Appearance of an infalling star in black holes with multiple photon spheres  

作　　者：Yiqian Chen Guangzhou Guo Peng Wang Houwen Wu Haitang Yang 

机构地区：[1]Center for Theoretical Physics,College of Physics,Sichuan University,Chengdu,610064,China [2]Department of Applied Mathematics and Theoretical Physics,University of Cambridge,Cambridge,CB30WA,UK

出　　处：《Science China(Physics,Mechanics & Astronomy)》2022年第12期109-121,共13页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.12105191,11947225,and 11875196);supported by the International Visiting Program for Excellent Young Scholars of Sichuan University。

摘　　要：Photon spheres play a pivotal role in the imaging of luminous objects near black holes.In this paper,we examine observational appearances of a star freely falling in hairy black holes,which can possess one or two photon spheres outside the event horizon.When there exists a single photon sphere,the total luminosity measured by distant observers decreases exponentially with time at late times.Due to successive arrivals of photons orbiting around the photon sphere different times,a specific observer would see a series of light flashes with decreasing intensity,which share a similar frequency content.Whereas in the case with two photon spheres,photons temporarily trapped between the photon spheres can cause a peak of the total luminosity,which is followed by a slow exponential decay,at late times.In addition,these photons lead to one more series of light flashes seen by the specific observer.

关 键 词：black hole gravitational lensing photon sphere observational appearance 

分 类 号：P145.8[天文地球—天体物理]