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Almost a century after its discovery, the phenomenon of amplitude and/or phase modulation, observed in a large percentage of the RR Lyrae stars, still lacks widely acceptable theoretical understanding.

On this website the 'Blazhko Project' is presented, an international collaboration focused on understanding the Blazhko effect. The project was founded in Vienna at the end of 2003. Its aim is to combine spectroscopic and photometric data from a sample of well-selected Blazhko and non-Blazhko stars, in order to reveal decisive information on the physical mechanism responsible for the modulation.


This investigation was initially (2004-2007) supported by the Austrian Fonds zur Förderung der wissenschaftlichen Forschung, FWF, project number P17097-N02. Now it is funded by the FWF projects P19962 en T359.