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Introdution JRGI Radiation Mechanism Summary

A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Dmitry Khangulyan, ISAS/JAXA (Japan)

in collaboration with F.Aharonian, M.Barkov, S.Bogovalov and S.Kelner

High Energy Phenomena in Relativistic Outflows III Barcelona, June 27 – July 1

1 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

Outline

Introduction: Fast Gamma Ray Variability in AGN Blob Fomation Process: JRGI scenario Mechanism at work: Scenario related Constrants on Radiation Mechanism Summary: Specific case of PKS

2 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

VHE o bservation of fast transients in AGNs

HESS observation of PKS2155-304 Lγ ≈ 1047erg s−1 LX ≈ 1046erg s−1 τ ≈ 200 s−1

3 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

Causality Constraint

Minimum variability time-scale Proper Variability τ ′ = ∆r ′ c Observer Variability τ = ∆r ′Γ(1 − cos θ) c δ−1 = 10−2 ∆r ′ ≈ 6 × 1014cm

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Introdution JRGI Radiation Mechanism Summary

What are the Blobs in Powerful Jets?

There are a lot of hypothetical blobs Internal Shocks, Magnetic Reconnection, Change in Accretion, Instabilities....

5 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

Fundamental Requirements on the blob properties

BLOBS MUST BE SMALL AND CONTAIN A LOT OF ENERGY (OR BE ABLE TO TRIGGER POWERFUL INTERACTION) instabilities

can be very small no energy

shocks

very intensive interaction at hydrodynamical scale

accretion

hydrodynamical scale a lot of energy

reconnection

a lot of energy hydrodynamical scale

6 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

Typical Hydrodynamical Length Scale

HD scale is determined by rg and Γj τ > rgΓ

δc =

⇒ MBH < 107M⊙ (e.g. Levinson&Bromberg, 2008)

Light black hole launch extremely powerful jets? Blazars with short VHE variability powered by double black holes? (e.g. Rieger&Mannheim, 2002)

These are possible options, but not necessary...

7 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

Blobs of external origin

If blobs have external origin, they can be very small as compared to the hydrodynamical scale of the jet.... External blobs contain no energy (as compared to the jet) I.e. external blobs must be able to trigger an intensive

• interaction. To be heavy?

Compact and heavy, i.e DENSE: stars?

Specific realization of such blob formation: Jet-Red Giant Interaction Scenario

8 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

Jet Red Giant Interaction Scenario (JRGI)

Sketch of the scenario Necessary Elements

Powerful jet Pram ≃ 103Lj,46z−2

17 θ−2 −1

dyn cm2 A Red Giant in the jet vicinity ∆M ≈ 6 × 1028Lj,46z−2

17 θ−2 −1 g

similar models: Barkov et al (2010); Araudo et al (2010)

9 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

If Ablated, then Trapped and Accelerated

Important Stages

Jet Crossing Time tjc ≈ 2.5 × 107z3/2

17 θ−1M−1/2 BH,8 s

Expansion texp ≈ 5×107R−1/2

∗,2

M1/2

c,30L−1/2 j,46 z17θ−1 s

Mc,sc 3 × 1029Lj,46R∗,2z17M−1

BH,8 g

Acceleration Mc,jc 2.5 × 1031Lj,46r 2

c,15M−1 BH,8 g

∆M ≈ 6 × 1028Lj,46z−2

17 θ−2 −1g

Sketch of the scenario

10 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

JRGI is very SHORT, apparently

Dynamics of the Cloud

Blob move relativistically Motion of the Cloud dΓc dt =

• 1

Γ2

c

− Γ2

c

Γ4

j

• Ljr 2

c

4ω2c2Mc Analytical approximation dg dy = 1 g2 − g2 D y2 D ≡ Ljr 2

c

4θ2Γ3

j z0c3Mc

.

