Stellar and Solar Magnetic Activity Cycles

研究人员将在三个基本的时间尺度上更好地了解冷恒星的活动：活动周期（数量级年），旋转（月）和短期（天）。主要的努力是继续目前正在洛厄尔天文台进行的太阳-恒星摄谱仪（SSS）项目。SSS光谱仪非常适合这项任务。它涵盖了几个重要的色球诊断线，包括Ca II H和K和H α，以及波长从5000到9000埃的大部分光谱。它是一种专用仪器，与洛厄尔天文台的1.1米约翰霍尔望远镜有关，该望远镜通过光纤馈送接收望远镜焦平面上的星光，但也配备了太阳能“望远镜”——一种原始纤维，将太阳视为一个未解析的圆盘。因此，阳光和星光通过相同的光学器件和探测器被记录下来——这是一个独特的优势。这样记录下来的光谱可以用几种方法来研究。响应太阳和恒星活动的光谱线中涌现的通量的时间序列观测揭示了活动周期的相位、幅度和形态。SSS的目标星表包括位于主序星上太阳位置附近的所有亮度超过7.1等的恒星（光谱类型大致为F5到K7，重点在F8和G8之间），以及太阳本身。对季节变率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。这提供了关于伴随各种振幅和形态周期的色球活动程度的见解。通过相关光谱线的广泛集合检查光谱到光谱的变化，揭示了太阳和恒星活动在短时间尺度和长时间尺度上的变化。这是一种解释太阳和恒星活动的新方法，是为这个项目开发的，将在拟议的拨款周期中充分利用。

The investigators will provide a better understanding of activity in cool stars on three essential timescales: activity-cycle (of order years), rotational (months), and short-term (days). The main effort is to continue the Solar-Stellar Spectrograph (SSS) project currently underway at Lowell Observatory. The SSS spectrograph is well suited for this task. It covers several important chromospheric diagnostic lines, including Ca II H and K and H alpha, as well as most of the optical spectrum from wavelengths 5000 to 9000 angstroms. It is a dedicated instrument, associated with Lowell Observatory's 1.1-meter John Hall telescope, which receives starlight from the telescope focal plane via a fiber-optic feed, but is also equipped with a solar "telescope" -- a raw fiber that sees the Sun as an unresolved disk. Sunlight and starlight are therefore recorded via the same optics and detectors -- a unique advantage. The spectra thus recorded can be studied in several ways. 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 all stars brighter than visual magnitude 7.1 lying near the Sun's location on the main sequence (roughly spectral types F5 through K7, with emphasis between F8 and G8), as well as the Sun itself. Examination of seasonal variability 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. This provides insights regarding the degree of chromospheric activity that accompanies cycles of various amplitudes and morphologies. 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. This is a new method of interpreting solar and stellar activity, developed for this project that will be fully exploited in the proposed grant cycle.