Phys. Rev. Lett. 125, 101102 (2020) – GW190521: A Binary Black Hole Merger with a Total Mass of $150\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$

The heaviest black hole merger detected to date provides evidence for a progenitor black hole in a theoretically forbidden gap and for a resulting black hole in the long-sought intermediate mass range.
— Read on journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.101102