Global analysis of KOI-977: spectroscopy, asteroseismology, and phase-curve analysis
Global analysis of KOI-977: spectroscopy, asteroseismology, and phase-curve analysis
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KOI-977 的全局分析：光谱学、星震学和相位曲线分析
DOI：
10.1088/0004-637x/799/1/9
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Y. et al.
中科院分区：
文献类型：
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作者：
Hirano;T.;Masuda;K.;Sato;B.;Benomar;O.;Takeda;Y. et al.
我们提出了一个全球性的分析KOI-977，开普勒探测到的行星宿主候选者之一。开普勒输入星表（KIC）报告说KOI-977是一颗红巨星，几乎没有发现过它附近的行星。我们的全球分析包括光谱和星震测定恒星参数（如质量和半径）和径向速度（RV）测量。我们的分析显示，KOI-977确实是一颗红巨星，可能在红团中，但它的估计半径（R = 0.093 Au）远大于KOI-977.01的轨道距离（R = 0.027 Au），该距离是根据它的周期（P球为1.35天）和宿主星星的质量估计的。RV测量显示出一个小的变化，这也与在KOI-977.01周期折叠的光变曲线中看到的椭圆变化的幅度相矛盾。因此，我们得出结论，KOI-977.01是一个假阳性，这意味着我们测量半径和RVs的红巨星与产生类似凌日信号的物体（即食双星）不同。在这个假设的基础上，我们还进行了光变曲线分析，包括过境/日食和相位曲线变化的建模，采用不同的稀释因子D值，它被定义为红巨星和食双星之间的流量比。同时拟合短步频数据中的整个折叠光变曲线和个别凌日，发现食双星的质量和半径比与D = 20时的太阳型星星和晚型星星（如M矮星）的质量和半径比是一致的。
We present a global analysis of KOI-977, one of the planet host candidates detected by Kepler. The Kepler Input Catalog (KIC) reports that KOI-977 is a red giant, for which few close-in planets have been discovered. Our global analysis involves spectroscopic and asteroseismic determinations of stellar parameters (eg, mass and radius) and radial velocity (RV) measurements. Our analyses reveal that KOI-977 is indeed a red giant, possibly in the red clump, but its estimated radius (≳ 20 R☉= 0.093 AU) is much larger than KOI-977.01's orbital distance (∼ 0.027 AU) estimated from its period (P orb∼ 1.35 days) and host star's mass. RV measurements show a small variation, which also contradicts the amplitude of ellipsoidal variations seen in the light curve folded with KOI-977.01's period. Therefore, we conclude that KOI-977.01 is a false positive, meaning that the red giant, for which we measured the radius and RVs, is different from the object that produces the transit-like signal (ie, an eclipsing binary). On the basis of this assumption, we also perform a light curve analysis including the modeling of transits/eclipses and phase-curve variations, adopting various values for the dilution factor D, which is defined as the flux ratio between the red giant and eclipsing binary. Fitting the whole folded light curve as well as individual transits in the short cadence data simultaneously, we find that the estimated mass and radius ratios of the eclipsing binary are consistent with those of a solar-type star and a late-type star (eg, an M dwarf) for D≳ 20.