Download Optical Variability of BL Lac Object OJ 287

Optical Variability of
BL Lac Object OJ 287
Wu Jianghua
2005.8
Properties of Blazars
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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/
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Sillanpaa et al. (1988) predicted a new outburst
in 1994-96 from the historical light curves;
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The OJ-94 project was organized (Takalo et al.
1996);
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More than 50 astronomers from 10 countries;
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From radio, infrared, optical, UV, to X-ray;
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Time span: 19931997.
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
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12-year cyclic optical outburst;
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Double-peaked structure of the outburst;
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The first peak is narrow and thermal while the
second is broad and synchrotronic.
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Extremely stable color during the outburst;
Models for Cyclic Outbursts
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Binary black hole models (Sillanpaa et al.
1988; Lehto & Valtonen 1996; Valtaoja et al.
2000; Liu & Wu 2002);
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Beaming model (Villata et al. 1996; 1998);
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Precessing disc model (Katz 1996);
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Microlensing effect;
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Lighthouse effect;
Our Monitoring Program
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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
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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
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Interference filter with multi-peaks + objective
prism + Schmidt telescope
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Make photometric measurements exactly
simultaneously in multi-wavebands
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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!