When two black holes merge, the late stage of gravitational wave emission is a superposition of exponentially damped sinusoids. According to the black hole no-hair theorem, this ringdown spectrum depends only on the mass and angular momentum of the final black hole. Observation of more than one ringdown mode can test this fundamental prediction of general relativity. In this seminar, I report a strong observational evidence for a multimode black hole ringdown spectrum using the gravitational wave event GW190521 with a Bayes factor of 56. I will discuss the data analysis behind the discovery. The work is based on arXiv:  2105.05238 and arXiv: 2209.00640. / 双黑洞并合后期发出的引力波辐射由指数衰减的正弦振荡模式描述。根据黑洞无毛定理，这种铃宕谱只由黑洞的质量和角动量描述。观测到黑洞振动引力波的多个铃宕模式可以在非常基本的程度上验证广义相对论对于黑洞的描述。本次报告我将讨论在GW190521事件中以贝叶斯因子56的证据观测到了(3,3,0)铃宕模式，我将讨论导致发现的分析技术。本报告的内容发表于论文arXiv: 2105.05238 和 arXiv: 2209.00640.

个人简介：Dr. Yifan Wang is a postdoc / junior scientist at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute). He obtained the B.Sc. degree from the University of Science and Technology of China and the Ph.D. degree from the Chinese University of Hong Kong. His research interests are searching for gravitational-wave from compact binary coalescence, testing general relativity, etc. / 王一帆博士现为马克斯普朗克引力物理研究所（阿尔伯特爱因斯坦研究所）博士后。他于中国科学技术大学和香港中文大学取得学士和博士学位。研究兴趣为致密双星并合引力波搜索，用引力波检验广义相对论等。