北天极附近矮星的光谱
Spectroscopy of Dwarf Stars Around the North Celestial Pole
摘要：
新的空间飞行任务（例如，NASA-TESS和ESA-PLATO）将对天球大范围内的明亮恒星进行分析，寻找地外行星。天文地震观测将寻找具有类似太阳振荡的系外行星宿主恒星。为了实现所有的目标，一个完整的恒星物体的特性是很重要的。然而，只有不到30%的亮矮星的大气参数是准确的。在这项研究中，我们观测了所有明亮（V < 8等）和比F5光谱级更冷的矮星的高分辨率（R = 60，000）光谱，这些矮星位于天球最北端的区域，半径为20°，距离α（2000）= 161 $^\circ$ 03和δ（2000）= 86 $^\circ$ 60，这是初步的ESO-PLATO区域之一的中心。对140颗慢转恒星的光谱大气参数进行了测定，其中73%是首次测定。大多数（83%）被调查的恒星都在TESS天体列表中，所有这些恒星都在初步的PLATO场中。我们的结果与其他最近的研究相比，没有系统的差异。比较我们的结果与以前的高分辨率光谱测定的39颗恒星，我们发现只有7 $\pm$ 73 K的差异，0.02 $\pm$ 0.09的log g，和-0.02 $\pm$ 0.09 dex的金属丰度。我们还确定了基本的运动学和轨道参数为这个样本的恒星。从运动学的观点来看，我们几乎所有的恒星都属于银河系的薄盘子结构。推导出的银河系中心金属丰度梯度为-0.066 $\pm$ 0.024 dex/kpc（2.5σ显著性），垂直金属丰度梯度为-0.102 $\pm$ 0.099 dex/kpc（1σ显著性），符合最新的由内而外的薄盘形成模型，包括考虑恒星迁移的模型。
英文摘要：
New space missions (e.g., NASA-TESS and ESA-PLATO) will perform an analysis of bright stars in large fields of the celestial sphere searching for extraterrestrial planets. Asteroseismic observations will search for exoplanet-hosting stars with solar-like oscillations. In order to achieve all the goals, a full characterization of the stellar objects is important. However, accurate atmospheric parameters are available for less than 30% of bright dwarf stars of the solar neighborhood. In this study we observed high-resolution (R = 60,000) spectra for all bright (V < 8 mag) and cooler than F5 spectral class dwarf stars in the northern-most field of the celestial sphere with radius of 20° from the α(2000) = 161$^\circ$03 and δ(2000) = 86$^\circ$60 that is a center of one of the preliminary ESO-PLATO fields. Spectroscopic atmospheric parameters were determined for 140 slowly rotating stars, for 73% of them for the first time. The majority (83%) of the investigated stars are in the TESS object lists and all of them are in the preliminary PLATO field. Our results have no systematic differences when compared with other recent studies. Comparing our results for 39 stars with previous high-resolution spectral determinations, we find only a 7 $\pm$ 73 K difference in effective temperatures, 0.02 $\pm$ 0.09 in log g, and -0.02 $\pm$ 0.09 dex in metallicities. We also determined basic kinematic and orbital parameters for this sample of stars. From the kinematical point of view, almost all our stars belong to the thin disk substructure of the Milky Way. The derived galactocentric metallicity gradient is -0.066 $\pm$ 0.024 dex/kpc (2.5σ significance) and the vertical metallicity gradient is -0.102 $\pm$ 0.099 dex/kpc (1σ significance) that comply with the latest inside-out thin disk formation models, including those with stellar migration taken into account.
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