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  • The Large-Scale Cosmic-Ray ...
    Abdo, A. A; Allen, B. T; Aune, T; Berley, D; Casanova, S; Chen, C; Dingus, B. L; Ellsworth, R. W; Fleysher, L; Fleysher, R; Gonzalez, M. M; Goodman, J. A; Hoffman, C. M; Hopper, B; Hüntemeyer, P. H; Kolterman, B. E; Lansdell, C. P; Linnemann, J. T; McEnery, J. E; Mincer, A. I; Nemethy, P; Noyes, D; Pretz, J; Ryan, J. M; Parkinson, P. M. Saz; Shoup, A; Sinnis, G; Smith, A. J; Sullivan, G. W; Vasileiou, V; Walker, G. P; Williams, D. A; Yodh, G. B

    The Astrophysical journal, 06/2009, Letnik: 698, Številka: 2
    Journal Article

    Results are presented of a harmonic analysis of the large-scale cosmic-ray (CR) anisotropy as observed by the Milagro observatory. We show a two-dimensional display of the sidereal anisotropy projections in right ascension (R.A.) generated by the fitting of three harmonics to 18 separate declination bands. The Milagro observatory is a water Cherenkov detector located in the Jemez mountains near Los Alamos, New Mexico. With a high duty cycle and large field of view, Milagro is an excellent instrument for measuring this anisotropy with high sensitivity at TeV energies. The analysis is conducted using a seven-year data sample consisting of more than 95 billion events, the largest such data set in existence. We observe an anisotropy with a magnitude around 0.1% for CRs with a median energy of 6 TeV. The dominant feature is a deficit region of depth (2.49 - 0.02 stat. - 0.09 sys.) X10-3 in the direction of the Galactic north pole centered at 189 deg R.A. We observe a steady increase in the magnitude of the signal over seven years.