Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory


J. Abraham, Karlsruhe Institute of Technology, Campus South
M. Aglietta, Fermi National Accelerator Laboratory
C. Aguirre, National Technical University of Athens
D. Allard, Charles University
I. Allekotte, Consejo Nacional de Investigaciones Científicas y Técnicas
P. Allison, Universidade Estadual do Sudoeste da Bahia
C. Alvarez, The Ohio State University
J. Alvarez-Muñiz, Pierre Auger Observatory
M. Ambrosio, Case Western Reserve University
L. Anchordoqui, Universidade Estadual de Feira de Santana
J. C. Anjos, Università degli Studi dell'Aquila
C. Aramo, Case Western Reserve University
K. Arisaka, Universidade Federal Fluminense
E. Armengaud, Universidad Michoacana de San Nicolás de Hidalgo
F. Arneodo, Louisiana State University
F. Arqueros, University of Wisconsin-Milwaukee
T. Asch, Instituto de Astronomía y Física del Espacio
H. Asorey, Consejo Nacional de Investigaciones Científicas y Técnicas
B. S. Atulugama, Universidade Federal da Bahia
J. Aublin, Centro de Investigacion y de Estudios Avanzados
M. Ave, Charles University
G. Avila, Karlsruhe Institute of Technology, Campus North
J. Bacelar, University of Colorado Boulder
T. Bäcker, Universidad Complutense de Madrid
D. Badagnani, Rheinisch-Westfälische Technische Hochschule Aachen
A. F. Barbosa, Università degli Studi dell'Aquila
H. M.J. Barbosa, Università degli Studi di Napoli Federico II
M. Barkhausen, FOM-Institute of Subatomic Physics - NIKHEF
D. Barnhill, Universidade Federal Fluminense
S. L.C. Barroso, Università degli Studi dell'Aquila
P. Bauleo, Universidad Mayor de San Andres Bolivia
J. Beatty, Universidade Estadual do Sudoeste da Bahia

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Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius A. Also the events detected simultaneously by the surface and fluorescence detectors (the 'hybrid' data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction. © 2006 Elsevier B.V. All rights reserved.

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Astroparticle Physics