Johannsen Tim, Broderick Avery E, Plewa Philipp M, Chatzopoulos Sotiris, Doeleman Sheperd S, Eisenhauer Frank, Fish Vincent L, Genzel Reinhard, Gerhard Ortwin, Johnson Michael D
Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada.
Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
Phys Rev Lett. 2016 Jan 22;116(3):031101. doi: 10.1103/PhysRevLett.116.031101. Epub 2016 Jan 19.
In general relativity, the angular radius of the shadow of a black hole is primarily determined by its mass-to-distance ratio and depends only weakly on its spin and inclination. If general relativity is violated, however, the shadow size may also depend strongly on parametric deviations from the Kerr metric. Based on a reconstructed image of Sagittarius A^{} (Sgr A^{}) from a simulated one-day observing run of a seven-station Event Horizon Telescope (EHT) array, we employ a Markov chain Monte Carlo algorithm to demonstrate that such an observation can measure the angular radius of the shadow of Sgr A^{*} with an uncertainty of ∼1.5 μas (6%). We show that existing mass and distance measurements can be improved significantly when combined with upcoming EHT measurements of the shadow size and that tight constraints on potential deviations from the Kerr metric can be obtained.
在广义相对论中，黑洞阴影的角半径主要由其质量与距离之比决定，并且仅微弱地依赖于其自旋和倾角。然而，如果广义相对论不成立，阴影大小可能也会强烈依赖于与克尔度规的参数偏差。基于由七台望远镜组成的事件视界望远镜（EHT）阵列进行的模拟一天观测运行所重建的人马座A*（Sgr A*）图像，我们采用马尔可夫链蒙特卡罗算法来证明这样的观测能够以约1.5微角秒（6%）的不确定性测量Sgr A*阴影的角半径。我们表明，将现有的质量和距离测量结果与EHT即将进行的阴影大小测量相结合时，能够显著改进这些测量结果，并且可以对与克尔度规的潜在偏差获得严格限制。
