Barber, K.Bellido Caceres, J.Clay, R.Cooper, M.Dawson, B.Herve, A.Holmes, V.Sorokin, J.Wahrlich, P.Whelan, B.Winnick, M.2012-05-212012-05-212011Astroparticle Physics, 2011; 34(8):627-6390927-65051873-2852http://hdl.handle.net/2440/71070We present the results of searches for dipolar-type anisotropies in different energy ranges above 2.5 × 10¹⁷ 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. © 2011 Published by Elsevier B.V.en© 2011 Elsevier B.V. All rights reserved.Journal article002010512310.1016/j.astropartphys.2010.12.0070002889302000072-s2.0-7955159239031303Bellido Caceres, J. [0000-0002-0833-9194]Clay, R. [0000-0002-9040-9648]Dawson, B. [0000-0002-4271-3055]