盘介导的角动量输运解决了旋转双星系统中的质量增积问题
Disc-mediated angular momentum transport resolves the mass-gain problem in rotating binaries
- University of Cambridge（剑桥大学）
- University of Geneva（日内瓦大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究提出盘介导角动量输运模型，解决旋转双星中质量增积问题，使吸积星在临界旋转下仍能高效吸积，效率达0.4-1，与观测相符。
AI中文摘要：
大部分恒星在其生命周期中会与一个近距离伴星相互作用，在此过程中，质量和角动量的转移塑造了它们的演化和最终命运。标准的旋转受限吸积模型预测，吸积星在仅获得其质量的一小部分后便达到临界旋转，从而严重抑制了进一步的吸积。这与需要大量质量增积的相互作用后系统的观测结果相矛盾。我们引入了一种针对恒星伴星质量转移的盘介导角动量输运方案。该方案基于一种新颖的微扰解析星-盘边界模型，该模型允许在吸积星接近临界旋转时继续质量流入。此外，该模型重现了先前的数值结果，即对超临界旋转的扰动导致盘施加负扭矩，在允许持续质量流入的同时提取多余的角动量。我们使用MESA在详细的双星演化计算中实现了这一机制，并考虑了差分旋转，计算了覆盖主星质量、轨道周期和质量比的网格。旋转受限模型预测$\beta_{\rm eff}\lesssim 0.1$，而盘模型在接近临界旋转时产生持续的质量流入，在大部分参数空间内有效质量转移效率为$\beta_{\rm eff}\sim 0.4$-$1$。由此产生的吸积星性质与观测到的相互作用后sdOB+Be双星系统大体一致。因此，盘介导的角动量输运可能代表了标准双星演化模型中一个关键缺失的要素，对快速旋转恒星和致密天体前身星具有重要意义。
英文摘要：
A large fraction of stars interact with a close companion during their lifetime, in which the transfer of mass and angular momentum shapes their evolution and final fate. Standard rotationally limited accretion models predict that accretors reach critical rotation after gaining only a small fraction of their mass, severely suppressing further accretion. This is in tension with observations of post-interaction systems that require substantial mass gain. We introduce a disc-mediated angular momentum transport prescription for mass-transfer onto stellar companions. This is based on a novel perturbative, analytic star-disc boundary model that allows for continued mass inflow as the accretor approaches critical rotation. Furthermore, the model reproduces previous numerical results in which perturbations to super-critical rotation result in negative torques exerted by the disc, extracting excess angular momentum while allowing continued mass inflow. We implement this mechanism in detailed binary evolution calculations with differential rotation using MESA, and compute grids spanning primary mass, orbital period, and mass ratio. Whereas rotationally limited models predict $β_{\rm eff}\lesssim 0.1$, the disc model yields sustained mass inflow near critical rotation, with effective mass-transfer efficiencies of $β_{\rm eff}\sim 0.4$-$1$ across much of the parameter space. The resulting accretor properties are broadly consistent with observed post-interaction sdOB+Be binaries. Disc-mediated angular momentum transport may therefore represent a key missing ingredient in standard binary evolution models, with important implications for rapidly rotating stars and compact-object progenitors.
