We use spectroscopy of variable stars as a tool to derive the pulsational quantum numbers l and m, which describe the nonradial pulsation. Mode identification is a first step towards asteroseismology and is therefor important for constraining the stellar model. The advantage of spectroscopic in comparison to photometric data is the possibility to measure modes with high l- and m-values. Those high degree modes have very small photometric amplitudes due to geometric cancellation effects.

There are three different approaches for the mode identification by measuring the line profile variations of spectral absorption lines: the comparison of the line profile variations with a stellar surface velocity model, the equivalent width method and doppler imaging.

For these purposes we need data obtained by high resolution time series spectroscopy preferably echelle spectra. High quality data with a spectral resolution of 50000 and a signal to noise ratio better than 400 should be achieved in order to study line profile variations of Delta Scuti stars, which pulsate with a multitude of different modes.

To be continued...