Discovery of a binary quasar at z=1.76

We present the serendipitous discovery of a physical pair of quasars with estimated cosmological redshift z = 1.76. Long-slit spectroscopic observations of the candidate quasar GQ 1114+1549A were conducted with the OSIRIS instrument at the Gran Telescopio Canarias. The orientation of the slit allowed OSIRIS to also capture the spectrum of GQ 1114+1549B, an object with angular separation of ΔΘ = 8.76 arcsec from GQ 1114+1549A. Spectral analysis on the Si IV and C IV, C III] emission lines confirmed the quasar nature of GQ 1114+1549A, as well as that of its newly discovered companion. The relative intensity for the emission lines and the shape of the continuum of the two objects were found to be significantly different, rendering the hypothesis of the system being a gravitationally lensed quasar highly unlikely. The projected physical distance between the two quasars was therefore estimated to be 75 kpc.