Periodic light variations from the triple-disk system around supermassive binary black holes

Abstract

We investigate accretion flows around supermassive binary black holes (BBHs) with the orbital eccentricity e = 0.5, the semi‐major axis a = 0.01 pc, and the low mass ratio of the secondary black hole (BH) to the primary BH q = 0.1. In the simulations we consider a triple‐disk system composing of two accretion disks around BHs and one circumbinary disk surrounding the two. The circumbinary disk works as a mass reservoir. We confirm that a non‐axisymmetric accretion disk is formed around each BH. The X‐ray luminosity of the secondary BH exhibits the double peaks every binary orbit, whereas that of the primary BH shows a single peak. Such properties can not be seen in the case of equal mass BBHs and therefore provide a potentially important observational signature of supermassive BBHs with low mass ratios.