Reviewing recent results on blazars - INAF IASF...

Reviewing recent results on

blazars

Imma Donnarumma

INAF-IAPS

Rome, Italy

14 October 2013 I. Donnarumma Black oles, jets and outflows

Kathmandu, 14-18 October 2013

I. DonnarummaINAF-IAPS

Rome, Italy

Reviewing recent

results on blazars

Outline

Try to address the following questions:

How do blazars behave?

How many flavors of variability are we observing?

Is it possible to collect all observational evidences in a self-

consistent scenario?

What do we have to expect in the next future? What do we

really need in order to increase our knowledge?

14 October 2013 I. Donnarumma

Blazars SEDs and standard modeling

Focussing on FSRQs: the main

observational tools

• Opacity to gamma-rays in the blazarenvironement

• The radio emission and blob ejecta

• Timescale of the Compton branch (γ-ray and VHEs) variability

These are carrying out several information, oftencontrasting each other, making hard

to find a unique solution!!


Gamma-ray opacity inside the BLRs


Pountanen & Stern 2010

BLR spectrum for various ionization parameters. Quasar

spectrum (black line), a multicolor disk with Tmax=105 K.

Signatures of BLRs in the gamma-ray

spectrum

The gamma-ray spectrum shows signature

of the opacity of the region crossed by the

propagating blob.

The GeV breaks observed in blazars are

well described by γ-ray absorption via

photon–photon pair production on He II

and HI recombination continuum photons.


The brightest flares of 3C 454.3 in

December 2009 – November 2010


Bonnoli et al. 2011

Vercellone et al. 2011

All these authors agree

with the standard

interpretation that the

blob dissipates at

sub-parsec scale within

the BLRs

But this is not

the end of the

story…..

Pacciani et al. 2010

Radio-gamma connection

in 3C 454.3Jorstad et al. 2013


Optical, IR, and mm-wave variations in 2009–

2011 indicates that the events seen at different

wavelengths were co-spatial.

The VLBI core of the parsec scale jet was

active during all three high-energy events:

ejection of superluminal knots with Γ∼30

for the most dramatic outbursts.

The duration of the outbursts matches the

time needed for a knot to pass through the

mm-wave VLBI core.

Linear polarization variations observed at

γ-ray peak.

γ-ray radiation timescale significantly shorter

than at lower frequencies.

Interpreted according to the turbolent

Extreme Multi-zone model (Marsher et al.

2012).


See also the recent findings of

Isler et al. 2013

The “flaring BLRs” (MgII line)

suggest the presence of an additional

component of the BLR, possibly filled

with BLR material dragged by the

relativistic jet as it propagates

downstream of the BH or perhaps

associated with a sub-relativistic

outflow arising from an accretion disk

Leon-tavares et al. 2013

Challenging the standard view of BLRs

Even farther (70 light years) from the BH:

the case of 4C +71.07 (z=2.178)


Connection of the active γ-ray state

with the superluminal knot propagating down

the jet from the mm-wave core located at ~14 pc

from the central engine

(NASA Press Release, Blazar Boston Group)

Variability timescale and the location

of the gamma-ray dissipation region


Ghisellini & Tavecchio 2009

Flat gamma-ray spectra


PKS 1424-418 (z=1.52)

Tavecchio, Pacciani, Donnarumma et al. 2013

PMN 2345-155 (z=0.621)

Ghisellini, Tavecchio et al. 2013GB6 1239+0443 (z=1.762)

Pacciani, Donnarumma et al. 2012

GB6 1239+0443 z=1.762

Archival data: SDSS (photometry + spectrum), GALEX,

MOJAVE, PLANCK

We confirm the association of SDSS

J123932.75+0445.3 with the gamma-ray emitting

source with a larger dataset (using

INTEGRAL/OMC images), and looking for the

other candidates in the Swift/UVOT images

We derived the disk luminosity and then the BH

mass from the CIV line width (Vestergaard 2006),

(ASSEF 2011)

The 30 days integrated gamma-ray spectrum lacks

absorption features as predicted by (Poutanen &

Stern 2010) and (Tavecchio & Mazin 2009) at 5

GeV/(1+z)

Very Hard Gamma-ray spectra favor dissipation beyond the BLRs;

Pacciani, Donnarumma et al. 2012


Transition from red to blue blazar

Broken power-law observed in X-

ray (typical of Intermediate BL Lac

objects) suggesting a highly

efficient acceleration mechanism (γp

> 103)

Gamma-ray dissipation region

larger by a factor of 3 with respect

to the average s tate; slightly

higher Г (12 vs 16), consistent with

two distinct dissipation regions..

