SBS-0909- A NEW DOUBLE GRAVITATIONAL LENS OR BINARY QUASAR(532 )

The z = 1.377, B = 17.0 mag quasar SBS 0909+532 A, B is a double with two images separated by Delta theta = 1.'' 107 +/- 0.'' 006. Because t he faint image has an emission line at the same wavelength as the Mg I I 2798 Angstrom emission line of the quasar, and it lacks the broad Mg Ib absorption feature expected for a star with the same colors (a K s tar), we conclude that image B is a quasar with similar redshift to im age A. The relative probabilities that the double is the smallest sepa ration (4.7 h(-1) kpc for Omega(0) = 1) correlated quasar pair or a gr avitational lens are similar to 1:10(6). If the object is a lens, the mean lens redshift is [z(i)ota] = 0.5 with 90% confidence bounds of 0. 18 < z(i)ota < 0.83 for Omega(0) = 1. If the lens is an elliptical gal axy, 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, an d Delta B = 1.29 magnitudes, which is difficult to reconcile with the lensing hypothesis.