Simultaneous gravitational and electromagnetic wave observations of merging black hole binaries ( BHBHs ) can provide unique opportunities to study gravitation physics , accretion and cosmology . Here we perform fully general-relativistic , hydrodynamic simulations of equal-mass , nonspinning BHBHs coalescing in a circumbinary disk . We evolve the metric using the Baumgarte-Shapiro-Shibata-Nakamura ( BSSN ) formulation of Einstein ’ s field equations with standard moving puncture gauge conditions . We handle the hydrodynamics via a high-resolution shock-capturing scheme . These initial simulations are exploratory in nature and simplified accordingly . We track the inspiral starting from a binary separation of 10 M , where M is the total binary mass . We take the disks to have an inner radius at R _ { in } \approx 15 M to account for the hollow created by the binary torques . Our disks extend to R \approx 65 M and have an initial scale height of H / R \approx 0.03 - 0.11 . The gas is governed by a \Gamma -law equation of state , with \Gamma equal to 5 / 3 , 4 / 3 , and 1.1 . Disks are allowed to relax in the “ early inspiral ” epoch to provide quasistationary realistic initial data . We then evolve the spacetime metric and matter during the “ late inspiral and merger ” epochs . The later simulations are designed to track BHBH inspiral following disk-binary decoupling , through merger and ringdown , terminating before viscosity has time to fill the hollow about the black hole remnant . We compute the gas flow and accretion rate and estimate the electromagnetic luminosity due to bremsstrahlung and synchrotron emission as a perturbation for optically thin disks . The synchrotron component of the luminosity peaks in the infrared band and should be detectable by WFIRST and possibly the LSST for a 10 ^ { 8 } M _ { \odot } binary embedded in a disk with a density n \sim 10 ^ { 12 } \mbox { cm } ^ { -3 } at z = 1 , beginning with a maximum value of L \sim 10 ^ { 46 } n _ { 12 } ^ { 2 } M _ { 8 } ^ { 3 } \mbox { erg } \mbox { s } ^ { -1 } at decoupling , and decreasing steadily over a timescale of \sim 100 M _ { 8 } hours to a value of L \sim 10 ^ { 45 } n _ { 12 } ^ { 2 } M _ { 8 } ^ { 3 } \mbox { erg } \mbox { s } ^ { -1 } at merger .