Collaborative Research: Predicting the Observational Signatures of Accreting Black Holes

由于黑洞（BH）的定义是不可见的，所以天文学家探测它们的唯一方法就是观察吸积到（或落入）黑洞的物质。考虑到黑洞附近的强引力、强辐射和强磁场，这种吸积是复杂的，只能通过在超级计算机上运行复杂的数值模型来理解，这并不奇怪。伊利诺伊大学、普林斯顿大学和加州大学伯克利分校之间的一项研究合作将模拟黑洞吸积在强吸积和弱吸积之间的行为，在这种情况下，已知会发生一些有趣的现象，如流出物质的喷射和吸积中的不寻常振荡。这项工作将有助于解开与黑洞有关的谜团，比如喷流是如何形成的，以及吸积流的结构是如何随时间变化的。该团队将通过讲座和可视化向公众传达黑洞天体物理学的兴奋，并通过黑洞暑期学校向未来几代学生传达。黑洞吸积和流出理论是现代天体物理学和引力物理学许多领域的核心。该合作小组已经开发了一种数值技术，可以在高吸积率和低吸积率极限下对黑洞的吸积进行几乎从头开始的建模。该团队计划开发新的数值技术和代码，适用于研究困难的中等吸积速率体系，这与恒星质量黑洞周围的喷流、准周期振荡和状态转变有关。对模型的补充包括辐射力、对的产生和输运、非热粒子的产生和输运以及无碰撞等离子体效应，所有这些对于在黑洞天体物理学中长期存在的问题上取得进展至关重要，例如在中等吸积速率下吸积的结构和观测外观（光谱、时间变异性、极化）。以及关于大规模磁场的起源和维持的问题，这些磁场被认为是这些系统中相对论性喷流的动力。该组织将通过公开发布使他们的新代码可供其他人使用。

Since black holes (BH) are by definition invisible, the only way that astronomers can detect them is by observing material accreting onto (or falling into) the black hole. Given the strong gravity, intense radiation and powerful magnetic fields near black holes, it is not surprising that such accretion is complex and can only be understood by running sophisticated numerical models on supercomputers. A research collaboration between the University of Illinois, Princeton University and the University of California-Berkeley will model the behavior of BH accretion in the realm intermediate between strong and weak accretion, when interesting effects such as jets of outflowing material and unusual oscillations in the accretion are known to take place. This work will help to unravel mysteries related to black holes, such as how the jets form and how the structure of the accretion flow changes over time. The team will communicate the excitement of black-hole astrophysics to the public through lectures and visualizations, and to future generations of students through a black hole summer school.The theory of black-hole (BH) accretion and outflows is central to many areas of modern astrophysics and gravitational physics. The collaboration team has developed numerical techniques that permit nearly ab initio modeling of black-hole accretion in both the high- and low-accretion-rate limits. The team plans to develop new numerical techniques and codes suitable for studying the difficult, intermediate-accretion-rate regime, which is associated with jets, quasi-periodic oscillations, and state transitions around stellar-mass black holes. Additions to the models include radiation forces, pair production and transport, nonthermal particle production and transport, and collisionless plasma effects, all of which are critical for making progress on long-standing problems in black-hole astrophysics, such as the structure and observational appearance (spectrum, time variability, polarization) of accretion at intermediate accretion rates, as well as questions about the origin and maintenance of large-scale magnetic fields believed to power relativistic jets from such systems. The group will make their new codes available for others to use through public releases.