THE STELLAR OBLIQUITY AND THE LONG-PERIOD PLANET IN THE HAT-P-17 EXOPLANETARY SYSTEM
THE STELLAR OBLIQUITY AND THE LONG-PERIOD PLANET IN THE HAT-P-17 EXOPLANETARY SYSTEM
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HAT-P-17 系外行星系统中的恒星倾角和长周期行星
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发表时间：
2013
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通讯作者：
Ming
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作者：
B. Fulton;A. Howard;J. Winn;S. Albrecht;G. Marcy;J. Crepp;G. Bakos;J. Johnson;J. Hartman;H. Isaacson;H. Knutson;Ming
我们给出了HAT-P-17多行星系统内行星的测量投影倾角——恒星自转轴与轨道角动量之间的天空投影角度。我们通过模拟Keck/HIRES径向速度（rv）中的Rossiter-McLaughlin效应来测量恒星的天空投影倾角。反常的RV时间序列显示出相对于凌日中间时间的不对称性，通常表明倾角非零，但在这种情况下，至少部分不对称性可能是由于对流蓝移，增加了λ测定的不确定性。我们采用了Hirano等人的半解析方法，其中包括宏观湍流、仪器增宽和对流蓝移的影响，以准确地模拟由行星遮挡旋转恒星部分引起的净RV异常。倾角测量是检验行星形成和迁移理论的重要工具。迄今为止，约50颗类木行星的测量倾角跨越了从顺行到逆行的整个范围，围绕冷恒星运行的行星优先显示恒星旋转和行星轨道的对齐。我们的结果与这种模式是一致的，这种模式是由低温恒星和近地行星的对流包层中的潮汐相互作用产生的。此外，我们对这个系统1.8年的新rv表明，外行星的轨道比以前认为的更不受约束，轨道周期现在在10-36年的范围内。
We present the measured projected obliquity—the sky-projected angle between the stellar spin axis and orbital angular momentum—of the inner planet of the HAT-P-17 multi-planet system. We measure the sky-projected obliquity of the star to be deg by modeling the Rossiter–McLaughlin effect in Keck/HIRES radial velocities (RVs). The anomalous RV time series shows an asymmetry relative to the midtransit time, ordinarily suggesting a nonzero obliquity—but in this case at least part of the asymmetry may be due to the convective blueshift, increasing the uncertainty in the determination of λ. We employ the semi-analytical approach of Hirano et al. that includes the effects of macroturbulence, instrumental broadening, and convective blueshift to accurately model the anomaly in the net RV caused by the planet eclipsing part of the rotating star. Obliquity measurements are an important tool for testing theories of planet formation and migration. To date, the measured obliquities of ∼50 Jovian planets span the full range, from prograde to retrograde, with planets orbiting cool stars preferentially showing alignment of stellar spins and planetary orbits. Our results are consistent with this pattern emerging from tidal interactions in the convective envelopes of cool stars and close-in planets. In addition, our 1.8 yr of new RVs for this system show that the orbit of the outer planet is more poorly constrained than previously thought, with an orbital period now in the range of 10–36 yr.