Researchers show that masses of binary black hole mergers are overestimated, since a large gravitational redshift is not taken into account. Such a phenomenon occurs due to time dilation in a close neighborhood of any black hole. This fact allows us to explain a high mass gap between observed binary neutron stars and calculated binary black hole mergers. They also present other reasons why masses of black hole mergers are determined incorrectly.
This video is adapted from 10.3390/galaxies10020052