C. Vignali (1), W.N. Brandt (2), O. Shemmer (2), A. Steffen (2), D.P.
  Schneider (2), S. Kaspi (3,4) (Dipartimento di Astronomia, Universita' di
  Bologna, Italy; (2) Department of Astronomy and Astrophysics, Pennsylvania
  State University, University Park, USA; (3) Wise Observatory, Tel Aviv
  University, Israel; (4) Physics Department, Technion, Haifa, Israel)