Blazhko effect

The Blazhko effect, which is sometimes called long-period modulation, is a variation in period and amplitude in RR Lyrae type variable stars. It was first observed by Sergey Blazhko in 1907 in the star RW Draconis.[1][2]

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 a non-linear resonance among either the fundamental or the first overtone pulsation mode of the star and a higher mode.[3][4]The second, known as the magnetic model, assumes the variation to be caused by the magnetic field being inclined to the rotational axis, deforming the main radial mode. [5] The third model assumes that cycles in the convection cause the alternations and the modulations.[6]

Observational evidence based on Kepler (spacecraft) observations indicates much of the Blazhko effect's two-cycle light curve modulation is due to simple period-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 than the daytime maximum.[7]

References

  1. ↑ Horace A. Smith (2004). RR Lyrae Stars. Cambridge University Press. p. 103. ISBN 0-521-54817-9.
  2. ↑ Blazhko, S. (1907), "Mitteilung über veränderliche Sterne", Astronomische Nachrichten, 175: 325, Bibcode:1907AN....175..325B
  3. ↑ Kolláth, Z.; Molnár, L.; Szabó, R. (2011), "Period-doubling bifurcation and high-order resonances in RR Lyrae hydrodynamical models", MNRAS, 414: 1111, arXiv:1102.0157Freely accessible, Bibcode:2011MNRAS.414.1111K
  4. ↑ Buchler, J. R.; Kolláth, Z. (2011), "On the Blazhko Effect in RR Lyrae Stars", ApJ, 731: 24, arXiv:1101.1502Freely accessible, Bibcode:2011ApJ...731...24B
  5. ↑ Katrien Kolenberg (2008). "Explanations for the Blazhko effect in RR Lyrae stars". The Blazhko Project. Retrieved 2008-12-17.
  6. ↑ Stothers, R. B. (2010), "Observational Evidence of Convective Cycles as the Cause of the Blazhko Effect in RR Lyrae Stars", PASP, 122: 536, Bibcode:2010PASP..122..536S
  7. ↑ Szabó, R.; Kolláth, Z.; Molnár, L.; et al. (2010), "Does Kepler unveil the mystery of the Blazhko effect? First detection of period doubling in Kepler Blazhko RR Lyrae stars", MNRAS, 409: 1244, arXiv:1007.3404Freely accessible, Bibcode:2010MNRAS.409.1244S

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