Possible electromagnetic manifestations of merging black holes

The accretion disk response to a loss of 5% of the mass of the accretor formed by a stellar-mass binary black hole coalescence has been simulated. The parameters of the initial binary system correspond to the gravitational-wave source GW170814. We performed a series of simulations of models with radiative and convective heat transfer mechanisms and various accretion rates. The models took into account radiation pressure and adiabatic vertical gas expansion. Reducing the mass of the accretor due to emission of gravitational waves led to a strong hydrodynamic disturbance of the disk that developed in less than one second into a shock wave. As a result of shock heating, the luminosity of convective disks increased by 3–5 orders of magnitude and reached $10^{43}$ erg s$^{-1}$. The luminosity of radiative disks increased by 1–2 orders of magnitude, to $10^{40}$ erg s$^{-1}$. If the source is as far as 540 Mpc (as in the case of the GW170814 event), disk brightening could be detected by the XMM-Newton X-ray observatory.