PHOTOMETRIC PROPERTIES FOR SELECTED ALGOL-TYPE BINARIES. II. AO SERPENTIS AND V338 HERCULIS
PHOTOMETRIC PROPERTIES FOR SELECTED ALGOL-TYPE BINARIES. II. AO SERPENTIS AND V338 HERCULIS
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DOI：
10.1088/0004-6256/139/4/1360
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发表时间：
2010-02
期刊：
影响因子：
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通讯作者：
Y.-G. Yang;S.-M. Hu;D. Guo;J.-Y. Wei;H. Dai
中科院分区：
文献类型：
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作者：
Y.-G. Yang;S.-M. Hu;D. Guo;J.-Y. Wei;H. Dai
本文首次对2009年4月至7月在山东大学威海天文台观测到的半独立食双星AO蛇双星进行了多波段光度测量。利用2003年版本的Wilson-Devinney码，（重新）推导了AO Ser和类似天体V338 Her的光度解。AO Ser的光谱类型和轨道周期分别为A2和P = 0.8793天，V338 Her的光谱类型和轨道周期分别为F1V和P = 1.3057天。结果表明，这两个双星都是低质量比的系统，其次级成分填充在它们的罗氏叶中。AO Ser和V338 Her的主成分填充系数分别为f = 58.6%和f = 54.2%。从AO Ser和V338 Her的O−C曲线中发现，存在长期周期变化和周期变化。AO Ser的周期和半振幅分别为17.32（±0.01）yr和0.0051（±0.0001）d， V338 Her的周期和半振幅分别为29.07（±0.04）yr和0.0116（±0.0015）d。这种循环振荡可以归因于通过假定的第三体产生的光时效应，也可以归因于次级分量上的循环磁活动。对于AO Ser，长期周期以dP/dt =−5.35（±0.03）× 10−7天（年-1）的速率减小，这可能是由于系统的质量和角动量损失造成的。考虑到周期的减小，原生质对AO Ser的填充因子增大，最终填充其罗氏叶。同时，V338 Her的长期周期增加速率dP/dt = +1.44（±0.24）× 10−7天（年-1），表明质量从质量较小的组分向质量较大的组分转移。这也会导致原液的填充系数增加。当原星填充它们的罗氏叶时，AO Ser和V338 Her可能演变成接触星，正如热松弛振荡理论所预测的那样。
We present the first multiband photometry for the semidetached eclipsing binary AO Serpentis, observed on seven nights between 2009 April and July at the Weihai Observatory of Shandong University. By using the 2003 version of the Wilson–Devinney code, the photometric solutions of AO Ser and a similar object V338 Her were (re)deduced. The spectral types and orbital periods are A2 and P = 0.8793 days for AO Ser, F1V and P = 1.3057 days for V338 Her. The results reveal that two binaries are low mass ratio systems, whose secondary components fill their Roche lobes. The fill-out factors of the primary components are f = 58.6% for AO Ser and f = 54.2% for V338 Her, respectively. From the O − C curves of AO Ser and V338 Her, it is discovered that secular period changes with cyclic variations exist. The periods and semiamplitudes are 17.32(±0.01) yr and 0.0051(±0.0001) days for AO Ser, 29.07(±0.04) yr and 0.0116(±0.0015) days for V338 Her, respectively. This kind of cyclic oscillation may be attributed to either the light-time effect via an assumed third body or perhaps cyclic magnetic activity on the secondary component. For AO Ser, the long-term period decreases at a rate of dP/dt = −5.35(±0.03) × 10−7 days yr-1, which may be caused by mass and angular momentum loss from the system. Considering the period decreasing, the fill-out factor of the primary for AO Ser will increase and it will finally fill its Roche lobe. Meanwhile, the secular period increase rate for V338 Her is dP/dt = +1.44(±0.24) × 10−7 days yr-1, indicating that mass transfers from the less massive component to the more massive component. This will also cause the fill-out factor of the primary to increase. When the primaries fill their Roche lobes, AO Ser and V338 Her may evolve into contact stars, as predicted by the theory of thermal relaxation oscillations.