Abstract: Black holes are the simplest objects in the universe, which can be described in theory only by three physical quantities: mass, spin and electric charge (usually negligible). Precise measurement of these physical quantities is the cornerstone of in-depth study of black holes. With the progress of observational technology and computing power, these properties can be measured precisely at present for some sources. I will take the mass and spin measurements of Cygnus X-1 as an example to show the relevant research efforts. The black hole spin is a more important intrinsic parameter, and the reporter will focus on the different approaches to the spin measurement as well as the achievements made in the past few years. Finally, some prospects are made for the related measurements.
Bio: Prof. Lijun Gou received his bachelor's degree in astronomy from Nanjing University in 1998, master's degree from Nanjing University in 2001 and PhD from Pennsylvania State University in 2007, and then worked as a postdoctoral and research scientist at the Harvard-Smithsonian Astrophysics Center at Harvard University. Since 2012, he has been a research professor at the National Astronomical Observatory of the Chinese Academy of Sciences (NAOC) and also works as the adjunct professor at the University of the Chinese Academies. He has been the executive editor of China National Astronomical magazine since 2019, and works as editorial board for two magazines, Physics, and The innovation. His main research interest is high-energy astrophysics, including black holes and gravitational waves, and so on. He has published more than 40 SCI papers with a total citation of over 2500 times. In 2021, collaborating with international team, he has accurately measured the mass and spin parameter of Cygnus X1, the first black hole system in human history, and it has been confirmed to be the heaviest and fastest rotating black hole in X-ray binaries. The results were published in the February 2021 issue of the journal of Science.