HS 0818 + 1227 : discovery of a new double gravitationally lensed QSO ?

We announce the discovery of a new gravitationally lensed QSO within the Hamburg Quasar Survey (HQS). HS 0818+1227 is at redshift z = 3.115 ± 0.001 and consists of two components separated by 2. ′′1 with R-magnitudes of 18.6 and 19.8 respectively. The two components have identical redshifts (4v ≤ 220 km/s) and identical emission line spectra with a flux ratio fA/fB = 8. In particular, both have the same large OVI/CIV emission line ratio. Close to the fainter image B there is an extended source which cannot be separated from B and which contributes to the spectrum of B at λ ≥ 5500 Å . Subtraction of a downscaled spectrum of A from B (fB − fA/8) reveals a residual with a spectrum similar to that of a neighbouring galaxy 5′′ apart which is at redshift 0.39. The system bears similarity to UM 673 where the lensing galaxy is very close to the fainter image. Further galaxies are within roughly 20′′. The suspected lensing galaxy (R ' 20.6, MV ' −21.5) is apparently member of a group (chain) of galaxies with several bright members within 60kpc · h−1 50 .