Time delay and lens redshift for the doubly imaged BAL quasar SBS 1520+530 *,**
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
2 Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
3 Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 août, Bat. B5C, Liège 1, Belgium
4 Universidad Católica de Chile, Departamento de Astronomia y Astrofisica, Casilla 306, Santiago 22, Chile
5 California Institute of Technology, Pasadena, CA 91125, USA
6 European Sourthern Observatory, Casilla 19, Santiago, Chile
7 Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Canary Islands, Spain
8 Observatoire Midi-Pyrénées, 14 avenue Édouard Belin, 31400 Toulouse, France
Corresponding author: I. Burud, email@example.com
Accepted: 4 June 2002
We present optical R-band light curves of the gravitationally lensed quasar SBS 1520+530 derived from data obtained at the Nordic Optical Telescope. A time delay of days (1σ) is determined from the light curves. In addition, spectra of SBS 1520+530 obtained at the Keck Observatory are spatially deconvolved in order to extract the spectrum of the faint lensing galaxy, free of any contamination by the light from the bright quasar images. This spectrum indicates a lens redshift , in agreement with one of the absorption systems found in the quasar spectra. The best mass model of the system includes a second nearby galaxy and a cluster of galaxies in addition to the main lensing galaxy. Adopting this model and an , cosmology, our time-delay measurement yields a Hubble constant of (1σ error).
Key words: gravitational lensing / quasars: individual: SBS 1520+530 / cosmology: cosmological parameters
Based on observations made with the Nordic Optical, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias and the W. M. Keck Observatory which is operated jointly by the California Institute of Technology, the University of California and the National Aeronautics and Space Administration.
© ESO, 2002