AI 中文总结
本研究针对银河系双中子星偏心率分布的双峰间隙问题，提出前身星与中子星质量非单调关系且第二代中子星诞生 kick 足够小的机制，通过COMPAS代码模拟可重现观测分布，为解释相关观测提供自然途径。
AI 中文摘要
通过脉冲星计时探测银河系双中子星（DNS）为研究大质量恒星及双星演化提供了独特契机。观测到的DNS群体呈现出明显的双峰偏心率分布，在测得的中间偏心率范围$0.4 \rsim e_{\rm m} \rsim 0.58$内不存在相关系统，其起源尚不明确。我们提出，若前身星质量与中子星（NS）质量的关系为非单调关系，且第二代中子星获得的诞生 kick 足够小，这一可能的间隙可自然产生。我们使用群体合成代码COMPAS阐释该情景，发现我们的DNS群体模型能较好地重现观测到的轨道周期-偏心率分布，包括明显的双峰特征。尽管需要更大的观测样本以得出更可靠的结论，我们的结果表明该模型为解释当前银河系DNS的观测结果提供了一条自然途径，该途径通过孤立双星演化实现。
英文摘要
The detection of Galactic double neutron stars (DNSs) through pulsar timing offers a unique opportunity to probe massive stellar and binary evolution. The observed DNS population exhibits an apparently bimodal eccentricity distribution, with an absence of systems at measured intermediate eccentricities, $0.4 \lesssim e_{\rm m} \lesssim 0.58$, whose origin remains unclear. We propose that this possible gap can arise naturally if the relationship between the progenitor masses and neutron star (NS) masses is non-monotonic, provided that the second-born NS receives a sufficiently small natal kick. We illustrate this scenario using the population synthesis code COMPAS, and find that our DNS population model can reproduce the observed orbital period-eccentricity distribution relatively well, including the apparent bimodality. Although a larger observed sample is required to draw more robust conclusions, our results suggest that this model provides a natural pathway for explaining current observations of Galactic DNSs through isolated binary evolution.
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