Supermassive Black Hole Binaries in the Multi-messenger Context of Ground and Spaceborne VLBI
Evidence of a gravitational wave background suggests the existence of a population of sub-parsec supermassive black hole binaries (SMBHBs), with characteristic angular separations on the order of 1–10 μas. Spaceborne extensions of Very Long Baseline Interferometry (VLBI) and the next-generation ground arrays introduce...