A Luminous and Isolated Gamma-Ray Flare from the Blazar B2 1215+30

A. U. Abeysekara, S. Archambault, A. Archer, W. Benbow, R. Bird, M. Buchovecky, J. H. Buckley, V. Bugaev, K. Byrum, M. Cerruti, X. Chen, L. Ciupik, W. Cui, H. J. Dickinson, J. D. Eisch, M. Errando, A. Falcone, Q. Feng, J. P. Finley, H. FleischhackL. Fortson, A. Furniss, G. H. Gillanders, S. Griffin, J. Grube, M. Hütten, N. Håkansson, D. Hanna, J. Holder, T. B. Humensky, C. A. Johnson, P. Kaaret, P. Kar, M. Kertzman, D. Kieda, M. Krause, F. Krennrich, S. Kumar, M. J. Lang, G. Maier, S. McArthur, A. McCann, K. Meagher, P. Moriarty, R. Mukherjee, T. Nguyen, D. Nieto, R. A. Ong, A. N. Otte, N. Park, V. Pelassa, M. Pohl, A. Popkow, E. Pueschel, J. Quinn, K. Ragan, P. T. Reynolds, G. T. Richards, E. Roache, C. Rulten, M. Santander, G. H. Sembroski, K. Shahinyan, D. Staszak, I. Telezhinsky, J. V. Tucci, J. Tyler, S. P. Wakely, O. M. Weiner, A. Weinstein, A. Wilhelm, D. A. Williams, S. Fegan, B. Giebels, D. Horan, A. Berdyugin, J. Kuan, E. Lindfors, K. Nilsson, A. Oksanen, H. Prokoph, R. Reinthal, L. Takalo, F. Zefi

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B2 1215+30 is a BL-Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes and subsequently confirmed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory with data collected between 2009 and 2012. In 2014 February 08, VERITAS detected a large-amplitude flare from B2 1215+30 during routine monitoring observations of the blazar 1ES 1218 +304, located in the same field of view. The TeV flux reached 2.4 times the Crab Nebula flux with a variability timescale of <3.6 hr. Multiwavelength observations with Fermi-LAT, Swift, and the Tuorla Observatory revealed a correlated high GeV flux state and no significant optical counterpart to the flare, with a spectral energy distribution where the gamma-ray luminosity exceeds the synchrotron luminosity. When interpreted in the framework of a onezone leptonic model, the observed emission implies a high degree of beaming, with Doppler factor δ > 10, and an electron population with spectral index p < 2.3.

Original languageEnglish (US)
Article number205
JournalAstrophysical Journal
Issue number2
StatePublished - Feb 20 2017

Bibliographical note

Funding Information:
R.M. acknowledges support from the Alliance Program at Ecole Polytechnique and Columbia University. VERITAS research is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, and the Smithsonian Institution, and by NSERC in Canada.

Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.


  • BL Lacertae objects: individual (B2 1215+30, VER J1217+301)
  • galaxies: active
  • galaxies: jets
  • galaxies: nuclei
  • gamma rays: galaxies


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