Stellar and Solar Magnetic Activity Cycles

该计划是洛厄尔天文台太阳-恒星摄谱仪（SSS）项目的延续。它的目的是在三个基本时间尺度上更好地了解冷恒星的活动：活动周期（以年为单位）、旋转（以月为单位）和短期（以天为单位）。SSS光谱仪涵盖了几个重要的色球诊断线，包括Ca II H&amp；K和Ha，以及5000-9000 A的大部分光谱。它是一种专用仪器，与洛厄尔天文台的1.1米望远镜有关。它通过光纤馈送接收星光，但也配备了一个单独的光纤馈送，将太阳视为一个未解析的圆盘。因此，阳光和星光的记录是一致的。PI计划通过以下方式研究SSS光谱：[1]对响应太阳和恒星活动的光谱线中涌现通量的时间序列观测揭示了存在的活动周期的相位、幅度和形态。SSS的目标列表包括位于主序上太阳位置附近的恒星（大致光谱类型为F5 - K7），重点是与太阳非常相似的最低进化恒星，以及太阳本身对太阳和恒星的季节变化的研究揭示了旋转调制的程度——发射水平的变化不是由活动周期引起的，而是由活动区域穿过可见半球引起的光谱间的变异性，通过相关光谱线的广泛集合进行检查，揭示了太阳和恒星活动在短期和长期时间尺度上的变化。提议者目前正在观察太阳和大约100颗特别有趣的恒星（从最初调查的大约300颗恒星中选出）。他们的数据库包括自1994年以来大约1000天内记录的大约3000次太阳观测，以及16,000个恒星光谱。提出的太阳时间序列从第22周期的衰退期到第23周期的衰退期。周期性和长期的活动在他们的许多目标恒星中都是明显的，包括许多现在已经停止活动的香港威尔逊山天文台项目。需要进一步的观测来研究周期过程中不同时间尺度上的恒星活动——特别是那些现在由希巴谷天体测量（以及地面光谱和光度测定）确定为低活动、未进化的“太阳双胞胎”候选恒星。

The proposed program is a continuation of the Solar-Stellar Spectrograph (SSS) project at Lowell Observatory. Its purpose is to provide a better understanding of activity in cool stars on three essential timescales: activity-cyclic (on the order of years), rotational (months), and short-term (days). The SSS spectrograph covers several important chromospheric diagnostic lines, including Ca II H&K and Ha, as well as most of the optical spectrum from 5000-9000 A. It is a dedicated instrument, associated with Lowell Observatory's 1.1-m telescope. It receives starlight via a fiber optic feed, but is also equipped with a separate fiber feed that sees the Sun as an unresolved disk. Sunlight and starlight are therefore recorded identically. The PI proposes to study SSS spectra in the following ways:[1] Time series observations of the emergent flux in spectral lines responsive to solar and stellar activity reveals the phase, amplitude, and morphology of activity cycles present. The SSS target list includes stars lying near the Sun's location on the main sequence (roughly spectral types F5 - K7), with emphasis on minimally evolved stars very similar to the Sun, as well as the Sun itself.[2] Examination of seasonal variability for the Sun and stars reveals the degree of rotational modulation - the change in emission level arising not from the activity cycle, but from the passage of active regions across the visible hemispheres.[3] The spectrum-to-spectrum variability, examined across a broad ensemble of related spectral lines, reveals changes in solar and stellar activity on both short and long timescales.The proposers are currently observing the Sun and approximately 100 particularly interesting stars (selected from about 300 stars initially surveyed). Their database comprises approximately 3000 observations of the Sun recorded over roughly 1000 days since 1994, as well as 16,000 stellar spectra. The proposers' solar time series runs from the declining phase of Cycle 22 to the declining phase of Cycle 23. Cyclic and long-term activity is apparent in many of their stellar targets, including a large number included in the now inactive Mount Wilson Observatory HK project. Further observations are required to study stellar activity on various timescales over the course of the cycles -- in particular, those stars now identified from Hipparcos astrometry (and from ground-based spectroscopy and photometry) as low-activity, unevolved, "solar twin" candidates.