State of the Field: Extreme Precision Radial Velocities
Debra Fischer, Guillem Anglada-Escude, Pamela Arriagada, Roman V. Baluev, Jacob L. Bean, Francois Bouchy, Lars A. Buchhave, Thorsten Carroll, Abhijit Chakrabort… 展开作者
Debra Fischer, Guillem Anglada-Escude, Pamela Arriagada, Roman V. Baluev, Jacob L. Bean, Francois Bouchy, Lars A. Buchhave, Thorsten Carroll, Abhijit Chakraborty, Justin R. Crepp, Rebekah I. Dawson, Scott A. Diddams, Xavier Dumusque, Jason D. Eastman, Michael Endl, Pedro Figueira, Eric B. Ford, Daniel Foreman-Mackey, Paul Fournier, Gabor Furesz, B. Scott Gaudi, Philip C. Gregory, Frank Grundahl, Artie P. Hatzes, Guillaume Hebrard, Enrique Herrero, David W. Hogg, Andrew W. Howard, John A. Johnson, Paul Jorden, Colby A. Jurgenson, David W. Latham, Greg Laughlin, Thomas J. Loredo, Christophe Lovis, Suvrath Mahadevan, Tyler M. McCracken, Francesco Pepe, Mario Perez, David F. Phillips, Peter P. Plavchan, Lisa Prato, Andreas Quirrenbach, Ansgar Reiners, Paul Robertson, Nuno C. Santos, David Sawyer, Damien Segransan, Alessandro Sozzetti, Tilo Steinmetz, Andrew Szentgyorgyi, Stephane Udry, Jeff A. Valenti, Sharon X. Wang, Robert A. Wittenmyer, Jason T. Wright
The Second Workshop on Extreme Precision Radial Velocities defined circa 2015 the state of the art Doppler precision and identified the critical path challenges for reaching 10 cm/s measurement precision. The presentations and discussion of key issues for instrumentation and data analysis and the workshop recommendations for achieving this precision are summarized here.
Beginning with the HARPS spectrograph, technological advances for precision radial velocity measurements have focused on building extremely stable instruments. To reach still higher precision, future spectrometers will need to produce even higher fidelity spectra. This should be possible with improved environmental control, greater stability in the illumination of the spectrometer optics, better detectors, more precise wavelength calibration, and broader bandwidth spectra. Key data analysis challenges for the precision radial velocity community include distinguishing center of mass Keplerian motion from photospheric velocities, and the proper treatment of telluric contamination. Success here is coupled to the instrument design, but also requires the implementation of robust statistical and modeling techniques. Center of mass velocities produce Doppler shifts that affect every line identically, while photospheric velocities produce line profile asymmetries with wavelength and temporal dependencies that are different from Keplerian signals.
Exoplanets are an important subfield of astronomy and there has been an impressive rate of discovery over the past two decades. Higher precision radial velocity measurements are required to serve as a discovery technique for potentially habitable worlds and to characterize detections from transit missions. The future of exoplanet science has very different trajectories depending on the precision that can ultimately be achieved with Doppler measurements.
Photon-weighted barycentric correction and its importance for precise radial velocities
当重心校正应用于精确的径向速度测量时，通常的做法是仅在观测的光子加权中点时间计算其值，而不是在整个曝光上积分。然而，由于重心校正不随时间线性变化，这导致在导出的径向速度中的系统误差。这种二阶效应的典型量级为10 cm s $^{-1}$，但它取决于几个参数，例如天文台的纬度、目标在天空中的位置和曝光时间。我们表明，有现实的观察情况下，误差可以达到超过1毫秒$^{-1}$。因此，我们建议在这种情况下工作的仪器总是记录和存储曝光计通量曲线（或类似的测量），以用作重心校正的光子权重。在现有的数据中，如果通量曲线不再可用，我们认为，在重心校正的二阶误差可以减轻通过添加一个修正项假设恒定的通量。
Towards Extremely Precise Radial Velocities: I. Simulated Solar Spectra for Testing Exoplanet Detection Algorithms
最近和即将推出的稳定光谱仪正在推动多普勒光谱学的前沿，以检测和表征低质量行星。这些仪器的规格是如此令人印象深刻，以至于恒星的固有变化预计会限制它们对大多数目标恒星的多普勒精度（Fischer et al. 2016）。为了充分发挥它们的潜力，天文学家必须开发新的策略来区分真实的多普勒频移和恒星的内在变化。由于恒星黑子、光斑和其他与旋转相关的变化，恒星的变化特别令人担忧，因为恒星的旋转周期通常包括在潜在的行星轨道周期范围内。为了通过多普勒行星调查稳健地探测和准确地描述低质量行星的特征，系外行星界必须开发能够联合建模行星扰动和恒星固有变化的统计模型。为了实现这一目标，本文介绍了用SOAP 2.0（arXiv：1409.3594）创建的极高分辨率的太阳光谱的模拟，其中包括多个不断变化的恒星斑点。我们预计这组数据将有助于未来的研究开发，测试和比较统计方法测量物理径向速度之间的污染恒星的变化。
Properties of Radial Velocities measurement based on LAMOST-II Medium-Resolution Spectroscopic Observations
径向速度（RV）是一个基本的物理量，它可以通过恒星光谱的多普勒频移来确定。RV测量的精度取决于我们使用的光谱的分辨率和波长校准的准确性。本文通过模板匹配法对LAMOST-II中分辨率（R ~ 7500）光谱的1,594,956条（每条光谱有两个波段）径向速度进行了测量。一组RV标准星用于重新校准测量的零点，而一些由中/高分辨率观测得到的RV参考星用于评估测量的精度。与参考组相比，我们的测量精度可以达到0.0227kms/1。利用单星多次观测数据估算了光谱的本征精度，在信噪比为10、20、50时，本征精度分别达到1.36、1.08、0.91 km s/1。
