Physical Properties of the Low-Mass Eclipsing Binary NSVS 02502726
Physical Properties of the Low-Mass Eclipsing Binary NSVS 02502726
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DOI：
10.1088/0004-6256/145/1/16
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发表时间：
2012-11
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影响因子：
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通讯作者：
Jae Woo Lee;J. Youn;Seung-Lee Kim;Chung-Uk Lee
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文献类型：
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作者：
Jae Woo Lee;J. Youn;Seung-Lee Kim;Chung-Uk Lee
nsv 02502726是由两颗低质量恒星组成的双线分离食双星。我们在2009年和2011年获得了$BVRI$光度跟踪观测，以测量双星物理性质的改善。每组光曲线，包括2008年cCakirli等人给出的数据，都使用Wilson-Devinney二进制代码与先前发表的径向速度曲线同时进行分析。该系统明显的季节光变化可以用一个星斑和一个星斑参数随时间变化的双斑模型来模拟。基于合成模型计算的23次日食时间和1个星历历历历元，对nsv 02502726的轨道周期进行了研究，发现其周期经历了$-5.9\ × 10^{-7}$ d yr$^{-1}$的连续减小，周期和半振幅分别为2.51年和0.0011 d的正弦变化。时间的变化可以解释为由于看不见的第三个天体的存在而产生的光传播时间效应，或者是这种效应和由于磁性恒星风制动而造成的角动量损失的结合。两个分量的质量和半径分别为：$M_1$=0.689$\pm$0.016 M$_\odot$, $M_2$=0.341$\pm$0.009 M$_\odot$, $R_1$=0.707$\pm$0.007 R$_\odot$, $R_2$=0.657$\pm$0.008 R$_\odot$。结果与cCakirli等人的结果非常不同，初级星的半径（0.674$\pm$0.006 R$_\odot$）小于次级星的半径（0.763$\pm$0.007 R$_\odot$）。我们将本文给出的物理参数与当前的低质量恒星模型进行了比较，发现主星的测量值最适合于79-Myr等时线。初等星与低质量双星的经验质量-半径关系很好地吻合，但次级星超大约85%。
NSVS 02502726 has been known as a double-lined, detached eclipsing binary that consists of two low-mass stars. We obtained $BVRI$ photometric follow-up observations in 2009 and 2011 to measure improved physical properties of the binary star. Each set of light curves, including the 2008 data given by \cCakirli et al., was simultaneously analyzed with the previously published radial-velocity curves using the Wilson-Devinney binary code. The conspicuous seasonal light variations of the system are satisfactorily modelled by a two-spot model with one starspot on each component and by changes of the spot parameters with time. Based on 23 eclipse timings calculated from the synthetic model and one ephemeris epoch, an orbital period study of NSVS 02502726 reveals that the period has experienced a continuous decrease of $-5.9\times10^{-7}$ d yr$^{-1}$ or a sinusoidal variation with a period and semi-amplitude of 2.51 yrs and 0.0011 d, respectively. The timing variations could be interpreted as either the light-travel-time effect due to the presence of an unseen third body, or as the combination of this effect and angular momentum loss via magnetic stellar wind braking. Individual masses and radii of both components are determined to be $M_1$=0.689$\pm$0.016 M$_\odot$, $M_2$=0.341$\pm$0.009 M$_\odot$, $R_1$=0.707$\pm$0.007 R$_\odot$, and $R_2$=0.657$\pm$0.008 R$_\odot$. The results are very different from those of \cCakirli et al. with the primary's radius (0.674$\pm$0.006 R$_\odot$) smaller the secondary's (0.763$\pm$0.007 R$_\odot$). We compared the physical parameters presented in this paper with current low-mass stellar models and found that the measured values of the primary star are best fitted to a 79-Myr isochrone. The primary is in good agreement with the empirical mass-radius relation from low-mass binaries, but the secondary is oversized by about 85%.