Verlag der Oesterreichischen Akademie der Wissenschaften
Communications in Asteroseismology vol:145 pages:16-20
Almost a century after its discovery, the phenomenon of amplitude and/or phase modulation (Blazhko effect), observed in a large percentage of the RR Lyrae stars, still lacks widely acceptable theoretical understanding. Recent attempts to theoretically explain the Blazhko effect have focused on two alternatives: the magnetic models and the resonance models, both involving the presence of nonradial pulsation components. In the course of the past decades, large photometric data bases have yielded important statistics on the phenomenology of the Blazhko effect, which impose additional constraints upon the applicability of the models. On the other hand, the new approach of studying the Blazhko effect through line profile analysis, can provide essential information on the nature of the pulsation components responsible for the modulation. The answer to this century-old question will definitely clarify similar phenomena observed in other types of pulsating stars.