Low latency search for gravitational waves from black-hole-neutron-star binaries in coincidence with short gamma-ray bursts

We propose a procedure to be used in the search for gravitational waves from black-hole-neutron-star coalescing binaries, in coincidence with short gamma-ray bursts. It is based on two recently proposed semianalytic fits, one reproducing the mass of the remnant disk surrounding the black hole which forms after the merging as a function of some binary parameters, the second relating the neutron star compactness, i.e., the ratio of mass and radius, with its tidal deformability. Using a Fisher matrix analysis and the two fits, we assign a probability that the emitted gravitational signal is associated to the formation of an accreting disk massive enough to supply the energy needed to power a short gamma-ray burst. This information can be used in low-latency data analysis to restrict the parameter space searching for gravitational wave signals in coincidence with short gamma-ray bursts and to gain information on the dynamics of the coalescing system and on the internal structure of the components. In addition, when the binary parameters are measured with high accuracy, it will be possible to use this information to trigger the search for off-axis gamma-ray burst afterglows.