The extreme HBL behaviour of Markarian 501 during 2012
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Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2018-12
Department
Swiss Federal Institute of Technology Zurich
University of Udine
Osservatorio Astronomicodi Roma
University of Padova
University of Rijeka
Saha Institute of Nuclear Physics
Max-Planck-Institut fur Physik (Werner-Heisenberg-Institut) Munchen
Complutense University
Instituto Astrofisico de Canarias
University of Lódz
Deutsches Elektronensynchroton DESY
Deutsches Elektronen-Synchrotron
Barcelona Institute of Science and Technology
University of Siena
University of La Laguna
Università di Padova and INFN
Technische Universität Dortmund
University of Würzburg
University of Turku
Autonomous University of Barcelona
University of Barcelona
University of Tokyo
Universitat Autonoma de Barcelona
Bulgarian Academy of Sciences
Metsähovi Radio Observatory
Department of Electronics and Nanoengineering
University of Udine
Osservatorio Astronomicodi Roma
University of Padova
University of Rijeka
Saha Institute of Nuclear Physics
Max-Planck-Institut fur Physik (Werner-Heisenberg-Institut) Munchen
Complutense University
Instituto Astrofisico de Canarias
University of Lódz
Deutsches Elektronensynchroton DESY
Deutsches Elektronen-Synchrotron
Barcelona Institute of Science and Technology
University of Siena
University of La Laguna
Università di Padova and INFN
Technische Universität Dortmund
University of Würzburg
University of Turku
Autonomous University of Barcelona
University of Barcelona
University of Tokyo
Universitat Autonoma de Barcelona
Bulgarian Academy of Sciences
Metsähovi Radio Observatory
Department of Electronics and Nanoengineering
Major/Subject
Mcode
Degree programme
Language
en
Pages
23
Series
Astronomy and Astrophysics, Volume 620
Abstract
A multiwavelength campaign was organized to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on board the Swift and Fermi spacecraft, and the telescopes operated by the GASP-WEBT collaboration. Mrk 501 showed a very high energy (VHE) gamma-ray flux above 0.2 TeV of ∼ 0.5 times the Crab Nebula flux (CU) for most of the campaign. The highest activity occurred on 2012 June 9, when the VHE flux was ∼ 3 CU, and the peak of the high-energy spectral component was found to be at ∼ 2 TeV. This study reports very hard X-ray spectra, and the hardest VHE spectra measured to date for Mrk 501. The fractional variability was found to increase with energy, with the highest variability occurring at VHE, and a significant correlation between the X-ray and VHE bands. The unprecedentedly hard X-ray and VHE spectra measured imply that their low- and high-energy components peaked above 5keV and 0.5 TeV, respectively, during a large fraction of the observing campaign, and hence that Mrk 501 behaved like an extreme high-frequency- peaked blazar (EHBL) throughout the 2012 observing season. This suggests that being an EHBL may not be a permanent characteristic of a blazar, but rather a state which may change over time. The one-zone synchrotron self-Compton (SSC) scenario can successfully describe the segments of the SED where most energy is emitted, with a significant correlation between the electron energy density and the VHE gamma-ray activity, suggesting that most of the variability may be explained by the injection of high-energy electrons. The one-zone SSC scenario used reproduces the behaviour seen between the measured X-ray and VHE gamma-ray fluxes, and predicts that the correlation becomes stronger with increasing energy of the X-rays.Description
Keywords
astroparticle physics, acceleration of particles, radiation mechanisms: non-thermal, BL Lacertae objects: general, BL Lacertae objects: individual: Mrk501, 115 Astronomy and space science
Other note
Citation
MAGIC Collaboration , VERITAS Collaboration , FACT Collaboration , Hovatta , T , Lähteenmäki , A , Tornikoski , M & Tammi , J 2018 , ' The extreme HBL behaviour of Markarian 501 during 2012 ' Astronomy and Astrophysics , vol. 620 . https://doi.org/10.1051/0004-6361/201833704