Signals embedded in the radial velocity noise - Periodic variations in the τ Ceti velocities
Signals embedded in the radial velocity noise - Periodic variations in the τ Ceti velocities
复制标题
嵌入径向速度噪声中的信号 - τ Ceti 速度的周期性变化
DOI：
10.1051/0004-6361/201220509
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发表时间：
2012
影响因子：
6.5
通讯作者：
D. Pinfield
中科院分区：
文献类型：
--
作者：
M. Tuomi;H. Jones;J. Jenkins;C. Tinney;R. P. Butler;S. Vogt;J. Barnes;R. Wittenmyer;S. O’Toole;J. Horner;J. Bailey;B. Carter;D. Wright;G. Salter;D. Pinfield
上下文目前，径向速度系外行星巡天探测最小质量太阳系外行星的能力受到仪器精度、数据缺乏和“抖动”的限制。抖动是噪声中任何未知特征的总称，反映了对恒星物理学（星震学、星点、磁周期、颗粒化和其他恒星表面现象）缺乏详细的了解，以及可能低估了仪器噪声。
目标。我们研究了星星HD 10700（τ Ceti）的一组广泛的径向速度，以确定恒星表面不均匀性、活动和望远镜仪器系统引起的抖动特性，并对行星信号进行全面搜索径向速度。
方法.我们对描述径向速度数据的统计模型进行贝叶斯比较，以量化数据中显著信号的数量以及过量噪声的大小和性质。我们通过将人工信号添加到HD 10700的“平坦”径向速度数据中，并通过查看我们的统计噪声模型中哪一个接收到最大的后验概率，同时仍然能够从数据中正确提取人工信号来实现我们的目标。我们利用各种噪声成分来评估数据中的噪声属性，并分析HD 10700的HARPS，AAPS和HIRES数据，以量化这些属性并搜索以前未知的低振幅开普勒信号。
结果根据我们的分析，具有指数衰减的移动平均分量的时间尺度从几个小时到几天，高斯白色噪声解释了所有三个数据集的抖动。拟合相应的噪声参数的统计模型的显着改善的结果，使我们的数值实验中的振幅低于1 m s-1水平的非常弱的信号的检测。我们检测到显着的周期性，没有活动引起的对应物的组合径向速度。这些信号中的三个可以单独在HARPS数据中看到，另外两个可以通过利用AAPS和Keck数据来推断。这些周期可以被解释为对应于在动力学稳定的闭合圆形轨道上的行星，其周期分别为13.9、35.4、94、168和640天，最小质量分别为2.0、3.1、3.6、4.3和6.6 M/s。
Context. The abilities of radial velocity exoplanet surveys to detect the lowest-mass extra-solar planets are currently limited by a combination of instrument precision, lack of data, and 'jitter'. Jitter is a general term for any unknown features in the noise, and reflects a lack of detailed knowledge of stellar physics (asteroseismology, starspots, magnetic cycles, granulation, and other stellar surface phenomena), as well as the possible underestimation of instrument noise.
Aims. We study an extensive set of radial velocities for the star HD 10700 (τ Ceti) to determine the properties of the jitter arising from stellar surface inhomogeneities, activity, and telescope-instrument systems, and perform a comprehensive search for planetary signals in the radial velocities.
Methods. We performed Bayesian comparisons of statistical models describing the radial velocity data to quantify the number of significant signals and the magnitude and properties of the excess noise in the data. We reached our goal by adding artificial signals to the 'flat' radial velocity data of HD 10700 and by seeing which one of our statistical noise models receives the greatest posterior probabilities while still being able to extract the artificial signals correctly from the data. We utilised various noise components to assess properties of the noise in the data and analyse the HARPS, AAPS, and HIRES data for HD 10700 to quantify these properties and search for previously unknown low-amplitude Keplerian signals.
Results. According to our analyses, moving average components with an exponential decay with a timescale from a few hours to few days, and Gaussian white noise explains the jitter the best for all three data sets. Fitting the corresponding noise parameters results in significant improvements of the statistical models and enables the detection of very weak signals with amplitudes below 1 m s-1 level in our numerical experiments. We detect significant periodicities that have no activity-induced counterparts in the combined radial velocities. Three of these signals can be seen in the HARPS data alone, and a further two can be inferred by utilising the AAPS and Keck data. These periodicities could be interpreted as corresponding to planets on dynamically stable close-circular orbits with periods of 13.9, 35.4, 94, 168, and 640 days and minimum masses of 2.0, 3.1, 3.6, 4.3, and 6.6 M⊕, respectively.