A1 Refereed original research article in a scientific journal
X-ray spectral components of the blazar and binary black hole candidate OJ 287 (2005-2020)
Authors: Komossa S, Grupe D, Parker ML, Gomez JL, Valtonen MJ, Nowak MA, Jorstad SG, Haggard D, Chandra S, Ciprini S, Dey L, Gopakumar A, Hada K, Markoff S, Neilsen J
Publisher: OXFORD UNIV PRESS
Publication year: 2021
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 504
Issue: 4
First page : 5575
Last page: 5587
Number of pages: 13
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stab1223
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/66412666
We present a comprehensive analysis of all XMM-Newton spectra of OJ 287 spanning 15 yr of X-ray spectroscopy of this bright blazar. We also report the latest results from our dedicated Swift UVOT and XRT monitoring of OJ 287, which started in 2015, along with all earlier public Swift data since 2005. During this time interval, OJ 287 was caught in extreme minima and outburst states. Its X-ray spectrum is highly variable and encompasses all states seen in blazars from very flat to exceptionally steep. The spectrum can be decomposed into three spectral components: Inverse Compton (IC) emission dominant at low-state, supersoft synchrotron emission that becomes increasingly dominant as OJ 287 brightens, and an intermediately-soft (Gamma(x) = 2.2) additional component seen at outburst. This last component extends beyond 10 keV and plausibly represents either a second synchrotron/IC component and/or a temporary disc corona of the primary supermassive black hole (SMBH). Our 2018 XMM-Newton observation, quasi-simultaneous with the Event Horizon Telescope observation of OJ 287, is well described by a two-component model with a hard IC component of Gamma(x) = 1.5 and a soft synchrotron component. Low-state spectra limit any long-lived accretion disc/corona contribution in X-rays to a very low value of L-x/L-Edd < 5.6 x 10(-4) (for M-BH,M- primary = 1.8 x 10(10) M-circle dot). Some implications for the binary SMBH model of OJ 287 are discussed.
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