Oscillation frequencies in multi-mode d Scuti stars can be used to do a seismic test of the theories of stellar evolution. However, asteroseismology on d Scuti stars has until now produced very few convincing results. This lack of results reflects our inability to identify the oscillation modes which is mainly due to the very complex oscillation spectra in these stars. We have realised that multi-wavelength observations of the oscillations are nessesary in order to do a prober mode identification. We present the results from such a multi-wavelength multisite campaign on the photometrically well observed d Scuti star FG Virginis. We have developed new techniques where the oscillations are measured via the changes in equivalent width and via the radial velocity shifts of several spectral lines from time series medium-dispersion spectra. From the measured oscillation amplitudes and phases at different wavelength of the ten dominant frequencies, a preliminary mode identification is proposed and we discuss what we have learned about FG Vir from this investigation.
A Half Century of Stellar Pulsation Interpretation
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