Abstract:
Two guest-observer XMM-Newton pointings of the blazar OJ 287 in 2005 are
introduced, along with part of the radio, mm, near-IR, and optical data obtained during a
coordinated and intensive WEBT campaign, during longer-term monitoring observations
performed by teams of the ENIGMA network, and during other independent observing
programs (like VLBA observations). In that year OJ 287 showed an interesting variable behavior in the optical band. An optical outburst, well matched by our WEBT observations,
is claimed in the period Oct.-Nov. 2005, and the XMM-Newton X-ray observations are performed in correspondence with two active optical states (an intermediate flare and such out-
burst). X-ray data indicates different flux levels, spectral slopes, and emission components,
and VLBA radio maps are consistent with a jet precession model. This appreciable observing effort is still ongoing (a further XMM-Newton pointing is planned in 2008), joined with
further parallel/multi-monitoring observing programmes devoted to this interesting object
