来自稳定质量转移的黑洞自旋的多样分布
A Diverse Distribution of Black Hole Spins from Stable Mass Transfer
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中文总结 AI 辅助
该研究通过建模稳定质量转移双星的潮汐自旋提升，发现黑洞自旋分布多样，其与质量比呈反相关，或可解释GW190412，还讨论了未来需纳入的额外物理因素。
中文摘要 AI 辅助
引力波观测已发现超过300个并合双黑洞，但其起源仍不确定。近期研究表明，其中许多可能来自孤立恒星双星，其轨道通过稳定质量转移收缩。若此成立，它们的自旋或可区分该形成通道与其他路径。我们通过对经历稳定质量转移的双星进行详细建模，研究黑洞前身恒星的潮汐自旋提升。我们通过求解潮汐激发的振荡模式计算潮汐力矩，并预测由此产生的黑洞自旋。我们发现，黑洞自旋的多样分布受前身星质量转移历史的强烈影响：若双星仅经历A类或B类质量转移，可形成具有中等自旋（0.1≲χₑff≲0.3）的黑洞；前者在分离时可达到超同步状态，后者中供体通常仅被部分剥离，留下膨胀的包层，其中会激发强潮汐。若同时发生A类和AB类质量转移，产生的黑洞自旋几乎可忽略。由于质量转移历史由质量比和初始双星周期共同决定，我们的结果预测黑洞自旋与质量比呈反相关，这与有限的观测证据一致。我们的结果还可能解释GW190412的情况——一个具有高质量比的中等自旋双星。我们讨论了方法的局限性，以及未来需纳入的额外物理因素（如非线性潮汐、C类和L2质量转移）。
英文摘要
Gravitational wave observations have found over 300 merging binary black holes, yet their origins remain uncertain. Recent work showed that many may come from isolated stellar binaries whose orbits shrink through stable mass transfer. If true, their spins may help to distinguish this channel from other formation pathways. We investigate the tidal spin up of black hole progenitor stars with detailed modeling of binaries undergoing stable mass transfer. We calculate the tidal torques by solving tidally excited oscillation modes and predict the resulting black hole spins. We find a diverse spin distribution strongly affected by the mass transfer histories of the progenitors. Binaries can form black holes with moderate spins ($0.1\lesssimχ_\mathrm{eff}\lesssim0.3$) if they only go through case A or case B mass transfer. In the former case, they can become super-synchronized upon detachment, while in the latter case, the donor is usually only partially stripped, leaving a puffy envelope where strong tides are excited. If both case A and case AB mass transfer occur, the resulting black hole spins are almost always negligible. As the mass transfer history is jointly determined by mass ratio and initial binary period, our results predict an anti-correlation between black hole spins and mass ratio, consistent with limited evidence from data. Our results can also potentially explain the case of GW190412, a moderately-spinning binary with a high mass ratio. We discuss the limitations of our methods and additional physics (e.g., nonlinear tides, case C, and L2 mass transfer) that need to be incorporated in future work.
