A volume-limited sample of hot subdwarf stars

热亚矮星（sdO/Bs）构成了一个突出的暗淡蓝色恒星群。它们的形成尚不清楚，因为只有当原始恒星在经过红巨星分支后几乎完全失去外壳时，它们才能形成。二元相互作用可能在解释这种质量损失方面发挥了重要作用，并提出了几种形成情景。根据不同形成情景计算的演化轨迹通常与观测到的热亚矮星样本进行比较。然而，由于迄今为止所有观测样本的不完全性和非均匀性，这种模型与观测数据之间的比较总是受到相当严重的选择效应的影响。在这里，我们建议编制第一个完整的、体积有限的热亚矮星样本，以消除这些选择效应，并对进化情景施加更强的约束。完整的样品将被光谱观察，数据分析管道将被开发和测试，为将来的大型光谱调查做准备。

Hot subdwarf stars (sdO/Bs) constitute a prominent population of faint blue stars. Their formation is still unclear, because they can only be formed if the progenitor star loses its envelope almost entirely after passing the red-giant branch. Binary interactions likely play an important role to explain this mass loss and several formation scenarios have been proposed. Evolutionary tracks calculated for the diverse formation scenarios are usually compared to observed samples of hot subdwarf stars. However, this comparison between models and observational data is always biased by quite severe selection effects due to the incompleteness and inhomogeneity of all the observed samples so far. Here we propose to compile the first complete, volume-limited sample of hot subdwarfs to eliminate those selection effects and put much stronger constraints on evolutionary scenarios. The complete sample will be observed spectroscopically and a data analysis pipeline will be developed and tested to prepare for the large spectroscopic surveys in the future.