Black hole accretion disc impacts

TL;DR

This paper develops an analytic model to predict the luminosity and spectral signatures of flares caused by supermassive black hole impacts on accretion discs, aiding in the detection of black hole binaries.

Contribution

It introduces a new analytic model that includes relativistic effects and photon diffusion, and assesses the observability of impact flares in quasars with supermassive black hole binaries.

Findings

Impact flares can outshine host quasars at certain wavelengths up to z=0.6.

The model predicts observable signatures for moderate mass ratio binaries.

The code for light curve computation is publicly available.

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 {\lambda} = 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.