Branching ratio of Type Ib/c supernovae into GRB-supernovae

We study centered and decentered nucleation of black holes in core-collapse of massive stars in binaries. By Bekenstein's gravitational-radiation recoil mechanism, a newly nucleated black hole typically leaves the central core prematurely. With low probability, the black hole remains centered and matures to a high-mass black hole which spins rapidly if the binary is compact. GRB030329/SN2003dh demonstrates that Type Ib/c supernovae are the parent population of long GRBs, whose branching ratio is ${\cal R}=(2-4)\times 10^{-3}$. We identify ${\cal R}$ with the low probability of centered nucleation in compact binaries. Decentered events are predicted to produce a single short burst in gravitational radiation. Centered events are predicted to produce a second, long-burst in gravitational radiation powered by a luminous black hole. These signatures are of interest to LIGO, VIRGO and TAMA.