Spins of the Supermassive Black Hole in M87: New Constraints from TeV Observations
Spins of the Supermassive Black Hole in M87: New Constraints from TeV Observations
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DOI：
10.1086/587740
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发表时间：
2008-02
期刊：
影响因子：
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通讯作者：
Jian-Min Wang;Yan-Rong Li;Jian-cheng Wang;Shu Zhang
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文献类型：
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作者：
Jian-Min Wang;Yan-Rong Li;Jian-cheng Wang;Shu Zhang
在附近著名的射电星系M87中检测到的TeV γ射线快速变化意味着在银河系中心超大质量黑洞的视界附近有一个非常紧凑的发射区（5-10史瓦西半径）。TeV光子由于与黑洞周围的对流主导吸积流（ADAF）的辐射场相互作用而受到稀释的影响，因此可以用于探测黑洞周围的最内部区域。我们计算了ADAF辐射场对TeV光子的光学深度，发现它强烈地依赖于黑洞的自旋。我们发现，对于最大旋转黑洞和非旋转黑洞，10 TeV光子的透明半径分别为5 R_ {\mathrm {S}\，}和13 R_ {\mathrm {S}\，}.通过观测，计算出的透明半径强烈表明黑洞在星系中快速旋转。TeV的光子可以作为一个强大的诊断估计在未来的星系黑洞自旋。
The rapid TeV γ-ray variability detected in the well-known nearby radio galaxy M87 implies an extremely compact emission region (5-10 Schwarzschild radii) near the horizon of the supermassive black hole in the galactic center. TeV photons are affected by dilution due to interaction with the radiation field of the advection-dominated accretion flow (ADAF) around the black hole, and can thus be used to probe the innermost regions around the black hole. We calculate the optical depth of the ADAF radiation field to the TeV photons and find it strongly depends on the spin of the black hole. We find that transparent radii of 10 TeV photons are of 5R_ {\mathrm {S}\,} and 13R_ {\mathrm {S}\,} for the maximally rotating and nonrotating black holes, respectively. With the observations, the calculated transparent radii strongly suggest the black hole is spinning fast in the galaxy. TeV photons could be used as a powerful diagnostic for estimating black hole spins in galaxies in the future.