%0 Journal Article
%T Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
%A Pierre Auger Collaboration (Abreu, P. et al
%A Pastor, S.
%J Journal of Cosmology and Astroparticle Physics
%D 2011
%V 06
%N 6
%I Iop Publishing Ltd
%@ 1475-7516
%G English
%F PierreAugerCollaborationAbreu+Pastor2011
%O ISI:000292332400022
%O exported from refbase (https://references.ific.uv.es/refbase/show.php?record=676), last updated on Fri, 15 Jul 2011 12:53:12 +0000
%X The Pierre Auger Collaboration has reported. evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > E-th = 5.5 x 10(19) eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > E-th are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above E-th/Z (for illustrative values of Z = 6, 13, 26). If the anisotropies above E-th are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies.
%K ultra high energy cosmic rays
%K cosmic ray experiments
%R 10.1088/1475-7516/2011/06/022
%U http://arxiv.org/abs/1106.3048
%U https://doi.org/10.1088/1475-7516/2011/06/022
%P 022-17pp