Issue |
A&A
Volume 572, December 2014
|
|
---|---|---|
Article Number | A121 | |
Number of page(s) | 16 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201424254 | |
Published online | 09 December 2014 |
First broadband characterization and redshift determination of the VHE blazar MAGIC J2001+439⋆
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, Japan
21 Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Department of Physics, University of 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, USA 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), Lausanne, Switzerland
27 Now at Department of Physics & Astronomy, UC Riverside, CA 92521, USA
28 Now at Finnish Centre for Astronomy with ESO (FINCA), Turku, Finland
29 Also at INAF-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 INAF Istituto di Radioastronomia, 40129 Bologna, Italy
34 Dipartimento di Fisica e Astronomia, via Ranzani 1, 40127 Bologna, Italy
35 Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA
36 Isaac Newton Institute of Chile, St. Petersburg Branch, St. Petersburg, Russia
37 Pulkovo Observatory, 196140 St. Petersburg, Russia
38 Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia
39 National Radio Astronomy Observatory, PO Box 0, Socorro, NM 87801, USA
40 Agenzia Spaziale Italiana (ASI) Science Data Center, 00133 Roma, Italy
41 Department of Physics, Purdue University, 525 Northwestern Ave, West Lafayette, IN 47907, USA
42 Department of Physics and Mathematics, College of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara-shi, 252-5258 Kanagawa, Japan
43 University of Missouri-St. Louis, St. Louis, Missouri, USA
44 Physics Department, California Polytechnic State University, San Luis Obispo, CA 94307, USA
Received: 22 May 2014
Accepted: 1 September 2014
Aims. We aim to characterize the broadband emission from 2FGL J2001.1+4352, which has been associated with the unknown-redshift blazar MG4 J200112+4352. Based on its gamma-ray spectral properties, it was identified as a potential very high energy (VHE; E> 100 GeV) gamma-ray emitter. We investigate whether this object is aVHE emitter, characterize its gamma-ray spectrum, and study the broadband emission within the one-zone synchrotron self-Compton (SSC) scenario, which is commonly used to describe the emission in blazars. Moreover, we also intend to determine the redshift of this object, which is a crucial parameter for its scientific interpretation.
Methods. The source was observed with MAGIC first in 2009 and later in 2010 within a multi-instrument observation campaign. The MAGIC observations yielded 14.8 h of good quality stereoscopic data. Besides MAGIC, the campaign involved, observations with Fermi-LAT, Swift-XRT/UVOT, the optical telescopes KVA, Goddard Robotic Telescope, Galaxy View observatory, Crimean Astrophysical observatory, St. Petersburg observatory, and the Owens Valley Radio Observatory. The object was monitored at radio, optical and gamma-ray energies during the years 2010 and 2011. We characterize the radio to VHE spectral energy distribution and quantify the multiband variability and correlations over short (few days) and long (many months) timescales. We also organized deep imaging optical observations with the Nordic Optical Telescope in 2013 to determine the source redshift.
Results. The source, named MAGIC J2001+439, is detected for the first time at VHE with MAGIC at a statistical significance of 6.3σ (E > 70 GeV) during a 1.3 h long observation on 2010 July 16. The multi-instrument observations show variability in all energy bands with the highest amplitude of variability in the X-ray and VHE bands. Besides the variability on few-day timescales, the long-term monitoring of MAGIC J2001+439 shows that, the gamma-ray, optical, and radio emissions gradually decreased on few-month timescales from 2010 through 2011, indicating that at least some of the radio, optical and gamma-ray emission is produced in a single region by the same population of particles. We also determine for the first time the redshift of this BL Lac object through the measurement of its host galaxy during low blazar activity. Using the observational evidence that the luminosities of BL Lac host galaxies are confined to a relatively narrow range, we obtain z = 0.18 ± 0.04. Additionally, we use the Fermi-LAT and MAGIC gamma-ray spectra to provide an independent redshift estimation, z = 0.17 ± 0.10. Using the former (more accurate) redshift value, we adequately describe the broadband emission with a one-zone SSC model for different activity states and interpret the few-day timescale variability as produced by changes in the high-energy component of the electron energy distribution.
Key words: galaxies: active / BL Lacertae objects: individual: MAGIC J2001+435 / BL Lacertae objects: individual: MAGIC J2001+439 / gamma rays: galaxies
Appendix A is available in electronic form at http://www.aanda.org
© ESO, 2014
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