The recent gravitational-wave merger event, GW190521, has challenged our understanding of stellar-mass black hole (BH) formation. The primary and secondary BHs are both inferred to fall inside the pair-instability (PI) mass gap. Here we propose that the formation of such binaries is possible through gas accretion onto the BH remnants of Population III stars born in high-redshift (z>10) minihalos. Once the parent halo has grown to the atomic-cooling limit, even brief episodes of gas accretion in the dense central regions of the halo can increase the masses of Population III remnant BHs above the PI limit. Starting with a binary black hole (BBH) with an initial mass of O(100) M _⊙ we find that it would only need to spend about 100Myr in the inner few parsecs of an atomic-cooling halo to accrete about 50M _⊙ of material and resemble a system similar to GW190521. The dynamical friction timescale for the binary to sink to the dense inner region of its parent halo is comparable or shorter than the accretion timescale required to increase their mass above the PI limit. Once in the core of the halo, the binary can enter a phase of hyper-Eddington accretion, where it would only take a few thousand years to exceed the PI limit through accretion. Even more massive BBHs could form through this channel, and be detectable by detectors with improved low-frequency sensitivity. Single Population III BH remnants would also grow through accretion and could later form binaries dynamically. As little as a few percent of Population III BH remnants may be sufficient to match the rate of massive BBH mergers inferred from GW190521 of .

最近的重力波合并事件GW190521挑战了我们对恒星质量黑洞（BH）形成的理解。主要和次要BH均被推断为落入配对不稳定性（PI）质量差距之内。在这里，我们建议通过气体积聚到高红移（z > 10）微晕中出生的种群III恒星的BH残余物上形成这种双星是可能的。一旦母体的光环增长到原子冷却极限，即使在光环的密集中心区域出现短暂的气体积聚，也可以使III号族残留BH的质量增加到PI极限以上。与二进制黑洞（BBH），用O（100）的初始质量开始中号 _⊙我们发现，这将只需要在原子冷却光环的内几秒差距大约要花100Myr到共生约50中号 _⊙的材料，类似于GW190521的系统。二元沉没到其母体晕的稠密内部区域的动摩擦时标与将其质量增加到PI极限以上所需的吸积时标相当或更短。一旦进入光环的核心，二进制文件就可以进入超爱丁顿增生阶段，在此阶段，通过增生超过PI限制仅需几千年。更大的BBH可能通过此通道形成，并且可以被具有改进的低频灵敏度的检测器检测到。单一种群III BH残留物也会通过吸积而增长，并且以后可以动态形成二进制。仅有百分之三的BH人口剩余可能足以匹配从GW190521推断的BBH大规模合并的速度。