A calorimetric test for Kerr black holes in gamma-ray bursts

Cosmological gamma-ray bursts are potentially associated with systems harboring a black rotating black hole. Calorimetry on yet "unseen" emissions in gravitational waves from a surrounding torus may provide a measure for its rotational energy. We introduce a compactness parameter $\alpha=2\pi\int fdE$ for the fluence $E$ and frequency $f$ in gravitational waves. For black hole-torus systems, $\alpha\simeq 2\pi Ef\simeq 0.005-0.05$ may exceed the upper bound $\alpha^*\simeq 0.005$ for rapidly rotating neutron stars. A duration in gravitational radiation consistent with the redshift corrected durations of the BATSE catalogue defines an association with long GRBs. This promises a new test for Kerr black holes as objects in Nature.