LIGO detects most massive black hole merger to date

Man, that is some seriously interesting phenomena:

"The black holes appear to be spinning very rapidly—near the limit allowed by Einstein's theory of general relativity," explains Charlie Hoy of the University of Portsmouth and a member of the LVK. "That makes the signal difficult to model and interpret. It's an excellent case study for pushing forward the development of our theoretical tools."

It's like nature handed us a stress test for general relativity

Does the spinning of a spherical object cause any gravitational waves?

The rotating mass drags space time around it, called frame dragging, which is different from gravitational waves. Gravitational waves consists of oscillations, which is caused by change of mass, wobbling of spinning objects, or several masses orbiting around a barycentre.