Veritas observations of the gamma-ray binary LS I+61 303

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Acciari V. A., Beilicke M., Blaylock G., Bradbury S. M., Buckley J. H., Bugaev V., ...More

ASTROPHYSICAL JOURNAL, vol.679, no.2, pp.1427-1432, 2008 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 679 Issue: 2
  • Publication Date: 2008
  • Doi Number: 10.1086/587736
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1427-1432
  • Keywords: acceleration of particles, binaries : general, gamma rays : observations, stars : individual (LS I+61 303), DISCOVERY, EMISSION, MODEL, MODULATION, SPECTRA, ARRAY
  • Middle East Technical University Affiliated: Yes


LS I +61 303 is one of only a few high-mass X-ray binaries currently detected at high significance in very high energy gamma-rays. The system was observed over several orbital cycles ( between 2006 September and 2007 February) with the VERITAS array of imaging air Cerenkov telescopes. A signal of gamma-rays with energies above 300 GeV is found with a statistical significance of 8.4 standard deviations. The detected flux is measured to be strongly variable; the maximum flux is found during most orbital cycles at apastron. The energy spectrum for the period of maximum emission can be characterized by a power law with a photon index of Gamma = 2.40 +/- 0.16(stat) +/- 0.2(sys) and a flux above 300 GeV corresponding to 15% - 20% of the flux from the Crab Nebula.