Gravitational waves or electromagnetic counterpart ? No need to choose

Binary black holes emit gravitational waves (GWs) as they inspiral towards coalescence. Searches for electromagnetic counterparts to GWs rely on looking for common sources producing both waves. Here, we take a different approach: we investigate the impact of the binary binary hole onto its outer circumbinary disk in the radiation/wave zone, using general relativistic hydrodynamical simulations and a general relativistic ray-tracing code. We show that in the radiation/wave zone, retardation effects and GWs leave an imprint onto the disk, leading to quasi-periodic patterns in the electromagnetic lightcurve.