Nature. 2016 Jul 21;535(7612):388-90. doi: 10.1038/nature18007. Epub 2016 Jun 22.
Our current understanding of the curved space-time around supermassive black holes is based on actively accreting black holes, which make up only ten per cent or less of the overall population. X-ray observations of that small fraction reveal strong gravitational redshifts that indicate that many of these black holes are rapidly rotating; however, selection biases suggest that these results are not necessarily reflective of the majority of black holes in the Universe. Tidal disruption events, where a star orbiting an otherwise dormant black hole gets tidally shredded and accreted onto the black hole, can provide a short, unbiased glimpse at the space-time around the other ninety per cent of black holes. Observations of tidal disruptions have hitherto revealed the formation of an accretion disk and the onset of an accretion-powered jet, but have failed to reveal emission from the inner accretion flow, which enables the measurement of black hole spin. Here we report observations of reverberation arising from gravitationally redshifted iron Kα photons reflected off the inner accretion flow in the tidal disruption event Swift J1644+57. From the reverberation timescale, we estimate the mass of the black hole to be a few million solar masses, suggesting an accretion rate of 100 times the Eddington limit or more. The detection of reverberation from the relativistic depths of this rare super-Eddington event demonstrates that the X-rays do not arise from the relativistically moving regions of a jet, as previously thought.
我们目前对超大质量黑洞周围弯曲时空的理解是基于正在积极吸积的黑洞，它们只占总星系的百分之十或更少。对这一小部分的 X 射线观测揭示了强烈的引力红移，表明其中许多黑洞正在快速旋转；然而，选择偏差表明，这些结果不一定反映了宇宙中大多数黑洞的情况。潮汐破坏事件，即一颗围绕着其他休眠黑洞的恒星被潮汐撕裂并吸积到黑洞上，为研究其他百分之九十的黑洞周围的时空提供了一个短暂的、无偏见的视角。对潮汐破坏事件的观测迄今为止揭示了吸积盘的形成和吸积驱动喷流的开始，但未能揭示来自内部吸积流的发射，这使得能够测量黑洞的自旋。在这里，我们报告了对引力红移铁 Kα 光子在潮汐破坏事件 Swift J1644+57 中内部吸积流上反射产生的回波的观测。从回波时标，我们估计黑洞的质量为几百万个太阳质量，这表明吸积率是爱丁顿极限的 100 倍或更高。在这种罕见的超爱丁顿事件的相对论深度探测到回波表明，X 射线并非如先前认为的那样来自喷流的相对论运动区域。
