The recent detection of GW190521 stimulated ideas on how to populate the predicted black hole (BH) pair-instability (PI) mass gap. One proposal is the dynamical merger of two stars below the PI regime forming a star with a small core and an oversized envelope. We outline the main challenges this scenario faces to form one BH in the gap. In particular, the core needs to avoid growing during the merger, and the merger product needs to retain enough mass, including in the subsequent evolution, and at core collapse (CC). We explore this scenario with detailed stellar evolution calculations, starting with ad hoc initial conditions enforcing no core growth during the merger. We find that these massive merger products are likely to be helium-rich and spend most of their remaining lifetime within regions of instabilities in the Herzsprung–Russell diagram, such as luminous blue variable eruptions. An energetic estimate of the amount of mass loss neglecting the back reaction of the star suggests that the total amount of mass that can be removed at low metallicity is ≲1 M _⊙. This is small enough that at CC our models are retaining sufficient mass to form BHs in the PI gap similar to the recent ones detected by LIGO/Virgo. However, mass loss at the time of merger, the resulting core structure, and the mass loss at CC still need to be quantified for these models to confirm the viability of this scenario.

最近对 GW190521 的检测激发了关于如何填充预测的黑洞 (BH) 对不稳定性 (PI) 质量间隙的想法。一个提议是在 PI 范围以下的两颗恒星的动态合并，形成一颗具有小核心和超大包络的恒星。我们概述了这种情况在差距中形成一个 BH 所面临的主要挑战。特别是核心需要在合并过程中避免增长，合并产品需要保留足够的质量，包括在随后的演变中，以及核心崩溃（CC）。我们通过详细的恒星演化计算来探索这种情况，从在合并期间强制没有核心增长的临时初始条件开始。我们发现这些大规模的合并产物很可能富含氦气，并且在赫兹普朗-罗素图中的不稳定性区域内度过剩余生命的大部分时间，如夜光蓝变喷发。忽略恒星逆反应的质量损失量的能量估计表明，在低金属丰度下可以去除的质量总量为 ≲1中号 _⊙。这足够小，以至于在 CC 我们的模型保留了足够的质量以在 PI 间隙中形成 BH，类似于最近由 LIGO/Virgo 检测到的 BH。然而，合并时的质量损失、由此产生的核心结构和 CC 处的质量损失仍然需要对这些模型进行量化，以确认这种情况的可行性。