AAS 207th Meeting, 8-12 January 2006
Session 5 White Dwarfs: Properties and Companions
Poster, Monday, 9:20am-7:00pm, January 9, 2006, Exhibit Hall

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[5.06] Mode Identification of DAVs with Time Series Spectroscopy

S. E. Thompson (Colorado College)

I analyze optical time series spectroscopy of pulsating white dwarf stars in order to identify the spherical degree of each pulsation mode; a necessary quantity to accurately probe the stellar interior with asteroseismology. Because of the wavelength dependence of limb-darkening, the observed line-shape variations of the broad Hydrogen Balmer lines depend on the spherical degree of the mode. Thompson et al. (2004) discovered that constrained fitting of the spectral lines enable mode identification where direct measurements of the spectra failed. Chromatic amplitudes (plots of wavelength versus mode amplitude) created from these fits revealed the first pulsation mode on a DAV with a spherical degree higher than 2. As a variation of this analysis I measure the free parameters of these fits, quantifying the periodic line shape variations of each spectrum with two values calculated from the fitted Gaussian and Lorentzian areas. To identify the spherical degree, these values are compared to fits of simulated spectra created from model atmospheres of white dwarf stars.

I apply this new analysis to spectra of the low amplitude DAV, G185-32 and to the high amplitude DAV, G29-38. I make preliminary mode identifications and constraints on some of the largest amplitude modes in each star. Simulations of series of model spectra show that noise prevents identification of all but the largest amplitude modes in G29-38 and the high spherical degree mode in G185-32. Using these same simulations I have begun to estimate the quality of data necessary to obtain unambiguous identifications of all prominent modes on the brightest DAVs with time series spectroscopy.

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