Constraining Emission Mechanism in AGN jets byModeling Gamma-ray Rapid Variability（ガンマ線短時間変動のモデル化による活動銀河核ジェットの放射への制限）

ASJ meeting, 9-11 September 2015

Shinya Saito (Rikkyo University)
L. Stawarz (Jagiellonian University), T. Takahashi (ISAS/JAXA), Y. Tanaka (Hiroshima University)

Location of Emission Zone in Blazars• Kinetic luminosity of FSRQs (flat spectrum radio quasars) is comparable to accretion power
during flares.
– 12 –• The site and structure of the emission region is controversial.
• Variability of a few hours is observed with Fermi-LAT. (Foschini+11, Saito+13, Brown +13, Rani+13, Hayashida+15)
16
et al.:→PKSLocation
1510-089 of emission site: R < cδΓΔt/(1+z) ≒ 10 cm ~ 100 RG (Δt=2hours, Γ=10 )Fermi-LAT (MAGIC simultaneous)Fermi-LAT (Low state)

Aleksic+14: PKS1510-089

Fermi best fit model, extrapolated-910Fermi extrapolated+EBL attenuation
AGILE-GRID (Flare-II)
AGILE-GRID (Low intermediate)
MAGIC observed
MAGIC de-absorbed-10105992

nsepinedsoxiistlyriledchily

10-1110-12Fermi10-11MAGIC
10102

Energy [GeV]

Integral flux (>100 GeV) [cm-2 s-1]

E2dN/dE [erg cm-2 s-1]

Fermi-LAT (High state)

-9×10
1

0.9

Exponential fit (χ2=4.45/3)-3

slope: (1.30± 0.15)× 10 s-1

Aleksic+11: 4C 21.35

0.8
0.7
0.6

Linear fit (χ2=5.68/3)-13slope = (3.7± 0.8)×10 cm-2s-1 • s-1

Background - constant fit (χ2=2.34/4)

0.5
0.4

10 min

0.3
0.2

MAGIC

0.1
0

21:50:00

22:00:00

22:10:00

22:20:00
Time (UT)•Fig.
Smoothconnectionof GeVand TeV
spectra4. The γ-ray
SED constructedfrom AGILE,Fermi-LAT
and during GeV flare.
MAGICdata. The AGILE-GRID
data (greyfilled squares)
cor-Fig. 2.— PKS
17 cm,→Suggestingco-spatialityof GeV/TeV
emissionzone
locating
outside>101222+21
light curve above
100 GeV, in 6BLR;
minutes bins
(black filledcircles).
respond to the data of Flare-II (from MJD 55977.5 to 55991.5).
+ was− carried out on MJD 55364. The black solid line is a fit with an exThe observation
sinceVHE photon
absorbedin BLR
due toThe Fermi-LAT
spectrumis(blackopen circles)
combines
all γγ→e e .

events of time intervals coincident with the MAGIC observa-ponential function and the black dotted line a fit with a linear function. The grey opention window (MJD 55976 to 55991 and from 56001 to 56020)squares denote the fluxes from the background events and the grey dashed line is a fit with
•withVariabilityof showing
severaltheminutes
in fitTeV
range
the blue lines
log parabola
to thedata anda constant function to these points.
its statistical uncertainty (the thinner lines). The fit and the errors

Time-dependent modeling of FSRQ flaresConstraining emission zone of FSRQs by• Modeling time evolution of SEDs during flares.
• Fitting simulated GeV gamma-ray light curves to observed ones.

Flare1(Saito et al., 2015, ApJ, 809, 171)• “Finer time resolution” is important since anapparently coherent flare would be resolved into
superposition of sub-flares with better resolution.
• The brightest gamma-ray flares with excellent
photon statistics and apparently coherent time
profile in three hour binning were modeled.

Flare2

PKS1510­089(Fermi-LAT)

12-hour bin

６-hour bin

３-hour binical jet geometry Modelingshown in Figure
7.2.Flaring
EvolutionLightof electronenergytheCurves• A
hell
propagating
the conicaljetassumption
is obtainedof bysolvingthesingle-zone alongmodel with
underlying
internal
shock.

e totalpopulationof relativistic
electrons,
assuming that electron• “BLAZAR”
model(Moderski+03,05)
Q=0

0. Assumea thinofshell
moving along
jet.of external radiation fields
energydensities
magnetic
fieldtheand1. Electron injection (Q) during a certain section.

