Does Kepler unveil the mystery of the Blazhko effect? First detection of period doubling in Kepler Blazhko RR Lyrae stars

Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.11). 07/2010; 409(3). DOI: 10.1111/j.1365-2966.2010.17386.x
Source: arXiv


The first detection of the period doubling phenomenon is reported in the Kepler RR Lyrae stars RR Lyr, V808 Cyg and V355 Lyr. Interestingly, all these pulsating stars show Blazhko modulation. The period
doubling manifests itself as alternating maxima and minima of the pulsational cycles in the light curve, as well as through
the appearance of half-integer frequencies located halfway between the main pulsation period and its harmonics in the frequency
spectrum. The effect was found to be stronger during certain phases of the modulation cycle. We were able to reproduce the
period-doubling bifurcation in our non-linear RR Lyrae models computed by the Florida–Budapest hydrocode. This enabled us
to trace the origin of this instability in RR Lyrae stars to a resonance, namely a 9:2 resonance between the fundamental mode
and a high-order (ninth) radial overtone showing strange-mode characteristics. We discuss the connection of this new type
of variation to the mysterious Blazhko effect and argue that it may give us fresh insights into solving this century-old enigma.

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Available from: J. M. Nemec
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