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

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

doi:10.1086/587736

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)

Publication Type: Article / Article
Volume: 679 Issue: 2
Publication Date: 2008
Doi Number: 10.1086/587736
Journal Name: ASTROPHYSICAL JOURNAL
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

Abstract

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.