AAS 200th meeting, Albuquerque, NM, June 2002
Session 85. Stars: Disks, Shells and Variability
Oral, Thursday, June 6, 2002, 2:00-3:30pm, Ballroom A

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[85.06] Implications of Observed Oscillation Frequencies for the delta Scuti Star FG Vir

J.A. Guzik, P.A. Bradley (Los Alamos National Laboratory)

Breger et al. (1998) have reported photometric detection of 21 frequencies, and eight additional probable frequencies of pulsation for the \delta Scuti star FG Vir. A number of groups (e.g. Breger et al. 1999; Guzik et al. 2000; Viskum et al. 1998; Templeton et al. 2001) have calculated evolutionary models of this star to attempt to reproduce the observed pulsation spectrum. FG Vir has a moderate rotation rate of 30-50 km/sec, which induces rotational splitting of modes and complicates the expected frequency spacing. Our standard one-dimensional evolutionary models that match the observed luminosity and have a radial (\ell=0) mode corresponding to the spectroscopically-identified radial mode at 140.7 \muHz approximately match most of the observed modes, but have difficulty matching the 243.7 \muHz mode spectroscopically identified as \ell=2. We also find that the g-modes at 106.5 and 111.8 \muHz are sensitive to the convective core size. Convective overshoot and element diffusion, as well as additional mixing induced by differential rotation or nonradial g-mode oscillations may alter the composition profile of the star. Here we investigate modifications to the composition profile of FG Vir that can improve the frequency agreement.

This research was performed under the auspices of the U.S. Department of Energy by Los Alamos National Laboratory under Contract No. W-7405-ENG-36.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.