交通灯曲线项目。X. HD 17156 b的圣诞过境
The Transit Light Curve Project. X. A Christmas Transit of HD 17156b
摘要：
2007年12月25日，HD 17156 b凌日，它具有所有已知凌日系外行星中最长的轨道周期和最高的轨道偏心率。还介绍了恒星径向速度的新测量结果。所有的数据结合起来，并与恒星演化建模，以获得完善的系统参数。该行星的质量和半径分别为3.212 - 0.082 ^{+0.069}木星质量和1.023 - 0.055 ^{+0.070}木星半径。相应的恒星性质为1.263 - 0.047 ^{+0.035}太阳质量和1.446 - 0.067 ^{+0.099}太阳半径。这颗行星比具有相同质量和平衡温度的理论太阳组成气体巨星小1 σ，这可能是重元素富集的迹象。中星时的测量误差在1分钟以内，并且没有显示出与线性星历的偏差（因此没有证据表明其他行星的轨道扰动）。我们为未来的凌日和上合提供星历表。有18%的可能性，轨道平面的方向足够接近边缘，以便在上合点发生二次日食。对次日食的观测将揭示一颗行星的热发射光谱，这颗行星经历了异常大的潮汐加热和日照变化。
英文摘要：
Photometry is presented of the Dec. 25, 2007 transit of HD 17156b, which has the longest orbital period and highest orbital eccentricity of all the known transiting exoplanets. New measurements of the stellar radial velocity are also presented. All the data are combined and integrated with stellar-evolutionary modeling to derive refined system parameters. The planet's mass and radius are found to be 3.212_{-0.082}^{+0.069} Jupiter masses and 1.023_{-0.055}^{+0.070} Jupiter radii. The corresponding stellar properties are 1.263_{-0.047}^{+0.035} solar masses and 1.446_{-0.067}^{+0.099} solar radii. The planet is smaller by 1 sigma than a theoretical solar-composition gas giant with the same mass and equilibrium temperature, a possible indication of heavy-element enrichment. The midtransit time is measured to within 1 min, and shows no deviation from a linear ephemeris (and therefore no evidence for orbital perturbations from other planets). We provide ephemerides for future transits and superior conjunctions. There is an 18% chance that the orbital plane is oriented close enough to edge-on for secondary eclipses to occur at superior conjunction. Observations of secondary eclipses would reveal the thermal emission spectrum of a planet that experiences unusually large tidal heating and insolation variations.
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