Modeling the Emission Processes in Blazars Markus Böttcher Ohio University Athens, OH

Outline Leptonic and Hadronic Models of Blazars Recent Modeling Results Hybrid Leptonic/Hadronic Blazar Models and “Orphan” TeV Flares Recent Observational Results on 3C279

Blazar Models Relativistic jet outflow with  ≈ 10 Injection, acceleration of ultrarelativistic electrons Q e ( ,t)  Synchrotron emission F Compton emission F    -q Seed photons: Synchrotron (within same region [SSC] or slower/faster earlier/later emission regions [decel. jet]), Accr. Disk, BLR, dust torus (EC) Injection over finite length near the base of the jet. Additional contribution from  absorption along the jet Leptonic Models

Blazar Models Relativistic jet outflow with  ≈ 10 Injection, acceleration of ultrarelativistic electrons and protons Q e,p ( ,t)  Synchrotron emission of primary e - F Proton- induced radiation mechanisms: F    -q Proton synchrotron Hadronic Models p  → p  0  0 → 2  p  → n  + ;  + →  +     → e + e  → secondary  -, e-synchrotron Cascades …

Time-dependent leptonic blazar modeling Solve simultaneously for evolution of electron distribution, and co-moving photon distribution, = - (  n e ) + Q e ( ,t) - ________ ∂n e ( ,t) ∂t ∂ ∂∂. rad. + adiab. losses escape ______ n e ( ,t) t esc,e = n ph,em ( ,t) – n ph,abs ( ,t) - _______ ∂n ph ( ,t) ∂t. Sy., Compton emission escape ______ n ph ( ,t) t esc,ph SSA,  absorption. el. / pair injection

Spectral modeling results along the Blazar Sequence: Leptonic Models High-frequency peaked BL Lac (HBL): No dense circumnuclear material → No strong external photon field Synchrotron SSC Low magnetic fields (~ 0.1 G); High electron energies (up to TeV); Large bulk Lorentz factors (  > 10)

Spectral modeling results along the Blazar Sequence: Leptonic Models Radio Quasar (FSRQ) Plenty of circumnuclear material → Strong external photon field Synchrotron External Compton High magnetic fields (~ a few G); Lower electron energies (up to GeV); Lower bulk Lorentz factors (  ~ 10)

Spectral modeling results along the Blazar Sequence: Hadronic Models HBLs:Low co-moving synchrotron photon energy density; high magnetic fields; high particle energies → High-Energy spectrum dominated by featureless proton synchrotron initiated cascades, extending to multi-TeV, peaking at TeV energies LBLs: Higher co-moving synchrotron photon energy density; lower magnetic fields; lower particle energies → High-Energy spectrum dominated by p  pion decay, and synchrotron-initiated cascade from secondaries → multi-bump spectrum extending to TeV energies, peaking at GeV energies

The Blazar Sequence NOT an a-priori prediction of leptonic or hadronic jet models! Variations of B,, , … chosen as free parameters in order to fit individual objects along the “blazar sequence”. Consistent prediction: Strong > 100 GeV emission from LBLs, FSRQs are only expected in hadronic models!

Example: Modeling SEDs and Variability of BL Lacertae in 2000 Modeling of SEDs in X-ray low and high state Böttcher & Reimer (2004)

Analytical parameter estimates SL motion up to  app ~ 7.1 =>  > 8 ~ Optical/X-ray variability => R B < 1.6*10 15 D 1 cm ~ Synchrotron peak flux => B sy ≈ 3.6 D 1 -1  B 2/7 G Optical – X-ray time delay => B RX ≈ 1.6 D 1 -1/3  -2/3 G (where  = u ext /u B ) => B ~ 2 G Location of synchrotron peak => ~ 1.4*10 3 D 1 -1/2 Location of synchrotron cutoff =>  2 ~ 4*10 4 D 1 -1/2 (qu.)  2 ~ 2*10 5 D 1 -1/2 (act.) Total luminosity => L j,e > D 1 -4 erg/s (in electrons only) ~

Fitting the spectral variability of BL Lac in 2000 L inj = 3*10 40 erg/s  1 = 1100  2 = 4*10 4 → 5*10 4 q = 2.6 → 2.2 D = 17  B = 1 B = 1.4 G R B = 2.5*10 15 cm

Fit to X-ray hardness- intensity diagrams

Fit to color-magnitude correlation Best fit to spectrum and variability for flaring scenario with electron injection spectrum hardening during flare Possible physical interpretation: Change in magnetic- field orientation with respect to shock front in the jet (?)

