Binary neutron star mergers as engines of short gamma-ray bursts: delayed vs. prompt collapse

Inspiralling and merging binary neutron stars (NSNSs) are not only promising sources of detectable gravitational waves, but they are also possible progenitors of short gamma-ray bursts. We have recently performed magnetohydrodynamic simulations in full general relativity which show that a jet is launched from the poles of the spinning black hole formed following magnetized NSNS mergers. For the cases we explored the black hole-disk remnant arises from the ``delayed" collapse of a hypermassive NSNS that forms following an equal-mass merger. Now we have varied both the initial NS compaction and binary mass ratio to explore the formation of jets for cases in which the merger leads to ``prompt'' collapse.