Amplitude Ratios as Mode Characterizors in delta Scuti stars

Seismology of delta Scuti stars holds great potentials for testing theories of stellar structure and evolution. The ratio of mode amplitudes in light and in equivalent width of spectral lines can be used for mode identification. However, the amplitude ratios (AR) predicted from theory are usually inconsistent with observations. We here present the first results from a campaign aimed at calibrating observationally the absolute values of the AR.