Astronomers may have spotted light from colliding black holes - Engadget

When that happens, the newly unified black hole can be sent off in an unusual direction through the disk, sparking a gas reaction days or weeks after the gravitational waves appear.

The timing of the flare lined up with this, and it even gradually faded away over the course of a month.

Researchers effectively eliminated other phenomenons as possible causes, such a black hole ‘eating’ a star, a supernova or a flare from the supermassive black hole itself.