S E M I N A R IDepartament d'Astronomia i Astrofísica
Universitat de València
Linear and nolinear dynamics of "toroidal neutron stars"
SISSA, International School for Advanced Studies, Trieste, Itàlia
Seminari del Departament d'Astronomia i Astrofísica
Dijous 03 abril 2003
I present axisymmetric general relativistic hydrodynamics simulations of constant angular momentum compact discs orbiting a Schwarzschild black hole. These discs are expected as a result of stellar gravitational collapse or binary neutron star merger, can reach very high rest-mass densities and behave effectively as 'toroidal neutron stars'. Our attention is here focussed on the dynamical response of these objects to perturbations. I show that, upon the introduction of perturbations, these systems either become unstable to the run-away instability or exhibit a strikingly regular oscillatory behaviour resulting in a quasi-periodic variation of the mass accretion rate as well as of the density distribution. Despite being axisymmetric, the perturbed discs experience large variations of the rest-mass distribution hence emitting considerable amounts of gravitational radiation. The strength of the gravitational waves emitted can be up to two orders of magnitude larger than the one expected in stellar-core collapse making these new sources of gravitational waves potentially detectable.