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-ray flares from AGN jet/RG interactions
Maxim V. Barkov1,2 Felix A. Aharonian1,3 Sergey V. Bogovalov4 ValentМ Bosch-Ramon3 Stanislav R. Kelner 1,4 Dmitriy Khangulyan 5
MPI fЭr Kernphysik, Heidelberg, Germany 2 Space Research Institute, Russia 3 Dublin Institute for Advanced Studies, Ireland 4 National research nuclear university-MEPHI, Russia Institute of Space and Astronautical Science/JAXA, Japan
1

5

HEA 2010 22 December 2010


Outline
1 2 3 4 5

Observations of M87 Model: Tidal disruption and pp production Resulting radiation of the M87 Very fast variability Discussion and Conclusions

Based on: MVB, F.A. Aharonian, V. Bosch-Ramon, ApJ (2010) 724, 1517 MVB, F.A. Aharonian, S.V. Bogovalov, S.R. Kelner and D. Khangulyan submited to Phys. Rev. D (2010) arxiv:1012.1787
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Magnetically driven Jet Structure
Sketch of the jet with characteristic magnetic field strength and bulk Lorentz factors at typical distances from a BH with mass MBH = 108 M and Lj = 1046 erg s-1 .

j =
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, 4rg



1 , j

Bc

2 z

Lj c

1/2

G
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M87 observations

The parameters of the M87 BH and Jet M Ljet
BH

6.4 в 109 M 2 в 1044 ergs s-1 1017 cm
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radiative active area (in radio) r
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H.E.S.S., MAGIC, VERITAS observations of M87
Several flashes were observed in 2006, 2008, 2009. Variability on scales t 1day The flux L 3 в 1040 ergs s-1 E
,max

20TeV.

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Tidal interaction
In the case of FRI galaxy the ram pressure of the jet is not enough to destroy RG outer layers. If the star approaches to BH closer than the tidal radius zT = RRG the jet.
MBH MRG 1/3

, the outer layers of the star can be ablated by

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Star envelop evolution
pj = Fj ^ pc ( - 1)ec c Ec = ec drc = cs = dt Fj = Lj 1014 erg cm-2 s-1 2 zjc 2

3 3 4 Fj rc 4 rc = ^ 3 3( - 1)c c 1/2 2 d 2 zc Fj rc = cMc dt 2

^^ ( - 1)E Mc

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Par ticle acceleration
AGN jets are likely magnetically dominated at z Bj 4Lj 2 2 2 j
1/2

zT .
-1 j

cz

- -1 100 Lj,44 z161 -1

G

for this magnetic field strength, one can estimate the acceleration timescale: t
acc

=

E E 0.1 E2 Bj-1 s , ,2 acc q Bj c E 10).

where is the acceleration efficiency parameter ( The maximum energy of protons is Ep
max



3 q Bj rc 107 Bj,2 rc 2

,14



-1/2

TeV.

The maximum energy of electrons is Ee
max



qc -1/2 10 Bj,2 as Bj

-1/2

TeV,

This electron maximum energy is not enough high to explain the obser vations!
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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 the RG-jet scenario: the characteristic cooling time for pp collisions is 1015 = 105 n nc
-1 c,10

t

pp



s

E /Ep = 0.17 [2 - exp(-t /tpp )]

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VHE light curve and the cloud evolution
The adopted parameter values are: Lj = 2 в 1044 erg s-1 , MBH = 6.4 в 109 M , -1 = 0.5, MRG = 1 M , zjc 2.5 в 1016 cm, Mc 1.3 в 1028 gr.

Obser vations: The flux L 3 в 1040 ergs s-1 Variability a scale of t 1day

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Analytical model of the optimal radiation case
mass of the cloud Mc = the distance zjetcross = ^ L6 6 M j 7505 c 6 G
4 MBH G3 Lj 7 RG tv 3M 4 m 6 BH p 1/5

3/2 3/2 21/2 ^ tv


RG

1/15

3.16 в 1022 MRG 4 MBH

3/2

m

3/2 3/2 pc

M



9


1/ 5

.

4/15

- luminosity L =

109 3

^j 3 L8 tv
3 c 3 G 4 mp 8

/5

for the galaxy M87
Adopting typical parameter values for M87, Lj = 2 в 1044 erg s-1 , MBH = 6.4 в 109 M , -1 = 1, tv = 2 в 105 days, MRG = 1 M , one gets zjc 3.6 в 1016 cm, Mc 1.4 в 1028 gr, and -1 = 1, L 4 в 1040 erg s

-1

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Analytical model of the optimal radiation case
mass of the cloud Mc = the distance zjetcross = ^ L6 6 M j 7505 c 6 G
4 MBH G3 Lj 7 RG tv 3M 4 m 6 BH p 1/5

3/2 3/2 21/2 ^ tv


RG

1/15

3.16 в 1022 MRG 4 MBH

3/2

m

3/2 3/2 pc

M



9


1/ 5

.

