Volume 552, April 2013
|Number of page(s)||6|
|Published online||10 April 2013|
Very high energy gamma-ray observation of the peculiar transient event Swift J1644+57 with the MAGIC telescopes and AGILE
IFAE, Edifici Cn., Campus UAB, 08193
2 INAF National Institute for Astrophysics, 00136 Rome, Italy
3 Università di Siena, and INFN Pisa, 53100 Siena, Italy
4 Universidad Complutense, 28040 Madrid, Spain
5 Technische Universität Dortmund, 44221 Dortmund, Germany
6 Max-Planck-Institut für Physik, 80805 München, Germany
7 Inst. de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
8 University of Łódź, 90236 Lodz, Poland
9 Depto. de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Spain
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 Università di Udine, and INFN Trieste, 33100 Udine, Italy
15 Inst. de Astrofísica de Andalucía (CSIC), 18080 Granada, Spain
16 Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, 10000 Zagreb, Croatia
17 Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
18 Università dell’Insubria, Como, 22100 Como, Italy
19 Institut de Ciències de l’Espai (IEEC-CSIC), 08193 Bellaterra, Spain
20 Tuorla Observatory, University of Turku, 21500 Piikkiö, Finland
21 Japanese MAGIC Consortium, Division of Physics and Astronomy, Kyoto University, Japan
22 Inst. for Nucl. Research and Nucl. Energy, 1784 Sofia, Bulgaria
23 Universitat de Barcelona (ICC/IEEC), 08028 Barcelona, Spain
24 Università di Padova and INFN, 35131 Padova, Italy
25 INAF/Osservatorio Astronomico and INFN, 34143 Trieste, Italy
26 Università di Pisa, and INFN Pisa, 56126 Pisa, Italy
27 ICREA, 08010 Barcelona, Spain
28 Now at École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
29 Supported by INFN Padova
30 Now at: DESY, Zeuthen, Germany
31 Now at: Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Finland
32 Also at Instituto de Fisica Teorica, UAM/CSIC, 28049 Madrid, Spain
33 Università di Trieste, and INFN Trieste, 34127 Trieste, Italy
34 Agenzia Spaziale Italiana (ASI) Science Data Center, 00044 Frascati, and INAF-Oar, 00040 Monteporzio Catone, Italy
Accepted: 15 February 2013
Context. On March 28, 2011, the BAT instrument on board the Swift satellite detected a new transient event that in the very beginning was classified as a gamma ray burst (GRB). However, the unusual X-ray flaring activity observed from a few hours up to days after the onset of the event made a different nature seem to be more likely. The long-lasting activity in the X-ray band, followed by a delayed brightening of the source in infrared and radio activity, suggested that it is better interpreted as a tidal disruption event that triggered a dormant black hole in the nucleus of the host galaxy and generated an outflowing jet of relativistic matter.
Aims. Detecting a very high energy emission component from such a peculiar object would be enable us to constrain the dynamic of the emission processes and the jet model by providing information on the Doppler factor of the relativistic ejecta .
Methods. The MAGIC telescopes observed the peculiar source Swift J1644+57 during the flaring phase, searching for gamma-ray emission at very-high energy (VHE, E > 100 GeV), starting observations nearly 2.5 days after the trigger time. MAGIC collected a total of 28 h of data during 12 nights. The source was observed in wobble mode during dark time at a mean zenith angle of 35°. Data were reduced using a new image-cleaning algorithm, the so-called sum-cleaning, which guarantees a better noise suppression and a lower energy threshold than the standard analysis procedure.
Results. No clear evidence for emission above the energy threshold of 100 GeV was found. MAGIC observations permit one to constrain the emission from the source down to 100 GeV, which favors models that explain the observed lower energy variable emission. Data analysis of simultaneous observations from AGILE, Fermi and VERITAS also provide negative detection, which additionally constrain the self-Compton emission component.
Key words: radiation mechanisms: non-thermal / galaxies: active / gamma rays: general
© ESO, 2013
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