太阳和恒星光谱中的“终极”信息内容：光球线不对称和波长偏移
'Ultimate' Information Content in Solar and Stellar Spectra: Photospheric line asymmetries and wavelength shifts
摘要：
光谱线不对称和波长偏移是太阳和恒星大气中流体动力学的特征。理论可以精确地预测理想化的谱线，但观测到的光谱受到混合物、太少合适的谱线、不精确的实验室波长和仪器缺陷的限制。目标：二等分线和位移提取，直到最高质量的太阳和恒星光谱的“最终”精度限制，以了解恒星物理，观测技术和实验室数据的限制。方法：对太阳和明亮的太阳型恒星的光谱图集进行了检查，以获得具有最准确的实验室波长的数千条“未混合”线，产生平分线和偏移，作为类似线组的平均值，从而最大限度地减少光度噪声和随机混合的影响。研究结果：对于太阳光谱，平分线的形状和位移提取以前很少研究的物种（铁II，钛I，钛II，铬II，钙I，C I），使用最近确定的非常准确的实验室波长。在南河三和其他F型恒星中，光谱连续区附近的平分线向蓝弯曲，揭示了向上移动的光球颗粒中的线饱和和阻尼翼。由“天体物理学”噪声、有限的仪器分辨率、叠加的大地吸收和不准确的波长所设定的精确度限制，共同将绝对线移研究限制在大约50-100 m/s。结论：分辨率R = 300，000的光谱学将使许多恒星的平分线研究成为可能。规避线混合和旋转涂抹配置文件中的天体物理噪声的剩余限制，最终可能需要跨空间分辨恒星盘光谱。
英文摘要：
CONTEXT: Spectral-line asymmetries and wavelength shifts are signatures of hydrodynamics in solar and stellar atmospheres. Theory may precisely predict idealized lines, but observed spectra are limited by blends, too few suitable lines, imprecise laboratory wavelengths, and by instrumental imperfections. AIMS: Bisectors and shifts are extracted until the 'ultimate' accuracy limits in highest-quality solar and stellar spectra, to understand limits set by stellar physics, observational techniques, and limitations in laboratory data. METHODS: Spectral atlases of the Sun and bright solar-type stars were examined for thousands of 'unblended' lines with the most accurate laboratory wavelengths, yielding bisectors and shifts as averages over groups of similar lines, thus minimizing effects of photometric noise and of random blends. RESULTS: For solar spectra, bisector shapes and shifts were extracted for previously little-studied species (Fe II, Ti I, Ti II, Cr II, Ca I, C I), using recently determined very accurate laboratory wavelengths. In Procyon and other F-type stars, a blueward bend in the bisector near the spectral continuum reveals line saturation and damping wings in upward-moving photospheric granules. Accuracy limits set by 'astrophysical' noise, finite instrumental resolution, superposed telluric absorption, and inaccurate wavelengths, together limit absolute lineshift studies to approximately 50-100 m/s. CONCLUSIONS: Spectroscopy with resolutions R = 300,000 will enable bisector studies for many stars. Circumventing remaining limits of astrophysical noise in line-blends and rotationally smeared profiles may ultimately require spectroscopy across spatially resolved stellar disks.
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