The same source is then able to change not only its flux by

orders of magnitude but also their color 14 October 2013 I. Donnarumma

High z, high power, high synchrotron

peak objects: the 4 Fermi blue blazarsPadovani, Giommi & Rau 2012


RX J0035.2+1515. CRATES J0630−2406

SUMSS J053748−571828.CRATES J1312−2156

These are thought (radio properties) to be FSRQs with their

emission lines swamped by the non-thermal continuum (see

also Ghisellini et al. 2012)

• Hard gamma-ray spectrum Г=1.96 good candidate for the

detection of hard photons

• Optical, X-ray and gamma-ray flaring activity started on October 2012

• Major γ-ray outburst in April 2013 ( F(>100 MeV) > 310-6 ph cm-2 s-1)

• Multifrequency data: IR-O (SMARTS), X-ray (Swift), γ-rays (Fermi)

The far emitting region of PKS 1424-418

(z=1.52) Tavecchio, Pacciani, Donnarumma et al. 2013


PKS 1424-418 (z=1.52):

the light curve and observed SED

The γ-ray light (0.3-300 GeV) curve varied on

daily time scale (as reported in the inset in the

figure) ; the vertical lines indicate the two epochs

for which the SED modeling was performed (the

large set of simultaneous data).

IR-O data (0.4-2.2 μm): variation of

2.5 mag with respect to the lower state

(green points, Wise and SMARTS

data).

X-ray (2-10 keV): 6.2 10-12 cm-2 s-1

comparable with other states;

γ-rays: 3-day averaged spectra with

higher energy photons detected in the

20-40 GeV bin14 October 2013 I. Donnarumma

PKS 1424-418 (z=1.52):

fixing the location of the γ-ray dissipation region with the

following steps

• Ld~1046 erg s-1 estimated from the luminosity of

the broad MGII (BLR/disc ratio of 0.1).

• We then derived RBLR and Rtorus are together with

profile of the energy density of the BLR and the

dusty torus (in the comoving frame of the jet,

Г=20).

• High opacity is thus expected at 25 GeV due to H

Lyα photons of the BLR (τ~σT nLyα RBLR/5

~11).

• Suppression of the 3 order of magnitude

expected at the energies of the last two bins (rest-

frame)

All these arguments favor a gamma-ray dissipation region

beyond the sphere of influence of BLR, in the region dominated

from the dusty torus14 October 2013 I. Donnarumma

Further clues from the SED modeling

• The IC peak energy is well constrained on April 2 allowing us to constrain γ’p , the

Lorentz factor of electrons emitting at the peak;

• The sync peak energy is well constrained from above thanks to the SMARTS data;

By injecting the value of γ’p in the

derived sync frequency, we obtain an

upper limit to the magnetic field

B’< 3 x 10-2 , much lower than

typical values found in FSRQs.

consistent with a region far

from the central engine.

Moreover, the ratio of luminosity

between LIC and Lsyn allows the

external energy density to be derived

(10^-4 cgs) which locate the emission

region at 5-10 pc.


PKS 1424-418:

the short term variability

The long term trend of the γ-ray emission is consistent with

the inferred light-crossing time, tvar = R/cδ ∼ 35 d, and with

the radiative cooling time-scale, of the order of 30 d for the

γ-ray emitting electrons; but daily variations are detected as

well. This problem arises also for other FSRQs for which a

far emission region is inferred….


The extreme variability of PKS

1222+216


Tavecchio et al. 2011

• VHE photons detected

during a gamma-ray

flare, with variation

occurred on 10 minute

timescale;

• Opacity argument

moves the emission

region beyond the BLRs

The fast variability is hard

to be interpreted in the

standard scenario of a

conical jet.

Magnetic reconnection (MR) at workGiannios et al. 2013


The location of the dissipation region (Rdiss) and the scale length (l’)of MR is highly

model dependent. Magnetic reconnection driven by instabilities in the jet:

e.g. the jet in not axisymmetric at the launching region field structures in the jet with a size of the order of BH horizon (Rdiss~0.3-1 pc and l’≤1016 cm)

envelope

Magnetic field lines of opposite polarity meet inthe reconnection plane ,

liberating magnetic energy that heats the plasma and accelerate particles to the

Alfven speed.

The reconnection layer can generate a large number of plasmoids (envelope and

monster) , explaining both daily and ultra-fast (minutes/hours timescale) .

monster

Summary and conclusions

The standard models of blazars seems to be challenged by the

observtional properties observed by several objects (the Radio-

γ-ray connection, γ-ray Opacity, short timescale of vriability)

In particular, further investigations of the far emitting region scenario are

foreseen:

• the monitoring of blazar with hard γ-ray spectra in Fermi catalog will

contribute to improve the sample of objects with hard emission (which

are actually special candidates for Cherenkov Observatories)

• the radio monitoring and polarization measurements for a larger sample

of objects will be crucial as well.


• Improving gamma-ray sensitivity at >10 GeV (synergy with

CTA)

• Applying magnetic reconnection to jet structure to reproduce

both rapid variability at parsec scale and the polarization

swings (as in the case of the Crab)

• Exploring ultrafast variability in X-rays and TeV with LOFT

and CTA

• Tracing the jet evolution on long timescale with SKA

Possible Advances in blazars studies

achievable by


Chandra LOFT/LAD

Synergy between LOFT and CTA:timescale variability never explored so far:

sec - timescales in X-rays and VHE gamma-rays!!

2s-bin

25-s rise time

7.5-s bin time

2-s bin time

CTA

simultation

Sol et al. 2013

Aharonian et al. 2007

14 October 2013

The case of PKS 2155-304

100-s rise time

20% enhancement with

respect to a flux level of

10-10 erg/cm2/sI. Donnarumma

Reviewing recent results on blazars - INAF IASF...

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