First Sagittarius A* Event Horizon Telescope Results. VI. Testing the Black Hole Metric
First Sagittarius A* Event Horizon Telescope Results. VI. Testing the Black Hole Metric
复制标题
DOI：
10.3847/2041-8213/ac6756
复制
发表时间：
2022-05
期刊：
影响因子：
--
通讯作者：
K. Akiyama;A. Alberdi;W. Alef;J. Algaba;R. Anantua;K. Asada;R. Azulay;U. Bach;A. Baczko
中科院分区：
文献类型：
--
作者：
K. Akiyama;A. Alberdi;W. Alef;J. Algaba;R. Anantua;K. Asada;R. Azulay;U. Bach;A. Baczko
天体物理黑洞有望用克尔度规来描述。这是唯一一种静止的、真空的、轴对称的度规，没有电磁电荷，满足爱因斯坦方程，并且在视界之外没有病理。我们对基于2017年射手座A*(SgrA*)EHT观测的Kerr预测的潜在偏差提出了新的限制。我们使用包含Kerr和非Kerr模拟的库来校准几何定义的黑洞阴影和观察到的环形图像大小之间的关系。我们使用对SgrA*的质量距离比的精确先验约束来表明，观测到的图像大小在克尔预测的∼10%以内。我们使用这些界限来约束参数上不同于克尔的度规，以及几个已知时空的电荷。为了考虑视界存在的替代方案，我们探索了SgrA*是一个致密天体的可能性，其表面要么吸收并热再发射入射辐射，要么部分反射入射辐射。根据观测到的图像大小和SgrA*的宽带光谱，我们得出结论，可以排除热表面，而不太可能有完全反射的表面。我们将我们的结果与更广泛的引力测试进行比较。与恒星质量黑洞和M87黑洞的边界一起，我们的观测进一步支持了所有黑洞的外部时空都是由克尔度规描述的，而与它们的质量无关。
Astrophysical black holes are expected to be described by the Kerr metric. This is the only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies Einstein’s equations and does not have pathologies outside of the event horizon. We present new constraints on potential deviations from the Kerr prediction based on 2017 EHT observations of Sagittarius A* (Sgr A*). We calibrate the relationship between the geometrically defined black hole shadow and the observed size of the ring-like images using a library that includes both Kerr and non-Kerr simulations. We use the exquisite prior constraints on the mass-to-distance ratio for Sgr A* to show that the observed image size is within ∼10% of the Kerr predictions. We use these bounds to constrain metrics that are parametrically different from Kerr, as well as the charges of several known spacetimes. To consider alternatives to the presence of an event horizon, we explore the possibility that Sgr A* is a compact object with a surface that either absorbs and thermally reemits incident radiation or partially reflects it. Using the observed image size and the broadband spectrum of Sgr A*, we conclude that a thermal surface can be ruled out and a fully reflective one is unlikely. We compare our results to the broader landscape of gravitational tests. Together with the bounds found for stellar-mass black holes and the M87 black hole, our observations provide further support that the external spacetimes of all black holes are described by the Kerr metric, independent of their mass.