Inferences from Observations of Blazhko RR Lyrae Stars

Though the pulsating RR Lyrae stars are used as ``standards" for distance determination and considered the prototypes of radially pulsating stars, several aspects of their pulsation have not been understood. A large fraction of the RR Lyrae stars show a periodic modulation of their pulsation cycle. For more than a century, this so-called Blazhko effect has eluded an explanation. Through recent photometric studies, new features in the frequency spectrum of Blazhko stars have been found. On the other hand, spectroscopic data permit an `in depth' study of the star's atmosphere. I discuss the recent results from photometry, spectroscopy and spectropolarimetry, and their implications for the proposed models of the Blazhko modulation.status: publishe