ABSTRACT

We present an analytic model for computing the luminosity and spectral evolution of flares

caused by a supermassive black hole impacting the accretion disc of another supermassive

black hole. Our model includes photon diffusion, emission from optically thin regions and

relativistic corrections to the observed spectrum and time-scales. We test the observability of

the impact scenario with a simulated population of quasars hosting supermassive black hole

binaries. The results indicate that for a moderate binary mass ratio of 0:3, and impact distances

of 100 primary Schwarzschild radii, the accretion disc impacts can be expected to equal or

exceed the host quasar in brightness at observed wavelength  = 510 nm up to z = 0:6. We

conclude that accretion disc impacts may function as an independent probe for supermassive

black hole binaries. We release the code used for computing the model light curves to the

community.