In this seminar, I will present recent results concerning the analysis of gamma-ray bursts (GRB) afterglows and on the formation of binary neutron stars (BNSs). I will show a new model of the very high energy emission of GRB afterglows from the synchrotron self-Compton radiation of laterally-structured jets, and make predictions for GW 170817-like events. Concerning the formation of BNSs, I will present results obtained with population synthesis, that show an evolution of the dominant progenitors evolutionary tracks with redshift.