Discovery of a candidate binary supermassive black hole in a periodic quasar from circumbinary accretion variability

Wei Ting Liao, Yu Ching Chen, Xin Liu, A. Miguel Holgado, Hengxiao Guo, Robert Gruendl, Eric Morganson, Yue Shen, Tamara Davis, Richard Kessler, Paul Martini, Richard G. McMahon, Sahar Allam, James Annis, Santiago Avila, Manda Banerji, Keith Bechtol, Emmanuel Bertin, David Brooks, Elizabeth Buckley-GeerAurelio Carnero Rosell, Matias Carrasco Kind, Jorge Carretero, Francisco Javier Castander, Carlos Cunha, Chris D'Andrea, Luiz Da Costa, Christopher Davis, Juan De Vicente, Shantanu Desai, H. Thomas Diehl, Peter Doel, Tim Eifler, August Evrard, Brenna Flaugher, Pablo Fosalba, Josh Frieman, Juan Garcia-Bellido, Enrique Gaztanaga, Karl Glazebrook, Daniel Gruen, Julia Gschwend, Gaston Gutierrez, Will Hartley, Devon L. Hollowood, Klaus Honscheid, Ben Hoyle, David James, Elisabeth Krause, Kyler Kuehn, Marcos Lima, Marcio Maia, Jennifer Marshall, Felipe Menanteau, Ramon Miquel, Andres Plazas Malagon, Aaron Roodman, Eusebio Sanchez, Vic Scarpine, Michael Schubnell, Santiago Serrano, Mathew Smith, R. Chris Smith, Marcelle Soares-Santos, Flavia Sobreira, Eric Suchyta, Molly Swanson, Gregory Tarle, Vinu Vikram, Alistair Walker

Research output: Contribution to journalArticlepeer-review


Binary supermassive black holes (BSBHs) are expected to be a generic byproduct from hierarchical galaxy formation. The final coalescence of BSBHs is thought to be the loudest gravitational wave (GW) siren, yet no confirmed BSBH is known in the GW-dominated regime. While periodic quasars have been proposed as BSBH candidates, the physical origin of the periodicity has been largely uncertain. Here, we report discovery of a periodicity (p = 1607 ± 7 d) at 99.95 per cent significance (with a global p value of ∼10-3 accounting for the look elsewhere effect) in the optical light curves of a redshift 1.53 quasar, SDSS J025214.67-002813.7. Combining archival Sloan Digital Sky Survey data with new, sensitive imaging from the Dark Energy Survey, the total ∼20-yr time baseline spans ∼4.6 cycles of the observed 4.4-yr (rest frame 1.7-yr) periodicity. The light curves are best fit by a bursty model predicted by hydrodynamic simulations of circumbinary accretion discs. The periodicity is likely caused by accretion rate modulation by a milli-parsec BSBH emitting GWs, dynamically coupled to the circumbinary accretion disc. A bursty hydrodynamic variability model is statistically preferred over a smooth, sinusoidal model expected from relativistic Doppler boost, a kinematic effect proposed for PG1302-102. Furthermore, the frequency dependence of the variability amplitudes disfavours Doppler boost, lending independent support to the circumbinary accretion variability hypothesis. Given our detection rate of one BSBH candidate from circumbinary accretion variability out of 625 quasars, it suggests that future large, sensitive synoptic surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time may be able to detect hundreds to thousands of candidate BSBHs from circumbinary accretion with direct implications for Laser Interferometer Space Antenna.

Original languageEnglish (US)
Pages (from-to)4025-4041
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Jan 1 2021


  • Black hole physics
  • Galaxies: Active
  • Galaxies: High-redshift
  • Galaxies: nuclei
  • Quasars: General
  • Surveys

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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