The prospect of an inner accretion disk or torus around a black hole producing gravitational waves may be anticipated from non-axisymmetries associated with QPOs, as currently observed in the electromagnetic spectrum in some of the X-ray binaries and, at low frequencies, in SgrA* (e.g., [581]). Non-axisymmetries are a natural outcome of various processes including instabilities, as discussed in Chapter 9. Their output in gravitational radiation may well be energetic on the basis of the energy losses inferred from the observed black hole spin down shown in Fig. 11.5. Long GRBs and perhaps some of the CC-SNe, therefore, offer a unique possibility for identifying Kerr black holes as objects in Nature by calorimetry on all their emission channels [604].

Introduction

Taking advantage of the nearly all-sky monitoring capability of gravitational-wave detectors, blind searches for long gravitational-wave bursts (GWBs) might be optimal in view of the beaming factor of long GRBs from fb < 10 (θ > 25 deg) up to a few hundred (θ ~ 4 deg, [214, 608, 258]). Blind searches are also expected to be competitive with current X-ray/optical surveys for detecting the shock break-out associated with an emerging CC-SNe, as they last only tens of minutes to at most a few hours. Blind searches naturally include long GRBs with no detectable supernovae, e.g., the long event GRB 060614 of duration 102 s discovered by Swift and the halo event GRB 070123 discovered by IPN (see Table 1.1 in Chapter 1).