Off-equatorial deflections and gravitational lensing in Kerr spacetime and the effect of spin  

作　　者：Tingyuan Jiang Xiaoge Xu Junji Jia 姜霆远;许笑歌;贾俊基(School of Physics and Technology,Wuhan University,Wuhan 430072,China;Department of Astronomy&MOE Key Laboratory of Artificial Micro-and Nano-structures,School of Physics and Technology,Wuhan University,Wuhan 430072,China)

机构地区：[1]School of Physics and Technology,Wuhan University,Wuhan 430072,China [2]Department of Astronomy&MOE Key Laboratory of Artificial Micro-and Nano-structures,School of Physics and Technology,Wuhan University,Wuhan 430072,China

出　　处：《Chinese Physics C》2025年第3期277-298,共22页中国物理C(英文版)

基　　金：Partially Supported by the Wuhan University Students Innovation and Entrepreneurship Program。

摘　　要：This paper investigates off-equatorial plane deflections and gravitational lensing of both null signals and massive particles in Kerr spacetime in the weak deflection limit,considering the finite distance effect of the source and detector.This is the effect caused by both the source and detector being located at finite distances from the lens although many researchers often use the deflection angle for infinite distances from sources and detectors.The deflection in both the and directions is computed as a power series of M/r_(0) and r_(0)/rsd,where M,rs.d are the spacetime mass and source and detector radi,respectively,and r_(0) is the minimal radial coordinate of the trajectory.The coefficients of these series are simple trigonometric functions of Ge,the extreme value of the coordinate of the trajectory.A set of exact gravitational lensing equations is used to solve for ro and Ge for given deviation angles so and Sp of the source,and two lensed images are always obtained.The apparent angles and their magnifications of these images and the time delays between them are solved.Additionally,their dependences on various parameters,particularly spacetime spin a,are analyzed in depth.We find that generally two critical spacetime spin values exist that separate the case of test particles reaching the detector from different sides of the z axis from the cases in which the images appear from the same side in the celestial plane.Three potential applications of these results are discussed.

关 键 词：deflection angle gravitational lensing Kerr spacetime equatorial plane massive particle perturbative method 

分 类 号：P14[天文地球—天体物理]