Star-Jet Interactions and Gamma-Ray Flares
Maxim V. Barkov1
1 ABBL RIKEN, Wako, JapanCTA Japan meeting
14 January 2016

My collaborators

Felix A. Aharonian
Sergey V. Bogovalov
Valentí Bosch-Ramon
Anton V. Dorodnitsyn
Stanislav R. Kelner
Dmitriy V. Khangulyan
Manel PeruchoStar-Jet Interactions and γ-Ray Flares

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Outline
1

VHE short variability and MAIN Ingredients (Jet&Star)

2

A low power jet (M87)

3

A powerful jet and heavy cloud (3C454.3)

4

A few comments about IC310

5Conclusions

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PKS 2155–304 observations

The observed parameters of the PKS 2155−304 flares (H.E.S.S. data)Lγ ≈ 1047 erg s−1
τ ≈ 200 s
LX ∼ 1046 erg s−1(Aharonian et al 2007)

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What are the Blobs in Powerful Jets?
There are a lot of hypothetical blobs

Internal Shocks, Magnetic Reconnection, Change in Accretion,
Instabilities....

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Blobs of external origin

If blobs have external origin, they can be very small as comparedto 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, BLR clouds?
Specific realization of such blob formation:
Jet-Red Giant Interaction Scenario

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Main IngredientsStars around BH

AGN jetRelativistic outflow (Γbulk ∼ 10 − 100, likely
depends on the distance)

Moves with Keplerian velocity:

Narrow: typically one adopts θ ' Γ−1 , i.e.,V∗ ' 600MBH Rpc

1/2

Cross section:−1/2km/s

Density (quite uncertain): ρ∗ ' ρ0 R −a

ω ' 1017 Γ−1
1.5 Rpc cm

Mass injection between 10−2 and 10−1 pc:
Ṁ∗ ' 2 × 10

1/2 Z0.1
ρ M−5 0 BH,81/2−aΓ1.5xdx [pc3 yr−1 ] ,0.01

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Probability to get a star to a jet
Murphy et al. 1991
it was revealed that “a” spans a quite broad range depending on
the mass accumulated in the central parsec
It was obtained that a = 7/2 for ρ̄ = 106 M pc−3 and a = 1/2 forρ̄ = 108 M pc−3

Mass injection appears to depend very weakly on a1/2−1Ṁ∗ ' 2 × 102 MBH,8 M Γ−1
1.5 yrfor 10−2 < Rpc < 0.1
One can expect HUNDREDS of stars entering per year
which can contain a few Red Giants or young stars per year...

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VHE variability in M87

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H.E.S.S., MAGIC, VERITAS observations of M87
Several flashes were observed in 2006, 2008, 2010.
Variability on scales t ∼ 1day
The flux Lγ ∼ 1042 ergs s−1

Eγ,max ' 20TeV.

(Aharonian et al 2006; Abramowski et al. 2011; Aliu et al. 2011)

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Cloud/Star — Jet interaction(Barkov et al 2010, 2012b)

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Star envelope evolution (Numerical results)

Uniform cloud(Bosch-Ramon et al 2012)
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p-p interaction
The cloud density can be very high making the pp interactions to be
the most plausible mechanism for the gamma-ray production in theRG-jet interaction scenario: in this case the characteristic cooling timefor pp collisions istpp ≈1015−1 −1= 105 nc,10cf scf nc

χ ≡ Eγ /Ep = 0.17 [2 − exp(−tv /tpp )]Star-Jet Interactions and γ-Ray Flares

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VHE light curves and spectra (Numerical model)
ξ = 0.5 and Qp (E) ∝ E −2(Barkov et al 2012b)

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Fast variability in GeV blazars (3C454.3)

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3C454.3 observations

The observed parameters of the 3C454.3 flares (Fermi data)Lγ ≈ 2 × 1050 erg s−1
τr ≈ 4.5 h
LX ∼ 5 × 1047 erg s−1(Abdo et al. 2011; Vercellone et al. 2011)

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3C454.3 observations (2010 November)(Abdo et al 2011)

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Sketch and Plateau model−1 −3Ṁ∗ ≈ 1024 Lγ,49 ξ−1
Γj,1.5 g/s.

The cosmic ray/X-ray excite stellar wind (Basko et al. 1973; Dorodnitsyn et al.
2008),
5/2 −1/2
Ṁ ≈ 1024 α−12 R∗,2 M∗,0 χP0,6 g s−1
which providing limitations on the stellar radius
1/2 2/52F̄e M0,∗
 .
R∗,2 & 
α−12 χ
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Relativistic StageAt the relativistic stage, the dynamics of the cloud is described by thefollowing equation:
dg=dy



1− g2
g2

D,
y2D≡

Lj rc2,4θ 2 Γ3j z0 c 3 Mcg≡Γc,Γjy≡z.
z0Solutions of the equation shown as Fe ≡ L/Lmax vs Lorentz factor of
the cloud and as L/Lmax vs the observed time (t0 = z0 /Dδ Γj c). :D = 100, 10, 1 and 0.1. (Barkov et al 2012a)
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Radiation Model: GeometryStar-Jet Interactions and γ-Ray Flares

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The magnetic field shielding

In the framework of JRGI scenario the magnetic field shielding allows
to magnetic field remain low inside the blob (Barkov et al. 2012b).
Bc  Bj
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The Model Solution for the Main FlareD≡

Lj rc24θ 2 Γ3j z0 c 3 Mc
MBH ≈ 109 M

Lj ≥ 1048

erg s−1δb ≈ 20

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Dynamical light curve + Radiation spectra: Protonsynchrotron and secondary synchrotron

tacc /(2Γ2b ) ≈ 5 h.
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Radiation Model: limitations

