Discovery of a new gravitational lens

The faint QSO pair 1635 + 267 A + B, discovered in a slitless spectroscopy survey by Weedman (1982), are found to be at practically the same redshift of 1.961 + or - 0.003. Their redshift difference, determined with a cross-correlation technique, is found to be (3.2 + or - 8.5) x 10 to the -4th, which corresponds to a rest-frame velocity difference of only (33 + or - 86) km/s. This low value and the similarity of the spectra strongly argue that this is another case of a gravitational lens. Deep CCD images do not reveal the presence of a lensing object more than an arcsec away from either QSO image down to a red magnitude of 23.5. An absorption feature in the spectrum of the brighter QSO image may be a signature of the lens galaxy. This line is interpreted as the Mg II 2799 doublet, seen at redshift 1.118.