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The light curves of many Blazhko stars exhibit intervals in which successivepulsation maxima alternate between two levels in a way that is characteristicof period-doubling. In addition, hydrocode models of these stars have clearlydemonstrated period-doubling bifurcations. As a result, it is now generallyaccepted that these stars do indeed exhibit period-doubling. Here we presentstrong evidence that this assumption is incorrect. The alternating maximalikely result from the presence of one or more near-resonant modes which appearin the stellar spectra and are slightly but significantly offset from 3/2 timesthe fundamental frequency. We show that a previously proposed explanation forthe presence of these peaks is inadequate. The phase-slip of the dominantnear-resonant peak in RR Lyr is shown to be fully correlated with the parity ofthe observed alternations, providing further strong evidence that the processis nonresonant and cannot be characterized as period-doubling. The dominantnear-resonant peak in V808 Cyg has side-peaks spaced at twice the Blazhkofrequency. This apparent modulation indicates that the peak corresponds to avibrational mode and also adds strong support to the beating-modes model of theBlazhko effect which can account for the doubled frequency. The modulation alsodemonstrates the "environment" altering effect of large amplitude modes whichis shown to be consistent with the amplitude equation formalism.

Is the apparent period-doubling in Blazhko stars actually an illusion?