Apparent intensity F = g4 1 g2 − g2 1 y2 t0 ≈ 60Γj,1.5L−1

j,46Mc,25 s

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Introdution JRGI Radiation Mechanism Summary

JRGI can appear very BRIGHT

Energy Budget

Luminosity Lγ = 4Γ2

j ξFLj

r 2

c

ω2 Size of the Cloud rc ≈ 5 × 1014MBH,8

• Lγ,47

Lj,46ξ−1 cm Lmax = 2×1048ξ−1Lj,46Γ2

j,1.5 erg s−1

Etot ≈ 1050ξ−1Mc,25Γ3

j,1.5 erg

Apparent intensity F = g4 1 g2 − g2 1 y2 t0 ≈ 60Γj,1.5L−1

j,46Mc,25 s

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Introdution JRGI Radiation Mechanism Summary

Variability Pattern: fast cooling is required

Causality Limit τ > rc Γjc ≈ 4 × 102z−1/2

17

L1/2

γ,47L−1/2 j,46 ξ−1/2 −1

M3/2

BH,8 s

Interaction Duration τ ≈ 2z2

0θ2

r 2

c

Γjc2Mc Lj τ ≈ 60Γj,1.5L−1

j,46Mc,25 s

Change of Doppler Factor τ ≈ 2rc vsδ 5 × 104MBH,8L1/2

γ,47L−1/2 j,46 ξ−1/2 −1

δ−1 s

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Introdution JRGI Radiation Mechanism Summary

General Framework:Magnetically Driven Jets

Structure of the Jet Bj ≈ 120 L1/2

j,46z−1 17 θ−1 −1 G Bc ≈ 12z−1 17 L1/2 j,46 G

Γj ≈ ω 4rg

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Introdution JRGI Radiation Mechanism Summary

Synchrotron Self Compton: does NOT work in JRGI γ = 5×104 Eγ,11 ν16 1/2 B0 = 0.7 ν2

16

Eγ,11δ Pram,SSC ≈ 2 × 10−3 ν4

16

Eγ,11 dyn cm

15 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

External Inverse Compton t′

cool =

3 × 103s z7/4

17

(1 + f) L3/4

j,46M1/4 BH,8ν1/2 16

z17 ≫ L1/3

j,46M1/3 BH,8E4/3 γ,11

ν2/3

16

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Introdution JRGI Radiation Mechanism Summary

Klein-Nishina:severely absorbed t′

KN ≈ 102τ2Γj s

τγγ ≈ 40MBH,8Lj,46z−2

17

likely a general problem (Derishev, 2010)

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Introdution JRGI Radiation Mechanism Summary

Proton Synchrotron: in Powerful Jets

Maximum Energy Eγ,11 ≈ 1 B2E2

19

Eγ,max ≈ 400η−1δ GeV Hillas Criterion z3/2

17 L−1/2 γ,47 L−1/4 j,46 η−1/2 1

ξ1/2

−1 M−1 BH,8 < 0.2

Cooling Time τpsyn ≈ tsy δ ≈ 2 × 104η1/2

1

M1/2

BH,8z17L−3/4 j,46

s

18 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

EIC Models for PKS

Constraints

Lj,46 > 0.5

1 ξ−1MBH,8Γ2

j,1.5

Lj,46 > 10M2

BH,8Γ−2 j,1.5ξ−1 −1

Lj,46 > 0.007

M2

BH,8Γ10/3 j,1.5

τ 4/3

2

ν2/3

16

Lj,46 ≪ 0.4

M2

BH,8Γ6 j,1.5ν2 16

E4

11

Parameter Space

19 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

Proton Synchrotron Models for PKS

Constraints

Lj,46 > 0.5

1 ξ−1MBH,8Γ2

j,1.5

Lj,46 > 10M2

BH,8Γ−2 j,1.5ξ−1 −1

Lj,46 > 500

M2

BH,8Γ8/3 j,1.5

τ 4/3

2

Parameter Space

20 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

Conclusion

Short variability ⇒ external origin of the blobs Jet – star interaction can be a feasible origin of blobs RG can loose a large amount of material from atmosphere Interaction of (powerful) jets with the ablated atmosphere is likely lead to a formation of blobs Emission triggered by a blob may appear very short SSC and EIC(Klein-Nishina) do not work EIC(Thomson) or proton synchrotron may readily provide required flux level and variability timescale

21 / 23 A POSSIBLE SCENARIO of FORMATION of GAMMA RAY EMITTING BLOBS in AGN

Introdution JRGI Radiation Mechanism Summary

For non-blazar AGNs: observation of M87 (Raue, in prep)

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Introdution JRGI Radiation Mechanism Summary

For non-blazar AGNs: lightcurve of M87 (Barkov et al., in prep)

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