Comparison to Hadronic Model Parameters of synchrotron-proton blazar model fit (A. Reimer): D = 7 R B = 1.1*10 15 cm B = 40 G  e =  p = 1.8 n e /n p = 1.6  p,max = 7*10 9 High-energy emission dominated by  -synchrotron Hadronic processes => Detectable in > 100 GeV – TeV gamma-rays

Conclusions for BL Lac, if hadronic models could be ruled out: L inj = 3*10 40 erg/s  1 = 1100  2 = 4*10 4 → 5*10 4 q = 2.6 → 2.2 D = 17  B = 1 B = 1.4 G R B = 2.5*10 15 cm Electron acceleration out to ~ 25 GeV during flares Particle injection index 2.2, consistent with acceleration at relativistic, parallel shocks Magnetic field in equipartition with ultrarelativistic electron population

The Case of 1ES HBL at z = TeV source Recently displayed an “Orphan” TeV flare Date [MJD-52400] (Krawczynski et al. 2004) Primary sy +  -ray flare Secondary  -ray flare w/o sy flare Clearly unexpected in purely leptonic one- zone SSC models

Relativistic hadrons in leptonic jets Naturally expected in any realistic particle acceleration scenario For standard hadronic models:  p,max ~ 10 8 required (  p pion production on co-moving synchrotron photons) to work (  p *E ph > 300 MeV) But:  p pion production on external photons possible for much lower proton Lorentz factors (  p ~ 10 3 – 10 4 ) → Synchrotron mirror model for p  pion production

The Hadronic Synchrotron Mirror Model Constraint on R m from time delay: R m ~ 3  1 2  t 20 pc  m = 0.1  -1  = 10  1  t = 20  t 20 d

The Hadronic Synchrotron Mirror Model Estimate of reflected synchrotron photon density from R m and observed primary synchrotron flare u’ sy ~ 6.0x10 -3  1 -4 R ergs cm -3 Dominant contribution to p  pion production from protons with  p ~ 3,000  1 -1 E sy,1 -1 E sy ~ 10 keV Normalization of  0 decay flare to observed secondary TeV flare  Constraint on co-moving relativistic proton density: n’ p ~ 1.8x10 7  1 -3 E sy,1  r 17  R cm - 3 Reflected sy. photons are virtually invisible to ultrarel. electrons (Klein-Nishina)

The Hadronic Synchrotron Mirror Model Kinetic luminosity in relativistic protons in the jet: L kin p ~ 1.8x10 48 E sy,1 R  r 17  f -3 ergs/s Optical – soft X-ray synchrotron flare from  + decay products:  m ~ 0.05 mag Neutrino emission from charged pion decay unlikely to be detectable with current detectors (Reimer et al. 2005)

Some New Observational Results: INTEGRAL + Chandra ToO observations Coordinated with WEBT radio, near-IR, optical (UBVRIJHK) Triggered by Optical High State (R < 14.5) on Jan. 5, 2006 Addl. X-ray Observations by Swift XRT The Multiwavelength Campaign on 3C279 in Jan./Feb Preliminary

X-ray/  -ray observations during a period of optical-IR- radio decay The Multiwavelength Campaign on 3C279 in Jan./Feb Minimum at X-rays seems to precede optical/radio minimum by ~ 1 day. Preliminary

SED (Jan 15, 2006) basically identical to low states in 92/93 and 2003 in X-rays High flux, but steep spectrum in optical Indication for cooling off a high state? Did we miss the HE flare? The Multiwavelength Campaign on 3C279 in Jan./Feb Analysis is in progress …

Summary 1.Blazar SEDs successfully be modelled with both leptonic and hadronic jet models. 2.Blazar Sequence is NOT a prediction of either type of models. 3.Possible multi-GeV - TeV detections of LBLs or FSRQs and spectral variability may serve as diagnostics to distinguish between models. 4.Even in leptonically dominated models, relativistic hadrons might be present 5.One possible diagnostic for relativistic hadrons: Orphan TeV flares without simultaneous synchrotron flare.

Spectral Variability Signatures  2 = 2*10 4 → 4*10 4 q = 2.5 → 2.3 L inj,e = 2.5*10 40 erg/s → 3.5*10 40 erg/s  2 = 2*10 4 → 4*10 4 q = 2.5 → 2.3 (L inj,e adjusted so that dN inj,e /dt = const.) => Variability dominated by changing q is a good candidate!

Modeling the SEDs of BL Lac in 2000 L inj = 4*10 40 erg/s  1 = 1100  2 = 6*10 4 q = 2.15 D = 18  B = 0.5 B = 1.4 G R B = 2.5*10 15 cm L inj = 3*10 40 erg/s  2 = 2.3*10 4 q = 2.4 D = 16