Multiband light curves from eccentric accreting supermassive black hole binaries

We use long-run, high-resolution hydrodynamics simulations to compute the multiwavelength light curves (LCs) from thermal disk emission around accreting equal-mass supermassive black hole (BH) binaries, with a focus on revealing binary eccentricity. LCs are obtained by modeling the disk thermodynamics with an adiabatic equation of state, a local blackbody cooling prescription, and corrections to approximate the effects of radiation pressure. We find that modulation of multiband LCs on the orbital time scale are generally in phase (to within similar to 2% of a binary orbital period), but they contain pulse substructure in the time domain that is not necessarily reflected in BH accretion rates _M. We thus predict that binary-hosting active galactic nucleus (AGN) will exhibit highly correlated, in-phase, periodic brightness modulations in their low-energy disk emission. However, detectability of these modulations in multiwavelength observing campaigns could be compromised because observed stochastic variability in AGNs typically has a higher amplitude than our proposed signal. It is possible that observations over temporal baselines of many binary periods may make the signal more prominent, but this would need to be analyzed carefully. If jet emission is predicted by _M, then we predict a weaker correlation with low-energy disk emission due to the differing subpeak structure. For the binary parameters we explore, we show that LC variability due to hydrodynamics likely dominates Doppler brightening for all equal-mass binaries with disk Mach numbers less than or similar to 20. A promising signature of eccentricity is weak or absent "lump" periodicity. We find hints that a significant lag exists between M_ and low-energy disk emission for circular binaries, but they are in phase for eccentric binaries, which might explain some "orphan" blazar flares with no gamma-ray counterpart.