  We present a theoretical study of double compact objects as potential
short/hard gamma-ray burst (GRB) progenitors. An updated population synthesis
code StarTrack is used to calculate properties of double neutron stars and
black-hole neutron star binaries. We obtain their formation rates, estimate
merger times and finally predict their most likely merger locations and
afterglow properties for different types of host galaxies. Our results serve
for a direct comparison with the recent HETE-II and SWIFT observations of
several short bursts, for which afterglows and host galaxies were detected. We
also discuss the possible constraints these observations put on the
evolutionary models of double compact object formation. We emphasize that our
double compact object models can successfully reproduce at the same time short
GRBs within both young, star-forming galaxies (e.g., GRB 050709 and GRB
051221A), as well as within old, elliptical hosts (e.g., GRB 050724 and
probably GRB 050509B)
