Mid-sized black holes are harder to spot than their smaller or supermassive cousins (brothers) but powerful bursts of radiation from a faraway galaxy have maybe, if confirm, revealed one;
— Read on www.newscientist.com/article/2272871-blasts-of-intergalactic-radiation-hint-at-elusive-mid-sized-black-hole/

Blasts of intergalactic radiation hint at elusive mid-sized black hole

By Leah Crane

Space 29 March 2021

“The researchers found only one example of gravitational lensing, in which the light from the gamma-ray burst was warped by an object about 55,000 times as massive as the sun. An object that massive yet dim is probably a black hole – and if that is the case, it is far smaller than the smallest supermassive black hole we have ever seen and far larger than the largest “normal” one.”

What may be a medium-sized black hole was found through the detection of a gravitationally lensed gamma-ray burst