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The BAT AGN Spectroscopic Survey. XVIII. Searching for Supermassive Black Hole Binaries in X-Rays

Liu, Tingting and Koss, Michael and Blecha, Laura and Ricci, Claudio and Trakhtenbrot, Benny and Mushotzky, Richard and Harrison, Fiona and Ichikawa, Kohei and Kakkad, Darshan and Oh, Kyuseok and Powell, Meredith and Privon, George C. and Schawinski, Kevin and Shimizu, T. Taro and Smith, Krista Lynne and Stern, Daniel and Treister, Ezequiel and Urry, C. Megan (2020) The BAT AGN Spectroscopic Survey. XVIII. Searching for Supermassive Black Hole Binaries in X-Rays. Astrophysical Journal, 896 (2). Art. No. 122. ISSN 1538-4357. doi:10.3847/1538-4357/ab952d.

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Theory predicts that a supermassive black hole binary (SMBHB) could be observed as a luminous active galactic nucleus (AGN) that periodically varies on the order of its orbital timescale. In X-rays, periodic variations could be caused by mechanisms including relativistic Doppler boosting and shocks. Here we present the first systematic search for periodic AGNs using 941 hard X-ray light curves (14–195 keV) from the first 105 months of the Swift Burst Alert Telescope (BAT) survey (2004–2013). We do not find evidence for periodic AGNs in Swift-BAT, including the previously reported SMBHB candidate MCG+11−11−032. We find that the null detection is consistent with the combination of the upper-limit binary population in AGNs in our adopted model, their expected periodic variability amplitudes, and the BAT survey characteristics. We have also investigated the detectability of SMBHBs against normal AGN X-ray variability in the context of the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) survey. Under our assumptions of a binary population and the periodic signals they produce, which have long periods of hundreds of days, up to 13% true periodic binaries can be robustly distinguished from normal variable AGNs with the ideal uniform sampling. However, we demonstrate that realistic eROSITA sampling is likely to be insensitive to long-period binaries because longer observing gaps reduce their detectability. In contrast, large observing gaps do not diminish the prospect of detecting binaries of short, few-day periods, as 19% can be successfully recovered, the vast majority of which can be identified by the first half of the survey.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Liu, Tingting0000-0001-5766-4287
Koss, Michael0000-0002-7998-9581
Blecha, Laura0000-0002-2183-1087
Ricci, Claudio0000-0001-5231-2645
Trakhtenbrot, Benny0000-0002-3683-7297
Mushotzky, Richard0000-0002-7962-5446
Harrison, Fiona0000-0003-2992-8024
Ichikawa, Kohei0000-0002-4377-903X
Kakkad, Darshan0000-0002-2603-2639
Oh, Kyuseok0000-0002-5037-951X
Powell, Meredith0000-0003-2284-8603
Privon, George C.0000-0003-3474-1125
Schawinski, Kevin0000-0001-5464-0888
Shimizu, T. Taro0000-0002-2125-4670
Smith, Krista Lynne0000-0001-5785-7038
Stern, Daniel0000-0003-2686-9241
Treister, Ezequiel0000-0001-7568-6412
Urry, C. Megan0000-0002-0745-9792
Additional Information:© 2020. The American Astronomical Society. Received 2019 September 10; revised 2020 May 12; accepted 2020 May 19; published 2020 June 19. T.L., M.K., and G.C.P. thank the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611, for hosting the "Astrophysics of Massive Black Hole Mergers: From Galaxy Mergers to the Gravitational Wave Regime" workshop, where many stimulating discussions took place and this work was initiated. We thank the referee for a constructive report that helped improve the paper and Erin Kara for a helpful comment. T.L. is supported by NANOGrav National Science Foundation Physics Frontiers Center award No. 1430284. M.K. acknowledges support from NASA through ADAP award NNH16CT03C. L.B. acknowledges support from National Science Foundation grant AST-1715413. C.R. acknowledges support from the CONICYT+PAI Convocatoria Nacional subvencion a instalacion en la academia convocatoria año 2017 PAI77170080 and Fondecyt Iniciacion grant 11190831. K.O. acknowledges support from the National Research Foundation of Korea (NRF-2020R1C1C1005462). E.T. acknowledges support from CONICYT-Chile grants Basal-CATA AFB-170002, FONDECYT Regular 1160999 and 1190818, and Anillo de Ciencia y Tecnologia ACT1720033. G.C.P. acknowledges support from the University of Florida. This research has made use of data and/or software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC. We acknowledge the use of public data from the Swift data archive. Facility: Swift(BAT) - Swift Gamma-Ray Burst Mission.
Group:Astronomy Department, Space Radiation Laboratory
Funding AgencyGrant Number
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)2017 PAI77170080
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)11190831
National Research Foundation of KoreaNRF-2020R1C1C1005462
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1160999
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1190818
Anillo de Ciencia y TecnologiaACT1720033
University of FloridaUNSPECIFIED
Subject Keywords:Active galaxies ; Surveys ; X-ray sources
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Active galaxies (17); Surveys (1671); X-ray sources (1822)
Record Number:CaltechAUTHORS:20200624-104212632
Persistent URL:
Official Citation:Tingting Liu et al 2020 ApJ 896 122
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104004
Deposited By: George Porter
Deposited On:24 Jun 2020 19:20
Last Modified:16 Nov 2021 18:27

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