2015/08/13 by Chang-Shuo Yan, Youjun Lu, Xinyu Dai +1 · 5 citations
Physics and Astronomy · #Active galactic nucleus #Adaptive optics and wavefront sensing #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Binary black hole #Circumbinary planet #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gravitational wave #Parsec #Physics #Quasar #Stars #Supermassive black hole #astro-ph.GA #astro-ph.HE #gr-qc
paper · pdf · doi:10.1088/0004-637x/809/2/117
published as The Astrophysical Journal, 2015, 809, 117 · a typo in equation (2) and also in equation (5) of the Appendix is fixed; 9 pages, 7 figures
openalex publication_date 2015/08/13 · arxiv created 2015/09/08 · arxiv updated 2015/09/09 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
Supermassive binary black holes (BBHs) are unavoidable products of galaxy mergers and are expected to exist in the cores of many quasars. Great effort has been made during the past several decades to search for BBHs among quasars; however, observational evidence for BBHs remains elusive and ambiguous, which is difficult to reconcile with theoretical expectations. In this paper, we show that the distinct optical-to-UV spectrum of Mrk 231 can be well interpreted as emission from accretion flows onto a BBH, with a semimajor axis of ∼590 AU and an orbital period of ∼1.2 years. The flat optical and UV continua are mainly emitted from a circumbinary disk and a mini-disk around the secondary black hole (BH), respectively; and the observed sharp drop off and flux deficit at λ ∼ 4000–2500 Å is due to a gap (or hole) opened by the secondary BH migrating within the circumbinary disk. If confirmed by future observations, this BBH will provide a unique laboratory to study the interplay between BBHs and accretion flows onto them. Our result also demonstrates a new method to find sub-parsec scale BBHs by searching for deficits in the optical-to-UV continuum among the spectra of quasars.