Transit轻型曲线项目。XIII。超级地球GJ 1214 b的16次凌日
The Transit Light Curve Project. XIII. Sixteen Transits of the Super-Earth GJ 1214b
摘要：
我们提出了16个超级地球GJ 1214 b凌日的光学测光，使我们能够通过凌日时间来完善系统参数和寻找其他行星。在两条光变曲线中检测到星点交叉事件，发现恒星的变化只有百分之几。因此，在我们的分析中，特别注意由星点引起的系统误差。行星与恒星的半径比为0.11610+/-0.00048，由于未知的光点覆盖范围，可能会有百分之几的向上偏差。即使假设这个偏差可以忽略不计，行星的平均密度也可以是3.03+/-0.50 g cm^{-3}或1.89+/-0.33 g cm^{-3}，这取决于恒星半径是根据演化模型还是根据结合光变曲线参数的经验质光关系估算的。一个可能的解决方案是轨道是偏心的（e约等于0.14），这将有利于更高的密度，因此行星的大气层要薄得多。凌日时间被发现在大约15秒内是周期性的，排除了任何其他超级地球的存在，其周期在已知行星的两倍之内。
英文摘要：
We present optical photometry of 16 transits of the super-Earth GJ 1214b, allowing us to refine the system parameters and search for additional planets via transit timing. Starspot-crossing events are detected in two light curves, and the star is found to be variable by a few percent. Hence, in our analysis, special attention is given to systematic errors that result from star spots. The planet-to-star radius ratio is 0.11610+/-0.00048, subject to a possible upward bias by a few percent due to the unknown spot coverage. Even assuming this bias to be negligible, the mean density of planet can be either 3.03+/-0.50 g cm^{-3} or 1.89+/-0.33 g cm^{-3}, depending on whether the stellar radius is estimated from evolutionary models or from an empirical mass-luminosity relation combined with the light curve parameters. One possible resolution is that the orbit is eccentric (e approximately equal to 0.14), which would favor the higher density, and hence a much thinner atmosphere for the planet. The transit times were found to be periodic within about 15s, ruling out the existence of any other super-Earths with periods within a factor-of-two of the known planet.
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