Very-high-energy γ -ray observations of the Blazar 1ES 2344+514 with VERITAS

C. Allen, S. Archambault, A. Archer, W. Benbow, R. Bird, E. Bourbeau, R. Brose, M. Buchovecky, J. H. Buckley, V. Bugaev, J. V. Cardenzana, M. Cerruti, X. Chen, J. L. Christiansen, M. P. Connolly, W. Cui, M. K. Daniel, J. D. Eisch, A. Falcone, Q. FengM. Fernandez-Alonso, J. P. Finley, H. Fleischhack, A. Flinders, L. Fortson, A. Furniss, G. H. Gillanders, S. Griffin, J. Grube, M. Hütten, N. Håkansson, D. Hanna, O. Hervet, J. Holder, G. Hughes, T. B. Humensky, C. A. Johnson, P. Kaaret, P. Kar, N. Kelley-Hoskins, 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, S. O'Brien, A. O'Faoláin de Bhróithe, R. A. Ong, A. N. Otte, N. Park, A. Petrashyk, A. Pichel, M. Pohl, A. Popkow, E. Pueschel, J. Quinn, K. Ragan, P. T. Reynolds, G. T. Richards, E. Roache, A. C. Rovero, C. Rulten, I. Sadeh, M. Santander, G. H. Sembroski, K. Shahinyan, I. Telezhinsky, J. V. Tucci, J. Tyler, S. P. Wakely, A. Weinstein, A. Wilhelm, D. A. Williams

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Abstract

We present very-high-energy γ -ray observations of the BL Lac object 1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array System between 2007 and 2015. 1ES 2344+514 is detected with a statistical significance above the background of 20.8σ in 47.2 h (livetime) of observations, making this the most comprehensive very-high-energy study of 1ES 2344+514 to date. Using these observations, the temporal properties of 1ES 2344+514 are studied on short and long times-scales. We fit a constant-flux model to nightly and seasonally binned light curves and apply a fractional variability test to determine the stability of the source on different time-scales. We reject the constant-flux model for the 2007-2008 and 2014-2015 nightly binned light curves and for the long-term seasonally binned light curve at the > 3σ level. The spectra of the time-averaged emission before and after correction for attenuation by the extragalactic background light are obtained. The observed time-averaged spectrum above 200 GeV is satisfactorily fitted (χ2/NDF = 7.89/6) by a power-law function with an index Γ = 2.46 ± 0.06stat ± 0.20sys and extends to at least 8 TeV. The extragalactic-backgroundlight- deabsorbed spectrum is adequately fit (χ2/NDF = 6.73/6) by a power-law function with an index Γ = 2.15 ± 0.06stat ± 0.20sys while an F-test indicates that the power law with an exponential cut-offfunction provides a marginally better fit (χ2/NDF = 2.56/5) at the 2.1σ level. The source location is found to be consistent with the published radio location and its spatial extent is consistent with a point source.

Original languageEnglish (US)
Pages (from-to)2117-2123
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Volume471
Issue number2
DOIs
StatePublished - 2017

Bibliographical note

Funding Information:
This 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. We acknowledge the excellent work of the technical support staffat the Fred Lawrence Whipple Observatory and at the collaborating institutions in the construction and operation of the instrument. S. O'Brien is funded by a UCD Research Scholarship. The VERITAS Collaboration is grateful to TrevorWeekes for his seminal contributions and leadership in the field of VHE gamma-ray astrophysics, which made this study possible.

Keywords

  • Astroparticle physics
  • BL Lacertae objects: individual: 1ES 2344+514 = VER J2347+517
  • Gamma-rays: galaxies

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