Gravitational waves from newly born, hot neutron stars

We study the gravitational radiation associated with the non-radial oscillations of newly born, hot neutron stars. The frequencies and damping times of the relevant quasi-normal modes are computed for two different models of a proto-neutron star, at different times of evolution, from its birth until it settles down as a cold neutron star. We find that the oscillation properties of proto-neutron stars are remarkably different from those of their cold, old descendants, and that this affects the characteristic features of the gravitational signal emitted during the post-collapse evolution. The consequences on the observability of these signals by resonant-mass and interferometric detectors are analysed. We find that gravitational waves from the pulsations of a newborn proto-neutron star in the Galaxy could be detected with a signal-to-noise ratio of 5 by the first-generation interferometers, if the energy stored in the modes is greater than ∼10⁻⁸ M_⊙c², or by a resonant antenna if it is greater than ∼10⁻⁴ M_⊙c². In addition, since at early times the frequency of the space–time modes is much lower than that of a cold neutron star, they would also be detectable with the same signal-to-noise ratio if a comparable amount of energy is radiated into these modes.