arXiv 1305.58772013-05astro-ph.SR

利用天琴座和天鹅座V1504的开普勒光变曲线研究SU UMa星的超爆发和超驼峰

Study of Superoutbursts and Superhumps in SU UMa Stars by the Kepler Light Curves of V344 Lyrae and V1504 Cygni

Yoji Osaki, Taichi Kato

备注：: 26 pages, 14 figures, accepted for publication in PASJ, minor corrections
DOI：: 10.1093/pasj/65.5.95

摘要：

利用功率谱分析方法研究了SU UMa星、天琴座V344和天鹅座V1504的短周期Kepler公开光变曲线。我们确定V344 Lyr的轨道周期为Porb=0.087903（1）d。利用O-C图的补充资料，重新分析了天鹅座V1504一个完整超循环中负超峰的频率变化，证实其特征变化符合热潮汐不稳定性模型。提出了一种基于最小绝对收缩选择算子（Lasso）的二维周期分析方法。新方法给出了非常尖锐的功率谱峰，对研究激变变星的频率变化是非常有用的。我们还分析了正负超峰的同时频率变化。如果对它们进行适当的转换，就会发现它们是一致变化的，这表明它们代表了圆盘半径的变化。我们还研究了超爆发期间正超峰的频率（或周期）变化。这些变化可以通过结合盘半径变化和超爆发期间压力效应的变化来定性理解。在V344 Lyr的几次爆发的下降支中，观测到一个频率范围接近负超峰的振荡（我们称之为“脉冲负超峰”）。这些事件似乎发生在下一次超级爆发之前，并作为即将发生的超级爆发的“先导”。

英文摘要：

We have studied the short-cadence Kepler public light curves of SU UMa stars, V344 Lyr and V1504 Cyg extending over a period of more than two years by using power spectral analysis. We determined the orbital period of V344 Lyr to be Porb=0.087903(1) d. We also reanalyzed the frequency variation of the negative superhump in a complete supercycle of V1504 Cyg with additional data of the O-C diagram, confirming that its characteristic variation is in accordance with the thermal-tidal instability model. We present a new two-dimensional period analysis based on a new method of a least absolute shrinkage and selection operator (Lasso). The new method gives very sharp peaks in the power spectra, and it is very useful for studying of the frequency variation in cataclysmic variable stars. We also analyzed simultaneous frequency variations of the positive and negative superhumps. If they are appropriately converted, it is found that they vary in unison, indicating that they represent a disk-radius variation. We have also studied the frequency (or period) variations of positive superhumps during superoutbursts. These variations can be understood in a qualitative way by combining of the disk radius variation and the variation of pressure effects during a superoutburst. A sudden excitation of oscillation with a frequency range near to the negative superhump (which we call "impulsive negative superhump") was observed in the descending branch of several outbursts of V344 Lyr. These events seem to have occurred just prior to the next superoutburst, and to act as a "lead" of the impending superoutburst.

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