Variation in period and amplitude in RR Lyrae type variable stars
TheBlazhko effect, also known as the Tseraskaya–Blazhko effect,[1] and which is sometimes called long-period modulation, is a variation in period and amplitude inRR Lyrae type variable stars.Sergey Blazhko first reported its observation byLidiya Tseraskaya in 1907, in the star RW Draconis.[2][3]
The physics behind the Blazhko effect is currently still a matter of debate, with there being three primary hypotheses.In the first, referred to as the resonance model, the cause of the modulation is anon-linear resonance among either the fundamental or the first overtonepulsation mode of the star and a higher mode.[4][5] The second, known as the magnetic model, assumes the variation to be caused by themagnetic field being inclined to therotational axis, deforming the main radial mode. The magnetic model was ruled out in 2004 by high resolution spectro-polarimetric observations.[6] The third model assumes that cycles in theconvection cause the alternations and the modulations.[7]
Observational evidence based onKepler space telescope observations indicates much of the Blazhko effect's two-cycle light curve modulation is due to simpleperiod-doubling. Many RR Lyrae stars have a variability period of approximately 12 hours and ground-based astronomers typically make nightly observations about 24 hours apart; thus period-doubling results in brightness maximums during nightly observations that are significantly different from the daytime maximum.[8][9]
^Stothers, R. B. (2010), "Observational Evidence of Convective Cycles as the Cause of the Blazhko Effect in RR Lyrae Stars",Publications of the Astronomical Society of the Pacific,122 (891):536–540,Bibcode:2010PASP..122..536S,doi:10.1086/652909
