Title: The Göttingen Solar Radial Velocity Project: Sub-m/s Doppler precision from FTS observations of the Sun as a star Show Chinese title

Title: 哥廷根太阳径向速度项目：从太阳作为恒星的FTS观测中获得亚米每秒的多普勒精度

Abstract: Radial velocity observations of stars are entering the sub-m/s domain revealing fundamental barriers for Doppler precision experiments. Observations of the Sun as a star can easily overcome the m/s photon limit but face other obstacles. We introduce the G\"ottingen Solar Radial Velocity Project with the goal to obtain high precision (cm/s) radial velocity measurements of the Sun as a star with a Fourier Transform Spectrograph. In this first paper, we present the project and first results. The photon limit of our 2 min observations is at the 2 cm/s level but currently limited by strong instrumental systematics. A drift of a few m/s per h is visible in all observing days probably caused by vignetting of the solar disk in our fiber coupled setup, and imperfections of our guiding system adds further offsets in our data. Binning the data into 30 min groups shows m/s stability after correcting for a daily and linear instrumental trend. Our results show the potential of Sun-as-a-star radial velocity measurements that can possibly be achieved after a substantial upgrade of our spectrograph coupling strategy. Sun-as-a-star observations can provide crucial empirical information about the radial velocity signal of convective motion and stellar activity, and on the wavelength dependence of radial velocity signals caused by stellar line profile variations. Show Chinese abstract

Abstract: 恒星的径向速度观测正在进入亚毫秒/秒领域，揭示了多普勒精度实验的基本障碍。 作为恒星的太阳观测可以轻松克服毫秒/秒的光子极限，但面临其他障碍。 我们介绍了哥廷根太阳径向速度项目，旨在通过傅里叶变换光谱仪获得高精度（厘米/秒）的太阳径向速度测量结果。 在本文的第一篇中，我们介绍了该项目和初步结果。 我们2分钟观测的光子极限在2厘米/秒水平，但目前受强仪器系统误差限制。 在所有观测日中可见每小时几毫秒/秒的漂移，可能是由于我们光纤耦合设置中太阳盘的渐晕效应，以及我们导星系统的不完善进一步增加了数据中的偏移。 将数据分组为30分钟的组后，在校正了每日和线性仪器趋势后显示出毫秒/秒的稳定性。 我们的结果表明，经过对光谱仪耦合策略的重大升级后，太阳作为恒星的径向速度测量具有潜在的可能性。 太阳作为恒星的观测可以提供关于对流运动和恒星活动的径向速度信号以及由恒星线轮廓变化引起的径向速度信号波长依赖性的关键实证信息。