A Search for Signatures of Supermassive Black Hole Binaries in the Broad-Band Spectral Energy Distribution of Quasars

Abstract

Supermassive black hole binaries (SMBHBs) are of great interest to astrophysics, but have yet to be detected by observations at sub-parsec scales. One proposed method for detecting these sources is by identifying strongly periodic variations in their light curves, but this method and the results produced by it have been widely debated. In this study, we use a sample of quasars that have been proposed to exhibit periodic variability and search for evidence of a different signature in their spectral energy distributions (SEDs) that is also proposed as evidence of a SMBHB. Our method involves searching for a notch in the SED, which would be a consequence of a cavity in the circumbinary accretion disk caused by gravitational torques from the binary. While we do not find strong evidence of this phenomenon in our sample, we propose methods to improve our modeling capabilities as well as potential explanations for our findings.