2001/10/31 by S. Razzaque, Soebur Razzaque, John P. Ralston
Physics and Astronomy · #Anisotropy #Astrophysics #Astrophysics and Cosmic Phenomena #COSMIC cancer database #Cosmic ray #Dark Matter and Cosmic Phenomena #Gamma-ray bursts and supernovae #Geometry #Isotropy #Optics #Physics #Rotation (mathematics) #Ultra-high-energy cosmic ray #astro-ph #hep-ph
paper · pdf · doi:10.1088/1475-7516/2003/07/007
published as JCAP 0307 (2003) 007 · 10 pages, 3 figures, published version
arxiv created 2003/07/15 · openalex publication_date 2003/07/15 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The distribution of arrival directions of ultra-high energy cosmic rays may yield clues to their mysterious origin. We introduce a method of invariant statistics to analyse cosmic ray data which eliminates coordinate-dependent artifacts. When combined with maximum likelihood analysis, the method is capable of quantifying deviations of the distribution from isotropy with high reliability. We test our method against published AGASA events with energies above 4 × 10 19 eV. Angular cuts from observational limitations are taken into account. A model based on the Fisher distribution reveals the rotation of the Earth with the axis along the direction (5 h 53.36 m , 85.78°) in ( RA , DEC ) coordinates, which is within 5° of the equatorial north pole. Global anisotropy of the data, if any, hinges on finer understanding of detector acceptance than what is available from the published literature.