OJ 287 has all the characteristics of blazars, and it is one of the sources
studied the most extensively. Variability studies of the blazar concentrated
mostly on the frequencies lower than 1015 Hz, due to its weak emission at high
frequencies. In the UV range, Maraschi et al. (1986)
reported
variations on a timescale of two days. In the optical range, flux variations
of some periodicities were reported, with periods ranging from 13 minutes to
11.65 years (e.g. Visvanathan & Elliot 1973;
Frohlich et al. 1974; Kinman
1974; Carrasco et al. 1985; Valtaoja et al. 1985;
Xie et al. 1987; Sillanpää et al. 1988;
Kidger et al. 1992; Turner et al. 1994).
Long-term
variations reach 4 mag in the B band (Webb et al. 1988).
The question of the
existence of microvariations (lasting a few minutes to hours) in the optical
flux of blazars, until recently, remained unanswered. They are either
discrete events or parts of long term (night to night) variations
(Carini et al. 1992). Intraday variations in optical flux were reported by some authors
(e.g. Epstein et al. 1972; Visvanathan & Elliot 1973;
Frohlich et al. 1974;
McGimsey et al. 1975; Véron
& Véron 1975;
Carrasco et al. 1985; Valtaoja et al. 1985;
Miller et al. 1989; Carini et al. 1992;
Sillanpää et al. 1992;
Benitez et al. 1994; Sillanpää et al. 1994;
Takalo et al. 1994; Kidger et al. 1995).
The polarization level in
the optical region for OJ 287 ranged from 
to 
(Hagen-Thorn 1980), the position angle varied on
timescales from years to hours
(Takalo et al. 1994 and references therein). The polarization and position angle are
frequency-dependent (Valtaoja et al. 1991 and references
therein), the FDP
and the FDPA were variable with timescales from day to hours, and both the
strength and/or sign of the FDP or FDPA can also vary (Takalo et al. 1994
and references therein).
Microvariability of OJ 287 in the infrared was reported (e.g. Epstein et al. 1972; Wolstencroft et al. 1982; Holmes et al. 1984; Lorenzetti et al. 1989; Takalo et al. 1992; Kidger et al. 1994). At radio frequencies, intraday variability was also reported (e.g. Epstein et al. 1972; Valtaoja et al. 1985; Dreher et al. 1986; De Bruyn 1988; Kinzel et al. 1988), and there is a strong correlation between the variabilities in the optical and in radio with short (intraday) or long lags (Wagner & Witzel 1995 and references therein).
Since 1987, we have monitored OJ 287 and searched for rapid variability. However in 1990-1992 only variability with a timescale of one day was observed (Guibin et al. 1995). A large outburst during 1994 for OJ 287 was predicted by Sillanpää et al. (1988) based on an average 11.65 years interval between major outbursts. Sillanpää et al. (1996) claimed that the outburst had occurred in 1994 and the peak of the outburst was observed around November 10. In 1994-1995, we continued to search for the rapid variability and observed variability with timescales of minutes, hours and one day in OJ 287.