Young star clusters are likely the most common birthplace of massive stars across cosmic time and influence the formation of compact binaries in several ways. Here, we simulate the formation of black hole -- neutron star binaries (BHNSs) in young star clusters, by means of the binary population synthesis code \texttt{MOBSE} interfaced with the $N$-body code \texttt{NBODY6++GPU}. BHNSs formed in young star clusters (dynamical BHNSs) are significantly more massive than BHNSs formed from isolated binaries (isolated BHNSs): $\sim{}40$~\% of the dynamical BHNS mergers have total mass $>15$ M$_\odot$, while only $\sim{}0.01$~\% of the isolated BHNS mergers have mass in excess of this value. Hence, our models strongly support a dynamical formation scenario for GW190814, given its total mass $\sim{}26$ M$_\odot$, if this event is a BHNS merger. All our dynamical BHNSs are ejected from their parent star cluster before they reach coalescence. Thus, a significant fraction of BHNS mergers occurring in the field might have originated in a young star cluster. The mass spectrum of BHNS mergers from gravitational-wave detections will provide a clue to differentiate between dynamical and isolated formation of BHNSs.

中文翻译：

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年轻星团中黑洞-中子星双星动力学

年轻星团可能是整个宇宙时间中大质量恒星最常见的诞生地，并以多种方式影响致密双星的形成。在这里，我们通过与 $N$-body 代码 \texttt{NBODY6++ 接口的双星族合成代码 \texttt{MOBSE} 模拟黑洞——中子星双星（BHNSs）在年轻星团中的形成GPU}。在年轻星团中形成的 BHNS（动力 BHNS）比由孤立双星形成的 BHNS（孤立 BHNS）明显更大：$\sim{}40$~\% 的动力 BHNS 合并总质量 $>15$ M$_ \odot$，而只有 $\sim{}0.01$~\% 的孤立 BHNS 合并的质量超过该值。因此，我们的模型强烈支持 GW190814 的动态形成场景，如果该事件是 BHNS 合并，则考虑到其总质量 $\sim{}26$M$_\odot$。我们所有的动态 BHNS 在它们聚结之前都会从它们的母星团中弹出。因此，在该领域发生的很大一部分 BHNS 合并可能起源于年轻的星团。来自引力波探测的 BHNS 合并的质谱将为区分 BHNS 的动态形成和孤立形成提供线索。