TESTS OF GENERAL RELATIVITY IN THE STRONG-GRAVITY REGIME BASED ON X-RAY SPECTROPOLARIMETRIC OBSERVATIONS OF BLACK HOLES IN X-RAY BINARIES
TESTS OF GENERAL RELATIVITY IN THE STRONG-GRAVITY REGIME BASED ON X-RAY SPECTROPOLARIMETRIC OBSERVATIONS OF BLACK HOLES IN X-RAY BINARIES
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DOI：
10.1088/0004-637x/754/2/133
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发表时间：
2012-05
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通讯作者：
H. Krawczynski
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作者：
H. Krawczynski
虽然广义相对论（GR）已经在弱引力区得到了广泛的检验，但在强引力区的类似检验仍然缺失。本文探讨了利用X射线双星黑洞的X射线分光偏振观测来区分克尔度规和Johannsen & Psaltis提出的唯象度规的可能性（这不是爱因斯坦方程的真空解），从而检验GR的无毛定理。为此，我们已经开发了一个数值程序，计算吸积盘的径向亮度分布，并通过Kerr和非GR时空并行传输光子的波矢和偏振矢量。我们使用该代码来预测GR和非GR吸积黑洞系统的观测外观。我们发现，预测的能谱和能量依赖的偏振度和偏振方向强烈依赖于底层时空。然而，对于参数空间的大区域，GR和非GR度量导致非常相似的观测特征，使得难以在观测上区分这两种类型的模型。
Although general relativity (GR) has been tested extensively in the weak-gravity regime, similar tests in the strong-gravity regime are still missing. In this paper, we explore the possibility to use X-ray spectropolarimetric observations of black holes in X-ray binaries to distinguish between the Kerr metric and the phenomenological metrics introduced by Johannsen & Psaltis (which are not vacuum solutions of Einstein's equation) and thus to test the no-hair theorem of GR. To this end, we have developed a numerical code that calculates the radial brightness profiles of accretion disks and parallel transports the wave vector and polarization vector of photons through the Kerr and non-GR spacetimes. We used the code to predict the observational appearance of GR and non-GR accreting black hole systems. We find that the predicted energy spectra and energy-dependent polarization degree and polarization direction do depend strongly on the underlying spacetime. However, for large regions of the parameter space, the GR and non-GR metrics lead to very similar observational signatures, making it difficult to observationally distinguish between the two types of models.