Large-scale distribution of cosmic rays in right ascension as observed by the Yakutsk array at energies above 1018Â eV

We present the results of searches for anisotropy in the right ascension (RA) distribution of arrival directions of cosmic rays (CRs) detected with the Yakutsk array during the 1974-2008 observational period in the energy range above 1018 eV. Two methods of analysis are applied to two sub-samples of the data. Particularly, estimations of the first and second harmonic amplitudes are given, as well as the first harmonic phase in adjacent energy intervals. Analysis of variance demonstrates a significant contraction of the minimal width of the RA distribution in the energy bin (1019,1.78×1019) eV with respect to the isotropic distribution, which may be attributed to a possible source of CRs within the interval RA∈(15°,45°).