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arXiv 2303.08205astro-ph.SR
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IAG空间分辨太阳光谱图集:日面中心到边缘的观测

The IAG spectral atlas of the spatially resolved Sun: Centre-to-limb observations

M. Ellwarth, S. Schäfer, A. Reiners, M. Zechmeister

AI总结:

本研究利用哥廷根天体物理与地球物理研究所的傅里叶变换光谱仪,获取了高分辨率宁静太阳光谱,构建了含14个日心位置的日面中心到边缘光谱图集,为太阳大气、对流研究及视向速度相关观测提供参考。

摘要:

太阳表面的磁对流表现为米粒组织图案,会从谱线形状和波长两方面对谱线产生影响。由于观测角度不断变化,对应的观测高度也随之改变,这类诱发效应在观测到的太阳圆面上也往往会发生变化。对空间分辨太阳开展的日面中心到边缘观测,能够帮助我们了解不同日心观测位置下的光谱行为变化,提供与视向速度(RV)计算相关的临边昏暗、对流速度和谱线轮廓变化的关键信息。因此,视向速度测量和系外行星凌星光谱学都依赖精准的参考模板。我们旨在提供一份具有高光谱分辨率和高频精度的日面中心到边缘太阳光谱图集。该图集将有助于加深对太阳大气和对流过程的理解。我们使用位于哥廷根的天体物理与地球物理研究所的傅里叶变换光谱仪,对空间分辨的宁静太阳开展了高分辨率观测。我们的数据集覆盖4200Å到8000Å的波长范围,共包含165条光谱,光谱分辨率为Δν = 0.024cm⁻¹,对应在约6000Å处的分辨本领R为700000。我们发布了包含14个日心位置的日面中心到边缘太阳光谱图集。为验证一致性,我们研究了Fe I 约6175Å吸收线,并将我们的谱线轮廓与以往的日面中心到边缘观测结果以及模拟结果进行了对比。谱线轮廓和平分线轮廓总体上与以往的观测结果一致,但我们发现其与模型谱线轮廓存在差异,尤其是在靠近太阳边缘的区域。

英文摘要:

Solar surface magneto-convection appears as granulation pattern that impacts spectral lines in terms of both shape and wavelength. Such induced effects also tend to vary over the observed solar disc because of the changing observation angle and, thus, the changing observation height as well. Centre-to-limb observations of the resolved Sun offer an insight into the variable spectral behaviour across different heliocentric observing positions, providing crucial information about limb darkening, convective velocities, and line profile variability relevant to radial velocity (RV) calculations. Thus, RV measurements and exoplanet transit spectroscopy depend on precise reference templates. We want to provide a spectroscopic centre-to-limb solar atlas at high spectral resolution and high-frequency accuracy. The atlas shall help improve the understanding of the solar atmosphere and convection processes. We performed high-resolution observations of the resolved quiet Sun with a Fourier transform spectrograph at the Institut für Astrophysik und Geophysik in Göttingen. Our dataset contains a wavelength range from 4200Å to 8000Å. We obtained 165 spectra in total, with a spectral resolution of $Δν$ = 0.024cm$^{-1}$, corresponding to a resolving power $R$ of 700,000 at $\sim$6000Å. We present a centre-to-limb solar atlas containing 14 heliocentric positions. To check for consistency, we investigated the FeI ~6175Å absorption line and compared our line profiles with previous centre-to-limb observations and also with simulations. The line profile and also the bisector profiles are generally consistent with previous observations, but we have identified differences to model line profiles, especially close to the solar limb.

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