公共包层前吸积盘的三维模拟——II. 吸积效率与角动量输运
Three-dimensional simulations of accretion disks in pre-CE systems -- II. Accretion efficiency and angular momentum transport
- Macquarie University（麦考瑞大学）
- Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut（海德堡大学天文学中心计算天文研究所）
- Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles (ULB)（布鲁塞尔自由大学天文学与天体物理研究所）
- Monash University（蒙纳士大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过三维SPH模拟公共包层前的快速质量转移，发现吸积盘形成且吸积率远超爱丁顿极限，并由湍流角动量输运驱动，L₂质量损失显著减小轨道间距。
AI中文摘要：
公共包层事件之前的快速质量转移是双星演化中一个关键但了解甚少的阶段，它为公共包层旋近以及致密双星的形成设定了初始条件。我们使用Phantom代码，对这一时期吸积盘的形成进行了三维平滑粒子流体动力学模拟。我们模拟了从一颗7倍太阳质量的红巨星到一颗1.4倍太阳质量的中子星伴星的洛希瓣溢流的最后21年，质量转移率由一维MESA模型给定。在此时间间隔内，质量转移率从1.3×10⁻⁴增加到1.0×10⁻¹太阳质量每年。在模拟结束时，中子星周围形成了一个吸积盘，其质量为5.0×10⁻³太阳质量，半径为40倍太阳半径，纵横比H/R约为0.1。与Juarez-Garcia等人（2025）的基于网格的模拟直接比较表明，两种代码产生的盘质量一致，差异在6%以内。中子星的吸积率达到了5.2×10⁻³太阳质量每年，相当于质量注入率的14%，大大超过了爱丁顿极限。我们证明，这一吸积率与湍流角动量输运驱动一致，有效黏性参数α_eff约为0.03-0.06。离开双星系统的抛射物携带的比角动量约为L₂拉格朗日点的90%，相当于双星比轨道角动量的约10倍。这表明L₂质量损失有效地减小了双星轨道间距。
英文摘要：
Rapid mass transfer preceding a common envelope event is a critical yet poorly understood stage of binary stellar evolution, setting the initial conditions for the common envelope inspiral and for the formation of compact binary stars. We present three-dimensional smoothed particle hydrodynamics simulations of accretion disk formation during this phase using the Phantom code. We model the final $21~yr$ of Roche lobe overflow from a $7~M_{\odot}$ red giant onto a $1.4~M_{\odot}$ neutron star companion, with the mass transfer rate prescribed by a 1D MESA model. Over this interval, the mass transfer rate increases from $1.3\times10^{-4}$ to $1.0\times10^{-1}~M_\odot~yr^{-1}$. An accretion disk forms around the neutron star, reading a mass of $5.0\times10^{-3} ~ M_{\odot}$, a radius of $40~R_{\odot}$ and an aspect ratio H/R$\sim 0.1$ by the end of the simulation. A direct comparison with the grid-based simulation of Juarez-Garcia et al. (2025) shows that the two codes produce disk masses that agree to within 6%. The accretion rate onto the neutron star reaches $5.2\times10^{-3}~M_\odot~yr^{-1}$, corresponding to 14% of the mass injection rate and greatly exceeding the Eddington limit. We demonstrate that this accretion rate is consistent with being driven by turbulent angular momentum transport, with an effective viscosity parameter $α_{\rm eff}~=~0.03-0.06$. Ejecta leaving the binary system carries specific angular momentum approximately 90% that of the $L_{2}$ Lagrange point, equivalent to $\sim10$ times the binary's specific orbital angular momentum. This indicates that $L_{2}$ mass loss efficiently reduces the binary orbital separation.
