Pulsations and eclipse-time analysis of HW Vir
Pulsations and eclipse-time analysis of HW Vir
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DOI：
10.1093/mnras/sty2473
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发表时间：
2018-09
影响因子：
4.8
通讯作者：
A. Baran;R. Østensen;J. Telting;J. Vos;D. Kilkenny;M. Vučković;M. Reed;R. Silvotti;C. Jeffery-C.
中科院分区：
文献类型：
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作者：
A. Baran;R. Østensen;J. Telting;J. Vos;D. Kilkenny;M. Vučković;M. Reed;R. Silvotti;C. Jeffery-C.
我们分析了最近的K2数据的短周期食双星系统HW Vir，其中包括一个热的亚矮星B型主M-矮星的同伴。我们确定了日食的中间时间，计算了O-C图，以及次极小值的平均偏移。我们的结果表明，轨道周期是稳定的误差超过70天的观测过程中。有趣的是，发现主日食和次日食之间的轨道中间相位偏移为1.62秒。如果光的传播时间可以解释这种移动，那么sdB主星的质量应该是0.26 M，这对于星星的核心氦燃烧来说太低了。然而，我们认为这一结果不太可能是正确的，恒星的相对大小所引起的一些影响共同减少了有效的光旅行时间测量。在去除了由轨道引起的通量变化后，我们计算了振幅谱来寻找脉动。光谱清楚地显示了从接近轨道频率到4600 µHz的周期性信号，其中大部分峰值低于2600 µHz。振幅低于千分之0.1，太低，无法用地面测光检测到。因此，来自开普勒太空船的高精度数据揭示了HW Vir系统的主要是一颗脉动sdBV星星。我们认为，在HW Vir的主要脉动频谱不同于其他sdB星，由于其相对较快的旋转是（近）锁相的轨道。
We analysed recent K2 data of the short-period eclipsing binary system HW Vir, which consists of a hot subdwarf-B type primary with an M-dwarf companion. We determined the mid-times of eclipses, calculated O–C diagrams, and an average shift of the secondary minimum. Our results show that the orbital period is stable within the errors over the course of the 70 days of observations. Interestingly, the offset from mid-orbital phase between the primary and the secondary eclipses is found to be 1.62 s. If the shift is explained solely by light-travel time, the mass of the sdB primary must be 0.26 M⊙, which is too low for the star to be core-helium burning. However, we argue that this result is unlikely to be correct and that a number of effects caused by the relative sizes of the stars conspire to reduce the effective light-travel time measurement. After removing the flux variation caused by the orbit, we calculated the amplitude spectrum to search for pulsations. The spectrum clearly shows periodic signal from close to the orbital frequency up to 4600 µHz, with the majority of peaks found below 2600 µHz. The amplitudes are below 0.1 part-per-thousand, too low to be detected with ground-based photometry. Thus, the high-precision data from the Kepler spacecraft has revealed that the primary of the HW Vir system is a pulsating sdBV star. We argue that the pulsation spectrum of the primary in HW Vir differs from that in other sdB stars due to its relatively fast rotation that is (nearly) phase-locked with the orbit.