Multiwavelength SynchrotronCompton Spectral Analysis of Te V Blazars

Multiwavelength Synchrotron/Compton Spectral Analysis of Te. V Blazars and FSRQs: A New Approach Charles Dermer Justin Finke US Naval Research Laboratory Washington, DC USA Markus Böttcher (Ohio University) Hannah Krug (UMD) Outline Presentation at workshop: “Blazar Variability across the Electromagnetic Spectrum” École Polytechnique, Palaiseau, France April 22 -25, 2008 1. 2. 3. 4. Variability and Relativistic Motion Black Hole Jet Physics New Model Approach Synchrotron/SSC FSRQ Slowly varying/quiescent Te. V radiation

Variability and Relativistic Motion Observables: z ( d. L), F(t) (ergs cm-2 s-1), tvar (s) Energy Flux rb Causality argument for size scale Emitting region Internal energy density: • Compton catastrophe • Super-Eddington luminosities • Superluminal motion • gg pair production attenuation

G Black Hole Engine r. S Energy Sources: 1. Accretion Power 2. Rotation Power Blandford-Znajek process Dusty Torus Accretion Disk W SMBH Engine size = Schwarzschild radius Ejecta size r. S Minimum size scale indpt of G Hard to make shorter flares without loss of efficiency; increased jet power

Variability and Source Size Source size from direct observations: Spherical blob in comoving frame rb=r´b G (Comoving) Source size from temporal variability: Doppler Factor (Length contraction) See Begelman, Fabian, Rees (2008) Variability timescale implies maximum comoving region size scale

Variability and Source Size (Comoving) Source size from temporal variability: PKS 2155 -304 10 min Aharonian et al. (2007) Wrong!

Variability and Source Location G x 1/G Variability timescale implies engine size scale; comoving size scale factor ~d. D larger; emission location ~G 2 larger than values inferred for stationary region Rapid variability by energizing regions within the Doppler cone, but with loss of efficiency

Absolute Source Luminosity beaming factor Two-sided top-hat jet: Jorstad, this conf. EGRET blazar flares:

Jet Power of PKS 2155 -304 Loss of efficiency by factor If linear, requires M 9 10 Lot of energy carried away to be dissipated in radio jet (but duty cycle is small: what is time-averaged apparentisotropic luminosity? )

Energy Fluxes, Blobs and Blast Waves Use invariants to derive N. B. L′ = comoving luminosity, not absolute source luminosity L* x Blazar sequence ok

Doppler-Boosted Flux and Internal Photon Energy Density Solves Compton catastrophe, (internal) gg opacity constraint; consistent with superluminal motion observation

Generic pulse profiles Curvature limit Colliding shells produce generic pulse profiles Asymmetric profile from kinematics Dermer (2004) Specific frequency dependence

2. Black Hole Jet Physics Energy Sources: Accretion vs. Black Hole Rotation Two Component Synchrotron/ Compton Leptonic Jet Model Accretion disk spectra Location of g-ray Emission Region Far (>pc scale)—Finnish group; Boston U. group Near (sub-pc) scale—most theorists BL Lac: Synchrotron/SSC model FSRQ: External Compton model Soft Photon Sources: Accretion Disk Radiation scattered by BLR Dusty Torus Decelerating Jet Emission Sheath and Spine q Observer BLR clouds G Relativistically Collimated Plasma Outlfows Dusty Torus Accretion Disk W SMBH G Ambient Radiation Fields

One Zone vs. Multi-zone Models Observer One Zone Model for Highly Variable Emissions Multi-zone Jet Model q G Relativistically Collimated Plasma Outlfows BLR clouds Accretion Disk Marscher & Gear (1985) W SMBH Dusty Torus • • • Nonvarying component (EC/CMBR) Emission from Distant Knots (e. g. , M 87) Recollimation Shocks have different Ge. V signature than flares on spiral orbits G

Standard Blazar Modeling Hartman, Böttcher, et al. (2001) Dermer and Schlickeiser (2002) Solve kinetic equation for electrons (hadrons) assuming acceleration/injection Modify parameters Fit to SED Repeat Reduce c 2

Model Parameters in Standard Blazar Modeling Hartman, Böttcher, et al. (2001)

3 C 279 Temporally evolving SEDs Nonunique solutions; tedious to apply; higher order SSC emissions; guess parameters to fit synchotron/Compton spectrum Evolution of electron distribution with time: information about acceleration (e. g. , loop diagrams); Kataoka Correlated behavior for leptonic emissions z = 0. 538 Böttcher et al. 2007 L ~5 x 1048 x (f/1014 Jy Hz) ergs s-1

Another problem… Pair Production Attenuation Three sources of gg e+ e- Pair Production Attenuation 1. 2. 3. Internal Radiation Source environment (depends on global radiation field whereas Compton-scattered spectrum depends on local radiation field) Intergalactic Background Light (IBL) absorption Target Photon Flux: Requirement that gg optical depth be less than unity: D D

3. New Approach to Blazar Modeling Standard blazar model: randomly oriented B field and isotropic nonthermal particles Synchrotron component given by low energy radio/IR/opt/UV/X-ray spectrum (multi-zone) Electrons making synchrotron emission from flaring IR/opt/UV/X-rays (flaring zone) Same electrons that make flaring synchrotron make flaring g-ray emission I. Synchrotron/SSC model for BL Lacs (and GRBs) With this assumptions, flaring synchrotron radiation directly gives electron spectrum, uncertain to only 3 parameters: 1. Doppler factor d. D 2. Magnetic field B 3. Size scale rb′ of emission region But variability time scale tvar eliminates one parameter Therefore 2 parameter model

