The Changing Blazhko Effect of XZ Cygni
The Changing Blazhko Effect of XZ Cygni
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XZ Cygni 不断变化的 Blazhko 效应
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
G. Samolyk
中科院分区：
文献类型：
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作者：
A. Lacluyze;H. Smith;E. Gill;A. Hedden;K. Kinemuchi;A. M. Rosas;B. Pritzl;B. Sharpee;Christopher Wilkinson;K. W. Robinson;M. E. Baldwin;G. Samolyk
对天琴座RR变星Cygni XZ进行了新的CCD光度测量。一项对新旧光度法的分析证实了早先的结果，即XZ Cyg表现出布拉齐克效应，其布拉齐克周期随着时间的推移而改变。这些Blazhko周期的变化与XZ Cyg初周期的变化是不相关的。在20世纪上半叶，XZ Cyg的勃拉希克周期约为57.4天。从1965年开始，它的初级阶段经历了几个步骤的急剧下降。巧合的是，它的布拉齐克周期增加到约58.5天。1979年，初级期突然又增加了。在一段时间内，布拉齐克效应很小，之后，布拉齐克效应重新出现，周期约为57.5天。当它的布拉齐克周期接近57.5天时，XZ Cyg也显示出41.6天的第三纪周期。我们确认有证据表明，在20世纪上半叶获得的光度测量中有一个更长的3540天周期。天鹅座XZ与另外三颗天琴座RR星进行了比较，这三颗恒星似乎也显示出变化的勃氏期。观测到的XZ Cyg的Blazhko周期长度的变化限制了对Blazhko效应的可能解释。特别是，他们反对任何理论解释，即要求布拉希克周期与恒星的旋转周期完全相等或成正比。
New CCD photometry has been obtained for the RR Lyrae variable star XZ Cygni. An analysis of old and new photometry confirms earlier results that XZ Cyg exhibits the Blazhko effect and that its Blazhko period has changed over time. These changes in the Blazhko period are anticorrelated with observed changes in the primary period of XZ Cyg. During the first half of the 20th century, XZ Cyg had a Blazhko period of approximately 57.4 days. Beginning in 1965, its primary period underwent a steep decline in several steps. Coincidentally, its Blazhko period increased to about 58.5 days. In 1979, the primary period suddenly increased again. After an interval in which the Blazhko effect was small, the Blazhko effect reestablished itself, with a period of approximately 57.5 days. When its Blazhko period is near 57.5 days, XZ Cyg has also shown a tertiary period of 41.6 days. We confirm that there is evidence for a longer 3540 day period in photometry obtained during the first half of the 20th century. XZ Cyg is compared with three other RR Lyrae stars that also appear to show changing Blazhko periods. The observed changes in the length of the Blazhko period of XZ Cyg constrain possible explanations for the Blazhko effect. In particular, they argue against any theoretical explanation that requires that the Blazhko period be exactly equal, or directly proportional, to the rotation period of the star.