Fitting the HiRes Spectra

2005/07/20 by D. R. Bergman, Bergman, D. R.
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph

paper · pdf · doi:10.48550/arxiv.astro-ph/0507484

4 pages, 6 figures, Submitted to the 29th International Cosmic Ray Conference, Pune, India

arxiv created 2005/07/20 · arxiv updated 2019/08/13

Abstract

We fit the HiRes ultra-high energy cosmic ray (UHECR) spectrum measurements with broken power laws in order to identify features. These fits find the previously observed feature known as the Ankle at 10**18.5 eV, as well as evidence for a suppression at higher energies, above 10**19.8 eV. We use the integral spectrum and the E₁/2 test to identify this high energy suppression with the GZK suppression. Finally, we use a model of uniformly distributed extragalactic proton sources together with a phenomenological model of the galactic cosmic ray spectrum to compare the HiRes spectra to what should be expected from the GZK suppression, and to measure how the extragalactic sources must evolve and what the input spectral slope must be to fit the HiRes data. Fits using updated spectra will be presented in Pune.

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