Self Lensing Flares from supermassive black hole binaries

The self-lensing of a massive black hole binary (MBHB), which occurs when the two BHs are aligned close to the line of sight, is expected to produce periodic, short-duration flares. In this talk, I will present our recent work on self-lensing flares (SLFs) via simulated light curves with general-relativistic ray-tracing methods. I will report a suite of models covering eccentric binary orbits, black hole spins, unequal mass binaries, and different emission model geometries. I will highlight how these binary parameters alter the shape of the light curves, and I will show that if the binary orbit is observed nearly edge-on, we find a distinct feature in the SLF imprinted by the black hole shadow. We estimate that approximately 1% of the current binary candidates might already show this feature. I will propose search strategies for these sources, either by large time-domain surveys, such as the Vera Rubin Observatory’s LSST, or via EM follow-ups on GW wave detections by LISA. Our proposed BH tomography method could open a new way to measure BH shadow sizes in systems that are unresolvable by current VLBI facilities.