Transcript Slides

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 279
3C 279
Z=0.536
1 mas = 6.3 pc
3C 279 RESULTS
Monitoring of 3C 279 between 1996-2007
X-RAY
OPTICAL
RADIO
3C 279 : X-ray-optical Cross-Correlation
Chatterjee et al. 2008
(ApJ, 489, 79)
• Optical leads X-ray by ~ 19 Days
Correlation
Time
Window
X-ray and Optical : Superposed
Compare:
1. Time lag
between peaks
2. Energy output
of flares :
Area under the
curve
Time Lag (Days)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
-27
-24
-49
-15
-22
16
25
27
-3
-8
-3
-6
X/Op Ratio
0.4
0.62
0.67
0.44
1.4
0.18
0.38
0.3
0.95
0.98
0.87
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 Curves
SIMULATED
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
Upstream
x/op~1
Downstream
x/op<1
Sketch of emission regions at two
different locations in the jet
Upstream
∆t smaller
x/op~1
Downstream
∆t larger
x/op<1
Time Lag (Days)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
-27
-24
-49
-15
-22
16
25
27
-3
-8
-3
-6
X/Op Ratio
0.4
0.62
0.67
0.44
1.4
0.18
0.38
0.3
0.95
0.98
0.87
0.88
Larger time
delay,
Smaller ratio
Smaller time
delay,
Ratio ~1
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
Light Curves of 3C 120 between 2002 and 2007
X-RAY
OPTICAL
RADIO
Variability at
different
timescales
3C 120 X-Ray Power Spectral Density (PSD)
Break
Frequency
=10-5 Hz
Break
Time Scale
=2 Days
X-Ray PSD of
Cygnus X-1 : Break
BH Mass vs. Break
Time Scale
Credit : Uttley et al. (2004)
X-Ray PSD of
Cygnus X-1 : Break
BH Mass vs. Break
Time Scale
3C 120
Credit : Uttley et al. (2004)
3C 120 RESULTS : X-Ray/Radio
Light Curves of 3C 120 between 2002 and 2007
X-RAY
OPTICAL
RADIO
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 Hz
Break
Time Scale
=2 Days