超越太阳：我时钟中跳动的磁性心脏
Far beyond the Sun: I. The beating magnetic heart in Horologium
摘要：
毕星团的前成员$ι$ Horolosium（$ι$ Hor）是一颗类太阳恒星，拥有迄今为止已知最短的日冕活动周期（$P_{\rm cyc}\sim$ 1.6年）。$ι$ Hor的年龄为$\sim$ $625$ Myr，也是最年轻的恒星。对它的磁性的研究有可能为理解晚型恒星的周期活动和恒星磁性的起源提供基础信息。在这一系列的文章中，我们提出了一个综合项目的结果，旨在研究演变的磁场在这颗恒星，以及这种演变如何影响其周边环境。本文总结了这项调查的第一阶段，从长期观测活动的$ι$霍尔使用地面高分辨率分光偏振仪的结果。分析包括对恒星的磁活动和径向速度的精确测量，以及它们的多个时间尺度的变化。结合文献中报道的数值，我们表明，长期的色球活动演变的$ι$霍尔遵循的拍频模式，由两个周期性信号的叠加，类似的振幅在$P_{1} \simeq 1.97 \pm 0.02$年和$P_{2} \simeq 1.41 \pm 0.01$年。此外，使用最新的参数$ι$ Hor b结合我们的活动和径向速度测量，我们发现，恒星活动占主导地位的径向速度残差，使在这个系统中的其他行星的检测具有挑战性。最后，我们在这里报告的第一次测量的表面纵向磁场强度的$ι$霍尔，它显示不同的幅度内$\pm4$ G和担任估计的旋转周期的恒星（$P_{\rm rot} =~7.70^{+0.18}_{-0.67}$ d）。
英文摘要：
A former member of the Hyades cluster, $ι$ Horologii ($ι$ Hor) is a planet-hosting Sun-like star which displays the shortest coronal activity cycle known to date ($P_{\rm cyc}\sim$ 1.6 yr). With an age of $\sim$$625$ Myr, $ι$ Hor is also the youngest star with a detected activity cycle. The study of its magnetic properties holds the potential to provide fundamental information to understand the origin of cyclic activity and stellar magnetism in late-type stars. In this series of articles, we present the results of a comprehensive project aimed at studying the evolving magnetic field in this star and how this evolution influences its circumstellar environment. This paper summarizes the first stage of this investigation, with results from a long-term observing campaign of $ι$ Hor using ground-based high-resolution spectropolarimetry. The analysis includes precise measurements of the magnetic activity and radial velocity of the star, and their multiple time-scales of variability. In combination with values reported in the literature, we show that the long-term chromospheric activity evolution of $ι$ Hor follows a beating pattern, caused by the superposition of two periodic signals of similar amplitude at $P_{1} \simeq 1.97 \pm 0.02$ yr and $P_{2} \simeq 1.41 \pm 0.01$ yr. Additionally, using the most recent parameters for $ι$ Hor b in combination with our activity and radial velocity measurements, we find that stellar activity dominates the radial velocity residuals, making the detection of additional planets in this system challenging. Finally, we report here the first measurements of the surface longitudinal magnetic field strength of $ι$ Hor, which displays varying amplitudes within $\pm4$ G and served to estimate the rotation period of the star ($P_{\rm rot} =~7.70^{+0.18}_{-0.67}$ d).
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