Issue |
A&A
Volume 567, July 2014
|
|
---|---|---|
Article Number | A135 | |
Number of page(s) | 15 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201423364 | |
Published online | 29 July 2014 |
MAGIC long-term study of the distant TeV blazar PKS 1424+240 in a multiwavelength context⋆
1
IFAE, Campus UAB,
08193
Bellaterra,
Spain
2
Università di Udine, and INFN Trieste, 33100
Udine,
Italy
3
INAF National Institute for Astrophysics,
00136
Rome,
Italy
4
Università di Siena, and INFN Pisa, 53100
Siena,
Italy
5
Croatian MAGIC Consortium, Rudjer Boskovic Institute, University
of Rijeka and University of Split, 10000
Zagreb,
Croatia
6
Max-Planck-Institut für Physik, 80805
München,
Germany
7
Universidad Complutense, 28040
Madrid,
Spain
8
Inst. de Astrofísica de Canarias, 38200
La Laguna, Tenerife,
Spain
9
University of Łódź, 90236
Lodz,
Poland
10
Deutsches Elektronen-Synchrotron (DESY),
15738
Zeuthen,
Germany
11
ETH Zurich, 8093
Zurich,
Switzerland
12
Universität Würzburg, 97074
Würzburg,
Germany
13
Centro de Investigaciones Energéticas, Medioambientales y
Tecnológicas, 28040
Madrid,
Spain
14
Technische Universität Dortmund, 44221
Dortmund,
Germany
15
Inst. de Astrofísica de Andalucía (CSIC),
18080
Granada,
Spain
16
Università di Padova and INFN, 35131
Padova,
Italy
17
Università dell’Insubria, Como, 22100
Como,
Italy
18
Unitat de Física de les Radiacions, Departament de Física, and
CERES-IEEC, Universitat Autònoma de Barcelona, 08193
Bellaterra,
Spain
19
Institut de Ciències de l’Espai (IEEC-CSIC),
08193
Bellaterra,
Spain
20
Japanese MAGIC Consortium, Division of Physics and Astronomy,
Kyoto University, 606-8501
Kyoto,
Japan
21
Finnish MAGIC Consortium, Tuorla Observatory, University of Turku
and Department of Physics, University of Oulu, 900147
Oulu,
Finland
22
Inst. for Nucl. Research and Nucl. Energy,
1784
Sofia,
Bulgaria
23
Universitat de Barcelona, ICC, IEEC-UB, 08028
Barcelona,
Spain
24
Università di Pisa, and INFN Pisa, 56126
Pisa,
Italy
25
Now at: NASA Goddard Space Flight Center, Greenbelt MD 20771; and
Department of Physics and Department of Astronomy, University of
Maryland, College
Park
MD
20742,
USA
26
Now at: École polytechnique fédérale de Lausanne
(EPFL), 1015
Lausanne,
Switzerland
27
Now at: Department of Physics & Astronomy, UC Riverside,
CA 92521,
USA
28
Finnish Centre for Astronomy with ESO (FINCA),
Turku,
Finland
29
Also at: INAF via Tiepolo Giambattista,
34131
Trieste,
Italy
30
Also at Instituto de Fisica Teorica, UAM/CSIC, 28049
Madrid,
Spain
31
Now at: Stockholm University, Oskar Klein Centre for Cosmoparticle Physics,
106 91
Stockholm,
Sweden
32
Now at: GRAPPA Institute, University of Amsterdam,
1098 XH
Amsterdam, The
Netherlands
33
Kavli Institute for Particle Astrophysics and Cosmology, SLAC
National Accelerator Laboratory, Stanford University, Stanford, CA
94305,
USA
34
Cahill Center for Astronomy & Astrophysics, California
Institute of Technology, 1200 E
California Blvd, Pasadena, CA
91125,
USA
35
Department of Physics, Purdue University,
525 Northwestern Ave,
West Lafayette, IN
47907,
USA
36
Aalto University Metsähovi Radio Observatory,
Metsähovintie 114, 02540
Kylmälä,
Finland
37
AaltoUniversity, Department of Radio Science and
Engineering, 02150
Espoo,
Finland
38 Department of Physics, University of Crete, Greece
Received: 1 January 2014
Accepted: 29 April 2014
Aims. We present a study of the very high-energy (VHE; E> 100 GeV) γ-ray emission of the blazar PKS 1424+240 observed with the MAGIC telescopes. The primary aim of this paper is the multiwavelength spectral characterization and modeling of this blazar, which is made particularly interesting by the recent discovery of a lower limit of its redshift of z ≥ 0.6 and makes it a promising candidate to be the most distant VHE source.
Methods. The source has been observed with the MAGIC telescopes in VHE γ rays for a total observation time of ~33.6 h from 2009 to 2011. A detailed analysis of its γ-ray spectrum and time evolution has been carried out. Moreover, we have collected and analyzed simultaneous and quasi-simultaneous multiwavelength data.
Results. The source was marginally detected in VHE γ rays during 2009 and 2010, and later, the detection was confirmed during an optical outburst in 2011. The combined significance of the stacked sample is ~7.2σ. The differential spectra measured during the different campaigns can be described by steep power laws with the indices ranging from 3.5 ± 1.2 to 5.0 ± 1.7. The MAGIC spectra corrected for the absorption due to the extragalactic background light connect smoothly, within systematic errors, with the mean spectrum in 2009–2011 observed at lower energies by the Fermi-LAT. The absorption-corrected MAGIC spectrum is flat with no apparent turn down up to 400 GeV. The multiwavelength light curve shows increasing flux in radio and optical bands that could point to a common origin from the same region of the jet. The large separation between the two peaks of the constructed non-simultaneous spectral energy distribution also requires an extremely high Doppler factor if an one zone synchrotron self-Compton model is applied. We find that a two-component synchrotron self-Compton model describes the spectral energy distribution of the source well, if the source is located at z ~ 0.6.
Key words: gamma rays: galaxies / BL Lacertae objects: individual: PKS 1424+240
Appendix is available in electronic form at http://www.aanda.org
© ESO, 2014
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