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arXiv 1602.00322astro-ph.EPastro-ph.SR
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重新加载了Rossiter-McLaughlin效果:探索恒星-行星系统的三维自旋-轨道几何学、差分恒星自转和空间分辨恒星光谱

The Rossiter-McLaughlin effect reloaded: Probing the 3D spin-orbit geometry, differential stellar rotation, and the spatially-resolved stellar spectrum of star-planet systems

H. M. Cegla, C. Lovis, V. Bourrier, B. Beeck, C. A. Watson, F. Pepe

摘要:

当一颗行星经过它的主星时,它会挡住恒星表面的某些区域,这会导致谱线的扭曲和视线速度的改变,称为罗斯特-麦克劳克林(RM)效应。由于LOS速度部分取决于恒星的自转,RM波形对恒星-行星的排列很敏感(这提供了系统动力学历史的信息)。我们提出了一种新的RM建模技术,直接测量行星背后的空间分辨恒星光谱。这是通过调整(HARPS)光谱的连续通量由过境光变曲线,然后减去在-从过境光谱隔离行星后面的星光。该技术不假设任何形状的固有局部轮廓。在它,我们还允许差分恒星旋转和中心到肢体的对流蓝移的变化。我们将这种技术应用到HD 189733和比较三维磁流体动力学(MHD)模拟。我们拒绝刚体旋转的高置信度(> 99%的概率),这使我们能够确定被掩盖的恒星纬度和测量恒星倾角。反过来,我们确定天空投影(λ ~ -0.4 +/-0.2度)和真实的3D分辨率(psi ~ 7^+12_-4度)。我们也发现很好的协议与MHD模拟,没有显着的中心到肢体的变化,在当地的配置文件中检测。因此,这项技术提供了一个新的强大的工具,可以探测恒星光球,微分旋转,确定三维的几何形状,并消除天空投影的偏见,行星迁移理论。这种技术可以用现有的仪器来实现,但随着下一代高精度径向速度摄谱仪的出现,这种技术将变得更加强大。

英文摘要:

When a planet transits its host star, it blocks regions of the stellar surface from view; this causes a distortion of the spectral lines and a change in the line-of-sight (LOS) velocities, known as the Rossiter-McLaughlin (RM) effect. Since the LOS velocities depend, in part, on the stellar rotation, the RM waveform is sensitive to the star-planet alignment (which provides information on the system's dynamical history). We present a new RM modelling technique that directly measures the spatially-resolved stellar spectrum behind the planet. This is done by scaling the continuum flux of the (HARPS) spectra by the transit light curve, and then subtracting the in- from the out-of-transit spectra to isolate the starlight behind the planet. This technique does not assume any shape for the intrinsic local profiles. In it, we also allow for differential stellar rotation and centre-to-limb variations in the convective blueshift. We apply this technique to HD189733 and compare to 3D magnetohydrodynamic (MHD) simulations. We reject rigid body rotation with high confidence (> 99% probability), which allows us to determine the occulted stellar latitudes and measure the stellar inclination. In turn, we determine both the sky-projected (lambda ~ -0.4 +/- 0.2 degrees) and true 3D obliquity (psi ~ 7^+12_-4 degrees). We also find good agreement with the MHD simulations, with no significant centre-to-limb variations detectable in the local profiles. Hence, this technique provides a new powerful tool that can probe stellar photospheres, differential rotation, determine 3D obliquities, and remove sky-projection biases in planet migration theories. This technique can be implemented with existing instrumentation, but will become even more powerful with the next generation of high-precision radial velocity spectrographs.

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