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Radiation Model: Dynamical light curve + cooling timeStar-Jet Interactions and γ-Ray Flares

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A few comments about IC310

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TeV Flare in IC310

The observed parameters of the IC310 TeV flares (MAGIC data)Lγ ≈ 2 × 1044 erg s−1
τr ≈ 4.8 min
Aleksic et al (2014)

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Black Hole Magnetospheric Model:

Optimistic Total Energetic Budget∆V . hBbh RΩFcsin θ ,ΩF
1c ' 4rg

Lγ,ms < 4πR 2 cκρGJ ∆V ,Black Holemagnetospher

ρGJ = ΩF Bbh sin θ /(2πc)

2 r hc sin2 θ (2x larger compare toLγ,ms < 18 κBbhgBalandford-Znajek)
1/7−1/7ṁ < 4 × 10−3 ηαss βm M8
the maximum accretion ratecompatible with vacuum gap (similar to Levinson&Rieger 2011)p
Bd = 8πβm pg ,h = 1013 tvar,5 cm−1/7Lγ,ms < 1043 βm κtvar ,5 MBH,8 sin2 θ erg s−1
Lγ,observed ≈ 2 × 1044 erg s−1
Aleksic et al (2014)

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Black Hole Magnetospheric Model:

Optimistic Total Energetic Budget∆V . hBbh RΩFcsin θ ,ΩF
1c ' 4rg

Lγ,ms < 4πR 2 cκρGJ ∆V ,Black Holemagnetospher

ρGJ = ΩF Bbh sin θ /(2πc)

2 r hc sin2 θ (2x larger compare toLγ,ms < 18 κBbhgBalandford-Znajek)
1/7−1/7ṁ < 4 × 10−3 ηαss βm M8
the maximum accretion ratecompatible with vacuum gap (similar to Levinson&Rieger 2011)p
Bd = 8πβm pg ,h = 1013 tvar,5 cm−1/7Lγ,ms < 1043 βm κtvar ,5 MBH,8 sin2 θ erg s−1Lγ,observed ≈ 2 × 1044 erg s−1Aleksic et al (2014)

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Black Hole Magnetospheric Model:

Optimistic Total Energetic Budget∆V . hBbh RΩFcsin θ ,ΩF
1c ' 4rg

Lγ,ms < 4πR 2 cκρGJ ∆V ,Black Holemagnetospher

ρGJ = ΩF Bbh sin θ /(2πc)

2 r hc sin2 θ (2x larger compare toLγ,ms < 18 κBbhg
Balandford-Znajek)
1/7−1/7ṁ < 4 × 10−3 ηαss βm M8
the maximum accretion ratecompatible with vacuum gap (similar to Levinson&Rieger 2011)p
Bd = 8πβm pg ,h = 1013 tvar,5 cm−1/7Lγ,ms < 1043 βm κtvar ,5 MBH,8 sin2 θ erg s−1
Lγ,observed ≈ 2 × 1044 erg s−1
Aleksic et al (2014)

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Black Hole Magnetospheric Model:

Optimistic Total Energetic Budget∆V . hBbh RΩFcsin θ ,ΩF
1c ' 4rg

Lγ,ms < 4πR 2 cκρGJ ∆V ,Black Holemagnetospher

ρGJ = ΩF Bbh sin θ /(2πc)

2 r hc sin2 θ (2x larger compare toLγ,ms < 18 κBbhg
Balandford-Znajek)
1/7−1/7ṁ < 4 × 10−3 ηαss βm M8the maximum accretion ratecompatible with vacuum gap (similar to Levinson&Rieger 2011)p
Bd = 8πβm pg , h = 1013 tvar,5 cm−1/7Lγ,ms < 1043 βm κtvar ,5 MBH,8 sin2 θ erg s−1
Lγ,observed ≈ 2 × 1044 erg s−1
Lγ,observed  Lγ,msStar-Jet Interactions and γ-Ray Flares

Aleksic et al (2014)

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Conclusions

In the case of 3C454.3 the radiation in the GeV energy range canbe effectively produced through proton synchrotron radiation, Jitter
or EIC in the Thompson regime.
The process can render suitable conditions for energy dissipationand proton acceleration, which could explain the detected
day-scale TeV flares in 2010 from M87 via proton-proton collisions.
In IC310 magnetospheric model do not work.

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Based on:MVB, F.A. Aharonian and V. Bosch-Ramon, (M87); ApJ (2010) 724, 1517
MVB, F.A. Aharonian, S.V. Bogovalov, S.R. Kelner and D.V. Khangulyan,(PKS 2155−304 ); ApJ (2012) 749, 119V. Bosch-Ramon, M. Perucho and MVB, (M87); A&A (2012) 539, 69
MVB, V. Bosch-Ramon and F.A. Aharonian, (M87); ApJ (2012) 755, 170
D.V. Khangulyan, MVB, V. Bosch-Ramon, F.A. Aharonian andA. Dorodnitsyn, (3C454.3) ApJ (2013) 774, 113

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Thank you!!!

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Time variability

The shape of the function Fe can be treated as a time profile ofthe particle acceleration rate providing us with its thecharacteristic timescale. In the extreme case, when the blob
eclipses the entire jet (i.e. ω 2 /rc2 ∼ 1), this scale depends only
on the jet Lorentz factor Γj and power Lj , as well as on the massof the cloud Mc :∆t ≈ 200Γj,1 L−1
j,45 Mc,25 sStar-Jet Interactions and γ-Ray Flares

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