Fitting Routine Code written by Justin Finke Write SSC as a function of: d. D, B, rb′, z, Ne(g). Use electron spectrum to calculate SSC using Jones (1968) formula nsyn gives Ne(g) (CS 86 expression) Internal and IBL absorption calculated Leaves two unknowns to fit: d. D and B Minimize c 2

G Jet Power , ke Total jet power = sum of particle kinetic and magnetic field Minimum jet power for equipartition (minimum energy) magnetic field Minimize jet power for measured synchrotron flux • Jet power: total power available in jet (in observer frame) • Lj = 2 prb′b. G 2 c(u′B + u′p) (Celotti & Fabian 1993) • d. Lj / d. B = 0 Bmin (equipartition) • B < Bmin u′p >> u′B and f. SSC > fsyn Synchrotron spectrum implies minimum jet power; additionally fitting g rays gives deviation of model from minimum jet power

PKS 2155 -304 • • X-ray selected BL Lac z = 0. 116, d. L = 540 Mpc Detected by EGRET ~ August 2006: bright flares, detected by for PKS 2155 -304 – Swift (Foschini et al. 2007) (3 ks/day) – HESS (Aharonian et al. 2007) • Variability timescale: ~5 minutes • Beppo. SAX observed variability ~ 1 hr (Zhang et al. 2002).

Results HESS data: 28 July, 2007 Swift data: 30 July 2007 Model d. D B [m. G] tvar [s] Lj [1047 erg s-1] 1 872 2. 7 30 4. 4 3 367 3. 6 300 2. 7 5 185 2. 7 3000 2. 1 g′min = 1 Using IBL of Stecker et al. (2006). Unreasonably high d. D and Lj. LEdd = 1047 erg s-1 From radio obs. , d. D < 10 Can a lower IBL resolve problem?

Results Model d. D B [m. G] tvar [s] Lj [1047 erg s-1] 6 895 2. 5 30 4. 5 8 390 3. 0 300 2. 7 16 261 81 30 0. 5 18 139 57 300 0. 4 g′min = 100 Lower, Dermer (2007) IBL Better, but not satisfactory G < 10 on pc scales (Piner & Edwards 2004) GLAST could distinguish between these models

Variability Origin of highenergy cutoff in electron spectrum: • Acceleration and radiative cooling origin for variability? • t´acc = Nag´/n. B • Na > 105, not unreasonable? • Variability probably can’t be attributed to cooling. Adiabatic expansion makes rapid cooling

Correlated Variability HESS and Xrays correlated, but optical is not. Costamante (2007)

Results Model d. D B [m. G] tvar [s] Lj [1046 erg s-1] 25 246 89 30 3. 2 26 118 77 300 2. 1 27 64 47 3000 2. 2 Use electron spectrum to underfit optical data Limited by gg in blob X/g correlations depends on gg attenuation

Confidence Contours for B and d. D Model 26

Mrk 421 z = 0. 03, d. L = 130 Mpc 1994 flare observed by Whipple, EGRET, ASCA, IUE, & groundbased optical telescopes (Macomb et al. 1995) Variability observed down to 1000 sec (Aharonian et al. 2002) Similar results to Mrk 421 IBL absorption still substantial! (explains difference with Kirk and Mastichiadis 1997) Model d. D B [m. G] tvar [s] Lj [1046 erg s-1] 31 248 0. 84 103 9. 5 32 105 0. 96 104 6. 6 33 63 0. 36 105 11

FSRQ Modeling Generalize technique of Georganopoulos, Kirk, and Mastichiadis (2001) for anisotropic radiation fields Compton kernel Dermer and Schlickeiser 1993; Dermer and Boettcher 2006 Dubus, Cerutti, Henri 2008 Valid for Compton scattering in the head-on approximation

Scattering of Shakura-Sunyaev Disk Radiation n (Hz)

gg Opacity from Shakura Sunyaev Radiation Field

4. Slowly Varying Quiescent Te. V Emission PKS 0637 -752 FSRQ Superluminal source Not a g-ray blazar (yet) Compton-scattered CMBR Jet X-rays Tavecchio et al (2000) Atoyan & Dermer (2004) Same process at multi-pc scale makes slowly varying Te. V emission in XBLs Böttcher et al. (in press) PKS 0637 -752 Schwartz et al (2000)

Slowly Varying Quiescent Te. V Emission 1 ES 1101 -232 at z = 0. 186 Requires low intensity IBL; corrected following Aharonian et al. (2006) Optical from ROTSE; X-ray from XMM Inner (outer) jet parameters: G = 25 (15) B = 0. 06 (10 m) G Lj = 2 x 1040 (1. 5 x 1041) ergs s-1 Injection index for outer jet: q = 1. 5 to g′max = 6 x 106

Slowly Varying Quiescent Te. V Emission Inner (outer) jet parameters: G = 25 B = 0. 05 G Lj = 1. 45 x 1041 ergs s-1

Summary • Kinematic issues for blazars • New Approach to fitting blazar spectra Compton scattering and opacity self-consistently calculated Synchrotron/SSC model for PKS 2155 -304 Large Doppler factors and jet luminosities: hard for SSC to explain g-rays from PKS 2155 -304 flare Developing approach for FSRQs • Model for slowly varying Te. V emission from BL Lac objects Evolving SED of blazars in GLAST era