DA and DB
pulsators, and provide a few examples of interesting pulsation behavior seen along the way. |
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