Constrain the ejecta of GW 170817
GW 170817 is the first GW event together with its electromagnetic counterparts, imply that neutron merger. We consider a simple model for the nonthermal emission from GW170817, in which a quasi-spherical ejecta is released in the merger event, with the kinetic energy distributed over the momentum. The ejecta drives a shock into the medium and gives rise to synchrotron radiation.