Impact of a binary black hole on its outer circumbinary disc

ABSTRACT Accreting supermassive binary black holes (SMBBHs) are potential targets for multimessenger astronomy as they emit gravitational waves (GW) while their environment emits electromagnetic (EM) waves. In order to get the most out of a joint GW–EM detection we first need obtain theoretically predicted EM signals unambiguously linked BBHs. that respect, this is series papers dedicated accreting pre-merger BBHs and associated observables. Here, extend our Numerical Observatory Violent systems, e-NOVAs, any space–time. Unlike previous studies, almost exclusively focused on inner regions, investigated impact BBH its outer circumbinary disc, located in radiation (or wave) zone, after implementing an approximate analytical space–time spinning, inspiralling e-NOVAs. We follow formation weak spiral structure disc density arising from retardation effects zone metric. Simulation data then post-processed with general-relativistic ray-tracing code incorporating same space–time, assuming SMBBH sources. The creates small $({\lt }1{{\ \rm per\ cent}})$ but unambiguous modulation light curve at semi-orbital period. This signal, although weak, fundamentally different axisymmetric around single BH providing lower limit disc. difference being found, study how parameters find optimal case which high source inclination mass ratio (from 0.1 1).