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arXiv 1402.6691astro-ph.SRastro-ph.IM
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高精度星载测光测量恒星差自转

Measuring stellar differential rotation with high-precision space-borne photometry

A. F. Lanza, M. L. Das Chagas, J. R. De Medeiros

摘要:

介绍了一种从高精度、均匀采样的光度时间序列中测量表面微分旋转幅度下限的方法。它适用于主序星晚型的光通量调制是由星点占主导地位。时间序列的自相关被用来选择恒星,允许准确确定星点旋转周期。一个简单的两个点模型一起应用贝叶斯信息标准,初步选择时间序列的间隔,显示几乎恒定面积的星点的差异旋转的证据。最后,通过基于蒙特卡罗马尔可夫链方法的后验贝叶斯分析,获得了差分旋转检测的意义及其幅度和不确定性的度量。我们将我们的方法应用于太阳和其他八颗恒星,这些恒星以前曾进行过斑点建模,以将我们的结果与以前的结果进行比较。我们发现,自相关是一个简单的方法,选择恒星的相干旋转信号,成功地测量差分旋转通过现场建模的先决条件。为了进行适当的蒙特卡罗马尔可夫链分析,有必要考虑现货建模中存在的不同参数之间的强相关性。对于行星宿主恒星开普勒-30,我们推导出了差旋相对振幅的下限ΔP / P = 0.0523 \pm 0.0016。我们证实,太阳作为一个恒星的光学通带是不适合测量的差异旋转,由于其光球活动区的快速演变。在一般情况下,我们的方法相比,更复杂和耗时的方法表现良好。

英文摘要:

We introduce a method of measuring a lower limit to the amplitude of surface differential rotation from high-precision, evenly sampled photometric time series. It is applied to main-sequence late-type stars whose optical flux modulation is dominated by starspots. An autocorrelation of the time series was used to select stars that allow an accurate determination of starspot rotation periods. A simple two-spot model was applied together with a Bayesian information criterion to preliminarily select intervals of the time series showing evidence of differential rotation with starspots of almost constant area. Finally, the significance of the differential rotation detection and a measurement of its amplitude and uncertainty were obtained by an a posteriori Bayesian analysis based on a Monte Carlo Markov Chain approach. We applied our method to the Sun and eight other stars for which previous spot modelling had been performed to compare our results with previous ones. We find that autocorrelation is a simple method for selecting stars with a coherent rotational signal that is a prerequisite for successfully measuring differential rotation through spot modelling. For a proper Monte Carlo Markov Chain analysis, it is necessary to take the strong correlations among different parameters that exist in spot modelling into account. For the planet-hosting star Kepler-30, we derive a lower limit to the relative amplitude of the differential rotation of ΔP / P = 0.0523 \pm 0.0016. We confirm that the Sun as a star in the optical passband is not suitable for measuring differential rotation owing to the rapid evolution of its photospheric active regions. In general, our method performs well in comparison to more sophisticated and time-consuming approaches.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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