modeling the sed and variability of 3c66a in 2003/2004
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Modeling the SED and variability of 3C66A in 2003/2004
Presented
By
Manasvita Joshi
Ohio University, Athens, OH
ISCRA, Erice, Italy 2006
Outline• Introduction
• Motivation
• Model Sketch
• Observational Constraints
• Parameter Estimates
• Motivation of Parameters
• Summary
Blazar ModelingRelativistic jet outflow with ≈ 10
Injection, acceleration of ultrarelativistic
electrons
Qe (,
t)
Synchrotronemission
F
Compton emission
F
-q
Seed photons:
Synchrotron (SSC), Accr. Disk + BLR (EC)
Injection over finite length near the base
of the jet.
Additional contribution from absorption
along the jet
Motivation• 3C66A - promising candidate for detection by new
generation of atmospheric Cherenkov telescopes (STACEE, VERITAS).
• Has been studied in radio, IR, optical, X-ray and -ray.
• Multiwavelength SED and correlated broadband spectral variability not been completely understood.
• Few attempts towards simultaneous observations, making it difficult to constrain physical emission models.
• Led to the organization of an intensive multiwavelength campaign from July 2003-April 2004.
• One-zone homogenous, time-dependent leptonic model considered.
• Particle distribution and spectrum of emitted radiation calculated self-consistently.
• Instantaneous and time-integrated spectra calculated for various sets of parameters.
Model Sketch
1. Emitting region as a sphere of constant co-moving radius RB.
2. Homogenous and tangled magnetic field B.
3. Ultra-relativistic non-thermal e-s injected at a time-dependent rate into the blob.
Basic assumptions:
• Solve simultaneously for evolution of electron distribution,
and co-moving photon distribution,
eesc
eee
e
t
tntQn
t
tn
,
,,
,
phesc
phabsphemph
ph
t
tntntn
t
tn
,,,
,,,
,
Rad. + Adiab. losses
el./pair inj.
escape
Sy., comp. emission
SSA, γγ absorption
escape
e- density
Photon density
• Synchrotron Self Absorption (SSA) calculated self-consistently.
• Pair production negligible for present choice of parameters.
• For Synchrotron Self Compton (SSC), isotropic (co-moving frame) radiation field assumed.
• External Inverse Compton (EIC) component not considered yet.
Modelling Strategy
• Code of Boettcher & Chiang (2002) used.
1. Reproduce broadband spectrum of 3C66A for equilibrium situation (quiescent state).
2. Adjust parameters to fit both (time-averaged) Spectral Energy Distribution (SED) and optical spectral variability patterns.
Spectral Energy DistributionHzsyn
15100.1
Hzcutoffsyn18
_ 10
Observational Constraints • SL motion up to , = Bulk Lorentz
Factor
• Optical variability, hr, cm
• Doppler Factor,
• Peak synchrotron flux ergs cm -2 s-1
99~ app
115102.2 DRB
15~10 1DD
11105~ syf
2~mint
Analytical Parameter Estimates
• and , = Equipartition Parameter
• Magnetic field, G
• Electron Lorentz Factor,
synchrotron peak,
synchrotron high-energy cutoff ,
7/2114.4 Be eDB
B
2/12/12/1
153
9.215101.3
G
BD
31 101.3
52 105.1
5.11 D 1Be Be
• Synchrotron cooling time scale in observer’s frame
s
• For optical frequencies, hr
• Particle spectral index, p ~ 4
• Particle injection spectral index, q ~ 3
• Disk injection luminosity, ergs/sec
2/115
2/32/13
, 9.215108.2
G
BDobssycool
2, obssycool
41108.6 injL
Boettcher et al., 2005
Motivation of Parameters
• VLBA observations indicate bending of jet in the line of sight
• Viewing angle, assuming
• Jet components don’t exhibit superluminal motion except one, hence Doppler Factor not well constrained.
• gives good fit.
• X-rays being dominated by outbursts.
4.2~obs
1
24D
hrscoolsyn 3.1,
Hzsyn141028.4
Hzssc211069.1
Hzsyn151013.1
HzSSC22109.2
.min46, coolsyn
HzcutoffSSC26
, 1042.2
Hzcutoffsyn18
_ 1004.1
HzcutoffSSC25
_ 1053.5
Boettcher et al., 2005
dayst 10
magR 53.0
• Optical spectral variability
Hardness
Brightness
Low brightness
High brightness
Slight positive correlation
No correlation
0.72
Brighter in B, Harder in B-R
Spectral Energy Distribution
absorption
ee
HzcutoffSSC25
, 1089.2
Summary
• & used to reproduce the SED.• Magnetic field allowed to evolve in time by
setting eB = 1.
• Flaring state of 3C66A simulated using Gaussian flaring profile.
• Optical and soft X-ray photons of flaring state produced by synchrotron emission.
• Hard X-ray and VHE photons from SSC emission.
24 4.2obs
• Object exhibits a positive correlation of brighter when harder for a 10 day period – May not apply for long term variability of over
a month.
• Synchrotron cooling, minimum variability & dynamical timescale all of the same order– Size of emission region
• absorption due to IIRB not significant till 100 GeV.
Summary contd…..
cmRB15104
JyHzF keV 96.01,
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