MOMO - V. Effelsberg, Swift, and Fermi study of the blazar and supermassive binary black hole candidate OJ 287 in a period of high activity
: Komossa S, Grupe D, Kraus A, Gonzalez A, Gallo LC, Valtonen MJ, Laine S, Krichbaum TP, Gurwell MA, Gomez JL, Ciprini S, Myserlis I, Bach U
Publisher: OXFORD UNIV PRESS
: 2022
: Monthly Notices of the Royal Astronomical Society
: MON NOT R ASTRON SOC
: 513
: 3
: 3165
: 3179
: 15
: 0035-8711
: 1365-2966
DOI: https://doi.org/10.1093/mnras/stac792
: https://academic.oup.com/mnras/article/513/3/3165/6553855
: https://research.utu.fi/converis/portal/detail/Publication/175529037
We report results from our ongoing project MOMO (Multiwavelength Observations and Modelling of OJ 287). In this latest publication of a sequence, we combine our Swift UVOT-XRT and Effelsberg radio data (2.6-44 GHz) between 2019 and 2022.04 with public SMA data and gamma-ray data from the Fermi satellite. The observational epoch covers OJ 287 in a high state of activity from radio to X-rays. The epoch also covers two major events predicted by the binary supermassive black hole (SMBH) model of OJ 287. Spectral and timing analyses clearly establish: a new UV-optical minimum state in 2021 December at an epoch where the secondary SMBH is predicted to cross the disc surrounding the primary SMBH; an overall low level of gamma-ray activity in comparison to pre-2017 epochs; the presence of a remarkable, long-lasting UV-optical flare event of intermediate amplitude in 2020-2021; a high level of activity in the radio band with multiple flares; and particularly a bright, ongoing radio flare peaking in 2021 November that may be associated with a gamma-ray flare, the strongest in 6 yr. Several explanations for the UV-optical minimum state are explored, including the possibility that a secondary SMBH launches a temporary jet, but the observations are best explained by variability associated with the main jet.
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