超大质量行星HD147506b的精细参数和光谱凌日
Refined parameters and spectroscopic transit of the super-massive planet HD147506b
摘要：
在本文中，我们报告了最近发现的凌日系外行星HD 147506 b（HAT-P-2b）的轨道参数的精确测定和罗西特-麦克劳克林效应的检测。这颗系外行星在短轨道周期下的大轨道偏心率是出乎意料的，与其他已知的凌日系外行星不同。我们使用安装在上普罗旺斯天文台（OHP）1.93米望远镜上的新光谱仪SOPHIE对HD 147506（HAT-P-2）进行了高精度径向速度光谱观测。我们获得了63个新的测量结果，包括5月14日的35个和6月11日的20个，当时这颗行星正在穿越它的母星。观测到的径向速度（RV）异常表明HAT-P-2b的轨道运动与其母星的自旋方向相同。轨道平面法线与恒星自转轴之间的天空投影角λ= 0.2 + 12.2 - 12.5度，与零一致。重新测定了行星半径和恒星半径，得到Rp = 0.951 + 0.039 - 0.053 RJup，Rs = 1.416 + 0.040 - 0.062 RSun。质量M_p = 8.62 +0.39 -0.55 M_Jup，HAT-P-2b的半径表明其密度为12.5 +2.6 -3.6 g cm^{-3}，这意味着该天体介于已知的密度为1 g cm^{-3}的近距离行星和密度大于50 g cm^{-3}的质量非常低的恒星之间。
英文摘要：
In this paper, we report a refined determination of the orbital parameters and the detection of the Rossiter-McLaughlin effect of the recently discovered transiting exoplanet HD147506b (HAT-P-2b). The large orbital eccentricity at the short orbital period of this exoplanet is unexpected and is distinguishing from other known transiting exoplanets. We performed high-precision radial velocity spectroscopic observations of HD147506 (HAT-P-2) with the new spectrograph SOPHIE, mounted on the 1.93 m telescope at the Haute-Provence observatory (OHP). We obtained 63 new measurements, including 35 on May 14 and 20 on June 11, when the planet was transiting its parent star. The radial velocity (RV) anomaly observed illustrates that HAT-P-2b orbital motion is set in the same direction as its parent star spin. The sky-projected angle between the normal of the orbital plane and the stellar spin axis, λ= 0.2 +12.2 -12.5 deg, is consistent with zero. The planetary and stellar radii were re-determined, yielding R_p = 0.951 +0.039 -0.053 R_Jup, R_s = 1.416 +0.040 -0.062 R_Sun. The mass M_p = 8.62 +0.39 -0.55 M_Jup and radius of HAT-P-2b indicate a density of 12.5 +2.6 -3.6 g cm^{-3}, suggesting an object in between the known close-in planets with typical density of the order of 1 g cm^{-3}, and the very low-mass stars, with density greater than 50 g cm^{-3}.
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