Mass composition modelling at sources of ultra-high energy cosmic rays

Extragalactic sources are thought to be the origin of the highest energy cosmic rays detected at Earth. In this work, we explore energy-dependent mass compositions of these sources taking a subset of the VCV catalog for distances with z=0.6. We use a power-law spectrum with an exponential cutoff to model individual sources above 10^18.7 eV. To be more realistic we use the individual distance and radio flux weight of the sources, while sharing other properties as the power law index, Z-dependent rigidity cut and nuclei fraction. We propagate the different nuclei using CRPropa and search for the best stable parameters that fit the features of the spectrum measured by the Pierre Auger Observatory. We show that the mass composition at the sources tends to have lighter nuclei, with H and He having the greatest contributions. The power law index found is 2 ± 0.1 and the rigidity cutoff 10²¹±^0.3 eV.