Curious case of the maximum rigidity distribution of cosmic-ray accelerators

Models of sources of ultra high energy cosmic rays (UHECR)s usually assume that these sources, despite significant variability between them, accelerate particles to the same maximum energy. Here, the authors improve on this assumption by assigning their array of sources a broken-power-law distribution of the maximum energies. They observe that a power law distribution necessitates that the source to source variation be small.