Gamma-ray bursts: LIGO/VIRGO sources of gravitational radiation

The status and prospects are reviewed for the presently most favored model for the inner engine of cosmological gamma-ray bursts (GRBs): the black hole–torus model. Support for this model is derived from recent GRB-phenomenology: a cosmological origin, a bi-modal distribution in their durations, and potentially a GRB/X-ray transient connection. The black hole–torus model operates by the rotation of the central Kerr black hole, which introduces two new mechanisms: in-situ pair-creation on open field-lines along the axis of rotation and a powerful magnetic black hole-to-torus coupling. The leptonic winds serve as input to the GRB-afterglow emissions. Long/short GRBs are identified with suspended/hyper-accretion onto rapidly/slowly rotating black holes. The suspended accretion state is expected to be accompanied by baryonic winds blown off the torus; if formed in stellar collapse, these winds may account for recently detected iron line-emissions and may have contributed to the chemical abundances in X-ray transients. This implies that HETE-II will detect afterglows from all bursts, but iron-line emission only from long bursts. In long bursts, the torus is expected to radiate most of the black hole luminosity in gravitational waves. This predicts that long GRBs are potentially the most powerful burst-sources of gravitational waves in the Universe. Their emissions trace a horizontal branch in the ḟ(f)-diagram, which can be tested by LIGO/VIRGO.