Analysing periodic amplitude changes in RR Lyrae and other types of variable stars

Various types of pulsating stars show periodic amplitude changes. The Fourier spectra of these stars typically exhibit a structure of either two or three close frequencies. But the existence of a close peak in the spectrum does not necessarily meAN that a second pulsation mode causes the variation in amplitude. Therefore, a test concerning the phasing behaviour at different stages of the beat cycle was applied to determine whether the cyclic behavior is caused by beating or by other effects. On this basis a comparison is drawn between several different types of pulsators. Nonlinear effects in RR Lyrae stars pose AN additional challenge to the method. For all examined stars we could show that two separate modes are present and that the amplitude changes are likely caused by beating.status: publishe