Observershell. The equation is written in the followingReform.
2. Calculate time evolution of electronenergy distribution (Nγ).

∂Nγ∂=−′∂t∂γ!

dγNγ ′dt"

Q = Q0electroninjection+Q(7.11)Rs

ten as,synchrotron /inverse Compton(KN) /adiabatic cooling
Saito et al.
GeV!
"
3. Calculateobserved
spectra∂N∂dγ
Qγ
Gamma-at eachfield=(BLRandHDT)
areassumed
as,moment.
−Nγ+
48

47.5

Synchrotron
SSC-9

ERC
ERCIR

log iFi (erg s-1 cm-2)

48.5(7.12)

log iLi (erg s-1)

47-10
UV pho- ∂r
2∂γ
drcβ
Γ
46.5
Γ Lext1Γ
ld not4.
es-Extract GeV banduext (R)and=46
2 1 + (R/R2
requiresmake GeV light curves.πcRext-11ext )45.5
tance aswhere Rext is the typical size and L45ext represents the! "and VHE-12luminosity of the external photon field.
Moderski+03
44.5
dγWe assumed
1 thedγ
2γ
a simpleelectron injection function
as 18broken
1012141620
2224
26=−(7.13)
expandpower-law which is written
as follows.
′ModelNalewajko+12)
drparametersβcΓ (PKS1510-089)
dt rad3(Barnacka+15,r$#ked in thee distribution: Q(γ) = K γ −p 1 + (γ/γ )4 (p−q)/4 (p=1.2,(2)q=3.4, γb=900, γmin=1, γmax=105)ebange dur48.5
48.5
Synchrotron
Synchrotrontionfunction(definedin7.3.3),
Nisnumberdensityofelectrons
BLR(0.12e18cm,0.055
erg/cm3,10eV),
HDT(1.9e18cm,5e-3 erg/cm3,0.15 eV)
SSC
SSCγKe is48 the normalization of the-9injection
function,pandrevealed
48-9-9Figure ERC
7.2: A figure illustrating the geometry taken into acc
ERC
q are 47.5
spectraland γb is an
ERCIR indices for injecting electrons,
ERCIR
GeV dur-Γ = 22
47.5
ctor etγ,
islocation
emittingshellmeasured
fromthe An shell which enLorentz
factorof
for thebreakenergy.
Theelectronθjet r= electronθ=47 0.3°
Tanakaobsthe47
whichwastakenfromModerski
et al. (2003).
-10-10-10
injection of Q(γ) is defined in the range of γ
<γ <rg s-1 cm-2)(erg s-1)

rg s-1 cm-2)(erg s-1)

rg s-1 cm-2)

log i (Hz)Constraints on the Location of Emission Zone
Length of section with electron injection (Re-Rs) was estimated to be 0.2x1018 cm.
• Simulations were performed for various locations of emission zone.
4Saito et al.
→ Location of gamma-ray emission zone was estimated to be (0.7 ± 0.2)x1018 cm from theSMBH.
•102

Sai

25
10

48.5

Synchrotron
SSC
EC/BLR
EC/HDT

48 20

00.2

0.4

0.6

0.8

1Rstart [1018 cm]

1.2

1.4

1.6

Rs = 1.5x1018 cm

30log L (erg s-1)

47.5

191.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3Rstart [1018 cm]

47 151046.520

Rs = 0.7x1018 cm

Rs = 0.1x1018 cm

46log F (erg s-1 cm-2)

40

2Flux (>100MeV) [10-6 ph cm-2 s-1]

PKS1510-089 γ-ray flare
50 (θobs=θjet = 2.6 )102

Flux (>100MeV) [10-6 ph cm-2 s-1]

