Blue large-amplitude pulsators (BLAPs) are a recently discovered class of pulsating star, believed to be proto-white dwarfs, produced by mass stripping of a red giant when it has a small helium core. An outstanding question is why the stars in this class of pulsator seem to form two distinct groups by surface gravity, despite predictions that stars in the gap between them should also pulsate. We use a binary population synthesis model to identify potential evolutionary pathways that a star can take to become a BLAP. We find that BLAPs can be produced either through common envelope evolution or through Roche lobe overflow, with a main-sequence star or an evolved compact object being responsible for the envelope stripping. The mass distribution of the inferred population indicates that fewer stars would be expected in the range of masses intermediate to the two known groups of pulsators, suggesting that the lack of observational discoveries in this region may be a result of the underlying population of pre-white dwarf stars. We also consider metallicity variation and find evidence that BLAPs at Z = 0.010 (half-solar) would be pulsationally unstable and may also be more common. Based on this analysis, we expect the Milky Way to host around 12 000 BLAPs and we predict the number density of sources expected in future observations such as the Legacy Survey of Space and Time at the Vera Rubin Observatory.

中文翻译：

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蓝色大振幅波轮的二元演化路径

蓝色大振幅脉动 (BLAP) 是最近发现的一类脉动恒星，被认为是原白矮星，是由具有小氦核的红巨星大规模剥离而产生的。一个悬而未决的问题是为什么这类脉动中的恒星似乎通过表面引力形成了两个不同的群体，尽管预测它们之间的间隙中的恒星也应该脉动。我们使用二元种群综合模型来识别恒星可以采取的潜在进化途径成为 BLAP。我们发现 BLAP 可以通过普通包络演化或罗氏瓣溢出产生，主序星或演化致密天体负责包络剥离。推断种群的质量分布表明，在两个已知的脉动群之间的质量范围内，预计恒星数量较少，这表明该区域缺乏观测发现可能是由于潜在的白前种群矮星。我们还考虑了金属丰度的变化，并发现证据表明 Z = 0.010（半太阳）的 BLAP 将是脉动不稳定的，并且可能更常见。基于这一分析，我们预计银河系将拥有大约 12,000 个 BLAP，我们预测未来观测（例如维拉鲁宾天文台的时空遗产调查）中预期的源数量密度。这表明该地区缺乏观测发现可能是由于潜在的前白矮星种群所致。我们还考虑了金属丰度的变化，并发现证据表明 Z = 0.010（半太阳）的 BLAP 将是脉动不稳定的，并且可能更常见。基于这一分析，我们预计银河系将拥有大约 12,000 个 BLAP，我们预测未来观测（例如维拉鲁宾天文台的时空遗产调查）中预期的源数量密度。这表明该地区缺乏观测发现可能是由于潜在的前白矮星种群所致。我们还考虑了金属丰度的变化，并发现证据表明 Z = 0.010（半太阳）的 BLAP 将是脉动不稳定的，并且可能更常见。基于这一分析，我们预计银河系将拥有大约 12,000 个 BLAP，我们预测未来观测（例如维拉鲁宾天文台的时空遗产调查）中预期的源数量密度。