paper

Candidate Electromagnetic Counterpart to the Binary Black Hole Merger Gravitational Wave Event S190521g

arXiv:2006.14122 · doi:10.1103/PhysRevLett.124.251102

Abstract

We report the first plausible optical electromagnetic (EM) counterpart to a (candidate) binary black hole (BBH) merger. Detected by the Zwicky Transient Facility (ZTF), the EM flare is consistent with expectations for a kicked BBH merger in the accretion disk of an active galactic nucleus (AGN), and is unlikely ()) due to intrinsic variability of this source. The lack of color evolution implies that it is not a supernovae and instead is strongly suggestive of a constant temperature shock. Other false-positive events, such as microlensing or a tidal disruption event, are ruled out or constrained to be ). If the flare is associated with S190521g, we find plausible values of: total mass , kick velocity at in a disk with aspect ratio (i.e., disk height at radius ) and gas density . The merger could have occurred at a disk migration trap (; , where is the mass of the AGN supermassive black hole). The combination of parameters implies a significant spin for at least one of the black holes in S190521g. The timing of our spectroscopy prevents useful constraints on broad-line asymmetry due to an off-center flare. We predict a repeat flare in this source due to a re-encountering with the disk in .

arXiv comment9 pages, 4 figures, accepted for publication in Physical Review Letters (June 25, 2020)

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