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
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!!
14 October 2013 I. Donnarumma
Gamma-ray opacity inside the BLRs
14 October 2013 I. Donnarumma
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.
14 October 2013 I. Donnarumma
The brightest flares of 3C 454.3 in
December 2009 – November 2010
14 October 2013 I. Donnarumma
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
14 October 2013 I. Donnarumma
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).
14 October 2013 I. Donnarumma
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)
14 October 2013 I. Donnarumma
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
14 October 2013 I. Donnarumma
Ghisellini & Tavecchio 2009
Flat gamma-ray spectra
14 October 2013 I. Donnarumma
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
14 October 2013 I. Donnarumma
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
14 October 2013 I. Donnarumma
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
14 October 2013 I. Donnarumma
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.
14 October 2013 I. Donnarumma
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….
14 October 2013 I. Donnarumma
The extreme variability of PKS
1222+216
14 October 2013 I. Donnarumma
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
14 October 2013 I. Donnarumma
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.
14 October 2013 I. Donnarumma
• 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
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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