Neutron star tidal disruption in mixed binaries: The imprint of the equation of state

We study the tidal disruption of neutron stars in black hole-neutron star coalescing binaries. We calculate the critical orbital separation at which the star is disrupted by the black hole tidal field for several equations of state describing the matter inside the neutron star, and for a large set of the binary parameters. When the disruption occurs before the star reaches the innermost stable circular orbit, the gravitational wave (GW) signal emitted by the system is expected to exhibit a cutoff frequency nu(GW tide), which is a distinctive feature of the waveform. We evaluate nu(GW tide) and show that, if this frequency will be found in a detected gravitational wave, it will allow one to determine the neutron star radius with an error of a few percent, providing valuable information on the behavior of matter in the stellar core.