Eccentric Binary Black Holes: Simulations in Full GR and MHD Reveal Novel Periodicities in Accretion, Jet Luminosity, and Synchrotron Spectra

We perform simulations of magnetohydrodynamic accretion onto equal-mass, non-spinning binary black holes in 3+1 full general relativity, treating the effects of orbital eccentricity. We find that binary black holes with non-negligible eccentricity accrete matter with periodicity that matches the binary orbital period, unlike quasi-circular binaries whose accretion rate modulates at ~0.7x the binary orbital period. Additionally, we find that the total jet luminosity is modulated at the orbital period for eccentric binaries, while quasi-circular binaries only exhibit long-term modulations. Performing a radiative transfer calculation of the dual jet synchrotron emission, we demonstrate that the optically thin synchrotron emission varies on the binary orbital period for eccentric binaries. Moreover, eccentric binaries spend more time in a low state, where the synchrotron emission is minimum, than in a high state, during which the synchrotron emission peaks. The quasi-circular binary case exhibits variability in its optically thin synchrotron emission but with no clear peak frequency. Our suite of simulations is an essential step in providing a comprehensive catalog of multimessenger theoretical models that will enable studies of supermassive binary black holes detectable across the electromagnetic and gravitational wave spectrum.