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Modeling the SED and variability of 3C66A in 2003/2004

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 Modeling.

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Modeling the SED and variability of 3C66A in 2003/2004

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  1. Modeling the SED and variability of 3C66A in 2003/2004 Presented By Manasvita Joshi Ohio University, Athens, OH ISCRA, Erice, Italy 2006

  2. Outline • Introduction • Motivation • Model Sketch • Observational Constraints • Parameter Estimates • Motivation of Parameters • Summary

  3. Blazar Modeling 0 Synchrotronemission Relativistic jet outflow with G≈ 10 Injection, acceleration of ultrarelativistic electrons nFn n g-q Qe (g,t) Compton emission g g1 g2 nFn Injection over finite length near the base of the jet. n Seed photons: Synchrotron (SSC), Accr. Disk + BLR (EC) Additional contribution from absorption along the jet

  4. 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.

  5. Model Sketch • 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.

  6. Basic assumptions: 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.

  7. Solve simultaneously for evolution of electron distribution, and co-moving photon distribution, Rad. + Adiab. losses el./pair inj. e- density escape escape SSA, γγ absorption Sy., comp. emission Photon density

  8. 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.

  9. 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.

  10. Spectral Energy Distribution

  11. Observational Constraints • SL motion up to , = Bulk Lorentz Factor • Optical variability, hr, cm • Doppler Factor, • Peak synchrotron flux ergs cm-2 s-1

  12. Analytical Parameter Estimates • and , = Equipartition Parameter • Magnetic field, G • Electron Lorentz Factor, synchrotron peak, synchrotron high-energy cutoff ,

  13. 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 Boettcher et al., 2005

  14. 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.

  15. Boettcher et al., 2005

  16. Optical spectral variability No correlation Slight positivecorrelation High brightness Low brightness Hardness Brightness

  17. Brighter in B, Harder in B-R 0.72

  18. Spectral Energy Distribution

  19. absorption

  20. 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.

  21. Summary contd….. • 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.

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