The activity of the blazar OJ 287 in 2005: XMM-Newton observations and coordinated campaign

Two guest‐observer XMM‐Newton observations of the peculiar blazar OJ 287 in 2005 are briefly presented, along with the multiwavelength data obtained during a coordinated intensive WEBT campaign, and data obtained within longer‐term independent monitor programs, performed also by other facilities. During that year OJ 287 showed an interesting variability trend in the optical band. The X‐ray observations, performed in correspondence with two active optical states (a flare and an outburst), indicate different flux levels, spectral slopes, and emission components, while VLBA radio maps are consistent with a jet precession model. A further XMM‐Newton observation of OJ 287 is granted and foreseen in spring 2008, providing the opportunity of a multifrequency campaign to be performed in conjunction with GLAST.