Large-scale cosmic-ray anisotropies above 4 EeV measured by the Pierre Auger Observatory
Date
2018
Authors
Aab, A.
Abreu, P.
Aglietta, M.
Albuquerque, I.
Albury, J.
Allekotte, I.
Almela, A.
Castillo, J.
Alvarez-Muñiz, J.
Anastasi, G.
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Journal article
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The Astrophysical Journal: an international review of astronomy and astronomical physics, 2018; 868(1):4-1-4-12
Statement of Responsibility
A. Aab ... J.M. Albury … J.A. Bellido … S.G. Blaess … R.W. Clay … M.J. Cooper … B.R. Dawson, J.A. Day … T.D. Grubb … T.A. Harrison, V.M. Harvey … G.C. Hill … S.J. Saffi … T. Sudholz … P. van Bodegom … [et al.] (The Pierre Auger Collaboration)
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Abstract
We present a detailed study of the large-scale anisotropies of cosmic rays with energies above 4 EeV measured using the Pierre Auger Observatory. For the energy bins [4, 8] EeV and E ≥ 8 EeV, the most significant signal is a dipolar modulation in R.A. at energies above 8 EeV, as previously reported. In this paper we further scrutinize the highest-energy bin by splitting it into three energy ranges. We find that the amplitude of the dipole increases with energy above 4 EeV. The growth can be fitted with a power law with index β = 0.79 ± 0.19. The directions of the dipoles are consistent with an extragalactic origin of these anisotropies at all the energies considered. Additionally, we have estimated the quadrupolar components of the anisotropy: they are not statistically significant. We discuss the results in the context of the predictions from different models for the distribution of ultrahigh-energy sources and cosmic magnetic fields.
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© 2018. The American Astronomical Society. All rights reserved.