| Affiliation: |
| AA(Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland. ), AB(Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland), AC(Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), AD(Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), AE(Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), AF(Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), AG(Observatoire de Paris-Meudon, Meudon, France) |