MOMO V. Effelsberg, Swift and Fermi study of the blazar and supermassive
  binary black hole candidate OJ 287 in a period of high activity
  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 disk 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 years. 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.
