Discovery of a Candidate Binary Supermassive Black Hole in a Periodic Quasar from Circumbinary Accretion Variability. (arXiv:2008.12317v2 [astro-ph.GA] UPDATED)

Discovery of a Candidate Binary Supermassive Black Hole in a Periodic Quasar from Circumbinary Accretion Variability. (arXiv:2008.12317v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Liao_W/0/1/0/all/0/1">Wei-Ting Liao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Y/0/1/0/all/0/1">Yu-Ching Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_X/0/1/0/all/0/1">Xin Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Holgado_A/0/1/0/all/0/1">A. Miguel Holgado</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guo_H/0/1/0/all/0/1">Hengxiao Guo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gruendl_R/0/1/0/all/0/1">Robert Gruendl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Morganson_E/0/1/0/all/0/1">Eric Morganson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shen_Y/0/1/0/all/0/1">Yue Shen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Davis_T/0/1/0/all/0/1">Tamara Davis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kessler_R/0/1/0/all/0/1">Richard Kessler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martini_P/0/1/0/all/0/1">Paul Martini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McMahon_R/0/1/0/all/0/1">Richard G. McMahon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Allam_S/0/1/0/all/0/1">Sahar Allam</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Annis_J/0/1/0/all/0/1">James Annis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Avila_S/0/1/0/all/0/1">Santiago Avila</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Banerji_M/0/1/0/all/0/1">Manda Banerji</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bechtol_K/0/1/0/all/0/1">Keith Bechtol</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bertin_E/0/1/0/all/0/1">Emmanuel Bertin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brooks_D/0/1/0/all/0/1">David Brooks</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Buckley_Geer_E/0/1/0/all/0/1">Elizabeth Buckley-Geer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rosell_A/0/1/0/all/0/1">Aurelio Carnero Rosell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kind_M/0/1/0/all/0/1">Matias Carrasco Kind</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carretero_J/0/1/0/all/0/1">Jorge Carretero</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Castander_F/0/1/0/all/0/1">Francisco Javier Castander</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cunha_C/0/1/0/all/0/1">Carlos Cunha</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+DAndrea_C/0/1/0/all/0/1">Chris D'Andrea</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Costa_L/0/1/0/all/0/1">Luiz da Costa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Davis_C/0/1/0/all/0/1">Christopher Davis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vicente_J/0/1/0/all/0/1">Juan De Vicente</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Desai_S/0/1/0/all/0/1">Shantanu Desai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Diehl_H/0/1/0/all/0/1">H. Thomas Diehl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Doel_P/0/1/0/all/0/1">Peter Doel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eifler_T/0/1/0/all/0/1">Tim Eifler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Evrard_A/0/1/0/all/0/1">August Evrard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Flaugher_B/0/1/0/all/0/1">Brenna Flaugher</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fosalba_P/0/1/0/all/0/1">Pablo Fosalba</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Frieman_J/0/1/0/all/0/1">Josh Frieman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garcia_Bellido_J/0/1/0/all/0/1">Juan Garcia-Bellido</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gaztanaga_E/0/1/0/all/0/1">Enrique Gaztanaga</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Glazebrook_K/0/1/0/all/0/1">Karl Glazebrook</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gruen_D/0/1/0/all/0/1">Daniel Gruen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gschwend_J/0/1/0/all/0/1">Julia Gschwend</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gutierrez_G/0/1/0/all/0/1">Gaston Gutierrez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hartley_W/0/1/0/all/0/1">Will Hartley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hollowood_D/0/1/0/all/0/1">Devon L. Hollowood</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Honscheid_K/0/1/0/all/0/1">Klaus Honscheid</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hoyle_B/0/1/0/all/0/1">Ben Hoyle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+James_D/0/1/0/all/0/1">David James</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Krause_E/0/1/0/all/0/1">Elisabeth Krause</a>, et al. (22 additional authors not shown)

Binary supermassive black holes are expected to be a generic byproduct from
hierarchical galaxy formation. The final coalescence of BSBHs is thought to be
the loudest gravitational wave siren in the universe, 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 days) at 99.95%
significance in the optical light curves of a quasar at z=1.53, SDSS
J025214.67-002813.7. Combining archival Sloan Digital Sky Survey data with new,
high signal to noise imaging from the Dark Energy Survey, the total ~20yr time
baseline spans ~4.6 cycles of the observed 4.4-yr (restframe 1.7-yr)
periodicity. The light curves are best characterized by a bursty model
predicted by hydrodynamic simulations of circumbinary accretion disks. The
periodicity is likely caused by accretion rate variability periodically
modulated by a milli-parsec BSBH emitting gravitational waves while still being
dynamically coupled to the circumbinary accretion disk. A characteristic 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 as the dominant mechanism,
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 Legacy Survey of Space and Time at Vera
C. Rubin Observatory may be able to detect hundreds to thousands of candidate
BSBHs from circumbinary accretion variability with direct implications for
Laser Interferometer Space Antenna.

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