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Title: A milliparsec supermassive black hole binary candidate in the galaxy SDSS J120136.02+300305.5

Galaxy mergers play a key role in the evolution of galaxies and the growth of their central supermassive black holes (SMBHs). A search for (active) SMBH binaries (SMBHBs) at the centers of the merger remnants is currently ongoing. Perhaps the greatest challenge is to identify the inactive SMBHBs, which might be the most abundant, but are also the most difficult to identify. Liu et al. predicted characteristic drops in the light curves of tidal disruption events (TDEs), caused by the presence of a secondary SMBH. Here, we apply that model to the light curve of the optically inactive galaxy SDSS J120136.02+300305.5, which was identified as a candidate TDE with XMM-Newton. We show that the deep dips in its evolving X-ray light curve can be well explained by the presence of a SMBHB at its core. A SMBHB model with a mass of the primary of M {sub BH} = 10{sup 7} M {sub ☉}, a mass ratio q ≅ 0.08, and a semi-major axis a {sub b} ≅ 0.6 mpc is in good agreement with the observations. Given that primary mass, introducing an orbital eccentricity is needed, with e {sub b} ≅ 0.3. Alternatively, a lower mass primary of Mmore » {sub BH} = 10{sup 6} M {sub ☉} in a circular orbit fits the light curve well. Tight binaries like this one, which have already overcome the 'final parsec problem', are prime sources of gravitational wave radiation once the two SMBHs coalesce. Future transient surveys, which will detect TDEs in large numbers, will place tight constraints on the SMBHB fraction in otherwise non-active galaxies.« less
Authors:
 [1] ;  [2] ;  [3]
  1. Department of Astronomy, Peking University, Beijing 100871 (China)
  2. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)
  3. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn (Germany)
Publication Date:
OSTI Identifier:
22356954
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 786; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; BINARY STARS; BLACK HOLES; GRAVITATIONAL WAVES; LIMITING VALUES; MASS; ORBITS; TRANSIENTS; VISIBLE RADIATION; X RADIATION; X-RAY GALAXIES