arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1609.00535astro-ph.SRastro-ph.EP
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2015年3月20日日食的径向速度观测-具有零自由参数的基准Rossiter-McLaughlin曲线

Radial velocity observations of the 2015 Mar 20 eclipse - A benchmark Rossiter-McLaughlin curve with zero free parameters

Ansgar Reiners, Ulrike Lemke, Florian Bauer, Benjamin Beeck, Philipp Huke

摘要:

2015年3月20日,我们在哥廷根天文物理研究所用太阳望远镜和FTS获得了159个太阳光谱,其中76个光谱是在日偏食期间拍摄的。我们获得的RV使用$I_2$作为波长参考,并确定RM曲线的峰-峰振幅几乎为1.4 km s $^{-1}$在典型的RV精度优于1 m s $^{-1}$。我们模拟磁盘集成太阳能RV使用表面速度,临边变暗,对流蓝移的信息从三维磁流体动力学模拟。我们确认,对流蓝移是至关重要的了解日食期间的太阳RV。我们最好的模型再现的观测结果的相对精度为10%,残差小于30 m s $^{-1}$。我们交叉检查参数化的速度场使用多普勒从太阳动力学天文台,并得出结论,磁盘集成的多普勒不提供正确的信息对流蓝移所需的MS $^{-1}$ RV工作。作为日食期间模拟RV的主要限制,我们确定了关于对流蓝移和线形作为太阳临边角函数的有限知识。我们怀疑,我们的模型线的轮廓是太浅,在肢体角大于$μ= 0.6$,导致不正确的加权的速度在整个太阳盘。其他的解释也不能被排除,比如在日食观测期间,磁区对流的抑制和未被发现的系统学。提出了精确观测日线剖面的建议。我们公布我们的RV采取日食期间作为基准曲线的代码计算RM效应和太阳表面速度和线轮廓的模型。

英文摘要:

On March 20, 2015, we obtained 159 spectra of the Sun as a star with the solar telescope and the FTS at the Institut für Astrophysik Göttingen, 76 spectra were taken during partial solar eclipse. We obtained RVs using $I_2$ as wavelength reference and determined the RM curve with a peak-to-peak amplitude of almost 1.4 km s$^{-1}$ at typical RV precision better than 1 m s$^{-1}$. We modeled disk-integrated solar RVs using surface velocities, limb darkening, and information about convective blueshift from 3D magneto-hydrodynamic simulations. We confirm that convective blueshift is crucial to understand solar RVs during eclipse. Our best model reproduced the observations to within a relative precision of 10% with residuals less than 30 m s$^{-1}$. We cross-checked parameterizations of velocity fields using a Dopplergram from the Solar Dynamics Observatory and conclude that disk-integration of the Dopplergram does not provide correct information about convective blueshift necessary for m s$^{-1}$ RV work. As main limitation for modeling RVs during eclipses, we identified limited knowledge about convective blueshift and line shape as functions of solar limb angle. We suspect that our model line profiles are too shallow at limb angles larger than $μ= 0.6$ resulting in incorrect weighting of the velocities across the solar disk. Alternative explanations cannot be excluded like suppression of convection in magnetic areas and undiscovered systematics during eclipse observations. Accurate observations of solar line profiles across the solar disk are suggested. We publish our RVs taken during solar eclipse as a benchmark curve for codes calculating the RM effect and for models of solar surface velocities and line profiles.

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