THE PULSATIONS OF ZZ CETI STARS .6. THE AMPLITUDE SPECTRA

Amplitude spectra of the light curves of ZZ Ceti stars often show peaks at harmonic frequencies and at 'cross-frequencies' which are related to the frequencies of the dominant peaks by expressions of the form \mf1 + nf2\ where m and n are small integers and f1, f2 are the frequencies of the dominant peaks. These peaks can be understood in terms of a model of the ionization zone of a pulsating ZZ Ceti star which has been described in previous papers. For stars where the (rotational) fine structure of the amplitude spectra is resolved, comparison with the model calculations provides a means of identifying the degree l of the excited modes.