SimProp v2r4: Monte Carlo simulation code for UHECR propagation

We introduce the new version of SimProp, a Monte Carlo code for simulating the propagation of ultra-high energy cosmic rays in intergalactic space. This version, SimProp v2r4, together with an overall improvement of the code capabilities with a substantial reduction in the computation time, also computes secondary cosmogenic particles such as electron-positron pairs and gamma rays produced during the propagation of ultra-high energy cosmic rays. As recently pointed out by several authors, the flux of this secondary radiation and its products, within reach of the current observatories, provides useful information about models of ultra-high energy cosmic ray sources which would be hard to discriminate otherwise