1. Department of Physics, University of California, Santa Cruz, 1156 High St, Santa Cruz, CA 95064, USA
2. Department of Physics and Astronomy, San José State University, One Washington Square, San Jose, CA 95192, USA
3. University of California Observatories, 1156 High Street, Santa Cruz, CA 95064, USA
4. Observatories of the Carnegie Institute of Washington, 813 Santa Barbara St, Pasadena, CA 91101, USA
5. Observatoire de Paris, LERMA, CNRS, 61 Av de l'Observatoire, F-75014 Paris, France