标题： BH-BH 合并有无电磁对应物：分层三体系统中稳定第三体质量转移的模型 显示英文标题

标题： BH-BH mergers with & without EM counterpart: A model for stable tertiary mass transfer in hierarchical triple systems

摘要： 三合星在观测到的恒星群体中很普遍。 与双星相比，它们的演化明显更复杂，受到独特的动力学、潮汐和质量转移过程的影响。 理解这些现象对于全面了解多星演化以及能量爆发事件的形成，包括引力波合并，是至关重要的。 我们的研究探讨了当第三颗恒星充满其洛希瓣并向内部双星转移质量时，三合星系统的演化，这可能形成具有独特特性的引力波源。 我们为经历来自第三颗恒星稳定质量转移的分层三合星开发了一个解析模型。 使用群体合成模拟，我们研究了第三颗恒星充满洛希瓣且内部双星为黑洞的三合星系统。 这些系统起源于经历化学均匀演化的内部双星。 我们的分析包括金属丰度为Z=0.005和Z=0.0005的群体，重点关注初始质量为20至100 M_sun的主成分，以及内部和外部轨道分离度分别高达40 R_sun和10^5 R_sun的系统。 我们的结果表明，质量转移主要导致内部双星轨道收缩、非零偏心率以及外部轨道扩张。 在具有CHE内部双星的系统中，9.5%会导致第三颗恒星向内部BBH转移质量。 我们预测引力波合并的形成效率很高，在Z=0.005时范围为85.1%到100%，在Z=0.0005时为100%，且延迟时间较短。 局部合并率预计在0.69到1.74 Gpc^-3 yr^-1之间。 其中一部分BBH合并进入LISA和aLIGO频率带，可能仍在吸积气体，可能产生强烈的电磁对应信号。 EM信号根据模型假设变化很大，如果允许环双星盘形成，其范围从小于0.03%到46.8%的所有合并。 显示英文摘要

摘要： Triple stars are prevalent within the population of observed stars. Their evolution, compared to binaries, is notably more complex, influenced by unique dynamical, tidal, and mass transfer processes. Understanding these phenomena is essential for a comprehensive insight into multistar evolution and the formation of energetic transients, including gravitational-wave mergers. Our study probes the evolution of triple star systems when the tertiary fills its Roche lobe and transfers mass to the inner binary, potentially forming GW sources with distinct properties. We develop an analytical model for hierarchical triples undergoing stable mass transfer from the tertiary. Using population synthesis simulations, we investigate triples with a Roche-lobe filling tertiary and an inner binary black hole. These systems originate from inner binaries undergoing chemically homogeneous evolution. Our analysis includes populations with metallicities of Z=0.005 and Z=0.0005, focusing on primary components with initial masses of 20 to 100 M_sun, and inner and outer orbital separations up to 40 R_sun and 10^5 R_sun, respectively. Our results show that mass transfer predominantly leads to orbital shrinkage of the inner binary, non-zero eccentricities, and expansion of the outer orbit. Among systems with CHE inner binaries, 9.5% result in mass transfer from the tertiary onto an inner BBH. We predict high formation efficiency of GW mergers, ranging from 85.1% to 100% at Z=0.005 and 100% at Z=0.0005, with short delay times. Local merger rates are projected to be between 0.69 to 1.74 Gpc^-3 yr^-1. A fraction of these BBH mergers, entering the LISA and aLIGO frequency bands, may still be accreting gas, potentially producing a strong electromagnetic counterpart. EM signals vary significantly based on model assumptions, ranging from less than 0.03% to 46.8% of all mergers if circumbinary disk formation is allowed.