optical variability of bl lac object oj 287 wu jianghua 2005.8
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Optical Variability of Optical Variability of BL Lac Object OJ 287BL Lac Object OJ 287
Wu JianghuaWu Jianghua
2005.82005.8
Properties of BlazarsProperties of Blazars
A subset of AGNs;A subset of AGNs; Rapid and strong variation Rapid and strong variation
without evident period;without evident period; High polarization, highly High polarization, highly
variable;variable; Power-law optical Power-law optical
continuum;continuum; Radio-loud, flat-spectrum;Radio-loud, flat-spectrum; Superluminal motion.Superluminal motion.
BL Lac (no emission line)BL Lac (no emission line)FSRQ (emission line)FSRQ (emission line)
Historical Light Curve of OJ 287Historical Light Curve of OJ 287
the only blazar with convincing evidence of periodic light curve
The OJ-94 ProjectThe OJ-94 Projecthttp://www.astro.utu.fi/oj94/http://www.astro.utu.fi/oj94/
Sillanpaa et al. (1988) predicted a new outbursSillanpaa et al. (1988) predicted a new outburst in 1994-96 from the historical light curves;t in 1994-96 from the historical light curves;
The OJ-94 project was organized (Takalo et al. The OJ-94 project was organized (Takalo et al. 1996);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: 1993Time span: 19931997.1997.
Color Behavior During OutburstColor Behavior During Outburst
Based on the observations of the 94-96 outburst
Properties of the Light CurvesProperties 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 The first peak is narrow and thermal while the
second is broad and synchrotronic.second is broad and synchrotronic.
Extremely stable color during the outburst;Extremely stable color during the outburst;
Models for Cyclic OutburstsModels for Cyclic Outbursts
Binary black hole models (Sillanpaa et al. 198Binary black hole models (Sillanpaa et al. 1988; Lehto & Valtonen 1996; Valtaoja et al. 2008; Lehto & Valtonen 1996; Valtaoja et al. 2000; Liu & Wu 2002);0; 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 ProgramOur Monitoring Program
Time span (JD 2453400 Time span (JD 2453400 2453489); 2453489);
Actual 26 nights;Actual 26 nights; Filter (BATC e, i, m);Filter (BATC e, i, m); Exposure time Exposure time
(180 (180 300 s). 300 s).
~ R ~ I
SF Analysis of the 94-peakSF Analysis of the 94-peak
a period of ~ 40 days, consistent with our monitoring results
ConclusionsConclusions The variation of OJ 287 shows a period of ~ 40 days The variation of OJ 287 shows a period of ~ 40 days
in its quiescent state; in its quiescent state; The variation of OJ 287 during the 1994-peak can be The variation of OJ 287 during the 1994-peak can be
resolved into two components: The first component resolved into two components: The first component can be considered as the continuing of the normal can be considered as the continuing of the normal blazar variation. It has the similar amplitude and blazar variation. It has the similar amplitude and timescale as those in quiescent state; The second timescale as those in quiescent state; The second component can be taken as a ‘low-frequency’ component can be taken as a ‘low-frequency’ modulation of the first component. It may be induced modulation of the first component. It may be induced by the BBH interaction.by the BBH interaction.
Constraints on the model of the outbursts…Constraints on the model of the outbursts…
Future Monitoring with New FacilitiesFuture Monitoring with New Facilities
Interference filter with multi-peaks + objective Interference filter with multi-peaks + objective prism + Schmidt telescopeprism + Schmidt telescope
Make photometric measurements exactly Make photometric measurements exactly simultaneously in multi-wavebandssimultaneously in multi-wavebands
Use timescale and color behavior of the Use timescale and color behavior of the variation to constrain the mechanisms of the variation to constrain the mechanisms of the variabilityvariability