Multiwavelength observations and modeling of 1ES 1959+650 in a low flux state

E. Aliu, S. Archambault, T. Arlen, T. Aune, M. Beilicke, W. Benbow, R. Bird, M. Böttcher, A. Bouvier, V. Bugaev, K. Byrum, A. Cesarini, L. Ciupik, E. Collins-Hughes, M. P. Connolly, W. Cui, R. Dickherber, C. Duke, J. Dumm, M. ErrandoA. Falcone, S. Federici, Q. Feng, J. P. Finley, G. Finnegan, L. Fortson, A. Furniss, N. Galante, D. Gall, G. H. Gillanders, S. Griffin, J. Grube, G. Gyuk, D. Hanna, J. Holder, G. Hughes, T. B. Humensky, P. Kaaret, M. Kertzman, Y. Khassen, D. Kieda, H. Krawczynski, F. Krennrich, M. J. Lang, A. S. Madhavan, G. Maier, P. Majumdar, S. McArthur, A. McCann, P. Moriarty, R. Mukherjee, T. Nelson, A. O'Faoláin De Bhróithe, R. A. Ong, M. Orr, A. N. Otte, N. Park, J. S. Perkins, A. Pichel, M. Pohl, A. Popkow, H. Prokoph, J. Quinn, K. Ragan, L. C. Reyes, P. T. Reynolds, E. Roache, D. B. Saxon, M. Schroedter, G. H. Sembroski, C. Skole, A. W. Smith, D. Staszak, I. Telezhinsky, M. Theiling, J. Tyler, A. Varlotta, V. V. Vassiliev, S. P. Wakely, T. C. Weekes, A. Weinstein, R. Welsing, D. A. Williams, B. Zitzer

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30 Scopus citations

Abstract

We report on the VERITAS observations of the high-frequency peaked BL Lac object 1ES 1959+650 in the period 2007-2011. This source is detected at TeV energies by VERITAS at 16.4 standard deviation (σ) significance in 7.6 hr of observation in a low flux state. A multiwavelength spectral energy distribution (SED) is constructed from contemporaneous data from VERITAS, Fermi-LAT, RXTE PCA, and Swift UVOT. Swift XRT data is not included in the SED due to a lack of simultaneous observations with VERITAS. In contrast to the orphan γ-ray flare exhibited by this source in 2002, the X-ray flux of the source is found to vary by an order of magnitude, while other energy regimes exhibit less variable emission. A quasi-equilibrium synchrotron self-Compton model with an additional external radiation field is used to describe three SEDs corresponding to the lowest, highest, and average X-ray states. The variation in the X-ray spectrum is modeled by changing the electron injection spectral index, with minor adjustments of the kinetic luminosity in electrons. This scenario produces small-scale flux variability of the order of ≲ 2 in the high energy (E > 1 MeV) and very high energy (E > 100 GeV) γ-ray regimes, which is corroborated by the Fermi-LAT, VERITAS, and Whipple 10 m telescope light curves.

Original languageEnglish (US)
Article number3
JournalAstrophysical Journal
Volume775
Issue number1
DOIs
StatePublished - Sep 20 2013

Keywords

  • BL Lacertae objects: general
  • galaxies: active
  • gamma rays: galaxies

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