Detectability of gravitational wave events by spherical resonant-mass antennas

We report on results of computer simulations of spherical resonant-mass gravitational wave antennas interacting with high-frequency radiation from astronomical sources. The antennas were simulated with three-mode inductive transducers placed on the faces of a truncated icosahedron. Overall, the spheres were modeled with a sensitivity of about three times the standard quantum limit. The gravitational radiation data used was generated by three-dimensional numerical computer models of inspiraling and coalescing binary neutron stars and of the dynamical bar-mode instability of a rapidly rotating star. We calculated energy signal-to-noise ratios for aluminum spheres of different sizes cooled to 50 mK. We find that by using technology that could be available in the next several years, spherical antennas can detect coalescing binaries out to slightly over 15 Mpc, the lower limit on the distance required for one event per year. For the rapidly rotating star, we find, for a particular choice of the radius at centrifugal hangup, spheres are sensitive out to about 2 Mpc. The event rate is estimated to be about 1 every 10 years at this distance.