2026/07/24 by Yue Xu, Fu-Guo Xie, Ya-Ping Li +2
Physics and Astronomy · #Accretion (finance) #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Binary black hole #Binary number #Binary system #Black hole (networking) #Circumbinary planet #Galaxies: Formation, Evolution, Phenomena #Mass ratio #Spectral energy distribution #X-ray binary #astro-ph.GA #astro-ph.HE
paper · pdf · open access · doi:10.3847/1538-4357/ae84c5
published in The Astrophysical Journal 1006(2), 239 (IOP Publishing)
openalex created_date 2026/07/29 · openalex publication_date 2026/07/30 · openalex updated_date 2026/08/05
Abstract Binary (super-)massive black holes (BHs) are expected to reside in the center of some galaxies. In this work, we revisit accretion onto binary massive BHs, incorporating recent advances in both accretion theory and the mass transfer rate between the two massive BHs. We focus on relatively bright systems with an Eddington ratio of 0.1 for a binary with total BH mass of 10 8 M ⊙ , but consider a wide range of mass ratios of 10 −4 ≤ q ≤ 0.5. The binary system consists of two mini-disks surrounding two individual BHs and a circumbinary disk surrounding the mass center of the binary BHs. Depending on the mass ratio, the two mini-disks could be hot accretion flows, standard thin (cold) disks, or Slim disks. The radiative contributions from all three disks, each potentially in different accretion modes, are taken into account self-consistently. The spectral energy distributions (SEDs) of the binary BH system show universal “notch” features from the near-IR to the UV bands, caused by the gap or cavity in the accretion disk, consistent with previous studies. Binaries with different mass ratios exhibit distinct SED properties, offering opportunities for testing (identifying candidates) with future broadband (IR up to X-rays) observations. We also investigate the evolution of these binary systems, and find that, for systems with initial mass ratios of q ≲ a few ×10 −3 , the mass ratio evolves toward an equilibrium value of q ∼ 10 −3 . For binary BH systems with a larger initial mass ratio, their mass ratio instead evolves toward unity.