The Jet in the Galactic Center: An Ideal Laboratory for Magnetohydrodynamics and General Relativity
Heino Falcke, Sera Markoff, Geoffrey C. Bower, Charles F. Gammie, Monika Moscibrodzka, Dipankar Maitra
备注：
invited talk to appear in "Jets on All Scales", IAU Symposium 275, G.E. Romero, R.A. Sunyaev & T. Belloni, eds., Cambridge University Press, 9 pages, LaTex, 4 figures
In this paper we review and discuss some of the intriguing properties of the Galactic Center supermassive black hole candidate Sgr A*. Of all possible black hole sources, the event horizon of Sgr A*, subtends the largest angular scale on the sky. It is therefore a prime candidate to study and image plasma processes in strong gravity and it even allows imaging of the shadow cast by the event horizon. Recent mm-wave VLBI and radio timing observations as well as numerical GRMHD simulations now have provided several breakthroughs that put Sgr A* back into the focus. Firstly, VLBI observations have now measured the intrinsic size of Sgr A* at multiple frequencies, where the highest frequency measurements have approached the scale of the black hole shadow. Moreover, measurements of the radio variability show a clear time lag between 22 GHz and 43 GHz. The combination of size and timing measurements, allows one to actually measure the flow speed and direction of magnetized plasma at some tens of Schwarzschild radii. This data strongly support a moderately relativistic outflow, consistent with an accelerating jet model. This is compared to recent GRMHD simulation that show the presence of a moderately relativistic outflow coupled to an accretion flow Sgr A*. Further VLBI and timing observations coupled to simulations have the potential to map out the velocity profile from 5-40 Schwarzschild radii and to provide a first glimpse at the appearance of a jet-disk system near the event horizon. Future submm-VLBI experiments would even be able to directly image those processes in strong gravity and directly confirm the presence of an event horizon.
Implementation of advanced Riemann solvers in a neutrino-radiation magnetohydrodynamics code in numerical relativity and its application to a binary neutron star merger
Extending the infrastructure of the BAM code towards resistive general-relativistic magnetohydrodynamics: tests and first applications
Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））；Institut für Physik und Astronomie, Universität Potsdam（波茨坦大学物理与天文学研究所）；Centro de Ciências Naturais e Humanas, Universidade Federal do ABC（ABC联邦大学自然与人文科学中心）
General-relativistic neutrino-radiation magnetohydrodynamics simulation of seconds-long black hole-neutron star mergers: Dependence on initial magnetic field strength, configuration, and neutron-star equation of state
GRMHD beyond Kerr: An extension of the HARM code for thin disks to non-Kerr spacetimes
近年来，随着新的和改进的探测器和望远镜的出现，基于黑洞的广义相对论测试激增。大部分携带强场特征的辐射都来自黑洞附近，对黑洞附近的建模对于对可能违反广义相对论的强大而准确的约束至关重要。作为第一步，本文提出了广义相对论磁流体动力学模拟薄吸积盘参数变形黑洞的推广克尔解决方案。该扩展是基于\textsc{harmpi}，一个公开的成员的\textsc{harm}家庭的代码，并使用现象学度量研究参数偏离克尔。扩展的模型被用来研究磁盘的结构，稳定性和辐射效率。我们还计算了Fe K $α$配置文件在简化的情况下，并提出了未来的展望。