4/15

- luminosity L =

109 3

^j 3 L8 tv
3 c 3 G 4 mp 8

/5

for the galaxy M87
Adopting typical parameter values for M87, Lj = 2 в 1044 erg s-1 , MBH = 6.4 в 109 M , -1 = 1, tv = 2 в 105 days, MRG = 1 M , one gets zjc 3.6 в 1016 cm, Mc 1.4 в 1028 gr, and -1 = 1, L 4 в 1040 erg s

-1

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Very fast variability

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PKS2155-304 observations

The observed parameters of the PKS2155-304 flares L 1047 erg s 200 s LX 1046 erg s
-1 -1

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AGN Jet ­ Red Giant interaction

Schematic illustration of the scenario. When a star crosses the AGN jet, the outer layers of its atmosphere are ablated due to the high jet ram pressure; During the interaction with the jet the cloud gets expanded and involved to the jet motion.
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Relativistic Stage
At the relativistic stage, the dynamics of the cloud is described by the following equation: dg = dy 1 -g g2
2

D , y2

D

2 L j rc , 4 2 3 z0 c 3 Mc j

g

c , j

y

z . z0

Solutions the equation shown as Fe L/Lmax cloud and as L/Lmax vs the observer's time (t0 Lorentz factor of the jet is assumed to be j = of the D-parameter were used: D = 100, 10, 1
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vs Lorentz factor of the = z0 /2D 2 c ). The j 30. The following values and 0.1.
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Energy Budget of the Cloud
The radiation of blazars is to be strongly Doppler boosted. The apparent luminosity L and the intrinsic luminosities are connected through the well known relation factor:
4 L = Lsc c =

1 2 -c 2 4 c j

4 3c Lj r 16 2

2 c

one can estimate the size of the blob: rc 5 в 1014 MBH,8 L
1/2 -1/2 -1/2 ,47 Lj,46 -1

cm

Another impor tant estimate can be obtained for the maximum apparent luminosity of the blob. It is achieved when the blob eclipses the whole jet, i.e. rc . In this case one obtains: L
max

= 4 в 1047 -1 Lj

2 ,46 j,1.5

erg s

-1

.

And the total energy of electromagnetic radiation which can be emitted by the cloud Etot 2.5 в 1049 -1 Mc,25 3,1.5 erg. j
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Time variability
The shape of the function Fe can be treated as a time profile of the par ticle acceleration rate providing us with the characteristic timescale. In the extreme case, when the blob eclipses the entire jet (i.e. 2 2 /rc 1), this scale depends only on the jet Lorentz factor j and power Lj , as well as on the mass of the cloud Mc : t 60
-1 j ,1.5 Lj,46

M

c,25

s

The blobs can change their speeds on timescales of ts 2rc /vs leading to the variability on a timescale ts / 5 в 102 MBH,8 L
1/2 -1/2 -1/2 -1 ,47 Lj,46 -1 2

s.

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Proton synchrotron radiation

Comparing the acceleration and cooling rates one can find the maximum energy of protons: Epeak = 1.8 в 1019 B2 E 300
-1/2



-1/2

eV,

and the corresponding maximum energy of synchrotron photons,
,max -1

GeV .

The acceleration of protons is accompanied by electrons,
- Esyn,e = 160e 1 MeV.
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Conclusions
If a RG is even slightly tidally disrupted by the SMBH, enough stellar material will be blown by the jet. The process can render suitable conditions for energy dissipation and proton acceleration, which could explain the detected day-scale TeV flares from M87 via proton-proton collisions. We show that the RG to the Lorentz factors synchrotron radiation. TeV flares on top of a gamma-ray variability
Based on: MVB, F.A. Aharonian, V. Bosch-Ramon, ApJ (2010) 724, 1517 MVB, F.A. Aharonian, S.V. Bogovalov, S.R. Kelner and D. Khangulyan submited to Phys. Rev. D (2010) arxiv:1012.1787
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fragmented envelope can be accelerated up of 100 and radiate effectively through proton The model can explain the minute-scale longer (typical time-scales of days) as observed from the blazar PKS 2155-304.


Thank you!!!

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