Table Of Content2009 Fermi Symposium, Washington, D.C., Nov. 2-5 1
Multiwavelength campaign of the gamma-ray flaring source
PKS2052−47
C.S. Chang1,E. Ros1,2, M.Kadler3,4,5,R.Ojha6,7, theFermi LAT Collaboration, theTANAMI team,
andtheF-GAMMAteam∗
1Max-Planck-Institutfu¨rRadioastronomie,AufdemHu¨gel69,D-53121Bonn,Germany
2Departamentd’AstronomiaiAstrof´ısica,UniversitatdeVale`ncia,E-46100Burjassot,Spain
3Dr. Remeis-Sternwarte&ECAP,Sternwartstr.7,D-96049Bamberg,Germany
4CRESST/NASAGoddardSpaceFlightCenter,Greenbelt,MD20771,USA
5USRA,10211WincopinCircle,Suite500Columbia,MD21044,USA
6USNO,3450MassachusettsAve.,NW,WashingtonDC20392,USA and
0 7NVI,Inc.,7257DHanoverParkway,Greenbelt,MD20770,USA
1
0
2
The flat-spectrum radio quasar PKS2052−47 experienced an optical flare in July−August, 2009. On August
n 9, the LAT detector onboard Fermi observed a flare from the source, which reached its active phase in the
a
following two months. To further investigate the physics and emissionmechanisms during the flaring state of
J
this source, we arranged a multiwavelength campaign from radio to gamma-ray to study its spectral energy
0 distribution (SED) and its brightness variations across the spectrum. Here we present the first results of this
1 multiwavelengthcampaign.
]
O
1. Introduction 2. Multiwavelength observations
C
.
h PKS2052−47isaflat-spectrumradioquasarwitha The multiwavelength campaign of PKS2052−47
p
redshiftof1.489[1]. EarlierAustraliaTelescopeCom- was arranged simultaneously with the scheduled
-
o pact Array (ATCA) and Chandra X-ray observations southern VLBI observations of TANAMI during
r showedthat the sourcehasa two-sidedjet atkilopar- early September 2009. The observation log is re-
t
s sec scales in the radio band, with no extended emis- ported in Table I. The participating facilities in-
a
[ sioninX-rays[2]. VeryLargeBaselineInterferometry clude: Ceduna-HobartInterferometer(CHI),thelarge
(VLBI) observations by TANAMI1 (Tracking Active APEX bolometer camera (LABOCA) [8] at the Ata-
1 Galactic Nuclei with Austral Milliarcsecond Interfer- cama Pathfinder EXperiment (APEX, in the frame-
v
ometry,see[3–5])showthattheparsec-scalestructure work of the F-GAMMA project, see [9]), the Ultra-
3
is very compact, with a high brightness-temperature Violet/Optical Telescope (UVOT) and X-Ray Tele-
6
5 core of 2 × 1012K and a size of (0.3 × 0.1)mas at scope (XRT) onboard Swift, and the Fermi Large
1 8.4GHz. At 22GHz the source is unresolved with a Area Telescope. The Swift target-of-opportunity ob-
. restoring beam of (1.9×1.3)mas. At 8.4GHz, a very servations covered five days centered at the date of
1
0 faint jet to the west is seen (see Figure 1). the TANAMI observations,andthe exposuretime for
eachobservationwasbetween1500and2500seconds.
