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

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

Citation Formats
V. A. Acciari et al. , “Veritas observations of the gamma-ray binary LS I+61 303,” ASTROPHYSICAL JOURNAL, vol. 679, no. 2, pp. 1427–1432, 2008, Accessed: 00, 2020. [Online]. Available: