Two colliding black holes created a phenomenon scientists have never seen before

[usonian]

1. The paper behind this is freely available at arxiv, as are many others.

https://arxiv.org/abs/2106.05575

Nature Astronomy would prefer that you not know this, and get you or your institution to pony up dollars to access it.

GW190521: A dynamical capture of two black holes
Rossella Gamba, Matteo Breschi, Gregorio Carullo, Piero Rettegno, Simone Albanesi, Sebastiano Bernuzzi, Alessandro Nagar

We analyze the gravitational-wave signal GW190521 under the hypothesis that it was generated by the merger of two nonspinning black holes on hyperbolic orbits. The best configuration matching the data corresponds to two black holes of source frame masses of 81+62?25M⊙ and 52+32?32M⊙ undergoing two encounters and then merging into an intermediate-mass black hole. Under the hyperbolic merger hypothesis, we find an increase of one unit in the recovered signal-to-noise ratio and a 14 e-fold increase in the maximum likelihood value compared to a quasi-circular merger with precessing spins. We conclude that our results support the first gravitational-wave detection from the dynamical capture of two stellar-mass black holes.