1. RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama 351-1198, Japan
2. Department of Physics & Astronomy, University of California, Irvine, Irvine, CA 92679, USA
3. Laser Interferometer Gravitational-Wave Observatory (LIGO), California Institute of Technology, Pasadena, CA 91125, and UC, Riverside, CA92521, USA