HE 0435-1223: A wide separation quadruple QSO and gravitational lens

We report the discovery of a new gravitationally lensed QSO, at a redshift , with four QSO components in a cross-shaped arrangement around a bright galaxy. The maximum separation between images is , enabling a reliable decomposition of the system. Three of the QSO components have , while component A is about 0.6 mag brighter. The four components have nearly identical colours, suggesting little if any dust extinction in the foreground galaxy. The lensing galaxy is prominent in the i band, weaker in r and not detected in g. Its spatial profile is that of an elliptical galaxy with a scale length of ~12 kpc. Combining the measured colours and a mass model for the lens, we estimate a most likely redshift range of . Predicted time delays between the components are 10 days. The QSO shows evidence for variability, with total g band magnitudes of 17.89 and 17.71 for two epochs separated by ~2 months. However, the relative fluxes of the components did not change, indicating that the variations are intrinsic to the QSO rather than induced by microlensing.

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