Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory

We present the results of searches for dipolar-type anisotropies in different energy ranges above $2.5\times 10^{17}$ eV with the surface detector array of the Pierre Auger Observatory, reporting on both the phase and the amplitude measurements of the first harmonic modulation in the right-ascension...

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Bibliographic Details
Main Authors: Collaboration, TPA, Abreu, P, Aglietta, M, Ahn, E, Albuquerque, I, Allard, D, Allekotte, I, Allen, J, Allison, P, Castillo, J, Alvarez-Muñiz, J, Ambrosio, M, Aminaei, A, Anchordoqui, L, Andringa, S, Antičić, T, Aramo, C, Arganda, E, Arqueros, F, Asorey, H, Assis, P, Aublin, J, Ave, M, Avenier, M, Avila, G
Format: Journal article
Language:English
Published: 2011
Description
Summary:We present the results of searches for dipolar-type anisotropies in different energy ranges above $2.5\times 10^{17}$ eV with the surface detector array of the Pierre Auger Observatory, reporting on both the phase and the amplitude measurements of the first harmonic modulation in the right-ascension distribution. Upper limits on the amplitudes are obtained, which provide the most stringent bounds at present, being below 2% at 99% $C.L.$ for EeV energies. We also compare our results to those of previous experiments as well as with some theoretical expectations.