Sun Lunan, Ruiz Milton, Shapiro Stuart L
Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Department of Astronomy & NCSA, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Phys Rev D. 2018 Nov 15;98(10). doi: 10.1103/physrevd.98.103008. Epub 2018 Nov 12.
Collapsing supermassive stars (SMSs) with masses ≳ 10 have long been speculated to be the seeds that can grow and become supermassive black holes (SMBHs). We previously performed general relativistic magnetohydrodynamic (GRMHD) simulations of marginally stable Γ = 4/3 polytropes uniformly rotating at the mass-shedding limit and endowed initially with a dynamically unimportant dipole magnetic field to model the direct collapse of SMSs. These configurations are supported entirely by thermal radiation pressure and reliably model SMSs with ≳ 10 . We found that around 90% of the initial stellar mass forms a spinning black hole (BH) remnant surrounded by a massive, hot, magnetized torus, which eventually launches a magnetically-driven jet. SMSs could be therefore sources of ultra-long gamma-ray bursts (ULGRBs). Here we perform GRMHD simulations of Γ ≳ 4/3, polytropes to account for the perturbative role of gas pressure in SMSs with ≲ 10 . We also consider different initial stellar rotation profiles. The stars are initially seeded with a dynamically weak dipole magnetic field that is either confined to the stellar interior or extended from its interior into the stellar exterior. We calculate the gravitational wave burst signal for the different cases. We find that the mass of the black hole remnant is 90%-99% of the initial stellar mass, depending sharply on Γ - 4/3 as well as on the initial stellar rotation profile. After ~ 250-550 ≈ 1 - 2 × 10(/10 ) s following the appearance of the BH horizon, an incipient jet is launched and it lasts for 10-10(/10 ) s, consistent with the duration of long gamma-ray bursts. Our numerical results suggest that the Blandford-Znajek mechanism powers the incipient jet. They are also in rough agreement with our recently proposed universal model that estimates accretion rates and electromagnetic (Poynting) luminosities that characterize magnetized BH-disk remnant systems that launch a jet. This model helps explain why the outgoing electromagnetic luminosities computed for vastly different BH-disk formation scenarios all reside within a narrow range (10 erg s), roughly independent of .
质量≳10 的坍缩超大质量恒星（SMSs）长期以来一直被推测为能够成长并成为超大质量黑洞（SMBHs）的种子。我们之前对处于质量损失极限下均匀旋转的临界稳定Γ = 4/3多方球进行了广义相对论磁流体动力学（GRMHD）模拟，并最初赋予其一个动力学上不重要的偶极磁场，以模拟SMSs的直接坍缩。这些构型完全由热辐射压力支撑，并可靠地模拟了质量≳10 的SMSs。我们发现，大约90%的初始恒星质量形成了一个被巨大、炽热、磁化的环面环绕的旋转黑洞（BH）遗迹，该环面最终会发射出磁驱动喷流。因此，SMSs可能是超长伽马射线暴（ULGRBs）的来源。在这里，我们对Γ≳4/3的多方球进行GRMHD模拟，以考虑气体压力在质量≲10 的SMSs中的微扰作用。我们还考虑了不同的初始恒星旋转剖面。恒星最初被赋予一个动力学上较弱的偶极磁场，该磁场要么局限于恒星内部，要么从其内部延伸到恒星外部。我们计算了不同情况下的引力波暴信号。我们发现，黑洞遗迹的质量为初始恒星质量的90% - 99%，这强烈取决于Γ - 4/3以及初始恒星旋转剖面。在黑洞视界出现后的约250 - 550≈1 - 2×10(/10 )秒，一个初始喷流被发射出来，持续约10 - 10(/10 )秒，这与长伽马射线暴的持续时间一致。我们的数值结果表明，布兰德福德 - 日纳杰克机制为初始喷流提供动力。它们也与我们最近提出的通用模型大致相符，该模型估计了表征发射喷流的磁化黑洞 - 盘遗迹系统的吸积率和电磁（坡印廷）光度。这个模型有助于解释为什么为截然不同的黑洞 - 盘形成场景计算出的出射电磁光度都处于一个狭窄的范围内（~10 erg s），大致与无关。
