Distribution of binary mergers around galaxies
  We use a stellar binary population synthesis code to find the lifetimes and velocities of several types of possible GRB progenitors: double neutron stars, black hole neutron stars, black hole white dwarfs, helium star mergers. Assuming that they are born in different types of galaxies we compute their spatial distribution and compare it with the observed locations of GRB afterglows within their hosts. We discuss constraints on the compact object merger model of GRBs imposed by this comparison and find that the observations of afterglows and their host galaxies appear inconsistent with the GRB compact object merger model. 
Tomasz Bulik and Krzysztof Belczynski