Lensing by Kerr black holes
Lensing by Kerr black holes
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DOI：
10.1103/physrevd.101.044031
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发表时间：
2020-02-14
影响因子：
5
通讯作者：
Lupsasca, Alexandru
中科院分区：
文献类型：
--
作者：
Gralla, Samuel E.;Lupsasca, Alexandru
解释天体物理黑洞的视界尺度观测需要对克尔时空中的零测地线有一般的了解。这些射线可以分为两类：一类是“直接”射线，它主要决定了一个给定源的观测外观；另一类是高度弯曲的射线，它产生了一个嵌套序列的主发射的指数衰减图像：所谓的“光子环”。我们开发了表征直射射线的启发式方法，并对高度弯曲的测地线进行了分析研究。我们定义了三个关键参数gamma， delta和tau，分别控制源的连续图像的退放大，旋转和时间延迟，从而提供了光子环的解析理论。这些可观测的参数编码了广义相对论的普遍效应，与发射物质的细节无关。
Interpreting horizon-scale observations of astrophysical black holes demands a general understanding of null geodesics in the Kerr spacetime. These may be divided into two classes: "direct" rays that primarily determine the observational appearance of a given source, and highly bent rays that produce a nested sequence of exponentially demagnified images of the main emission: the so-called "photon ring." We develop heuristics that characterize the direct rays and study the highly bent geodesics analytically. We define three critical parameters gamma, delta, and tau that respectively control the demagnification, rotation, and time delay of successive images of the source, thereby providing an analytic theory of the photon ring. These observable parameters encode universal effects of general relativity, independent of the details of the emitting matter.