OJ287 polarization and VLBI jet direction

First, a model of the variation of the jet direction is calculated, and the main parameters of the model are fixed by the long-term optical brightness evolution. Then this model is compared with the variation of the parsec-scale radio jet position angle in the sky.

Finally, the variation of the polarization angle is calculated using the same model, but using a magnetic field configuration which is at a constant angle relative to the optical jet. It is found that the model fits the data reasonably well if the field is almost parallel to the jet axis. This may imply a steady magnetic field geometry, such as a large-scale helical field.