The Mass of the Candidate Exoplanet Companion to HD 33636 from Hubble Space Telescope Astrometry and High-Precision Radial Velocities
The Mass of the Candidate Exoplanet Companion to HD 33636 from Hubble Space Telescope Astrometry and High-Precision Radial Velocities
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哈勃太空望远镜天体测量的 HD 33636 候选系外行星伴星的质量和高精度径向速度
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发表时间：
2007
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通讯作者：
V. Smith
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作者：
J. Bean;B. Mcarthur;G. Benedict;T. Harrison;D. Bizyaev;E. Nelan;V. Smith
我们已经确定了HD 33636的伴星的动力学质量，这表明它是一颗低质量的星星，而不是一颗系外行星。我们的结果是基于哈勃太空望远镜（HST）天体测量和地面径向速度数据的分析。我们已经获得了高节奏的径向速度测量跨越1.3年的HD 33636与Hobby-Eberly望远镜在麦当劳天文台。我们将这些数据与先前公布的速度相结合，创建了一个跨越9年的数据集。我们使用这个数据集来搜索，并对HD 33636系统中其他伴星的存在进行质量限制。我们使用HST精细制导传感器1 r对系统进行的高精度天体测量观测跨度为1.2年。我们同时模拟径向速度和天体测量数据，以确定视差，自行和摄动轨道参数的HD 33636。我们推导出的视差，πabs = 35.6 ± 0.2 mas，在不确定性范围内与依巴谷值一致。测得扰动周期P = 2117.3 ± 0.8天，半长轴aA = 14.2 ± 0.2mas，系统倾角i = 4.1° ± 0.1°。假设主星星星的质量为MA = 1.02 ± 0.03 M，我们得到伴星的质量为MB = 142 ± 11 MJup = 0.14 ± 0.01 M。这颗伴星的真实质量比根据光谱轨道参数估计的最小质量（M sin i = 9.3 MJup）大得多，这是因为它的轨道几乎是面对面的。这一结果表明，后续天体测量观测对于确定用径向速度方法探测到的系外行星候选者的真实质量具有重要价值。
We have determined a dynamical mass for the companion to HD 33636 that indicates it is a low-mass star instead of an exoplanet. Our result is based on an analysis of Hubble Space Telescope (HST) astrometry and ground-based radial velocity data. We have obtained high-cadence radial velocity measurements spanning 1.3 yr of HD 33636 with the Hobby-Eberly Telescope at McDonald Observatory. We combined these data with previously published velocities to create a data set that spans 9 yr. We used this data set to search for, and place mass limits on, the existence of additional companions in the HD 33636 system. Our high-precision astrometric observations of the system with the HST Fine Guidance Sensor 1r span 1.2 yr. We simultaneously modeled the radial velocity and astrometry data to determine the parallax, proper motion, and perturbation orbit parameters of HD 33636. Our derived parallax, πabs = 35.6 ± 0.2 mas, agrees within the uncertainties with the Hipparcos value. We find a perturbation period P = 2117.3 ± 0.8 days, semimajor axis aA = 14.2 ± 0.2 mas, and system inclination i = 4.1° ± 0.1°. Assuming the mass of the primary star to be MA = 1.02 ± 0.03 M⊙, we obtain a companion mass MB = 142 ± 11 MJup = 0.14 ± 0.01 M⊙. The much larger true mass of the companion relative to its minimum mass estimated from the spectroscopic orbit parameters (M sin i = 9.3 MJup) is due to the nearly face-on orbit orientation. This result demonstrates the value of follow-up astrometric observations to determine the true masses of exoplanet candidates detected with the radial velocity method.