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A candidate sub-parsec supermassive binary black hole system


The role of mergers in producing galaxies, together with the finding that most large galaxies harbour black holes in their nuclei1, implies that binary supermassive black hole systems should be common. Here we report that the quasar SDSS J153636.22+044127.0 is a plausible example of such a system. This quasar shows two broad-line emission systems, separated in velocity by 3,500 km s-1. A third system of unresolved absorption lines has an intermediate velocity. These characteristics are unique among known quasars. We interpret this object as a binary system of two black holes, having masses of 107.3 and 108.9 solar masses separated by 0.1 parsec with an orbital period of 100 years.

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Figure 1: The observed spectrum from the SDSS archive of the quasar SDSS J1536+0441.
Figure 2: Cross-correlation between the 4,200–4,450 Å region of the spectrum of J1536+0441 and the corresponding region of a composite quasar spectrum12.


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NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under cooperative agreement with the National Science Foundation (NSF). This paper has used data from the SDSS archive, the 2MASS archive, the ROSAT archive at the High Energy Astrophysics Science Archive Research Center (HEASARC), provided by NASA's Goddard Space Flight Center, the FIRST survey, and the NVSS. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the NSF, the US Department of Energy, the National Aeronautics and Space Administration (NASA), the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS website is at The 2MASS is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by NASA and the NSF.

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Correspondence to Todd A. Boroson.

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Boroson, T., Lauer, T. A candidate sub-parsec supermassive binary black hole system. Nature 458, 53–55 (2009).

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