Intensive monitoring of OJ 287

We present intensive optical, infrared, and radio monitoring observations of the BL Lac object OJ 287, taken between the years 1993-1998. Two large optical outbursts were detected at the predicted times in November 1994 and December 1995. The detection of these outbursts supports the binary black hole model for OJ 287. Optical and radio polarisation observations show large variability in the degree of polarisation and position angle, very similar to those observed during the 1983/84 outburst in OJ 287. The polarisation position angles show very similar behaviour during these observations, indicating that, at least, the magnetic field orientations in radio and optical bands are related in OJ 287. Optical and infrared light curves show continuous variability in time scales ranging from tens of minutes to years. In the radio bands we have observed some of the lowest ever measured flux levels. During the first optical outburst in November 1994 the observed radio flux was very low, but during the second optical outburst radio bands also showed high flux levels. This is a puzzling observation, which can hopefully be used for discriminating between different outburst models. On top of the large outbursts OJ 287 has displayed flaring activity in time scales from days to weeks and shorter time scale flickering. Based partly on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway and Sweden in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias. Based partly on observations collected at the German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institute für Astronomie, Heidelberg, jointly with the Spanish National Commission for Astronomy. Based partly on observations carried out at Observatorio Astronomico National, San Pedro Martir, Baja California, Mexico. Based partly on observations made with the IAC-80 Telescope and the Carlos Sánchez Telescope operated on the island of Tenerife by the Instituto de Astrofísica de Canarias at the Spanish Observatorio del Teide.