SEARCH FOR RESONANCE EFFECTS IN LONG-PERIOD CEPHEIDS

Light curves of classical Cepheids with period longer than 8 days have been Fourier decomposed with the purpose of studying the characterist ics of high order Fourier parameters, and to detect possible effects o f resonances between pulsation modes other than the well known resonan ce at P similar to 10 d. The possible effects of two expected resonanc es have been tentatively identified: P-0/P-1 = 3/2 at P-0 similar to 2 4 d and P-0/P-3 = 3 at P-0 similar to 27 d. The identification is not completely certain owing to the poor number of Cepheids. The limitatio n could be overcome by observing accurately other relatively faint Cep heids in our Galaxy, and several Cepheids in nearby, galaxies.(1)