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arXiv 1107.2106astro-ph.EP
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用星点测量凌日行星的自旋轨道对准

Using Star Spots to Measure the Spin-orbit Alignment of Transiting Planets

Philip A. Nutzman, Daniel C. Fabrycky, Jonathan J. Fortney

摘要:

对数十颗凌日行星的光谱跟踪揭示了恒星赤道与其所在行星轨道之间的对齐程度。在这里,我们确定了一种方法,适用于斑点星,可以揭示相同的信息,从光度发现数据,而不需要后续行动。一个适合于全球光变曲线的斑点模型,由恒星的自旋方向参数化,预测行星何时会经过这些斑点。在不同的凌日过程中观察几个点交叉,然后导致对自旋轨道对准的约束。在恒星斑点很小的情况下,可以获得恒星的倾角,从而获得真正的对准,而不仅仅是天空投影。随着CoRoT和开普勒等太空望远镜的出现,这种方法已经成为可能,它们在几乎连续的长时间基线上通过光度测量来监测凌日行星。我们将我们的方法应用于CoRoT-2,并发现投影的自旋-轨道对准角,λ = 4.7度+/- 12.3度,与先前采用Rossiter-McLaughlin效应的确定非常一致。母星CoRoT-2的大斑点限制了我们对恒星倾角的精确度:i_s = 84 deg +/- 36 deg,其中i_s < 90 deg(> 90 deg)表示旋转轴朝向(远离)视线倾斜。

英文摘要:

Spectroscopic follow-up of dozens of transiting planets has revealed the degree of alignment between the equators of stars and the orbits of the planets they host. Here we determine a method, applicable to spotted stars, that can reveal the same information from the photometric discovery data, with no need for follow-up. A spot model fit to the global light curve, parametrized by the spin orientation of the star, predicts when the planet will transit the spots. Observing several spot crossings during different transits then leads to constraints on the spin-orbit alignment. In cases where stellar spots are small, the stellar inclination, and hence the true alignment, rather than just the sky projection, can be obtained. This method has become possible with the advent of space telescopes such as CoRoT and Kepler, which photometrically monitor transiting planets over a nearly continuous, long time baseline. We apply our method to CoRoT-2, and find the projected spin-orbit alignment angle, lambda= 4.7 deg +/- 12.3 deg, in excellent agreement with a previous determination that employed the Rossiter-McLaughlin effect. The large spots of the parent star, CoRoT-2, limit our precision on the stellar inclination: i_s = 84 deg +/- 36 deg, where i_s < 90 deg (> 90 deg) indicates the rotation axis is tilted towards (away from) the line of sight.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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