Spectrum of very high energy gamma-rays from the blazar 1ES 1959+650 during flaring activity in 2002

M. K. Daniel, H. M. Badran, I. H. Bond, P. J. Boyle, S. M. Bradbury, J. H. Buckley, D. A. Carter-Lewis, M. Catanese, O. Celik, P. Cogan, W. Cui, M. D'Vali, I. De La Calle Perez, C. Duke, A. Falcone, D. J. Fegan, S. J. Fegan, J. P. Finley, L. F. Fortson, J. A. GaidosS. Gammell, K. Gibbs, G. H. Gillanders, J. Grube, J. Hall, T. A. Hall, D. Hanna, A. M. Hillas, J. Holder, D. Horan, T. B. Humensky, A. Jarvis, M. Jordan, G. E. Kenny, M. Kertzman, D. Kieda, J. Kildea, J. Knapp, K. Kosack, H. Krawczynski, F. Krennrich, M. J. Lang, S. L.E. Bohec, E. Linton, J. Lloyd-Evans, A. Milovanovic, P. Moriarty, D. Müller, T. Nagai, S. Nolan, R. A. Ong, R. Pallassini, D. Petry, B. Power-Mooney, J. Quinn, M. Quinn, K. Ragan, P. Rebillot, P. T. Reynolds, H. J. Rose, M. Schroedter, G. H. Sembroski, S. P. Swordy, A. Syson, V. V. Vassiliev, S. P. Wakely, G. Walker, T. C. Weekes, J. Zweerink

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The blazar 1ES 1959+650 was observed in a flaring state with the Whipple 10 m Imaging Atmospheric Cerenkov Telescope in 2002 May. A spectral analysis has been carried out on the data from that time period, and the resulting very high energy gamma-ray spectrum (E ≥ 316 GeV) can be well fitted by a power law of differential spectral index α = 2.78 ± 0.12stat ± 0.21sys. On 2002 June 4, the source flared dramatically in the gamma-ray range without any coincident increase in the X-ray emission, providing the first unambiguous example of an "orphan" gamma-ray flare from a blazar. The gamma-ray spectrum for these data can also be described by a simple power-law fit with α = 2.82 ± 0.15stat ± 0.30sys. There is no compelling evidence for spectral variability or for any cutoff to the spectrum.

Original languageEnglish (US)
Pages (from-to)181-187
Number of pages7
JournalAstrophysical Journal
Issue number1 I
StatePublished - Mar 1 2005


  • Gamma rays: observations
  • Techniques: spectroscopic


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