|
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.〔 〕 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. 〔 Z. Kollath, L. Molnar & R. Szabo, 2011, Monthly Notices of the Royal Astronomical Society, Vol 414 p. 1111; (also http://xxx.lanl.gov/abs/1102.0157) 〕 〔 J. R. Buchler & Z. Kollath, 2011, Astrophysical Journal, Vol 731, p. 24 (also http://xxx.lanl.gov/abs/1101.1502) 〕 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. 〔 〕 The third model assumes that cycles in the convection cause the alternations and the modulations. 〔 Stothers, R.B. 2010, Publications of the Astronomical Society of the Pacific Vol. 122, p. 536〕 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. 〔 R. Szabo et al. , 2010, Monthly Notices of the Royal Astronomical Society, Vol. 409, p. 1244 〕 ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Blazhko effect」の詳細全文を読む スポンサード リンク
|