On the secular variation of amplitudes in double-mode Cepheids

Abstract

Under the assumption that the resonant interactions among the fundamental, the first overtone and the third overtone radial modes cause the phenomenon of double periodicity of double-mode Cepheids, the secular variation of amplitudes is investigated theoretically. The magnitudes and period of the secular variation are determined in terms of mode-coupling constants. The possibility of alternate appearance of single and double periodicity in the vicinity of the resonance is suggested.