Observation of gamma-ray emission from the galaxy M87 above 250 GeV with VERITAS

V. A. Acciar, M. Beilicke, G. Blaylock, S. M. Bradbury, J. H. Buckley, V. Bugaev, Y. Butt, O. Celik, A. Cesarini, L. Ciupik, P. Cogan, P. Colin, W. Cui, M. K. Daniel, C. Duke, T. Ergin, A. D. Falcone, S. J. Fegan, J. P. Finley, G. FinneganP. Fortin, L. F. Fortson, K. Gibbs, G. H. Gillanders, J. Grube, R. Guenette, G. Gyuk, D. Hanna, E. Hays, J. Holder, D. Horan, S. B. Hughes, M. C. Hui, T. B. Humensky, A. Imran, P. Kaaret, M. Kertzman, D. B. Kieda, J. Kildea, A. Konopelko, H. Krawczynski, F. Krennrich, M. J. Lang, S. LeBohec, K. Lee, G. Maier, A. McCann, M. McCutcheon, J. Millis, P. Moriarty, R. Mukherjee, T. Nagai, R. A. Ong, D. Pandel, J. S. Perkins, M. Pohl, J. Quinn, K. Ragan, P. T. Reynolds, H. J. Rose, M. Schroedter, G. H. Sembroski, A. W. Smith, D. Steele, S. P. Swordy, A. Syson, J. A. Toner, L. Valcarcel, V. V. Vassiliev, S. P. Wakely, J. E. Ward, T. C. Weekes, A. Weinstein, R. J. White, D. A. Williams, S. A. Wissel, M. D. Wood, B. Zitzer

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Abstract

The multiwavelength observation of the nearby radio galaxy M87 provides a unique opportunity to study in detail processes occurring in active galactic nuclei from radio waves to TeV γ-rays. Here we report the detection of γ-ray emission above 250 GeV from M87 in spring 2007 with the VERITAS atmospheric Cerenkov telescope array and discuss its correlation with the X-ray emission. The γ-ray emission is measured to be pointlike with an intrinsic source radius less than 4.5′. The differential energy spectrum is fitted well by a power-law function: dΦ/dE = (7.4 ± 1.3stat ± 1.5sys)(£/TeV) (-2.31±0.17stat±0.2sys)10-9 m-2 s-1 TeV-1. We show strong evidence for a year-scale correlation between the γ-ray flux reported by TeV experiments and the X-ray emission measured by the ASM RXTE observatory, and discuss the possible short-timescale variability. These results imply that the γ-ray emission from M87 is more likely associated with the core of the galaxy than with other bright X-ray features in the jet.

Original languageEnglish (US)
Pages (from-to)397-403
Number of pages7
JournalAstrophysical Journal
Volume679
Issue number1
DOIs
StatePublished - May 20 2008

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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