Multi-Wavelength Time Variability of Active Galactic Nuclei

Ritaban Chatterjee

Advisor: Prof. Alan P. Marscher Collaborators: Svetlana Jorstad (B.U.),

Phil Uttley (U. Southampton, UK).

Why Time Variability?

3C 279Z=0.5361 mas = 6.3 pc

3C 279

3C 279 RESULTS

X-RAY

OPTICAL

RADIO

Monitoring of 3C 279 between 1996-2007

3C 279 : X-ray-optical Cross-Correlation

• Optical leads X-ray by ~ 19 Days

Chatterjee et al. 2008(ApJ, 489, 79)

Correlation Time Window

X-ray and Optical : Superposed

Compare:1. Time lag between peaks2. Energy output

of flares : Area under the

curve

Time Lag (Days) X/Op Ratio

1. -27 0.4

2. -24 0.62

3. -49 0.67

4. -15 0.44

5. -22 1.4

6. 16 0.18

7. 25 0.38

8. 27 0.3

9. -3 0.95

10. -8 0.98

11. -3 0.87

12. -6 0.88

Larger time delay,Ratio<1

Smaller time delay,Ratio ~1

• Optical => Synchrotron• X-ray=> Synchrotron self-Compton

(SSC)

• Simulation of time variable non-thermal radiation

Modeling of synchrotron (optical) and synchrotron self-Compton (X-ray) flares

B ~r-b, N0 ~r-n, R ~r

Real and Simulated Light Curves

Chatterjee et al. (submitted to ApJ)

Real and Simulated Light CurvesSIMULATED REAL

Chatterjee et al. (submitted to ApJ)

Downstream SSC (Green) maybe smaller than Synchrotron (Red)UPSTREAM DOWNSTREAM

Sketch of emission regions at two different locations in the jet

x/op~1 x/op<1

Upstream Downstream

∆t smallerx/op~1

∆t largerx/op<1

Upstream Downstream

Sketch of emission regions at two different locations in the jet

Larger time delay,Smaller ratio

Smaller time delay,Ratio ~1

Time Lag (Days) X/Op Ratio

1. -27 0.4

2. -24 0.62

3. -49 0.67

4. -15 0.44

5. -22 1.4

6. 16 0.18

7. 25 0.38

8. 27 0.3

9. -3 0.95

10. -8 0.98

11. -3 0.87

12. -6 0.88

CONCLUSIONS: LOCATION AND MECHANISM OF EMISSION

• X-ray and optical variations are highly correlated.

• X-ray/optical correlation changes over time.

• Contemporaneous X-ray and optical flares:

X/OP ≈ 1 => closer to the base of the jet

X/OP << 1 => farther from the base of the jet

3C 120 RESULTS : X-RAY

X-RAY

OPTICAL

RADIO

Light Curves of 3C 120 between 2002 and 2007

Variability atdifferent timescales

3C 120 X-Ray Power Spectral Density (PSD)

Break Frequency=10-5 HzBreakTime Scale=2 Days

X-Ray PSD of Cygnus X-1 : Break

Credit : Uttley et al. (2004)

BH Mass vs. Break Time Scale

X-Ray PSD of Cygnus X-1 : Break

Credit : Uttley et al. (2004)

BH Mass vs. Break Time Scale

3C 120

3C 120 RESULTS : X-Ray/Radio

X-RAY

OPTICAL

RADIO

Light Curves of 3C 120 between 2002 and 2007

X-ray Dips and 37 GHz Flares

X-ray/37 GHz Anti-correlation (X-ray leads 37GHz by 120 days)

Chatterjee et al. 2009 (in prep)

Possible Explanation of the X-ray Dip and Superluminal Ejection Correlation

1. Change in the magnetic field configuration in the accretion disk from turbulent to aligned => absence of viscous heating causes dips in X-ray production => aligned B field configuration facilitates shock to move towards the jet (Livio et al. 2003)

2. Corona is the base of the jet => decrease in the number density of electrons at the base of the jet => causes X-ray dips and increase in the speed of particles (continuity eqn.) => causes shock wave.

THE END

X-ray light curve :Sum of model flares & real data

Chatterjee et al. 2008(ApJ, 689, 79)

Optical light curve :Sum of model flares & real data

Chatterjee et al. 2008(ApJ, 689, 79)

3C 120 X-Ray Power Spectral Density (PSD)

Break Frequency=10-5 HzBreakTime Scale=2 Days