0
From July 2009, the Automatic Telescope for Op-
1
: tical Monitoring (ATOM) team reported a steady
v
increase of flux density from PKS2052-47, which
i 3. Preliminary results
X reached its high state and flared in the optical band
in August [6]. Right after this, the Fermi Large Area
r
a Telescope(LAT)observedagamma-rayflarefromthis As of December 2009, the data collected include:
source [7]. To understand the physics at work and Swift,Fermi LAT,andAPEXpreliminaryresults(see
emission mechanisms during its flaring state, we ar- Table I). The preliminary APEX flux density pre-
ranged a multi-wavelength campaign from radio to sented here was provided by the F-GAMMA team,
gamma-ray in early September 2009 in order to fol- and the final data calibration is in process. The
low its active phase. TANAMI and CHI simultaneous datasets will be cor-
related shortly. To illustrate the radio morphology
at parsec-scales, we show two TANAMI VLBI im-
ages of PKS 2052−47 obtained in February 2008 at
8 and 22GHz (Ojha et al., submitted to A&A, and
Kadler et al. in preparation)in Figure 1. Notice that
the image resolution of the 8GHz map is higher than
∗The F-GAMMA team (in alphabetical order): E. Angelakis,
that at 22GHz, due to the inclusion of a telescope in
L. Fuhrmann, T. P. Krichbaum, S. Larsson, N. Marchili, G.
Chile,equippedonlywithareceiverat8GHz,provid-
Nestoras,H.Ungerechts, andJ.A.Zensusetal.
1http://pulsar.sternwarte.uni-erlangen.de/tanami/ ing longer baselines to better resolve the source.
eConf C091122
2 2009 Fermi Symposium, Washington, D.C., Nov. 2-5
Figure 1: TheTANAMI VLBI images of PKS2052−47 at 8GHz (left, February 7, 2008) and 22GHz (right,
February 6, 2008). The axes are relative right ascension (RA) and declination (DEC) in milli-arcsecond (mas). On
thebottom right, the scale of 10 parsec (pc) is shown. The scales are different in both images.
Table I Observation log
Start date End date Facility Band Comments
2009-09-05 2009-09-06 CHI 6.6 GHz -
2009-09-05 2009-09-06 TANAMI 8 & 22 GHz -
2009-09-02 2009-09-06 APEX 345 GHz -
2009-09-04 2009-09-08 Swift UVOT 2000–3500 ˚A ∼2ksper day
2009-09-04 2009-09-08 Swift XRT 0.3–10 keV ∼2ksper day
2008-06-11 present FermiLAT 100 MeV–300 GeV All-skysurvey since June 11, 2008
We show a Swift/XRT spectrum in the 0.3−6 keV (SSC)peakappearstobehigherthanthesynchrotron
energyrangewith2.5ksintegrationinFigure2,taken emissionpeakinourresult. Thisisconsistentwiththe
on September 6, 2009. We used XSPEC version 12.5 resultsof[11],whichwasbasedonthehistoricaldata.
to fit an absorbed power-law to the spectrum with Tofurtherunderstandthephysicalprocessesinvolved
a fixed Galactic neutral hydrogen column density of in the active phase of PKS2052−47, SED modeling
2.79×1020 cm−2 [10], and obtained a photon index is needed. The results of this will be presented else-
of 1.53 ± 0.11. The value of the Cash statistic after where.
fittingis21.2with20degreesoffreedom. Thephoton
statistics above 6 keV were not sufficient to obtain
spectral data. 4. Outlook
We show a weekly-binned Fermi LAT light curve
(100MeV−100GeV) from August 2008 to July 2009 The multiwavelength campaign of PKS2052−47
in Figure 3, which is the first 11-month of the mis- provides an opportunity to investigate the emission
sion. We used Fermi Science Tools version v9r10 mechanismsandphysicalprocessesinvolvedinthisra-
and instrumental response functions (IRFs) version dio quasar during its flaring state. When all datasets
P6 V3 DIFFUSE to analyze LAT data. From Figure 3, willbecollected,wewillbeabletocomparetheVLBI
we could see that there is a gradual rise in the flux parsec-scaleimagesat8GHz and22GHz withthe re-
density with time, especially when time approached sults from the other wavelengths, especially that of
to July 2009. highenergies,toprobethesourceofhigh-energyemis-
We present a preliminary broadband SED of sion. Also, the varyingbroadbandSEDmodeling will
PKS2052−47 from radio to gamma-ray in Figure 4. be necessary to understand the source in its active
As shown in Figure 4, the synchrotron self-Compton phase.
eConf C091122
2009 Fermi Symposium, Washington, D.C., Nov. 2-5 3
PKS 2052−47
0.05
V−1
malized counts s ke−1 00..0012
nor 5×10−3
residuals 0.002
0.5 1 2 5
Energy (keV) Figure 3: Fermi LATpre-flare light curveof
Figure 2: Swift XRTspectrum of PKS2052−47 in the PKS2052−47 from 4th August 2008 to 4th July 2009.
