Binary Supermassive Black Holes at the Cores of Galaxies

Binary supermassive black holes are important for our understanding of the galaxies’ formation and evolution. Coalescing binaries are among the strongest emitters of gravitational waves in the universe. With high-resolution radio observations close pairs of massive black holes can be resolved spatially, providing a direct means of detection. The closest binaries can no longer be spatially resolved, and other methods of detection are in use. Recently, first hints for the influence of a supermassive binary black hole on the lightcurve of an X-ray outburst from a non-active galaxy were found.