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 . ^ { \scriptscriptstyle \prime \kern 0.0 pt \prime } 107 \pm 0 . ^ { \scriptscriptstyle \prime \kern 0.0 pt \prime } 006 .
Because the faint image has an emission line at the same wavelength as the MgII 2798 Å emission line of the quasar , and lacks 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 image A .
The relative probabilities that the double is the smallest separation ( 4.8 h ^ { -1 } kpc for \Omega _ { 0 } = 1 ) correlated quasar pair or a gravitational lens are \sim 1 : 10 ^ { 6 } .
If the object is a lens , the mean lens redshift is \langle z _ { l } \rangle = 0.5 with 90 % confidence bounds of 0.18 < z _ { l } < 0.83 for \Omega _ { 0 } = 1 .
If the lens is an elliptical galaxy , we expect it to be brighter than I < 19.5 mag .
The broad band 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 lensing hypothesis .