Topic: Why are LIGO/Virgo Black Holes So Massive?

Speaker: Xian Chen, Assistant professor, Peking University

Time: 9:30, August 18, 2022

Venue: Physics Building 301

Abstract: Measuring the mass and distance of a gravitational wave (GW) source is a fundamental problem in GW astronomy. The issue is becoming even more pressing since LIGO and Virgo have detected massive black holes that in the past were thought to be rare, if not entirely impossible. The waveform templates used in the detection are developed under the assumption that the sources are residing in a vacuum, but astrophysical models predict that the sources could form in gaseous environments, move with relatively large velocity, or reside in the vicinity of supermassive black holes.  In this talk, I will demonstrate how the above environmental factors could distort the GW signals and lead to a biased estimation of the physical parameters. In particular, I will highlight the ubiquity of such a bias among the GW sources produced in a major formation channel, i.e., in active galactic nuclei. If not appropriately accounted for, the above bias may alter our understanding of the formation, evolution, and detection of GW sources.

Bio: Dr. Xian Chen received his PhD from Peking University, and later moved on to the Kavli Institute for Astronomy and Astrophysics in Peking University, the Max-Planck Institute for Gravitational Physics in Germany, and the Pontificia Universidad Catolica de Chile for postdocs. In 2016 he came back to China and joined the Astronomy Department of Peking University as an assistant professor. Dr. Chen’s research mainly focuses on the relativistic dynamics and radiation processes close to black holes.