6101145.5
451051244.5

020246810 1214

Hours from MJD 55853.5

1618100012

14 10 16201820 30 22402426 50(Hz) MJD 55872
Hourslogfrom

Fig. 3.— The simulated time evolution of the broad-band SEDs oFig. 1.— Simulated profiles of the analyzed Flare 1 and Flare 2panels,in PKSrespectively).
1510–089 within
0.1–300
GeV
range (leftandinstants
right pan
Thethespectrawereextracted
at them
respectively), superposed on the 3-hour binned LAT light curve of
the source taken
fromdashed
Saito etlines
al. (2013).
respectively).
VerticalindicateSimulations
the energy denoted
range ofin1
figure by various color curves were performed for diﬀerent locationsof thespectral
emittingdatapoints
region along
the free-expanding
outflow,
as explaarchivalcorresponding
to the March2009
flare
2Light curve modeling of another flare in PKS 1510-089 also suggests emission
18 cm from the SMBH.
zone
locatingaround~10
Saito et al.
•

6

Saito et al.

1.4

1.6

48

947.5

9

1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4

Rstart [1018 cm]

4715

10

Rs = 2.3x1018 cm

46.5
4610

4710

46.5
461145.5

1145.545 5451244.5

010 0 12

Synchrotron
SSCEC/BLR
EC/HDTlog F (erg s-1 cm-2)

47.5

SSC
EC/BLR
EC/HDT

log L (erg s-1)

4820

48.5

10log F (erg s-1 cm-2)

Flux (>100MeV) [10 ph cm-2 s-1]

48.5

PKS1510-089
Synchrotron(θjet = θobs= 2.6°)225

log L (erg s-1-6)

2

Constraints on the Location of Emission Zone

141016 2018

2030 222440

log (Hz)
Hours fromMJD 55872

26 50

1244.51012141618
log

20222426(Hz)Fig. 3.— The simulated time evolution of the broad-band SEDs of PKS 1510–089 during the analyzed Flare 1 and Flare 2 (left and rigThethe rightinstants
marked as “1”, “2”, and “3” in Figure 1 (black, red, and green curve
Flare 2 panels,in PKS respectively).
1510–089 withinthespectra
0.1–300were
GeVextracted
range (leftatandpanels,Verticaldashedindicatethe energy
range inof the
100 MeV – 300 GeV. For a reference, in the plots we include also thcurve ofrespectively).
the source takenfrom Saito
et linesal. (2013).
Simulations
denotedarchival
spectral datapoints
to theoutflow,
March 2009
flare of the source from Barnacka et al. (2014).
locationsof the emitting
region alongcorresponding
the free-expanding
as explainedg model fits to the decaying phases of the flares are inserted as small figures inEmission zone for a highly collimated jet•8

Gamma-ray flaring light curves were simulated for a well-collimated jet (smallerjet opening angle of down to 0.3°: Γθjet ≒ 0.1), which is suggested by radio
studies (e.g. Jorstad+05, Clausen-Brown+13).
106Le ≒ 1046 erg/s
Le/LB > 100(MJD55853 ﬂare)

8best-fit location of18 (1018 cm)
the emissionzone
R (10cm)

Lacc ≒ 5x1045 erg/s

PKS 1510-089

Rstart (1018 cm)

4start64

200

Le ≒ 10472 erg/s
Le/LB > 10
1

2

300

jet opening angle (=(deg)jet viewing angle) (deg)2081Expected Broadband Light Curves

The Astrophysical Journal, 809:171 (10pp), 2015 August 20

VHE flux will be enhanced for thecollimated jet due to pronounced
emission from HDT.

•Monitoring flux change with timescale
down to hours will resolve the modeldegeneracy.

X-ray•HE

Different geometries give different
timescales and flux levels of the flare inother wavelengths.

VHE•

Opticalθjet=2.6°

θjet=0.3°

Summary•

We collected the brightest samples of gamma-ray flares, and performed timedependent modeling of gamma-ray flares in FSRQs with time resolution as goodas three hours.

•The estimated location of emission zone during gamma-ray flares in PKS
1510-089 is around ~1018 cm from the central SMBH, which is reconciled with
detection of VHE photons reported during GeV flares.

•Observed time profile a flare was found to be characterised not only by electron
cooling timescale, but also geometrical effect.

•

Exactly simultaneous observation of flares with time resolution down to hours willremove the degeneracy of model parameters.