Gravitational waves are created by any object that spins, such as the rotating remnants of stellar corpses, orbiting black holes or even two people “doing a do-si-do,” Dr. Mingarelli said.

The black hole candidate, which is about 2.5 to 4.5 times heavier than our sun, is heavier than the established limit of 2.5 suns for a neutron star — but lighter than the lightest known black ...