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

¹ Universität Potsdam, Am Neuen Palais 10, 14469 Potsdam, Germany
² Dept. of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
³ Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540, USA
⁴ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany

Corresponding author: L. Wisotzki, lutz@astro.physik.uni-potsdam.de

Received: 3 July 2002
Accepted: 19 August 2002

Abstract

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.