GR Virginis: A Deep Overcontact Binary
GR Virginis: A Deep Overcontact Binary
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DOI：
10.1086/425051
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发表时间：
2004-11
期刊：
影响因子：
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通讯作者：
S. Qian;Y.-G. Yang
中科院分区：
文献类型：
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作者：
S. Qian;Y.-G. Yang
利用两个新的ccd最小光时和从文献中收集的其他光电数据，研究了低质量比(q=0.122)过接触双星系统GR Vir的轨道周期变化。结果表明，GR-VIR的O-C残差在经历长期下降(dp/dt=-4.32×10-7d/yr-1)的同时，呈现出周期为19.3年、幅度为0.0140天的周期性变化。同时，1988年Cereda等人的光电观测。采用威尔逊-德文尼方法进行分析。与一些低质量比的过接触双星(如AW Uma)一样，GR VIR是一颗A型过接触双星，具有很高的过接触程度(f=78.6%)。结合光谱溶液和光度元素，确定了该体系的绝对参数：M_1=1.36M⊙，M_2=0.17M⊙，a=2.40R⊙，R_1=1.42R⊙，R_2=0.61R⊙，L_1=2.87 L⊙，L_2=0.48 L⊙。长期周期的减少被解释为从质量较大的分量向质量较小的分量的质量转移以及L2点质量外流造成的角动量损失的结果。GR Vir的情况类似于AW Uma的情况。这两个系统都表现出高度的过度接触、低质量比和长期的轨道收缩。随着其轨道周期的缩短，内外临界罗氏叶的收缩将导致共同的对流包络变得更深，直到最终不可避免地形成单颗快速自转的恒星。周期振荡可能是由看不见的第三分量(例如，白矮星)的存在或由初级分量上的磁活动引起的。
Orbital period variations of the low-mass ratio (q = 0.122) overcontact binary system, GR Vir, were investigated by using two new CCD times of minimum light and other photoelectric data compiled from literatures. It is found that the O - C residuals of GR Vir show a cyclic variation with a period of 19.3 yr and an amplitude of 0.0140 days while they are undergoing a long-term decrease (dP/dt = -4.32 × 10-7 days yr-1). Meanwhile, the 1988 photoelectric observations from Cereda et al. were analyzed using the Wilson-Devinney method. Like some low-mass ratio overcontact binary stars (e.g., AW UMa), GR Vir is an A-type overcontact binary with a high degree of overcontact (f = 78.6%). By combining the spectroscopic solutions with the photometric elements, the absolute parameters of the system are determined as follows: M1 = 1.36 M⊙, M2 = 0.17 M⊙, a = 2.40 R⊙, R1 = 1.42 R⊙, R2 = 0.61 R⊙, L1 = 2.87 L⊙, and L2 = 0.48 L⊙. The long-term period decrease is interpreted as the result of mass transfer from the more massive component to the less massive one in combination with the angular momentum loss due to mass outflow from the L2 point. The conditions in GR Vir resemble those in AW UMa. Both systems show a high degree of overcontact, low mass ratios, and secular shrinking of their orbits. As their orbital periods decrease, the shrinking of the inner and outer critical Roche lobes will cause the common convective envelope to become deeper, until finally the formation of single, rapid-rotation stars is inevitable. The period oscillation may by caused either by the presence of an unseen tertiary component (e.g., a white dwarf) or by magnetic activity on the part of the primary component.