SBS 0909+532: A New Double Gravitational Lens or Binary Quasar?

The z=1.377, B=17.0 mag quasar SBS 0909+532 A, B is a double with two imagesseparated by 1.107 +/- 0.006 arcsec. Because the faint image has an emissionline at the same wavelength as the MgII 2798 A emission line of the quasar, andlacks the broad MgIb absoption feature expected for a star with the same colors(a K star), we conclude that image B is a quasar with similar redshift to imageA. The relative probabilities that the double is the smallest separation (4.8/hkpc for \Omega_0=1) correlated quasar pair or a gravitational lens are \sim1:10^6. If the object is a lens, the mean lens redshift is $=0.5$ with 90%confidence bounds of 0.18 < z_l < 0.83 for \Omega_0=1. If the lens is anelliptical galaxy, we expect it to be brighter than I < 19.5 mag. The broadband flux ratio varies with wavelength, with \Delta I=0.31, \Delta R=0.58, and\Delta B=1.29 magnitudes, which is difficult to reconcile with the lensinghypothesis.Comment: 19 pages, 6 figures, ApJ in pres