吸积原磁星的GRMHD模拟 I. 对伽马射线暴喷流和高能爆炸的启示
GRMHD Simulations of Accreting Proto-Magnetars I. Implications for Gamma-Ray Burst Jets and Energetic Explosions
- Columbia University（哥伦比亚大学）
- Princeton Plasma Physics Laboratory（普林斯顿等离子体物理实验室）
- Center for Computational Astrophysics, Flatiron Institute（计算天体物理学中心，西蒙斯数据科学研究所）
- Massachusetts Institute of Technology（麻省理工学院）
- Canadian Institute for Theoretical Astrophysics, University of Toronto（加拿大理论天体物理研究所，多伦多大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
通过GRMHD模拟吸积原磁星，揭示其可产生对应长GRB等的喷流与外流，磁层-盘相互作用及偶极场强度会影响喷流特性与自旋演化。
AI中文摘要：
新形成的快速旋转、强磁化中子星（即“毫秒原磁星”）是伽马射线暴（GRB）和亮超新星的有潜力的中心引擎。尽管常被单独建模，但它们可能在恒星坍缩、中子星并合或吸积诱发坍缩时诞生于吸积盘环绕的环境中。我们开展了针对此类天体的轴对称GRMHD模拟，包含物理物态方程和带电电流弱相互作用。在保持弱磁化吸积 torus 固定的情况下，我们改变恒星偶极场强度，以覆盖磁压碎、磁引导吸积和离心推进器 regimes，并与其他相似的吸积黑洞进行对比。吸积会压缩恒星磁层并打开更多磁通量，产生的相对论性喷流功率超出孤立偶极自旋下降估计值数倍至约10倍。即使磁层仍被压缩至恒星表面，更强的磁场也会越来越多地阻碍吸积并增强外流。引导吸积模型显示出由等离子体团爆发和间歇性磁层吸积驱动的强喷流变异性，而推进器模型则产生更稳定、功率更强的喷流和快速自旋下降。盘-磁层相互作用还调节中子星增长的效率及其自旋方向（自旋加速或减速）；在自旋平衡附近，低效吸积会相对于基于外部物质供给率的估计值延迟其坍缩为黑洞。因此，吸积原磁星可产生能量与长GRB及GRB-超新星推断值相当的相对论性喷流和重子丰富外流。配套论文将探讨其对富中子 ejecta 和 r-过程核合成的启示。
英文摘要：
Newly formed, rapidly rotating, strongly magnetized neutron stars ("millisecond proto-magnetars") are promising central engines for gamma-ray bursts (GRBs) and luminous supernovae. Although often modeled in isolation, they can be born surrounded by accretion disks in stellar collapse, neutron-star mergers, or accretion-induced collapse. We present axisymmetric GRMHD simulations of hyperaccretion onto such objects, including a physical equation of state and charged-current weak interactions. Holding the weakly magnetized accretion torus fixed, we vary the stellar dipole field strength to span crushed-magnetosphere, magnetically channeled accretion, and centrifugal-propeller regimes, and compare with an otherwise similar accreting black hole. Accretion compresses the stellar magnetosphere and opens additional magnetic flux, producing relativistic jet powers that exceed isolated-dipole spin-down estimates by factors of a few to ~10. Even while the magnetosphere remains compressed against the stellar surface, stronger fields increasingly impede accretion and enhance outflows. Channeled-accretion models show strong jet variability driven by plasmoid eruptions and intermittent magnetospheric accretion, whereas the propeller model produces a steadier, more powerful jet and rapid spin-down. The disk-magnetosphere interaction also regulates how efficiently the neutron star grows and whether it spins up or down; near spin equilibrium, inefficient accretion can delay collapse to a black hole relative to estimates based on the external mass-supply rate. Accreting proto-magnetars can therefore power relativistic jets and baryon-rich outflows with energetics comparable to those inferred for long GRBs and GRB-supernovae. A companion paper explores implications for neutron-rich ejecta and r-process nucleosynthesis.
