高能天体物理研究组知识库

讨论了Kerr时空中扭曲盘发射谱线轮廓的计算问题.内容分成2部分,第1部分介绍Kerr时空中的测地运动、积分形式的测地运动方程组以及如何用Weierstrass椭圆函数去求解的问题.利用魏氏椭圆函数,Boyer-Lindquist(B-L)坐标和仿射参数σ可以半解析地表示成参数p的函数.之后介绍了一套基于以上结果发展的、快速计算Kerr时空中零测地线的公开程序一ynogk(Yunnan Observatory Geodesic Kerr).第2部分作为程序的应用,详细计算并讨论了Kerr时空中扭曲盘发射谱线的轮廓.其中扭曲盘的结构模型基于Bardeen和Petterson的结果,而发射线轮廓的计算则采用了光线追踪法.最后给出了计算结果及其讨论和分析.结果显示扭曲盘发射线轮廓同时依赖于观测者倾角、方位角以及发射率指数,并具有异于标准薄盘的发射线轮廓双峰结构的3峰甚至多峰结构.

The computations of emission line profiles of a warped disk around a Kerr black hole are discussed in this paper, which can be divided into two parts. In the first part, the geodesic motion in a Kerr spacetime and its equations with integral forms are presented. The equations are solved with the Weierstrass' elliptic functions and integrals. Making use of the elliptic functions, the Boyer-Lindquist (B-L) coordinates and the affine parameter a are expressed semi-analytically as the functions of the parameter p. Then a code named ynogk (Yunnan Observatory Geodesic Kerr) is introduced based on the above discussions to calculate the null geodesics fast in a Kerr spacetime. In the second part of the paper, as an application of ynogk, the emission line profiles of a warped disk are investigated in detail. Here the structure model of the disk is specified according to the results of Bardeen and Petterson in 1975, and the line profiles are computed with the ray-tracing method. Finally, the discussions and conclusions of the computing results are presented, which indicate that the line profiles are dependent mainly on the inclination and azimuthal angles of the observer and the index of emissivity, and have the three-horn even multiple-horn structures comparing to those of a standard thin accretion disk.