0.3−6 keVenergy range with 2.5 ksintegration This plot shows the light curvesince Fermi’s launch,
binnedto one week. Thex-axis is time in theunit of
observed on September6, 2009. The fitted model
mission elapsed time (MET), and they-axisis the
(solid line, upperpanel) is an absorbed power-law.
energy flux between 100MeV–100GeV in unitsof
The residual of fit is shown in thelower panel.
photon cm−2 s−1.
8
1
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1
7
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1
6
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106 107 108 109 101010111012101310141015101610171018101910201021102210231024102510261027
Frequency (Hz)
Figure 4: Thebroadband SED of PKS2052−47. Black filled pentagons: simultaneous data from our
multiwavelength campaign triggered in September2009, which includes APEX preliminary data, Swift UVOT/XRT,
and Fermi LATdata. Redopen circles: historical data from theNASAextragalactic database (NED),including the
EGRET detection. The highest energy bin of LAT data(right-most filled pentagon) has an error barwhich has the
same orderof magnitude as theflux density value.
eConf C091122
4 2009 Fermi Symposium, Washington, D.C., Nov. 2-5
Acknowledgments 3 R. Ojha et al., “Studying Black Holes in the
GLAST Era”, the 2nd Kolkata Conference on Ob-
We thank to M. B¨ock, C. Ricci, L. Barraga´n, and servational Evidence for Black Holes in the Uni-
J. Wilms for valuable discussions, and D. Thomp- verse, AIP Conference Proceedings, 1053, 395,
son for advice and encouragement. This research 2008.
was supported by the EU Framework 6 Marie Curie 4 M. Kadler et al., “The TANAMI Program:
Early Stage Training program under contract num- Southern-Hemisphere VLBI Monitoring of Rela-
ber MEST/CT/2005/19669ESTRELA. C. S. Chang tivistic Jets in Active Galaxies”, Bulletin of the
is a member of the International Max Planck Re- American Astronomical Society, 38, 732, 2007.
search School for Astronomy and Astrophysics. This 5 M. Boeck et al., “Extragalactic Jets from the
publication is based on data acquired with the At- TANAMI Sample as Seen by Fermi/LAT”, 2009
acama Pathfinder Experiment (APEX), a collabora- Fermi Symposium, eConf Proceedings C091122,
tion between the Max-Planck-Institut fu¨r Radioas- 2009 [arXiv:0912.4192].
tronomie, the European Southern Observatory, and 6 M.Hauseretal.,“Detectionofanopticalflarefrom
the Onsala Space Observatory. This research has PKS 2052−474”,ATel #2158, 2009.
been partially funded by the Bundesministerium fu¨r 7 C. S. Chang et al., “Fermi LAT detection of in-
WirtschaftundTechnologieunderDeutschesZentrum creasing gamma-ray activity of blazar PKS 2052-
fu¨r Luft- und Raumfahrt grant number 50OR0808. 474”, ATel #2160, 2009.
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Propulsion Laboratory, California Institute of Tech- 9 L.Fuhrmannet al.,“Simultaneous Radioto (Sub-
nology,under contractwith the NationalAeronautics )mm-MonitoringofVariabilityandSpectralShape
and Space Administration. Evolution of potential GLAST Blazars”, The first
GLASTSymposium,AIPConferenceProceedings,
921, 249, 2007.
10 P. M. W. Kalberla et al., “The Lei-
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eConf C091122
