DETECTION OF A DEGENERATE COMPANION OF THE SX PHOENICIS STAR KZ HYDRAE BY STUDYING ITS LONG-TERM VARIABILITY
DETECTION OF A DEGENERATE COMPANION OF THE SX PHOENICIS STAR KZ HYDRAE BY STUDYING ITS LONG-TERM VARIABILITY
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DOI：
10.1088/0004-6256/135/5/1958
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发表时间：
2008-04
期刊：
影响因子：
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通讯作者：
J. Fu;P. Khokhuntod;E. Rodriguez;C. Boonyarak;K. Marak;M. López-González;L. Zhu;S. Qian;Shi-You Jiang
中科院分区：
文献类型：
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作者：
J. Fu;P. Khokhuntod;E. Rodriguez;C. Boonyarak;K. Marak;M. López-González;L. Zhu;S. Qian;Shi-You Jiang
我们主要根据我们20年来广泛的光度观测，给出了SX Phoenicis(SX Phe)星KZ Hydrae(KZ Hya)的109个新的最大光周期，结合文献中的数据确定了一个一般星历。O-−C图显示，在轨道周期为2 6.8±0.2年的双星系统中，结合KZ Hya轨道运动的光行时效应，KZ Hya的周期持续增加。推导出的伴星质量不能小于0.83M☉。由于光谱上没有观测到伴星的迹象，而且观测到的颜色指数b−y排除了伴星是晚型主序星或矮星的可能性，KZ Hya成为第一颗探测到简并伴星的Sx Phe星。通过对观测光曲线的傅里叶谱进行分析，研究了它的脉动特性，同时利用同步多色紫外光β数据推导了它的基本参数，表明这颗星是一颗强的低金属度高幅度SX Phe类变星，它以基径向模式脉动。在这个变量的脉动中，没有检测到多周期的迹象或幅度的重大长期变化。
We present 109 new times of maximum light of the SX Phoenicis (SX Phe) star KZ Hydrae (KZ Hya) based mainly on our extensive photometric observations for two decades, leading to determination of a general ephemeris combined with the data in the literature. The O − C diagram reveals a continuously increasing period change combined with the light traveling time effect of the orbital motion of KZ Hya in a binary system with an orbital period of 26.8 ± 0.2 years. The deduced mass of the companion cannot be smaller than 0.83 M☉. Since no sign of the companion has ever been observed spectroscopically and the observed color index b − y excludes the possibility of the companion being a late-type main-sequence or dwarf star, KZ Hya becomes the first SX Phe star for which a degenerate companion is detected. The pulsation properties are studied by analyzing the Fourier spectra of the observed light curves while the fundamental parameters are deduced with the simultaneous multicolor uvbyβ data, showing this star to be a strong low-metallicity high-amplitude SX Phe-type variable pulsating in the fundamental radial mode. No signs of multiperiodicity or significant long-term changes in amplitude are detected in the pulsation of this variable.