No CrossRef data available.
Published online by Cambridge University Press: 12 April 2016
The detection of a variable period is very important as it gives information on the evolutionary state or on the binary nature of a pulsating star. If a pulsator is moving in a binary system, its light curve is frequency-modulated by the orbital period (light-time effect). Mode switching or chaos also may be the cause of the changes in the amplitude and period of the light variations.
The determination of period variability is difficult. Usually the conventional Fourier-spectrum cannot give any information about a possible period variation. The 0-C diagram is useful to detect a variable period, but it does not give the amplitude and phase values.