We present the results of long-term spectral monitoring of yellow hypergiants (YHGs) of northern hemisphere with a R ≥ 60 000 resolution. The spectra of these F–G stars of extreme luminosity, compactly located at the top of the Hertzsprung–Russell diagram revealed a variety of spectral features: various types of Hα profile, the presence (or absence) of forbidden and permitted emissions, as well as circumstellar components. Variability of spectral features of various nature is studied. Absolute luminosity, circumstellar envelope expansion rate and amplitude of pulsations are determined. The reliability of the YHG status for V1427 Aql is confirmed; manifestations of a significant dynamic instability of the upper layers of the atmosphere of ρ Cas after the 2017 ejection and stratification of its gas envelope are registered; the lack of companion in the system of the V509 Cas hypergiant is proven; a conclusion is made that the V1302 Aql hypergiant is approaching the low-temperature boundary of the Yellow Void.

中文翻译：

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黄色超人家庭的团结与多样性

我们提出的北半球用的黄特超巨星（YHGs）的长期频谱监测结果ř ≥60 000分辨率。这些极度发光的F–G星的光谱紧紧地位于赫兹普隆–罗素图的顶部，揭示了多种光谱特征：各种类型的Hα分布，存在（或不存在）禁止和允许的发射，如以及星际成分。研究了各种性质的光谱特征的可变性。确定绝对光度，星际包络线膨胀率和脉动幅度。确认了V1427 Aql的YHG状态的可靠性；大气层ρ的显着动态不稳定性的体现在2017年卡斯（Cas）弹射后对其气包层进行了分层登记; 事实证明，V509 Cas超大型系统中缺少同伴；结论是V1302 Aql超巨型设备已接近黄空的低温边界。