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Optical Variability of BL Lac Object OJ 287

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.

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Optical Variability of BL Lac Object OJ 287

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  1. Optical Variability of BL Lac Object OJ 287 Wu Jianghua 2005.8

  2. 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)

  3. Historical Light Curve of OJ 287 the only blazar with convincing evidence of periodic light curve

  4. The OJ-94 Projecthttp://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: 19931997.

  5. Optical Results of OJ-94 Double-peaked structure

  6. Color Behavior During Outburst Based on the observations of the 94-96 outburst

  7. 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;

  8. 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;

  9. Our Monitoring Program • Time span (JD 2453400  2453489); • Actual 26 nights; • Filter (BATC e, i, m); • Exposure time (180  300 s). ~ R ~ I

  10. The Finding Chart

  11. Nightly Mean Light Curve Amplitude: ~ 1 mag

  12. Color Behavior A weak bluer-when-brighter trend

  13. Structure Function Analysis a period of ~ 40 days

  14. The 94-peak Revisited

  15. SF Analysis of the 94-peak a period of ~ 40 days, consistent with our monitoring results

  16. 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…

  17. 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

  18. Interference filter with multi-peaks

  19. Light Path Diagram

  20. Test Observations

  21. Thanks!

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