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Optical Variability of BL Lac Object OJ 287 Wu Jianghua 2005.8 Properties of Blazars A subset of AGNs; Rapid and strong variation without evident period; High polarization, highly variable; Power-law optical continuum; Radio-loud, flat-spectrum; Superluminal motion. BL Lac (no emission line) FSRQ (emission line) Historical Light Curve of OJ 287 the only blazar with convincing evidence of periodic light curve The OJ-94 Project http://www.astro.utu.fi/oj94/ Sillanpaa et al. (1988) predicted a new outburst in 1994-96 from the historical light curves; The OJ-94 project was organized (Takalo et al. 1996); More than 50 astronomers from 10 countries; From radio, infrared, optical, UV, to X-ray; Time span: 19931997. Optical Results of OJ-94 Double-peaked structure Color Behavior During Outburst Based on the observations of the 94-96 outburst Properties of the Light Curves 12-year cyclic optical outburst; Double-peaked structure of the outburst; The first peak is narrow and thermal while the second is broad and synchrotronic. Extremely stable color during the outburst; Models for Cyclic Outbursts Binary black hole models (Sillanpaa et al. 1988; Lehto & Valtonen 1996; Valtaoja et al. 2000; Liu & Wu 2002); Beaming model (Villata et al. 1996; 1998); Precessing disc model (Katz 1996); Microlensing effect; Lighthouse effect; Our Monitoring Program Time span (JD 2453400 2453489); Actual 26 nights; Filter (BATC e, i, m); Exposure time (180 300 s). ~R ~I The Finding Chart Nightly Mean Light Curve Amplitude: ~ 1 mag Color Behavior A weak bluer-whenbrighter trend Structure Function Analysis a period of ~ 40 days The 94-peak Revisited SF Analysis of the 94-peak a period of ~ 40 days, consistent with our monitoring results Conclusions The variation of OJ 287 shows a period of ~ 40 days in its quiescent state; The variation of OJ 287 during the 1994-peak can be resolved into two components: The first component can be considered as the continuing of the normal blazar variation. It has the similar amplitude and timescale as those in quiescent state; The second component can be taken as a ‘low-frequency’ modulation of the first component. It may be induced by the BBH interaction. Constraints on the model of the outbursts… Future Monitoring with New Facilities Interference filter with multi-peaks + objective prism + Schmidt telescope Make photometric measurements exactly simultaneously in multi-wavebands Use timescale and color behavior of the variation to constrain the mechanisms of the variability Interference filter with multi-peaks Light Path Diagram Test Observations Thanks!