Discovery of Black Hole Spindown in the BATSE Catalogue of Long GRBs

The BATSE catalogue is searched for evidence of spindown of black holes or protoneutron stars (PNS) by extracting normalized light curves (nLC). The riLC are obtained by matched filtering, to suppress intermediate time scales such as due to the shock break-out of GRB jets through a remnant stellar envelope. We find consistency within a few percent of the nLC and the model template for spindown of an initially extremal black hole against high-density matter at the ISCO. The large BATSE size enables a study of the nLC as a function of durations T-90. The resulting chi(2)(red) is within a 2.350 sigma confidence interval for durations T-90 > 20 s, which compares favorably with the alternative of spindown against matter further out and spindown of a PNS, whose chi(2) fits are, respectively, outside the 4 sigma and 12 sigma confidence intervals. We attribute spindown against matter at the ISCO to cooling by gravitational-wave emission from non-axisymmetric instabilities in the inner disk or torus as the result of a Hopf bifurcation in response to energetic input from the central black hole. This identification gives an attractive outlook for chirps in quasi-periodic gravitational waves lasting tens of seconds of interest to LEGO, Virgo and the LCGT.