Discovery of a Candidate Binary Supermassive Black Hole in a Periodic Quasar from Circumbinary Accretion Variability
Abstract
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=16077 days) at 99.95% significance (with a global p-value of ~ 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 (restframe 1.7-yr) periodicity. The light curves are best fit by a bursty model predicted by hydrodynamic simulations of circumbinary accretion disks. The periodicity is likely caused by accretion rate modulation by a milli-parsec BSBH emitting GWs, dynamically coupled to the circumbinary accretion disk. 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 disfavors 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.
Keywords
Cite
@article{arxiv.2008.12317,
title = {Discovery of a Candidate Binary Supermassive Black Hole in a Periodic Quasar from Circumbinary Accretion Variability},
author = {Wei-Ting Liao and Yu-Ching Chen and Xin Liu and A. Miguel Holgado and Hengxiao Guo and Robert Gruendl and Eric Morganson and Yue Shen and Tamara Davis and Richard Kessler and Paul Martini and Richard G. McMahon and Sahar Allam and James Annis and Santiago Avila and Manda Banerji and Keith Bechtol and Emmanuel Bertin and David Brooks and Elizabeth Buckley-Geer and Aurelio Carnero Rosell and Matias Carrasco Kind and Jorge Carretero and Francisco Javier Castander and Carlos Cunha and Chris D'Andrea and Luiz da Costa and Christopher Davis and Juan De Vicente and Shantanu Desai and H. Thomas Diehl and Peter Doel and Tim Eifler and August Evrard and Brenna Flaugher and Pablo Fosalba and Josh Frieman and Juan Garcia-Bellido and Enrique Gaztanaga and Karl Glazebrook and Daniel Gruen and Julia Gschwend and Gaston Gutierrez and Will Hartley and Devon L. Hollowood and Klaus Honscheid and Ben Hoyle and David James and Elisabeth Krause and Kyler Kuehn and Marcos Lima and Marcio Maia and Jennifer Marshall and Felipe Menanteau and Ramon Miquel and Andrés Plazas Malagón and Aaron Roodman and Eusebio Sanchez and Vic Scarpine and Michael Schubnell and Santiago Serrano and Mathew Smith and R. Chris Smith and Marcelle Soares-Santos and Flavia Sobreira and Eric Suchyta and Molly Swanson and Gregory Tarle and Vinu Vikram and Alistair Walker and the DES Collaboration},
journal= {arXiv preprint arXiv:2008.12317},
year = {2020}
}
Comments
Accepted to MNRAS, 17 pages, 9 figures