Gravitational radiation from core-collapse supernovae

Asymmetric core-collapse supernova are promising sources of gravitational radiation. Asymmetries can arise because of both convective instabilities and rotation. Convective instabilities occur in two distinct, spatially well separated regions during the first second of the explosion: (i) inside the proto-neutron star immediately below the neutrinosphere and (ii) in the neutrino-heated 'hot-bubble' region interior to the outward propagating revived shock wave. The gravitational wave signature of both convective instabilities has recently been computed. One finds that for a supernova located at a distance of 10 kpc the maximum dimensionless gravitational wave amplitudes \h(TT)\ range from about 9 x 10(-23) to 3 x 10(-21) in two-dimensional models. Anisotropic emission of neutrinos resulting from the non-spherical stratification of the proto-neutron star also generates gravitational waves. The amplitudes can be larger than the wave amplitudes due to mass motions by a factor of 5-10. In three-dimensional simulations the gravitational wave amplitudes due to mass motion and anisotropic neutrino emission are reduced by an order of magnitude. Most of the gravitational radiation from convection inside the proto-neutron star is emitted in the frequency band 100-1000 Hz, while convective motions in the hot-bubble region generate waves from several 100 Hz down to a few Hz. Pre-supernova models of rotating stars have not yet been calculated. Thus, in order to predict the gravitational wave signature of rotational core collapse one has to rely on parameter studies of the collapse of likely initial models. A recent comprehensive study shows that the dimensionless gravitational wave amplitudes are in the range 4 x 10(-25) less than or similar to \h(TT)\ less than or similar to 4 x 10(-23) for a source at a distance of 10 Mpc. The spectra cover a frequency range of 50 Hz to 3 kHz, with most of the power being emitted between 500 Hz and 1 kHz.