Optical Variability of BL Lac Object OJ 287 Wu Jianghua

Properties of Blazars A subset of AGNs; A subset of AGNs; Rapid and strong variation without evident period; Rapid and strong variation without evident period; High polarization, highly variable; High polarization, highly variable; Power-law optical continuum; Power-law optical continuum; Radio-loud, flat-spectrum; Radio-loud, flat-spectrum; Superluminal motion. 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 Sillanpaa et al. (1988) predicted a new outburst in from the historical light curves; Sillanpaa et al. (1988) predicted a new outburst in from the historical light curves; The OJ-94 project was organized (Takalo et al. 1996); The OJ-94 project was organized (Takalo et al. 1996); More than 50 astronomers from 10 countries; More than 50 astronomers from 10 countries; From radio, infrared, optical, UV, to X-ray; From radio, infrared, optical, UV, to X-ray; Time span: 1993  Time span: 1993  1997.

Optical Results of OJ-94 Double-peaked structure

Color Behavior During Outburst Based on the observations of the outburst

Properties of the Light Curves 12-year cyclic optical outburst; 12-year cyclic optical outburst; Double-peaked structure of the outburst; Double-peaked structure of the outburst; The first peak is narrow and thermal while the second is broad and synchrotronic. The first peak is narrow and thermal while the second is broad and synchrotronic. Extremely stable color during the outburst; 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); 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); Beaming model (Villata et al. 1996; 1998); Precessing disc model (Katz 1996); Precessing disc model (Katz 1996); Microlensing effect; Microlensing effect; Lighthouse effect; Lighthouse effect;

Our Monitoring Program Time span (JD  ); Time span (JD  ); Actual 26 nights; Actual 26 nights; Filter (BATC e, i, m); Filter (BATC e, i, m); Exposure time Exposure time (180  300 s). (180  300 s). ~ R~ I

The Finding Chart

Nightly Mean Light Curve Amplitude: ~ 1 mag

Color Behavior A weak bluer-when- brighter 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 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. 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 … Constraints on the model of the outbursts …

Future Monitoring with New Facilities Interference filter with multi-peaks + objective prism + Schmidt telescope Interference filter with multi-peaks + objective prism + Schmidt telescope Make photometric measurements exactly simultaneously in multi-wavebands Make photometric measurements exactly simultaneously in multi-wavebands Use timescale and color behavior of the variation to constrain the mechanisms of the variability 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

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