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Chandra Observations of Candidate Subparsec Binary Supermassive Black Holes

Saade, M. Lynne and Stern, Daniel and Brightman, Murray and Haiman, Zoltán and Djorgovski, S. G. and D'Orazio, Daniel and Ford, K. E. S. and Graham, Matthew J. and Jun, Hyunsung D. and Kraft, Ralph P. and McKernan, Barry and Vikhlinin, Alexei and Walton, Dominic J. (2020) Chandra Observations of Candidate Subparsec Binary Supermassive Black Holes. Astrophysical Journal, 900 (2). Art. No. 148. ISSN 1538-4357. doi:10.3847/1538-4357/abad31.

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We present analysis of Chandra X-ray observations of seven quasars that were identified as candidate subparsec binary supermassive black hole (SMBH) systems in the Catalina Real-Time Transient Survey based on the apparent periodicity in their optical light curves. Simulations predict that close-separation accreting SMBH binaries will have different X-ray spectra than single accreting SMBHs, including harder or softer X-ray spectra, ripple-like profiles in the Fe K-α line, and distinct peaks in the spectrum due to the separation of the accretion disk into a circumbinary disk and mini disks around each SMBH. We obtained Chandra observations to test these models and assess whether these quasars could contain binary SMBHs. We instead find that the quasar spectra are all well fit by simple absorbed power-law models, with the rest-frame 2–10 keV photon indices, Γ, and the X-ray-to-optical power slopes, α_(OX), indistinguishable from those of the larger quasar population. This may indicate that these seven quasars are not truly subparsec binary SMBH systems, or it may simply reflect that our sample size was too small to robustly detect any differences. Alternatively, the X-ray spectral changes might only be evident at energies higher than probed by Chandra. Given the available models and current data, no firm conclusions are drawn. These observations will help motivate and direct further work on theoretical models of binary SMBH systems, such as modeling systems with thinner accretion disks and larger binary separations.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Saade, M. Lynne0000-0001-7163-7015
Stern, Daniel0000-0003-2686-9241
Brightman, Murray0000-0002-8147-2602
Haiman, Zoltán0000-0003-3633-5403
Djorgovski, S. G.0000-0002-0603-3087
D'Orazio, Daniel0000-0002-1271-6247
Graham, Matthew J.0000-0002-3168-0139
Jun, Hyunsung D.0000-0003-1470-5901
Kraft, Ralph P.0000-0002-0765-0511
McKernan, Barry0000-0002-9726-0508
Vikhlinin, Alexei0000-0001-8121-0234
Walton, Dominic J.0000-0001-5819-3552
Alternate Title:Chandra Observations of Candidate Sub-Parsec Binary Supermassive Black Holes
Additional Information:© 2020 The American Astronomical Society. Received 2020 February 18; revised 2020 July 22; accepted 2020 August 5; published 2020 September 11. We thank the anonymous referee for a very thorough report, which has improved the paper. Support for this work was provided by the National Aeronautics and Space Administration (NASA) through Chandra Award Number 18700580 issued by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the NASA under contract NAS8-03060. The work of D.S. was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Z.H. acknowledges support from NSF grant 1715661 and NASA grants 80NSSC19K0149 and NNX17AL82G. M.J.G. and S.G.D. were supported in part by NASA grant 16-ADAP16-0232 and NSF grants AST-1413600, AST-1518308, and AST-1749235. D.J.D. acknowledges funding from the Institute for Theory and Computation Fellowship. K.E.S.F. and B.M. were supported by NSF grant 1831412. H.D.J. was supported by the Basic Science Research Program through the National Research Foundation of Korea, funded by the Ministry of Education (NRF-2017R1A6A3A04005158).
Group:Astronomy Department, Space Radiation Laboratory
Funding AgencyGrant Number
NASA Chandra18700580
Institute for Theory and ComputationUNSPECIFIED
National Research Foundation of KoreaNRF-2017R1A6A3A04005158
Subject Keywords:Quasars ; Supermassive black holes ; Active galactic nuclei ; Active galaxies ; X-ray active galactic nuclei
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Quasars (1319); Supermassive black holes (1663); Active galactic nuclei (16); Active galaxies (17); X-ray active galactic nuclei (2035)
Record Number:CaltechAUTHORS:20200413-151905111
Persistent URL:
Official Citation:M. Lynne Saade et al 2020 ApJ 900 148
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102510
Deposited By: Tony Diaz
Deposited On:13 Apr 2020 22:40
Last Modified:16 Nov 2021 18:12

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