The comparison of an optical and X-ray counterpart of subparsec supermassive binary black holes

TL;DR

This study compares optical and X-ray spectral signatures of subparsec supermassive black hole binaries to identify potential observational markers for their detection and orbital characterization.

Contribution

It introduces a simulation-based comparison of optical and X-ray line profiles to detect SMBHBs and analyze their orbital phases.

Findings

SMBHBs cause distinct variability in optical and X-ray lines.

Line profile imprints depend on orbital phase.

Profiles can help reconstruct binary orbits.

Abstract

In this paper, we study and compare the optical and X-ray counterparts of subparsec supermassive black hole binaries (SMBHBs). With that aim, we simulated the profiles of optical spectral lines emitted from the broad line region (BLR) as well as X-ray spectral lines emitted from the relativistic accretion disks around both black holes and compared them with each other. The obtained results showed that SMBHBs could cause a specific, but different variability of the lines from the optical part and Fe K$\alpha$ line, leaving potentially detectable imprints in their profiles. Since these imprints depend on the orbital phase of the system, they could be used for reconstructing the Keplerian orbits of the components in the observed SMBHBs. Moreover, such signatures in the optical and X-ray line profiles of the observed SMBHBs could be used as a tool for the detection of these objects as well as for studying their properties.